1993 STS Head gasket or something else, hopefully???

[vikikul]

I really do not know much about cars but I’ve read a lot at this forum tonight. I just wonder if somebody else had a similar problem. My car had problems for a while: when you start it (after it sat overnight) the engine would miss and shake a little bit, also would smoke more than normal and it would run perfect when it warms up. Also, when I am leaving my garage I would have a knock in my brake pedal which would disappear shortly. With my limited knowledge I suggested my husband that it could be a problem with spark plugs, so he changed them although not wires (did not help).

I also periodically would get low on coolant. Actually, I had some obvious hose leak, where my husband tightened it, but I believe there is still some liquid under my car when I leave my garage. We had a crack in the radiator some time ago, and my husband changed it. I also had I beleive a water pump belt broken recently and we changed it too. The car is just getting old but it's still a really nice car.

Although my car never got hot before (it would run at about 235F), today my husband added some radiator sealant and the first time the car had the message that the engine was hot. I believed it has got to 250F when we stayed at the drive through and when we drove fast the temperature went back down.

My husband thinks it is probably the head gasket, which I really hate to think. I hope it would be an intake gasket or some other vacuum leak or maybe belt timing. I believe he is going to test some pressure in the radiator I believe (I do not really know for sure).

It seams like from my reading I do not have completely typical signs of the bad head gasket, but it seems like it is about right timing (135,000 miles), considering that we did not really changed coolant. I just wonder if anybody has any other ideas what it could be. My husband can fix the head gasket, but it sounds like a very time consuming project. And I really like my car too much to get rid of it. I would appreciate any input.

[cyrez00]

Hey, first thing you should do is read the codes.

procedure to be found here. http://www.caddyinfo.com/readingcodes.html

good luck.

Marc.

[TDK]

Victoria,

This site has a LOT of info on the head gasket subject - if you search for it. You will find out that there are many potential reasons for loss of coolant and overheating. For example, your comment about the temperature falling as the engine speed increased, might point out a loose belt - in turn due to a faulty tensioner.

Your keen observations such as noting leaks on the floor and the work completed so far - will prove to be critical in your success.

If you want to know definatively - if the headgasket could be leaking (or not), then have the coolant tested for combustion chamber gases.

Good luck and I'm certain others will offer additional assistance, including a logical checlklist, starting with the easy ones first.

[Ranger]

Are you saying that a '93 with 135K has never had a coolant change?

[jackc]

I believe there is still some liquid under my car when I leave my garage.

This could certainly account for the loss of coolant.

Don't immediately jump to the head gasket conclusion. There are several other possibilities to explore first. The cooling system definitely needs to be pressure-tested. Some parts stores will loan or rent good pressure testers that will let you pressurize the system overnight at home, to really find the leaks. I found about 4 on mine that way.

Change the coolant too, and be sure to add the GM leak-preventive tablets to the new coolant (put them in a radiator hose - not in the "overflow" tank. They'll just make a big gunky mess in there).

Replace the thermostat too. They're very inexpensive.

Check under the water-pump for signs of leakage.

Also be sure that coolant flows from the small hose that goes into the top of the surge "overflow" tank. This is where any trapped air is bled from the cooling system.

When its all said and done, it could be a head gasket. But some good-old testing and maintenance is in order first.

[vikikul]

Thanks a lot for everybody's inputs. We are going to try some things.

We actually own this car for almost 10 years and never changed coolant until we changed radiator not long time ago. My husband said it was just hard to access to drain it. Probably we should have. We'll know better next time. Actually today I drove it and it did not get hot, only I can tell that temperature gets a little bit higher when I go slower and decreases when I speed up.

I also did code diagnostic and it shows no PCM trouble codes.

Thanks again.

[KHE]

If it has been more than 2 years/24000 miles, it is due for another coolant change. If you can't get to the radiator drain, just remove the lower hose and let the coolant drain out.

[Stealth]

just based on the "not changed coolant in 10 years", i be doing a CO2 gas / combustion gases

in the coolant before i spend another dime. if you have a failed headgasket you are looking at

spending more than the car is worth to fix that. not changing the coolant in these engines is the

single most expensive mistake i can think off.

then get back to us ...

does your car have the 4500 or the 4600 engine? some of the late issue '93s had the N*

Thanks a lot for everybody's inputs. We are going to try some things.

We actually own this car for almost 10 years and never changed coolant until we changed radiator not long time ago. My husband said it was just hard to access to drain it. Probably we should have. We'll know better next time. Actually today I drove it and it did not get hot, only I can tell that temperature gets a little bit higher when I go slower and decreases when I speed up.

I also did code diagnostic and it shows no PCM trouble codes.

Thanks again.

[BodybyFisher]

Hey doing the radiator you changed your coolant. Change it every 24,000 miles and you will be ok

These engines can leak in so many places (radiator end tanks, resovior, heater pipes, water pump, water pump seal, crossover gaskets, hoses, clamps, etc). Don't panic, just find the leak.

Check your water pump belt, check the purge line to see if its clogged, if it is clogged you won't be able to get the air out. Check the water pump tensioner, thermostat, radiator cap, etc Don't think head gaskets until you check the simple things, we have a few members that see the glass as half EMPTY... and have not gotten the hint yet that DIAGNOSIS is the way to go FIRST.

If you do a search, you will NEVER see me diagnose HEAD GASKET first, EVER

[jackc]

I can tell that temperature gets a little bit higher when I go slower and decreases when I speed up.

Interesting.

Do the cooling fans come on? I believe they kick in at 225 degrees with the AC off, or run continuously when the AC is on. Been awhile since I checked mine, so I'm fuzzy on the details....

[Stealth]

testing is not diagnosing, it is testing. The conclusion reached through this

process is called diagnosis.

IMO, one tests the simple and inexpensive things 1st,

SPECIALLY if you are paying labor at $120 / hr.

the CO2 test is cheap and simple. it will determine or rule out if the

headgasket is the culprid. anyone can do it and avoid paying $120 / hr.

why would anyone want to spend day after day testing every

darn thing and leave the CO2 test for last? how hard can it be to

pour the CO2 detection agent into the coolant, ran the car at load, stop and

check for change in color of coolant?

when one is ill, usually the 1st test is a BLOOD test, it dont mean

one has a BLOOD disease. it is just that, at test to determine and/or

pinpoint a problem before moving on to serious things like scans, biopsy, etc..

one other thing .. the radiator was changed RECENTLY. the car does have new coolant

but the gaskets were exposed without protection for how many years?

for all i know, it is not the headgaskets. but based on the info that Virginia

provided, they are highly suspect and should be tested. IMO.

Hey doing the radiator you changed your coolant. Change it every 24,000 miles and you will be ok

These engines can leak in so many places (radiator end tanks, resovior, heater pipes, water pump, water pump seal, crossover gaskets, hoses, clamps, etc). Don't panic, just find the leak.

Check your water pump belt, check the purge line to see if its clogged, if it is clogged you won't be able to get the air out. Check the water pump tensioner, thermostat, radiator cap, etc Don't think head gaskets until you check the simple things, we have a few members that see the glass as half EMPTY... and have not gotten the hint yet that DIAGNOSIS is the way to go FIRST.

If you do a search, you will NEVER see me diagnose HEAD GASKET first, EVER

[vikikul]

Ok guys, Victorias husband here setting the record straight.....I bought the car in about 97 we're the second owner. The car had all the maintenance done by the the dealer before I got it. So I assume the antifreeze would have been changed sometime in the first 65,000 miles. Admitedly I never changed it until about 04 when the radiator gave it up at around 100k. But I've never had a car or even heard of a car being so sensitive about this until now. Most of the work I do is on heavy equipment where I know of machines with the same antifreeze until for some reason it looses it......10 years or more. But these are all cast block and head. Have rebuilt various diesel engines and allison trans....(Sure would be great if more companiies built turbo diesel cars)

Anyway it started missing a little at cold start ups a couple months ago. It runs great after about a minute. Tried plugs...no change. Still has orig. wires so that's next (been putting it off since it doesn't look like fun). I got more concerned a couple of days ago when I noticed some white smoke coming from the exhaust during this start-up period. But it doesn't have that sweet antifreeze smell at all. I've seen several Japanese burners warp heads or lose gaskets....nothing like that. I have a napa block tester....the deal with the blue fluid that turns yellow in the presense of exhaust gas.....no sign of leaky gasket.

The small hose going into the overflow has good flow. We did have a slight overheating episode at idle also but it hasn't repeated it. It did it for probably 20 minutes but as soon as you get up to speed all is well. The tensioner is good belt is good (I oiled and freed up when I did water pump 6 mos ago) Fans work fine.

Here are my thoughts.....possibly thermostat starting to fail. (explains overheating....maybe)

wires maybe but in my experience new plugs should have had some positive impact since the gaps tend to grow with time/wear. So maybe an injector is slobering too much fuel???????May explain the smoke/miss? I don't know if this is common/ possible ........Really weird since also not seen it smoke again since the morning of the overheating episode....thanks for replies

[Stealth]

good. you have done the CO2 test.

now you can start looking at the rest of the items.

BTW, how much did it cost you to have it done?

Ok guys, Victorias husband here setting the record straight.....I bought the car in about 97 we're the second owner. The car had all the maintenance done by the the dealer before I got it. So I assume the antifreeze would have been changed sometime in the first 65,000 miles. Admitedly I never changed it until about 04 when the radiator gave it up at around 100k. But I've never had a car or even heard of a car being so sensitive about this until now. Most of the work I do is on heavy equipment where I know of machines with the same antifreeze until for some reason it looses it......10 years or more. But these are all cast block and head. Have rebuilt various diesel engines and allison trans....(Sure would be great if more companiies built turbo diesel cars)

Anyway it started missing a little at cold start ups a couple months ago. It runs great after about a minute. Tried plugs...no change. Still has orig. wires so that's next (been putting it off since it doesn't look like fun). I got more concerned a couple of days ago when I noticed some white smoke coming from the exhaust during this start-up period. But it doesn't have that sweet antifreeze smell at all. I've seen several Japanese burners warp heads or lose gaskets....nothing like that. I have a napa block tester....the deal with the blue fluid that turns yellow in the presense of exhaust gas.....no sign of leaky gasket.

The small hose going into the overflow has good flow. We did have a slight overheating episode at idle also but it hasn't repeated it. It did it for probably 20 minutes but as soon as you get up to speed all is well. The tensioner is good belt is good (I oiled and freed up when I did water pump 6 mos ago) Fans work fine.

Here are my thoughts.....possibly thermostat starting to fail. (explains overheating....maybe)

wires maybe but in my experience new plugs should have had some positive impact since the gaps tend to grow with time/wear. So maybe an injector is slobering too much fuel???????May explain the smoke/miss? I don't know if this is common/ possible ........Really weird since also not seen it smoke again since the morning of the overheating episode....thanks for replies

[Ranger]

Wires are a possibility being that old. Leaky FPR is as well and could explain the white "smoke" (fuel vapor). Have you ever cleaned the TB (throttle Body), EGR valve and EGR "mouse holes"?

[TDK]

Victor (just a wild guess on my part),

That was a great post with a lot of quality info laid out in a logical manner.

Since you noted the injector issue, perhaps you could check the FPR (Fuel Pressure Regulator) for slight leakage through its diaphragm. When the vac line is removed, there should not be any fuel present. I am not certain where the FPR is located on your engine, but in any case DO NOT start the engine without the beauty cover installed - the engine will go wide open right now. A leaky FPR can cause hard starts etc due to excessive richness that the engine can not compensate for accurately. I'm less certain that it can cause any specific overheating issues, but then again a screwy fuel/air ratio can cause odd load factors, etc.

As others have noted, great that the coolant is free of exhaust gases. Now the "great game" begins on who can guess the cause.

BTW, be very carefull if you decide to replace plug wires! Some have fried the HVAC blower-speed control module, due to slightly misplaced wires. It would be a shame to start a snowball of repairs.

Since your are in the area, you may want to check if the injector lines are due to a replacement because of the material breaking down over time (a recall issue as well for some models).

That engine has "mouse holes" under the beauty cover at the phenolic spacers, which may need cleaning. It is possilbe that these have plugged and are contributing to the roughness.

For whatever reason, my '94 DeVille never had any misfire issues, but then again it operated near the top of its rpm range and back down again quite often. You may want to excercise the rings etc and literly blow the carbon out. The WOT procedure is as simple and fun as a number of trips in 2nd gear up to about 70mph and then let it backoff. The high vacuum loosens the top rings etc and generally cleans up the innards. Repeat until no 'mo smoke out the tailpipe

Again, good luck with the hunt.

Ranger - you ole dog! You musta posted before me by mere seconds ...

[Ranger]

The FPR on a '93 is on the fuel rail, inside the intake manifold. Since it is subjected to manifold vacuum there will be no vacuum line on the FPR nipple.

[BodybyFisher]

Ok guys, Victorias husband here setting the record straight.....I bought the car in about 97 we're the second owner. The car had all the maintenance done by the the dealer before I got it. So I assume the antifreeze would have been changed sometime in the first 65,000 miles. Admitedly I never changed it until about 04 when the radiator gave it up at around 100k. But I've never had a car or even heard of a car being so sensitive about this until now. Most of the work I do is on heavy equipment where I know of machines with the same antifreeze until for some reason it looses it......10 years or more. But these are all cast block and head. Have rebuilt various diesel engines and allison trans....(Sure would be great if more companiies built turbo diesel cars)

Anyway it started missing a little at cold start ups a couple months ago. It runs great after about a minute. Tried plugs...no change. Still has orig. wires so that's next (been putting it off since it doesn't look like fun). I got more concerned a couple of days ago when I noticed some white smoke coming from the exhaust during this start-up period. But it doesn't have that sweet antifreeze smell at all. I've seen several Japanese burners warp heads or lose gaskets....nothing like that. I have a napa block tester....the deal with the blue fluid that turns yellow in the presense of exhaust gas.....no sign of leaky gasket.

The small hose going into the overflow has good flow. We did have a slight overheating episode at idle also but it hasn't repeated it. It did it for probably 20 minutes but as soon as you get up to speed all is well. The tensioner is good belt is good (I oiled and freed up when I did water pump 6 mos ago) Fans work fine.

Here are my thoughts.....possibly thermostat starting to fail. (explains overheating....maybe)

wires maybe but in my experience new plugs should have had some positive impact since the gaps tend to grow with time/wear. So maybe an injector is slobering too much fuel???????May explain the smoke/miss? I don't know if this is common/ possible ........Really weird since also not seen it smoke again since the morning of the overheating episode....thanks for replies

If all of the platinum pads were in place on the old plugs, you might not see a big difference especially if your wires are weak and leaking.

I would replace the wires if they are original at this point for sure, use the OEM AC DELCO. I have a 96 and changing them is not bad, not sure if the 93 is as easy. Try running the engine with the beauty cover off (if the 93 has one) in the dark, and spritz the wires with a spray bottle filled with water and see if you see any arching. But they are old enough for you to just replace them.

You have done a lot diagnostics.

Try lifting the fuel rail, turn the key on to pressurize it and see if any injectors leak (don't turn the key to start, just to on). I don't think the OBD I cars will throw a misfire code (P030x) as the OBD II cars do. A bad injector will cause the miss in open loop that goes away when the O2 sensors take over and lean out the the mixture. We recently had a member that got rid of a miss by replacing an O2 sensor that was sluggish but not setting a code, but I don't believe the miss went away when the car warmed up.

Consider buying a coil and swapping it in to each position, we have seen bad coils cause fits, but again in your case, the miss goes away when it warms up I don't believe a bad coil would behave that way.

Take a look at your water pump belt again, check your cap, and I would just replace the thermostat if its more than 3 years old.

Have you pressurized your cooling system yet? Certain items like end tanks, hose clamps, rusted heater pipes, reservoir will only leak under pressure.

Keep at it, you will get it. Change those wires.

[vikikul]

Earlier someone asked ...... this is a northstar. The Co2 test was free since I bought the tool for a bulldozer engine problem I had. I think the tool is about $50 at napa it's called a block tester . BTW the dozer had a bad gasket and the fluid turned from blue to yellow in probably 2 seconds.

Where can I buy a decent book on this engine? I have no idea how to find the FPR. Can I just follow the fuel line? I had the beauty cover off just to see what was under there and size up things and did notice a strong gas smell....But I saw all the injectors in there and assumed it was normal but maybe not? Isn't this engine direct injection/fuel rail I didn't really pay close attention. Or is it tuned port injected? It just strikes me that it's running rich since while it misses if you gun it it seems to clear up quicker.

Also I noticed a couple of the vacuum fittings were really "rotten" one of them was falling apart on a little deal that seemed to be an electrically controlled "vacuum valve relay" just behind the air intake butterfly in fact one of the lines lead to the rubber boot that wraps around the butterfly. I patched it with little pieces of rubber hose but noticed no apparent vacuum leak. Have no idea what this thing does.

I hope to solve this problem since my wife loves the car even though it's old.....in fact she was crying when I thought it might have been the head gasket(before the test).....again thanks for the input....Anyone with diesel questions I'd be glad to try to answer.......

[vikikul]

I'll update after I change plug wires and thermostat (if I can find it). These engines run great but I must say they are a little different animal...thanks

[BodybyFisher]

I'll update after I change plug wires and thermostat (if I can find it). These engines run great but I must say they are a little different animal...thanks

Good observation. You need to throw away everything you know from cast iron engines. I had to relearn everything. Go to www.helpinc.com or ebay to find the FSM (factory service manual), you can not work on this engine without it. I am in the process of doing two big jobs right now and it has saved me a bunch of times..

By the way, if you buy the OEM wires (ac delco) they are impregnated with dialectic (? spelling) grease, using additional grease can create arching and mis-fires. Mike

[BodybyFisher]

Your engine it too different from mine for me to be able to help you in detail. We have users that are familiar with the 93 and 94. I need to buy a manual for that vintage NS, so that I can learn more about them. We had a member named The Fred who had a 94 NS with problems, that we were unable to resolve with him.

Your fuel pressure regulator is in the intake manifold, vacuum acts on it directly, it can leak fuel and you would never know it. Do not start the engine with that intake cover off, the engine will accelerate uncontrollably. The fuel pressure regulator on my car has a vacuum hose attached to it.

Replace all dry rotted vacuum hoses.

Have you checked for codes?

[vikikul]

Question...could a totally clogged EGR cause tendency to overheat? I wouldn't think so but this is a little out of my realm. I've never cleaned it or the "mouse holes" or the throttle body.....does anyone happen to have a photo of these "mouse holes" and a location? This cars just never caused much problems and in my line of work "if it ain't broke don't fix it" is more than a motto...it's necessity since stuff is breaking constantly with real problems. Not saying I'm opposed to some preventive maintenace but alot of the equipment we run takes a real beating. (try maintaining a few double barrel scapers for awile and you'll see what I mean). thanks guys

[vikikul]

My wife claims to have figured out the obd systems and says no codes.

[TDK]

Here is a link from a site search [see the upper right hand corner of this page] on "mouse holes", (which are actually the EGR passages on the '93-'94 engines). http://caddyinfo.ipbhost.com/index.php act=Search&CODE=show&searchid=002e61ce7cc857bd072850daae2a7633&search_in=posts&result_type=topics&highlite=mouse+holes.

I did not see any pictures during a quick read, but considering the repairs you have already completed, this job seems relatively minor.

I can sense your frustration with this relatively small, technical, "thorobred" engine - compared to "draft horse" style construction equipment designed for hard, unforgiving usage and serious repairs back to 100% duty.

Again - you are making progress, hang in there and good luck!

[jackc]

I have no idea how to find the FPR. Can I just follow the fuel line?

The FPR is inside the intake on the drivers side, firewall side (right rear corner if you're facing it from the front of the car). The fuel rail terminates into it inside the manifold. To remove it, you have to pull-up the fuel-rail/gasket assembly. Nothing holds it in place. No clips or anything, just o-rings. It may take some tugging, but it will come up. But you will have to create some slack in the injector harness which enters the intake just behind the throttle body, next to the fuel inlet. Be careful not to break the gasket. Its part of the fuel rail and runs $300 - $400.