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My Overheating problem...


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Car began over heating, so I took it in for a radiator flush and quick look over. Don't know how much inspection was done on the water pump, thermostat, etc., but I drove off with the car temporarily cured of over-heating, and running about 201 on the highway and 212-215 in town. After about a 40 minutes of driving with no problem, it overheated again. Let it sit for 6 hours, drove it some more, and it over heated very quickly, almost as if the water pump wasn't even moving coolant.

Would have understood the problem had it not run normal for a while after the coolant change. I would think if the water pump was shot, the coolant change wouldn't have had even a temporary effect.

The car has had some indicators of head gasket failure, but other than consuming about a pint of coolant every hundred miles, the car would not overheat. You could just keep adding coolant every so often, and it would otherwise run fine. Now it's overheating quite badly.

Any clues? I know there are a lot of overheating stories here, but every one seems a bit different.

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Another odd thing, is that I keep adding coolant up to half (about 2" below neck of cap) but the warning system keeps saying to "Check Coolant". Every time I add coolant, it never seems to be enough to get the "check coolant" light to go off. It will even get to the point where the coolant warms, completely fills (and overflows) the tank, but the warning system will still say "check coolant".

Something really seems odd, but I can't figure it out.

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Rent/borrow the test kit for checking for combustion gases in the coolant, from your local auto store.

If you "DO" have combustion gases in the coolant, that is a pretty sure sign of head gasket failure.

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Rent/borrow the test kit for checking for combustion gases in the coolant, from your local auto store.

If you "DO" have combustion gases in the coolant, that is a pretty sure sign of head gasket failure.

Sounds like a plan. I have suspected head gasket problems for quite a while, but up until recently, it's been manageable. I could add some coolant here and there with no overheating problems. Would a worsening of the problem explain the rapid overheating that's occuring?

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Rent/borrow the test kit for checking for combustion gases in the coolant, from your local auto store.

If you "DO" have combustion gases in the coolant, that is a pretty sure sign of head gasket failure.

Sounds like a plan. I have suspected head gasket problems for quite a while, but up until recently, it's been manageable. I could add some coolant here and there with no overheating problems.

Would a worsening of the problem explain the rapid overheating that's occuring?

Yes it would.

Sometimes in the early stages of head gasked failure, the problem isn't too bad.

But ... "IF" that is what it is... it only gets worse over time...

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I wanted to further elaborate on my overheating problem, just to see if these additional "clues" offer any indicators.

Thanks to Texas Jim for his previous input.

Check Coolant Level - The odd thing here, is that this warning light will not go off. Even if the surge tank is completely full to over flowing, the "Check Coolant Level" light still comes on. I find this totally baffling. Is the coolant level sensor in the surge tank, or somewhere else in the coolant system that's not getting the proper flow of coolant?

Bubbles in Coolant Surge Tank - Started the engine cold with the cap off, and saw periodic bubbles in the surge tank. If you revved the engine a bit, the bubble volume would increase. The level in the tank seem to rise and fall a little bit with each bubble. I did this check as to verify air in the system, but it didn't take the thermostat opening at 185+/- degrees to see the bubbles. They started within a minute or two.

No Heat? - Turned the heater up to 90 on the climate control, but there was no warm air coming out the vents at all. Among other problems, is this a sign that the coolant is not making it to the heater?

Car will overheat from idle - At this point, it doesn't take any driving around to overheat the car. It will overheat from idle in about 10 minutes from a 70 degree start up.

Summary - Although there had been suspected head gasket issues with the car, there was no over-heating, and only modest consumption of coolant. A rapid over heating problem then ensued. A flush of the system seemed to correct the problem (making me think the overheating was due to blockage), but within 40 minutes of driving, it began to, and still rapidly overheats. The heater doesn't seem to work.

Would this indicate that there is some type of blockage as well as the probable head gasket failure? While I could imagine the HG problem getting worse, it would have been a quantum leap in the severity of the problem overnight. The car went from totally drive-able to where you can't drive it at all in one day.

While I have not done the test on the coolant for exhaust gases, I'm resolute about there being a HG problem. I'm trying to determine if there is something else at play here. The Check Coolant Level light being on constantly and seemingly no coolant going through the heater make me think the rapid overheating is due to some type of blockage.

Again, your replies are appreciated.

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I wanted to further elaborate on my overheating problem, just to see if these additional "clues" offer any indicators.

Thanks to Texas Jim for his previous input.

Check Coolant Level - The odd thing here, is that this warning light will not go off. Even if the surge tank is completely full to over flowing, the "Check Coolant Level" light still comes on. I find this totally baffling. Is the coolant level sensor in the surge tank, or somewhere else in the coolant system that's not getting the proper flow of coolant?

The coolant sensor is "IN" the surge tank.

Bubbles in Coolant Surge Tank - Started the engine cold with the cap off, and saw periodic bubbles in the surge tank. If you revved the engine a bit, the bubble volume would increase. The level in the tank seem to rise and fall a little bit with each bubble. I did this check as to verify air in the system, but it didn't take the thermostat opening at 185+/- degrees to see the bubbles. They started within a minute or two.

To "ME" that indicates a pretty bad blown head gasket.

If it is bubbling like that... you could probably put your nose close to the opening and actually "SMELL" exhaust gases.

No Heat? - Turned the heater up to 90 on the climate control, but there was no warm air coming out the vents at all. Among other problems, is this a sign that the coolant is not making it to the heater?

This could be a blockage in the heater core, but I do not believe that it would make the car overheat.

To check this... take the two heater hoses off and using a small piece if tubing, hook them together with hose clamps. This will totally bypass the heater core.

Car will overheat from idle - At this point, it doesn't take any driving around to overheat the car. It will overheat from idle in about 10 minutes from a 70 degree start up.

Are the cooling fans working?

Summary - Although there had been suspected head gasket issues with the car, there was no over-heating, and only modest consumption of coolant. A rapid over heating problem then ensued. A flush of the system seemed to correct the problem (making me think the overheating was due to blockage), but within 40 minutes of driving, it began to, and still rapidly overheats. The heater doesn't seem to work.

If there is no "EXTERNAL" leak, modest use of coolant is one sign of a bad head gasket.

Would this indicate that there is some type of blockage as well as the probable head gasket failure? While I could imagine the HG problem getting worse, it would have been a quantum leap in the severity of the problem overnight. The car went from totally drive-able to where you can't drive it at all in one day.

While I have not done the test on the coolant for exhaust gases, I'm resolute about there being a HG problem. I'm trying to determine if there is something else at play here. The Check Coolant Level light being on constantly and seemingly no coolant going through the heater make me think the rapid overheating is due to some type of blockage.

See above...

Again, your replies are appreciated.

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Last, but not least, I disconnected the purge line and there was no flow at all of coolant with the engine running.

So, while there is certainly a head gasket problem, it also appears that the coolant flow is blocked. The line at the tank and the nipple are clear, but still no flow. Others have said this indicates a blockage back at the water pump. Not a mechanic, so I'm not quite sure how to get at it.

Would like to see the coolant flowing as it's supposed to before writing this one off as as an HG fatality.

Thanks, John.

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It does not indicate a block at the water pump, it indicates a block at the "bolt with a hole in it"

Trace the purge line across to the engine, and it will end up around the throttle body, remove the hose from that nipple at the "bolt with a hole in it" and use a 15 mm wrench to remove the "bolt with a hold in it" and clear it out with a drill bit or something.

DO NOT, I repeat DO NOT, blow air through the purge line from the coolant tank to clear it, you will only temporarily dislodge it. The clog MUST be removed by hand

Here is a photo of the bolt with a hole in it from a 96, this hole MUST be clear to allow air out of the system or the engine will overheat, as you will not be able to get enough coolant in and the water pump will cavitate....

Boltwithaholeinit.jpg

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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Bubbles in the tank with a clogged purge line, no heat from the heater core and overheating is not a good sign. Follow the advice in post #3 after you clear the purge line if you still have the same symptoms.

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It does not indicate a block at the water pump, it indicates a block at the "bolt with a hole in it"

Trace the purge line across to the engine, and it will end up around the throttle body, remove the hose from that nipple at the "bolt with a hole in it" and use a 15 mm wrench to remove the "bolt with a hold in it" and clear it out with a drill bit or something.

DO NOT, I repeat DO NOT, blow air through the purge line from the coolant tank to clear it, you will only temporarily dislodge it. The clog MUST be removed by hand

Here is a photo of the bolt with a hole in it from a 96, this hole MUST be clear to allow air out of the system or the engine will overheat, as you will not be able to get enough coolant in and the water pump will cavitate....

Boltwithaholeinit.jpg

Thanks for your input.

I found the connection you have pictured, but now I need to ask a few stupid "I'm not a mechanic" questions:

Is that a re-usable hose clamp that's on there? Looks like it requires a special tool to tighten or loosen.

If I destroy it taking it off, can I use a screw hose clamp to replace it?

The "bolt with a hole in it" will come off counter-clockwise?

I know, dumb questions, but I've never done much mechanically on any car, other than add fluids or change windshield wipers! I think I can handle this with a little more direction.

Thanks, John

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It does not indicate a block at the water pump, it indicates a block at the "bolt with a hole in it"

Trace the purge line across to the engine, and it will end up around the throttle body, remove the hose from that nipple at the "bolt with a hole in it" and use a 15 mm wrench to remove the "bolt with a hold in it" and clear it out with a drill bit or something.

DO NOT, I repeat DO NOT, blow air through the purge line from the coolant tank to clear it, you will only temporarily dislodge it. The clog MUST be removed by hand

Here is a photo of the bolt with a hole in it from a 96, this hole MUST be clear to allow air out of the system or the engine will overheat, as you will not be able to get enough coolant in and the water pump will cavitate....

Boltwithaholeinit.jpg

Thanks for your input.

I found the connection you have pictured, but now I need to ask a few stupid "I'm not a mechanic" questions:

Is that a re-usable hose clamp that's on there? Looks like it requires a special tool to tighten or loosen.

Your clamp may or may not be like that. Kinda depends on if it has ever been removed before.

If you do not have the special "Hose Clamp Pliers".. you may be able to get it with a small pair of Channel Lock pliers.

If I destroy it taking it off, can I use a screw hose clamp to replace it?

Yes...

The "bolt with a hole in it" will come off counter-clockwise?

Yes...

I know, dumb questions, but I've never done much mechanically on any car, other than add fluids or change windshield wipers! I think I can handle this with a little more direction.

Thanks, John

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It does not indicate a block at the water pump, it indicates a block at the "bolt with a hole in it"

Trace the purge line across to the engine, and it will end up around the throttle body, remove the hose from that nipple at the "bolt with a hole in it" and use a 15 mm wrench to remove the "bolt with a hold in it" and clear it out with a drill bit or something.

DO NOT, I repeat DO NOT, blow air through the purge line from the coolant tank to clear it, you will only temporarily dislodge it. The clog MUST be removed by hand

Here is a photo of the bolt with a hole in it from a 96, this hole MUST be clear to allow air out of the system or the engine will overheat, as you will not be able to get enough coolant in and the water pump will cavitate....

Boltwithaholeinit.jpg

Thanks for your input.

I found the connection you have pictured, but now I need to ask a few stupid "I'm not a mechanic" questions:

Is that a re-usable hose clamp that's on there? Mine is a spring type clamp, it gets removed by a pair of pliers

Looks like it requires a special tool to tighten or loosen. If it looks like that a simple pair of pliers should do it

If I destroy it taking it off, can I use a screw hose clamp to replace it? You should not destroy it, I have had mine off many times. I suppose you could use a screw type hose clamp

The "bolt with a hole in it" will come off counter-clockwise? Yes, my memory tells me its a 15mm size,

I know, dumb questions, but I've never done much mechanically on any car, other than add fluids or change windshield wipers! I think I can handle this with a little more direction.

There are no dumb questions, only the questions you don't ask. When you take that bolt out, you would see a hole through it, stick something through the hole, like a drill bit, skewer or pipe cleaner, then screw it back it, let us know if it is clogged in anyway, I found a long piece of silicone sealer stuck in one!

Thanks, John

Let use know how this turns out

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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Last, but not least, I disconnected the purge line and there was no flow at all of coolant with the engine running.

So, while there is certainly a head gasket problem, it also appears that the coolant flow is blocked. The line at the tank and the nipple are clear, but still no flow. Others have said this indicates a blockage back at the water pump. Not a mechanic, so I'm not quite sure how to get at it.

Would like to see the coolant flowing as it's supposed to before writing this one off as as an HG fatality.

Thanks, John.

This is why your car is overheating. Do not jump to the conclusion that the head gaskets are shot at this point. If the purge line does not flow coolant, the engine will overheat. Take off the hose and remove the obstruction and re-test the car.

If the information center displaye CHECK COOLANT LEVEL when the surge tank is filled to the proper level, the sensor is bad.

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

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Thanks to everyone for their input. Will be attempting the repair this weekend. Will let you know how it goes. je

Terrific let us know how it goes

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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Here's the latest....

Removed the "bolt with a hole in it", and it was completely clogged. The substance was white and kind of looked like crystals, but mushed between my fingers. Cleaned it thoroughly.

I also flushed the line that returns to the surge tank. Got some of that mushy white crap out of there too.

Started the car up, without any AC or heat on. The temp climbed more slowly than before cleaning the bolt, but did reach 222 at idle, at which time the fans kicked in and lowered the temp to 217-219 steady. Definitely an improvement, but still pretty warm.

Decided to take a short test drive in the neighborhood at low speeds. The temp climbed into the 230's under tow. I then turned onto a faster traffic street uphill. The temp shot up to the 240's, peaking at 250. I leveled out and the temp dropped into the 240's as I got back home.

I did notice some rather fast deviations in temps. It dropped rather fast at one point, then raised without a significant change in incline. Air in the system?

So, the car is not going straight into overheating mode, but is still running quite hot.

I've seen a few others talk of air in the coolant lines, and I thought that might be a player here. I've gone through adding coolant and removing hoses several times over. As of this writing, I'm letting the car cool, and then I plan to do a start-up with the radiator cap off, and look for a burp when the thermostat opens at about 185. I the plan to let it cool again, check the coolant level, then try another start up.

As for the heater, it blows completely cold air. That might not be a factor in the over-heating, but there appears to be major clogging or an overall corer failure there. If I'm smart enough, I'll check those lines too.

Thanks for your input thus far, and let me know what you think. je

Edit: 2 hours later...

Started up with the cap off, added some coolant, ran w/surge tank open until 200, then capped. Car idled at 201 for about 10 minutes.

Next test drive is pending...

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Sounds good. Check that bolt with a hole again to make sure its not clogged again.

You may have stabilized the cooling system at this point

Let us know what happens.

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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Sounds good. Check that bolt with a hole again to make sure its not clogged again.

You may have stabilized the cooling system at this point

Let us know what happens.

New question: At what temperature should you expect to see coolant escaping out the surge tank through the hose?

Took the car on about a 1/2 hour drive, and it was kind of a mixed bag. Had the AC running, temps were running about 217-222. Getting out on the highway (50mph) did not lower the temps. What did happen though, is that when I slowed to a stop from a steady 50mph, the temp spiked up to around 245. Pulled over and turned it off, and it purged about a pint of coolant. Added some coolant back, and drove back home with the AC off. Temps stayed in the 210 range, spiking to about 225 when coming to a dead stop from driving 50mph.

The coolant temp does not change gradually. It tends to raise and lower rather quickly.

Getting back to my question, I'm disappointed to see coolant on the pavement when the car hasn't truly over-heated. Is the spring on the radiator cap compressing too easily, or is there an inordinate amount of pressure building within the system?

I do plan on checking the bolt again. Whatever that was that plugged it before, may still be present in the system.

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I assume that you checked to make sure that your cap holds the required pressure of 16 to 18 psi, if it releases at 8 psi, your cooling system will spontaineously boil.

Is that cap new? The coolant 50/50? The fans work? The water pump belt is good? and not slipping? The thermostat is GOOD? The cooling system is holding pressure at temp?

If the heater is blowing cold is nothing is wrong with the actuators, that is an indication that your coolant is low. Check the bolt with a hole in it to see if it clogged again

If all is good, I would have the coolant checked for combustion by products by using the NAPA Balkamp tester or by taking it to a good radiator shop to see if you have a breached head gasket.

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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Spiking at 245 is not good and is a sign of overheating. Your symptoms sound like mine when my head gasket breached. Does your engine misfire in the morning when cold?

If you have combustion leaking directly into the coolant passage, you will superheat the coolant and it will spike, it will puke coolant quickly.

Stick your nose in the coolant tank and smell, do you smell exhaust fumes?

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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I assume that you checked to make sure that your cap holds the required pressure of 16 to 18 psi, if it releases at 8 psi, your cooling system will spontaineously boil.

Is that cap new? The coolant 50/50? The fans work? The water pump belt is good? and not slipping? The thermostat is GOOD? The cooling system is holding pressure at temp?

If the heater is blowing cold is nothing is wrong with the actuators, that is an indication that your coolant is low. Check the bolt with a hole in it to see if it clogged again

If all is good, I would have the coolant checked for combustion by products by using the NAPA Balkamp tester or by taking it to a good radiator shop to see if you have a breached head gasket.

Answers:

Cap: Have not had the cap tested. It's a 15psi cap. It might be part of the problem.

Coolant: Well, I was using 50/50 premix for all add backs, but I did pick up a container of straight anti freeze along the way, and was mixing. I could be slightly thin on the anti-freeze, but I wouldn't think much.

Thermostat: This was replaced 2 months ago.

Cooling system holding pressure: Don't know how to determine that.

Fans work. Come on at about 222-230

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Well a good radiator shop can test to see if your cooling system holds pressure with a pressure gage, it is the perfect way to find leaks and problems

If the cap is suspect, just keep in mind that if it does not hold 15 psi, and its just holding 8 and then blowing off, that could be your problem as the pressure drops. If you go back to high school science, you will recall that water boils at a lower temp the lower the pressure

I think we can assume that your coolant and stat are ok

I was concerned that you found gook in your purge system take another look at it

Did you smell inside the tank?

I think a cooling system test is in order at this point

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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Spiking at 245 is not good and is a sign of overheating. Your symptoms sound like mine when my head gasket breached. Does your engine misfire in the morning when cold?

If you have combustion leaking directly into the coolant passage, you will superheat the coolant and it will spike, it will puke coolant quickly.

Stick your nose in the coolant tank and smell, do you smell exhaust fumes?

The engine is slow to start, often taking several seconds to fire. It then gets off to a rumbling start, then seems to run OK after a minute or two.

As stated earlier in the thread, I'm pretty sure a bad head gasket is part of the problem. I'm just trying to sum up everything else that's not working, then go from there.

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