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1998 Seville STS
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Discussion Starter #1
GM,
On my home the other day, my 98 Seville STS overheated which I thought was due to a bad thermostat. As soon as I saw the error, the car went into limp mode, and I was able to park it in a fast food restaurant and await a flatbed to tow it to the mechanic.

As I was waiting, I called the mechanic, explained to him what had happened, and that I observed that coolant appeared to have leaked from the coolant reservoir cap. He explained that this was indicative that coolant was not getting to the engine, and that it appeared that the cause was most likely, the recently replaced thermostat. Well it turned out to be the water pump, the belt tensioner, as well as the Serpentine belt which was the cause, and these were replaced.

Now where my concern lies, is during the repair, the mechanic called and informed me that they noticed oil to be mixing with the coolant, and this was also indicative of a failing head gasket. I do not know if this is the case, since the car is and was operating fine, it throws no smoke, and yes I do wind up adding a quart of synthetic oil every week or so, but not so much on the coolant. Maybe adding a cup every few weeks, if that. So I do not know how to proceed.

Is the head gasket failing? The STS has officially 100K on it today. And if it is, is there anything that I can use over the counter like Steel Head that can repair it?

Thanks,
Serge
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Northstars with failing head gaskets (cylinder block head bolt hole thread failure) do not normally mix oil and coolant or vice versa.

The definitive yes or no for gasket failure is the cylinder block exhaust gas test.


I would advise against pouring in some very temporary magic fix in a bottle. Most of it renders the engine useless for subsequent disassembly and correct repair.

IF one or more head bolts are pulling due to thread failure then it's only a matter of time before more start to go - magic goop is the Dutch boy's finger in the dike leak.

The water pump drive belt tensioner pulley seizing is discussed at great length here, in Deville and in Northstar.

water pump drive pulleys.gif
Pulley and tensioner (Notes).JPG
 

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1998 Seville STS
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84 Posts
Discussion Starter #3
Thanks Sub,
Then what would you suppose would be the cause of oil in the coolant or vise versa? I am going to take the STS to another mechanic, tell me my concern, and see if he can conduct this CBEG test. Hopefully they should be familiar with this procedure?

Thanks,
Anthony
 

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Oil/coolant mix may be an indicator of a cracked block. There is no oil drainback passage hole anywhere near the coolant passages in a Northstar cylinder head gasket. IF #1 or #2 cylinder is the problem then there's a chance that the coolant passage next to the cam chain area could leak into the chaincase and contaminate the engine oil. HIGHLY unusual.

gasket.jpg
 

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White Diamond '03 DHS (with DTS floor shift)
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they noticed oil to be mixing with the coolant,
There is a possibility that "oil" could be trans fluid from a leaky trans fluid heat exchanger in the radiator side tank (not real common). If that is the case, I'd also expect to see some coolant in the trans fluid.

584777
 

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1998 Seville STS
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84 Posts
Discussion Starter #6
Ranger,
Is there any way that a mechanic can test to see if this is actually the case? I dunno, but I just don't think it's the block or the head.. Maybe it's just wishful thinking, since I love the car so much..

Thanks,
Serge
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
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19,866 Posts
Ranger,
Is there any way that a mechanic can test to see if this is actually the case? I dunno, but I just don't think it's the block or the head.. Maybe it's just wishful thinking, since I love the car so much..

Thanks,
Serge
=====================
I SMELL A RAT!

you said you had to occasionally add oil -
I assume you checked the oil level on the dip stick -

when you looked at the oil on the dip stick - what did it look like?
normal - used oil?
or white - foamy - nasty looking stuff?

also - when you removed the OIL fill cap -
was the inside of the cap full of nasty - white foamy crud -
or just looked "normal"?

--------------------

I suspect the overheating is caused by trapped air within the cooling system -
and the trapped air is caused by a clogged PURGE LINE -

this is something YOU could check - without taking the car to a shop -
 

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1998 Seville STS
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Discussion Starter #8
Thanks Bass,
When I check the oil as I did today via the dip stick, it was black. Other times it resembles a clear or opaque color which is sometimes hard to read due to the brown color of the dip stick. When I remove the cap, there is no white, or any other nasty looking stuff present.

If the overheating was caused by trapped air, then would have the coolant flush it underwent addressed it? Also how do I go about checking the purge line?

Also, I had read online that a few head gasket failures diagnosis's were actually the result of the coolant reservoir tank actually failing, and not the head gasket at all. I read that they would replace the tank, and the overheating stopped. Is this correct? I was thinking of replacing it, since mine is 22 years old.

As of today, she seems to be running just fine.. This weekend will be the test, when I will be putting 100 plus miles of some serious back and fourth parkway driving each day.

Thanks,
Serge
 

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The surge tank has no direct effect on coolant flow or overheating. It floats on the system to absorb coolant volume changes due to heating and cooling of the engine as well as absorb surges from rapid acceleration/deceleration events. The ONLY "flow" in the surge tank is the tiny amount of purge flow. It does pick up gunk and deposits and so should be removed and cleaned each 4 years during a coolant exchange.

At warm idle the purge line should flow a small stream from the water crossover bolt/nipple to the surge tank.

If your 1998 has the obsolete heated throttle body that may be the cause of the overheat due to clogs. Use a single correct sized length of reinforced rubber fuel hose and 2 band clamps to run the line directly from the hollow bolt/nipple to the surge tank nipple. Bypass the throttlebody circuit - not needed.

Water crossover assembled.gif
Coolant heated throttlebody.png
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
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19,866 Posts
Thanks Bass,
When I check the oil as I did today via the dip stick, it was black. Other times it resembles a clear or opaque color which is sometimes hard to read due to the brown color of the dip stick. When I remove the cap, there is no white, or any other nasty looking stuff present.

If the overheating was caused by trapped air, then would have the coolant flush it underwent addressed it? Also how do I go about checking the purge line?

Also, I had read online that a few head gasket failures diagnosis's were actually the result of the coolant reservoir tank actually failing, and not the head gasket at all. I read that they would replace the tank, and the overheating stopped. Is this correct? I was thinking of replacing it, since mine is 22 years old.

As of today, she seems to be running just fine.. This weekend will be the test, when I will be putting 100 plus miles of some serious back and fourth parkway driving each day.

Thanks,
Serge
=====================
When I check the oil as I did today via the dip stick, it was black. Other times it resembles a clear or opaque color which is sometimes hard to read due to the brown color of the dip stick. When I remove the cap, there is no white, or any other nasty looking stuff present.
so - your oil sounds "normal" - no coolant mixing with it -
as I said - I SMELLED A RAT!
EVERYONE - automatically jumps to FAILED HEAD GASKETS - whenever they look at a Northstar motor -

If the overheating was caused by trapped air,
then would have the coolant flush it underwent addressed it?

NO -
I suspect either the HOLLOW BOLT - or the PURGE LINE - or both - are clogged up -
thus preventing ANY coolant or air to pass through -

Also how do I go about checking the purge line?
when the engine is COLD -
the fast and easy method is to simply remove the PURGE LINE from the SERGE TANK -
then start the engine -
there should be a constant - gentle - flow of coolant - possibly mixed with some bubbles of air -

NOTE -
the purge line is too short to stick into the serge tank -
you will need a container of some sort to collect the coolant IF it does flow -
 

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1998 Seville STS
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84 Posts
Discussion Starter #11
GM,
Here is the latest update. So last night, when I decided to take my dog out for the last time, I decided to check out my cadillac to make sure everything was okay. And lo and behold, what I found, was a puddle of coolant under it! This was after earlier that morning, having dropped 700 clams for the initial repairs. So I was quite dismayed by this recent turn of events. I checked out the coolant reservoir, and it was bone dry. So I dropped it off back at the mechanic shop that very evening with a WTF? note along side my keys. So this morning, they contact me stating that they found what the problem was, a $10.00 piece of tubing that had deteriorated with age, the "water pump extension hose" was the source of this epic fail. So scratch off an additional 150 clams for this fix, and here in NJ, it's a whopping 90+ degrees today, and I am getting ready for my weekly commute down south and back.. I am interested to find out how she is going to do with this newest coolant fix. I'll be watching my guages most carefully.

Cheers,
Serge
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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No such terminology as a "water pump extension hose".

2 hoses attach to the water pump cover - the lower radiator hose and the heater circuit return hose.

2 hoses attach to the water crossover - the heater circuit hot supply and the purge line.

The surge tank "sits" on a T in the heater circuit return hose.

Thermostat and cover diagram.gif


Water crossover assembled.gif


Your temp gauge ticks correspond to these - Northstars all use the same temp sender. If all is well the needle should stay in the little green area and a bit to the right in heavy traffic - maybe even to the yellow dot.

Temp gauge - my numbers.jpg
 

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White Diamond '03 DHS (with DTS floor shift)
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they contact me stating that they found what the problem was, a $10.00 piece of tubing that had deteriorated with age,
I wonder if that could be the heater core tubes that run along the right head by the firewall?
 

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1998 Seville STS
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Discussion Starter #14
GM,
So here's the scoop. I'm here stranded at my location, because I suddenly smelled coolant and noticed the, "coolant level low" message appear on my dashboard. Once I was able to get the car back to a safe location, I popped the hood, where I noticed coolant all over the engine as well as on the underside of the hood itself. I also noticed a hissing sound, but I was unable to identify the location. Not the coolant reservoir, that was okay from the cap level. I am waiting for a flatbed to take it back to the mechanic.. Any ideas? Blown hose due to the 100 degree heat, or the purge line? Any imput would be helpful..

Thanks,
Serge
 

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White Diamond '03 DHS (with DTS floor shift)
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Realy hard to tell without seeing it. Could be as simple as a cracked radiator side tank or hose. I think only a cooling system pressure test will tell for sure. The good news is, the fact that you have coolant on the engine and underside of the hood pretty much rules out a HG.
 

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Discussion Starter #16 (Edited)
Ge M,
Well I just picked up the STS from the mechanic and he explained to me what exactly happened. First he told me that the water pump extension hose that they had installed 48 hours ago, failed. I dunno why, but it did, and they replaced it no charge. Then I was told that the cause of my Sunday disaster was the result of the upper radiator hose which became swollen due to the heat of the engine and the outside, and that it somehow dislodged itself from the plastic cover from where it nomally resides underneath, dropped down next to the water pump pulley, where the pulley wore a hole into the tubing. Hence why the sudden loss off coolant, most of it all over the place, and thermostat starting to go into towards one o'clock and beyond before I parked the vehicle. He also mentioned that the hoses where probably 20 plus years old, and that these things happen.

They also recommened that I use Dexcool red 50/50 for a coolant, and again, that the head gasket was beginning to fail, and to be on the lookout for white smoke. This again because there was some coolant when they dropped the oil pan. They also recommended that I find an engine specialist to repair the gasket, or add some sealer, but the type that goes directly into and mixes with the oil, and not the coolant.

One other item I found concerning, when I mentioned if he had looked at, or cleaned the coolant system tank puge line, he responded that the Cadillac does not have a purge line since the coolant tank somehow is connected directly into the engine. I didn't debate the issue.

So I fear I am back to square one, is the head gasket failing? Should I add some magic potion into the oil to seal the gasket? Mind you she has 100K original miles, so putting in a new moter for a 22 year old car doesn't seem feasible, but I could be wrong.. Suggestions, observations, recommendations?

Thanks,
Serge
 

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White Diamond '03 DHS (with DTS floor shift)
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The hose issue sounds plausible.


They also recommened that I use Dexcool red 50/50 for a coolant, and again, that the head gasket was beginning to fail, and to be on the lookout for white smoke.
First off, you won't see much "white smoke" (Steam) until it gets really bad.
Secondly, and more important is just how did he diagnose the HG failure?



They also recommended that I find an engine specialist to repair the gasket, or add some sealer, but the type that goes directly into and mixes with the oil, and not the coolant.
He is starting to loose credibility.



One other item I found concerning, when I mentioned if he had looked at, or cleaned the coolant system tank puge line, he responded that the Cadillac does not have a purge line since the coolant tank somehow is connected directly into the engine.
Find another mechanic that knows the Northstar.



Should I add some magic potion into the oil to seal the gasket?
NO!
First off, you are not sure that you have a HG problem.
Secondly, IF you do, it will be nothing more than a temporary fix.......... if that.
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
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Ge M,
Well I just picked up the STS from the mechanic and he explained to me what exactly happened. First he told me that the water pump extension hose that they had installed 48 hours ago, failed. I dunno why, but it did, and they replaced it no charge. Then I was told that the cause of my Sunday disaster was the result of the upper radiator hose which became swollen due to the heat of the engine and the outside, and that it somehow dislodged itself from the plastic cover from where it nomally resides underneath, dropped down next to the water pump pulley, where the pulley wore a hole into the tubing. Hence why the sudden loss off coolant, most of it all over the place, and thermostat starting to go into towards one o'clock and beyond before I parked the vehicle. He also mentioned that the hoses where probably 20 plus years old, and that these things happen.

They also recommened that I use Dexcool red 50/50 for a coolant, and again, that the head gasket was beginning to fail, and to be on the lookout for white smoke. This again because there was some coolant when they dropped the oil pan. They also recommended that I find an engine specialist to repair the gasket, or add some sealer, but the type that goes directly into and mixes with the oil, and not the coolant.

One other item I found concerning, when I mentioned if he had looked at, or cleaned the coolant system tank puge line, he responded that the Cadillac does not have a purge line since the coolant tank somehow is connected directly into the engine. I didn't debate the issue.

So I fear I am back to square one, is the head gasket failing? Should I add some magic potion into the oil to seal the gasket? Mind you she has 100K original miles, so putting in a new moter for a 22 year old car doesn't seem feasible, but I could be wrong.. Suggestions, observations, recommendations?

Thanks,
Serge
============================
Then I was told that the cause of my Sunday disaster was the result of the upper radiator hose which became swollen due to the heat of the engine and the outside, and that it somehow dislodged itself from the plastic cover from where it nomally resides underneath, dropped down next to the water pump pulley, where the pulley wore a hole into the tubing.
this is actually "CODE" for "I FORGOT TO SLIP THE RADIATOR HOSE INTO THE MOLDED-IN SUPPORT -
BUT I'M GONNA MAKE YOU PAY FOR IT ANYHOW!

They also recommened that I use Dexcool red 50/50 for a coolant,
OK - no problem with that -

and again, that the head gasket was beginning to fail,
HOW did they come to THIS conclusion? starting to smell a RAT -

and to be on the lookout for white smoke.
VERY rare for a Northstar motor to blow smoke due to a failed head gasket -

This again because there was some coolant when they dropped the oil pan.
BULLSHIT - BULLSHIT - BULLSHIT -
you CAN NOT drop the oil pan on a Northstar without REMOVING THE ENTIRE ENGINE -
or supporting the engine from above and DROPPING THE CRADLE -

They also recommended that I find an engine specialist to repair the gasket,
more CODE for "we don't want to work on your car - BECAUSE WE DON'T HAVE A FRIGGIN CLUE!

or add some sealer, but the type that goes directly into and mixes with the oil, and not the coolant.
sealer - that mixes with OIL - and NOT COOLANT - for a potential head gasket leak?
I have no words -
THAT just MIGHT be the most RIDICULOUS thing I have EVER heard!

and by the way - DO NOT put ANY type of "sealant" in the engine - ANYWHERE -

One other item I found concerning, when I mentioned if he had looked at, or cleaned the coolant system tank puge line, he responded that the Cadillac does not have a purge line since the coolant tank somehow is connected directly into the engine. I didn't debate the issue.
OH MY GOD!

So I fear I am back to square one, is the head gasket failing?
CHECK THE PURGE LINE - DO A BLOCK TEST - CHECK THE PURGE LINE - DO A BLOCK TEST -
CHECK THE PURGE LINE - DO A BLOCK TEST - CHECK THE PURGE LINE - DO A BLOCK TEST -
CHECK THE PURGE LINE - DO A BLOCK TEST - CHECK THE PURGE LINE - DO A BLOCK TEST -
CHECK THE PURGE LINE - DO A BLOCK TEST - CHECK THE PURGE LINE - DO A BLOCK TEST -
get the idea?

Should I add some magic potion into the oil to seal the gasket?
NO - NO - NO - NO - NO - NO - NO - NO - NO - NO - NO - NO - NO - NO - NO - NO - NO - NO - NO - NO -
NO - NO - NO - NO - NO - NO - NO - NO - NO - NO - NO - NO - NO - NO - NO - NO - NO - NO - NO - NO -
NO - NO - NO - NO - NO - NO - NO - NO - NO - NO - NO - NO - NO - NO - NO - NO - NO - NO - NO - NO -
NO - NO - NO - NO - NO - NO - NO - NO - NO - NO - NO - NO - NO - NO - NO - NO - NO - NO - NO - NO -
get the idea?

Suggestions,
CHECK THE PURGE LINE - DO A BLOCK TEST -

observations,
this guy is a CLOWN - and a THIEF!

recommendations?
go find a REAL MECHANIC
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Sergemaster, regarding your last post and what the "mechanic" told you - whoever it is is no mechanic and has you fished in - hook, line, and sinker.

IF that's what you were told then it's a blatant pack of lies. Posts 17 and 18 are true fact - from two long-term Northstar FWD owners, drivers, and mechanics. I'll add the third with this post. The purge line and the oil pan incorrect statements are most obvious.

Now sit down and read the several sticky threads on this overheat and head gasket subject in the Engines; Northstar forum. "Stickies" are marked with a push pin and are timeless info necessary for ALL owners of vehicles discussed in that forum.

EDIT: My 2002 STS has the original upper radiator hose and retainer channel in the radiator sight shield. I have had that sight shield off over a dozen times since Nov. of 2005, installed it and the hose correctly, driven the car all over the eastern U.S. on highways and back roads at ridiculous speeds and twists and turns and the hose has NEVER come loose. Another mechanic failure and coverup.

Note the purge line on the Northstar STS - show this to your "mechanic".

Butt plug & air box 2.JPG
Water crossover assembled.gif
 
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Discussion Starter #20
Thanks GM,
I have no intention of using this particular garage or mechanic again. The only reason that I did so initially, is because I was convinced that the issue was related to the thermostat which they had replaced. I will be using another mechanic/garage that I had found, but wasn't able to, because he was closed due to Corona. He's now open, so I am going to have him check the block as well as the purge line... On second thought, the purge line looks very similar to the "water pump extension hose" that the mechanic pointed out as the hose that failed due to age... I'm going to get that second opinion this weekend...

Cheers,
Serge
 
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