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2001 Eldorado Overheating


hms200

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Hello all...HELP!!

I read this entire thread with great interest due to an issue I'm troubleshooting. I posted a plea for help on another Caddy Owners forum and got a response from "Ranger" (I think I saw him in this thread/site as well). In any case, he questioned my purge line status so I'm researching. I knew nothing of that until now so I've not checked it yet. I was actually looking for and wondering where the bleed fitting was as I crawled around looking for thermostat location. This thread answers that questions as well, as to how air is purged from the cooling system.

Here is my post from the other site. Anybody please chime in if able...I'm really stumped and hoping for some pointers/advice.

Ranger confirmed that compression test results mean nothing in diagnosing blown HG's. I agree it doesn't prove they are not blown from info I've read, but I expected that it might give evidence if they are. Make sense? Also ALL the plugs were very clean.

Ranger was puzzled by me getting no positive results from block test and questioned how dealership had made their diagnosis. I have no clue...was done for prior owner so I had no benefit of any dialog with them on that.

Ranger also agreed I think with my hesitation on suspecting radiator/thermostat blockage as the culprit. I've not seen either really being at fault in such cases unless outward evidence of leaking or unless radiator/cooling system clearly has been neglected. No leaks and I see no evidence in service history of abuse/neglect from prior owner. Vehicle was well serviced all its life so far as I can determine.

Here is my post...

2001 Northstar - Head Gaskets blown or not?? I'm stumped!!

Hi gents...I purchased 2001 Eldorado that was diagnosed by Caddy dealership to have blown HG's. I've done a battery of tests before I go breaking into the engine, attempting to validate the blown HG's...but no definitive evidence yet...HELP!!

What I think I know:

1. Definitely overheating

2. Excessive back pressure boils coolant from tank quickly

3. Upper & Lower hoses hot and under pressure

4. Water Pump does NOT leak

5. Conducted block test (blue chemical test) multiple times correctly using reliable test ket - zero evidence of exhaust in coolant (tested 4 times)

6. No exhaust smell in coolant tank that I can detect

7. Zero white smoke from tailpipe

8. No water from tailpipe once it reaches normal operating temp (after initial condensation is gone)

9. No funky coolant smell in exhaust

10. I've also confirmed there is NO WATER in the oil and all spark plugs were clean; looked completely normal.

11. There was no evidence on the plugs of burning or blowing any coolant.

12. Both cooling fans are operating as they should.

13. I can make the engine overheat very quickly and easily with it simply sitting in my garage. With coolant level topped off I simply have to rev the engine up/down to ~2500 rpm's for maybe 5 minutes and then temp will start clocking past mid point. A few minutes later the boiling/surge begins in tank and also will continue once vehicle is turned off. I've read where many folks can drive-drive-drive with blown HG's without overheating so long as they avoid grades and severe speeds. For how fast mine heats up I would have expected major/clear results from troubleshooting if blown HG's...but nope, not so far.

14. Conducted compression test - "wet test" results as follows (dry tests were a bit lower but equally consistant):

Front Bank (Left to Right)

183 - 192 -191 - 180

Back Bank (Left to Right)

184 - 196 - 189 - 205

Ok...so unless somebody spots anything I'm missing, I'm not getting definitive evidence of blown HG's at this stage. Compression appears good (I think?), within reasonable spec and all cylinders within spec range of each other (within 10%)...yes? As I understand it, the Northstar CAN pass compression test but still have blown HG's due to nature of high compression engine under normal operating condition/load. Right? But other tests don't give me evidence either...so I'm reslly stumped!!

What are the odds that I have radiator blockage or a failed thermostat rather than blown HG's? Odds seem slim to me from all I've read about widespead failure of head bolts, but evidence sure is pointing away from HG's with all I see so far.

So all you really smart gents please chime in with your thoughts, questions, ideas.

Many thanks - Howard

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This is your first post here. Welcome Aboard

You piggy tailed on to another thread. I split it off to its own thread

Your problem needs its OWN thread, so that you can find it, and so that it is located by ITSELF.

Mike

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

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Your purge line lets air out of the system.

Do you know how to check it?

Do you know where it is located?

Do you understand the "bolt with a hole in it"?

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Your thread is curious

If you are getting overheating, the first thing you would do, since its so easy, would be to change the thermostat, immediately, and while you do that, check the water pump belt and tensioner and look for leaks.

Small cost while at the same time eliminating the potential for it to be bad

When you fill up the system make sure you end up with a 50/50 mix of coolant to water and that the CAP holds pressure, a bad cap will not hold pressure and allow the coolant to boil

Are you losing coolant? (at all)

Have you had the coolant checked for hydrocarbons at a radiator shop?

You say your Cooling fans coming on, are they running strong?, I have seen the motors go bad and they will just run weakly

Have you pressure tested the cooling system?

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Your thread is curious

If you are getting overheating, the first thing you would do, since its so easy, would be to change the thermostat, immediately, and while you do that, check the water pump belt and tensioner and look for leaks.

Small cost while at the same time eliminating the potential for it to be bad

When you fill up the system make sure you end up with a 50/50 mix of coolant to water and that the CAP holds pressure, a bad cap will not hold pressure and allow the coolant to boil

Are you losing coolant? (at all)

Have you had the coolant checked for hydrocarbons at a radiator shop?

You say your Cooling fans coming on, are they running strong?, I have seen the motors go bad and they will just run weakly

Have you pressure tested the cooling system?

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Thx...

Honestly my initial effort was to simply validate the dealership diagnosis of blown HG's and then proceed from there with the repairs. As I shared though, all tests I've performed thus far have not provided definitive verification.

Hydrocarbons...I performed the blue chemical block test multiple times with no positive results.

Cap...I had never considered that (forest from the trees) but you now are 2nd to suggest. Yes I will confirm that as well. Did have the 50/50, but now as I troubleshoot in the garage I've gone to straight water since I keep boiling it out. The 50/50 mix made no difference with the condition at hand, though the cap pressure I do need to validate.

Water pump belt is fine...no wear, no noise and functioning as it should.

Thermostat...yes, that's where it seems I'm headed to now, that and possibly radiator core replacement before I decide HG's by simple default. Was hoping for more definitive proof as to source of issue...not keen on swapping parts until problem found/fixed. I've honestly never seen a hard failed thermostat, but I do know that can happen at times so I do replace them as maintenance when appropriate.

Losing coolant...only as direct result of it boiling out of tank through overflow tube when cap blows. No leaks anywhere else.

Cooling fans...they seem to be running at normal speed...not limping along so far as I can tell.

Purge Line...yes I "now" understand all about it, though I didn't until Ranger aqsked the question and than I read up on it here. Yes, I pulled the bolt with hole and confirmed...it was/is completely clear. Water also flowed out thru the bolt fitting when I pulled it, so I know that's clear as well.

Howard

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Don't waste anymore money, if the dealer said HGs, you need to go to that, first (after the stat and cap since they are so cheap).

Have a good radiator shop with a tester, not the type you used, an electronic tester and have it tested now, if the dealer said that its HGs, you must eliminate that, and the coolant is the definitive test. Those testers you used are problematic, since you are adding water and coolant.

Get a test

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Purge Line...yes I "now" understand all about it, though I didn't until Ranger aqsked the question and than I read up on it here. Yes, I pulled the bolt with hole and confirmed...it was/is completely clear. Water also flowed out thru the bolt fitting when I pulled it, so I know that's clear as well.

Did you also check for coolant flow at the "other end" of that plumbing circuit?? That would be the hose that connects to a nipple near the top of the coolant reservoir; be sure coolant flows through that hose and the fitting into the reservoir is also clear.

The reservoir in a Northstar cooling system is an active, although low-flow, part of the design. Thinking of the reservoir as a surge tank or an overflow tank misses the function of the reservoir.

You are doing all the right things in trying to nail down your diagnosis; hang in there. From time to time I wonder how many Northstar cooling system issues have been incorrectly diagnosed as failed headgskets.

Jim

Drive your car.

Use your cell phone.

CHOOSE ONE !

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Don't waste anymore money, if the dealer said HGs, you need to go to that, first (after the stat and cap since they are so cheap).

Have a good radiator shop with a tester, not the type you used, an electronic tester and have it tested now, if the dealer said that its HGs, you must eliminate that, and the coolant is the definitive test. Those testers you used are problematic, since you are adding water and coolant.

Get a test

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Thx BBF...very wise advice I believe at this stage.

So...almost hate to ask (LOL)...

Timeserts, Norm's Solution, Studs...if you, which one would you go with?

Also...

I have no means to pull or drop the engine for this repair. Forums are very mixed on this, but can I successfully facilitate this repair with engine in the car? Norm (Norm's Solution) says I can, though difficult, if I tilt engine forward for rear bank. Huh?? How the heck do I tilt engine forward? Norm couldn't answer that question. :) I've read threads that say studs definitely can't be done withy engine in car due to clearance issues. That makes sense...but then drilling out the threads take clearance as well, even with a right angle drill.

HMS

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Purge Line...yes I "now" understand all about it, though I didn't until Ranger aqsked the question and than I read up on it here. Yes, I pulled the bolt with hole and confirmed...it was/is completely clear. Water also flowed out thru the bolt fitting when I pulled it, so I know that's clear as well.

Did you also check for coolant flow at the "other end" of that plumbing circuit?? That would be the hose that connects to a nipple near the top of the coolant reservoir; be sure coolant flows through that hose and the fitting into the reservoir is also clear.

The reservoir in a Northstar cooling system is an active, although low-flow, part of the design. Thinking of the reservoir as a surge tank or an overflow tank misses the function of the reservoir.

You are doing all the right things in trying to nail down your diagnosis; hang in there. From time to time I wonder how many Northstar cooling system issues have been incorrectly diagnosed as failed headgskets.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Thx Jim for your reply.

Actually, <red faced> no I didn't check the other end I'm ashamed to say...BUT I WILLLL!! :)

Folks...if it comes to this, can I make the head bolt repairs with engine in the car? I've read many mixed opinions on this. I have no facilities for pulling/dropping the engine. Also...is there a consensus out there, without opening a massive debate like I've seen everywhere, as to Timeserts, "Norm's Solution" (NS300L) or Studs? I think studs are out anyway for in-car repair due to clearance, yes?

HMS

Howard

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Don't waste anymore money, if the dealer said HGs, you need to go to that, first (after the stat and cap since they are so cheap).

Have a good radiator shop with a tester, not the type you used, an electronic tester and have it tested now, if the dealer said that its HGs, you must eliminate that, and the coolant is the definitive test. Those testers you used are problematic, since you are adding water and coolant.

Get a test

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Thx BBF...very wise advice I believe at this stage.

So...almost hate to ask (LOL)...

Timeserts, Norm's Solution, Studs...if you, which one would you go with?

Also...

I have no means to pull or drop the engine for this repair. Forums are very mixed on this, but can I successfully facilitate this repair with engine in the car? Norm (Norm's Solution) says I can, though difficult, if I tilt engine forward for rear bank. Huh?? How the heck do I tilt engine forward? Norm couldn't answer that question. smile.gif I've read threads that say studs definitely can't be done withy engine in car due to clearance issues. That makes sense...but then drilling out the threads take clearance as well, even with a right angle drill.

HMS

To discuss the repair at this point is pre-mature, I'd be thrilled if you didnt have a problem

When she is warmed up, is the upper hose hard?

If you have not replaced the cap, do so, and replace the thermostat, ESPECIALLY if she has overheated, its very easy, will you do it yourself?

if you get to a radiator shop, have them pressure test your cooling system...

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Purge Line...yes I "now" understand all about it, though I didn't until Ranger aqsked the question and than I read up on it here. Yes, I pulled the bolt with hole and confirmed...it was/is completely clear. Water also flowed out thru the bolt fitting when I pulled it, so I know that's clear as well.

Did you also check for coolant flow at the "other end" of that plumbing circuit?? That would be the hose that connects to a nipple near the top of the coolant reservoir; be sure coolant flows through that hose and the fitting into the reservoir is also clear.

The reservoir in a Northstar cooling system is an active, although low-flow, part of the design. Thinking of the reservoir as a surge tank or an overflow tank misses the function of the reservoir.

You are doing all the right things in trying to nail down your diagnosis; hang in there. From time to time I wonder how many Northstar cooling system issues have been incorrectly diagnosed as failed headgskets.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Thx Jim for your reply.

Actually, <red faced> no I didn't check the other end I'm ashamed to say...BUT I WILLLL!! smile.gif

Folks...if it comes to this, can I make the head bolt repairs with engine in the car? I've read many mixed opinions on this. I have no facilities for pulling/dropping the engine. Also...is there a consensus out there, without opening a massive debate like I've seen everywhere, as to Timeserts, "Norm's Solution" (NS300L) or Studs? I think studs are out anyway for in-car repair due to clearance, yes?

HMS

Howard

I would never attempt a head gasket job on this car with the engine in the car....

I would seriously consider the northstar performance studs as they have 2 inches of threads

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Don't waste anymore money, if the dealer said HGs, you need to go to that, first (after the stat and cap since they are so cheap).

Have a good radiator shop with a tester, not the type you used, an electronic tester and have it tested now, if the dealer said that its HGs, you must eliminate that, and the coolant is the definitive test. Those testers you used are problematic, since you are adding water and coolant.

Get a test

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Thx BBF...very wise advice I believe at this stage.

So...almost hate to ask (LOL)...

Timeserts, Norm's Solution, Studs...if you, which one would you go with?

Also...

I have no means to pull or drop the engine for this repair. Forums are very mixed on this, but can I successfully facilitate this repair with engine in the car? Norm (Norm's Solution) says I can, though difficult, if I tilt engine forward for rear bank. Huh?? How the heck do I tilt engine forward? Norm couldn't answer that question. smile.gif I've read threads that say studs definitely can't be done withy engine in car due to clearance issues. That makes sense...but then drilling out the threads take clearance as well, even with a right angle drill.

HMS

To discuss the repair at this point is pre-mature, I'd be thrilled if you didnt have a problem

When she is warmed up, is the upper hose hard?

If you have not replaced the cap, do so, and replace the thermostat, ESPECIALLY if she has overheated, its very easy, will you do it yourself?

if you get to a radiator shop, have them pressure test your cooling system...

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Yes, both hoses hard and hot.

Yes, will replace both the cap and thermostat before proceeding purther in any direction.

Yes, I'm handling all the repairs personally. I do not have a cooling system pressure tester though so I may be forced to try and set my mind more at ease by getting some shop bound diagnostics done that I'm not equipped to perform. Was told by a local shop that they also have a smoke tester to analysis the exhaust.

HMS

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almost every caddy i see for sale with bad headgaskets has a new radiator and waterpump. that is the progression for repairs. also, you have 2 caddys? neither has a VVT motor.

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almost every caddy i see for sale with bad headgaskets has a new radiator and waterpump. that is the progression for repairs. also, you have 2 caddys? neither has a VVT motor.

I see that quite often also - mechanics often throw a radiator and waterpump at the car in hope that it will fix the problem.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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Mechanics love Hope and Change or is that Change and Hope, :lol:

Its true, I have seen a bunch of overheaters and they change the WP, stat and radiator and HOPE for the best. No time for diagnosis you know

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Is there consensus that I maybe am in error with eliminating the low cost items guys before diving into the heads?

I know the radiator wasn't exactly cheap and maybe is one step further than some might go...but it wasn't insane priced either. Even if not any of these parts then I just rack the cost up to preventive maintenance on a 10 yo vehicle. Since I'm providing all labor then it seems like a pretty good investment to me. It also will sure make me more confident with all my busted knuckles, scrapes and scrathes to come if/when I have to attack the HB's. :) Not at all trying to deny what is probably my reality...rather, just trying to not be dumb about this either. It goes against my grain to do parts swapping as means to troubleshoot...but in this case it is what it is as I see it.

HMS

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Here are the facts

DEALER SAID HEAD GASKETS ARE BAD.... NOW, either he is INCOMPETENT or he is a THIEF or he is CORRECT

You have not however said HOW they determined that, what tests. Did they offer you a good deal on a 2011 at the same time?

You checked the coolant with the by products kit and could not duplicate the problem (the test you did can be problematic, if new coolant was added, if this is the beginning of a HG problem, etc)

The compression test looks good

Cooling fans are good

Purge line is clear and flowing coolant at the tank end of the line (correct?)

Coolant concentration is at least 50/50

The system appears to hold pressure because the upper hose is hard

Water pump belt is good and the tensioner is good (correct?)

PROBLEMS

No cooling system pressure test has been done, to test that the system holds pressure

The cap has not been replaced or tested

The thermostat has not been replaced

No independent test has been done by a radiator shop utilizing an electronic sniffer

Conclusion

While the test you did is not always a conclusive test, the dealer supposedly did a test, but you do not have the details as to what test they did, can you question them?

Something caused the dealer NOT to change the stat or cap, if they found combustion by products, but you did NOT find combustion by products,

How honest is your dealer?

You MUST confirm that there is a PROBLEM, independent of the dealer and so far you have NOT, go to a radiator shop, do NOT just ASSUME you have a head gasket problem without doing so. I would have had the stat and cap done this morning at 7:30, you seem to be dragging your feet, so forget about the stat and cap, take it to a radiator shop for an independent by products test, NOT using the liquid test that changes color.

Parts replacing when the dealer flagged this car for having bad head gaskets is foolish

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Make sure the solution used to test for combustion gases in the coolant is fresh. I have read of blue fluid not changing to green or yellow because it was sitting on the store shelf too long.

Also:

make sure both hoses get hot.

are you leaking colant out the exhaust or into the oil?

if your car is puking coolant, what happens first - does it overheat, or does it puke coolant than overheat?

again, getting back to a previous post of mine, I believe many of these issues are just air pockets in the coolant. Sometimes it's just the simplelest of things.

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Here are the facts

DEALER SAID HEAD GASKETS ARE BAD.... NOW, either he is INCOMPETENT or he is a THIEF or he is CORRECT

You have not however said HOW they determined that, what tests. Did they offer you a good deal on a 2011 at the same time?

You checked the coolant with the by products kit and could not duplicate the problem (the test you did can be problematic, if new coolant was added, if this is the beginning of a HG problem, etc)

The compression test looks good

Cooling fans are good

Purge line is clear and flowing coolant at the tank end of the line (correct?)

Coolant concentration is at least 50/50

The system appears to hold pressure because the upper hose is hard

Water pump belt is good and the tensioner is good (correct?)

PROBLEMS

No cooling system pressure test has been done, to test that the system holds pressure

The cap has not been replaced or tested

The thermostat has not been replaced

No independent test has been done by a radiator shop utilizing an electronic sniffer

Conclusion

While the test you did is not always a conclusive test, the dealer supposedly did a test, but you do not have the details as to what test they did, can you question them?

Something caused the dealer NOT to change the stat or cap, if they found combustion by products, but you did NOT find combustion by products,

How honest is your dealer?

You MUST confirm that there is a PROBLEM, independent of the dealer and so far you have NOT, go to a radiator shop, do NOT just ASSUME you have a head gasket problem without doing so. I would have had the stat and cap done this morning at 7:30, you seem to be dragging your feet, so forget about the stat and cap, take it to a radiator shop for an independent by products test, NOT using the liquid test that changes color.

Parts replacing when the dealer flagged this car for having bad head gaskets is foolish

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Wow...really??? WHAT set you off BBF? Dragging my feet? The dealer that did the diagnosis was the prior owners dealer, not mine. So I can't speak to their honesty. I CAN speak to a rather sloppy assembly under the hood though by them when they rebuilt the engine some 15K miles ago, as I mentioned in a prior post. Yes, they DID sell him a new Caddy actually and they DID offer him a give away price quote to trade this one in with their diagnosed issue. I bought the car from prior owner rather than him giving it away to dealer. Think I stated that earlier also?

Dragging my feet? I bought the cap/stat last night and both have been installed. Road tested... not overheating yet, but now I must get up on freeway where the true test should happen. Is it harmful to try and collect as much info as able before rushing quickly to another shop? All you guys have been extremely helpful and nice...and I greatly appreciate the time/effort from you all. If this had been my vehicle throughout the entire overheating event (before and after) plus the one that received the diagnosis from dealer then far less backtracking would be necessary. But I'm not and I wasn't...so recreating and stepping systematic. That's foolish? Also I had to reassemble a good many things from my earlier compression test effort as I'm sure you are aware. That was last night and morning activity. Took me 20 min to test new + old stat's side by side in boiling water (I was curious) and then another 15 min to actually install the new stat. Old one was fine btw...as I really fully expected would be the case. In all my years I've yet to see a failed stat...though I know it is possible. Um...took me ~10 seconds to replace the cap. :)

Changing what parts exactly is foolish BBF? Cap and stat...or are you bothered that I also bought a radiator core? You yourself agreed with the cap/stat so I guess it's the radiator that set you off? So you didn't like my logic that even that if none of these three parts are to blame then putting in a new $155 radiator core for a 10 yo vehicle can simply be considered good preventive maintenance worst case? I said myself that I'm not by nature a parts changer and that this goes against my character. But these are cheap and very much parts of the overall cooling system that isn't giving clear signals yet, thus could absolutely be the culprit from everything I've seen so far. Yes I will no doubt go get a shop test if my efforts validate nothing, as is so far the case.

Sure have not intended to rub anybody the wrong way BBF...but evidently I did with you? You often this rough with a person simply trying to figure something out on their own? I'm not a rookie under the hood...just a rookie with the Northstar and the entire associated HB/HG issue with same. Curious how many blown head gaskets I've diagnosed and replaced over the years? Not my first rodeo as I had said in a prior post.

HMS

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Make sure the solution used to test for combustion gases in the coolant is fresh. I have read of blue fluid not changing to green or yellow because it was sitting on the store shelf too long.

Also:

make sure both hoses get hot.

are you leaking colant out the exhaust or into the oil?

if your car is puking coolant, what happens first - does it overheat, or does it puke coolant than overheat?

again, getting back to a previous post of mine, I believe many of these issues are just air pockets in the coolant. Sometimes it's just the simplelest of things.

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Thank you winterset...

Yes, both hoses hot and both are under pressure.

No coolant out tailpipe and no coolant in oil.

I will provide results from highway test once it's done.

Btw...this is a project with no immediate urgency...not on foot. I just want to get this right and then do the job right.

HMS

HMS

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I have spent a lot of time with you, I don't parts replace or speak of replacing radiators, I always eliminate the simple things first. I said nothing to set you off.

By NOW you should have done the simple things, stat and cap, long before concluding to head gaskets or replacing a radiator, especially if the engine has overheated.

I have been positive, but in the post I reponded to, you are still talking about doing head gaskets before doing all simple things, i,e., stat and cap.... and especially getting the coolant checked for combustion by products, that is the most important thing

Not sure why have you have an attitude but please lose it, we are all on the same side here.

No need to go any further here, GO GET A TEST, the dealer said HEAD GASKET........... either confirm that or disprove that with a test

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Thx BBF...

As I had said before, I appreciate and respect all of your time/effort and all others that have replied. I don't have an attitude to lose, but I was a little shocked at tone of that reply from you. Perhaps I read it wrong...if so then my deepest apologies. You said it well...yes, we're all on the same side and I'm just a guy trying to dig down on this just as all others have done and are continuing to do. In any case, no offense intended here to you whatsoever and none taken on this end. I love my Deville and so bought this Eldorado for my wife so she can also get the Caddy thrill. Also, I bought the car with eyes wide open...so I'm definitely not trying to avoid what is appearing to be the obvious. Had just hoped to step my way to final validation verdict. I haven't jumped to anything, and yes I'll go get the shop tests done as well since I clearly can't properly complete it with the resources at my disposal. I've been pondering the Northstar HG job for quite some time while I was finishing up prior project on my daughters car (Kia blown HG's and many other misc repairs and preventive maintenance items on it), so that's why I've jumped forward to some of those questions from time to time...was curious. As the car sat, awaiting its turn on my projects list, I was completely resolved to blown HG's so I cranked the effort in my head and had already started my research based on that upcoming repair. The pre tear-down testing that I've gotten hung up on wasn't expected to be complicated and/or throw any shadows over anything as it has done...was just intended to quickly and easily validate the disgnosis before diving in head first. I've since learned from you and all others that the testing is much more involved than I had expected and not nearly so straight forward as I had thought...or maybe I should say I didn't get the proper key tests done right up front as best required for this specific engine and its associated issue/character.

So again BBF...please accept my thanks for all your responses and I do hope we'll continue to chat as I muddle thru this effort, regardless of which path it takes. Yes? :)

HMS

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Lets hope for the best. If your coolant testing is accurate maybe a damaged thermostat is all that it is or your system is releasing pressure due to a bad cap and boiling due to a loss of system pressure.

We have seen both occur, and yes, we have seen bad thermostats and I have had bad stats myself.

I would get a good radiator shop to test your coolant for by products to confirm or dispell the dealers results. Good Luck

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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