98 STS COOLANT SMELL NO VISABLE LEAKS

[triplekey]

I am not sure what to check. My 98 STS northstar engine red lined for the 1st time since this problem has started. The OBD told me to turn off the a/c and idle engine I did that and coasted to the side of the highway, by the time the car had stopped on its own the tempeture started going down to the middle again.

Just some history:

Car usually runs in middle of temp gauge under normal driving but when driving for a while and then get in traffic the gauge moves up. Most of the time to the next line past the middle then will work its way down towards the middle. but when the window is open after a warmed up engine i do smell coolant. My mechanic feels it may be a head gasket because of the things we tried below but i do not want to believe him as of yet. This is what we did so far....

changed the water pump, was leaking thought that was my smell.. no change.

losing coolant but none on floor

pressure tested the radiator holds good pressure.

tested the fans both do work at allotted time. never saw them on high speed though?

put diagnostic tool to check what temps the fans come on and off car doesn't seem to overheat much past the middle usually gets to 230 at the hight and then cools down to 198 i believe.

Any suggestions on what should be checked would be greatly appreciated.

Steve

[adallak]

Coolant smell is a good thing. Chances are it is only external, so no head gasket is involved. Read this thread for some recommendations and do not listen to the mechanic.

http://caddyinfo.ipbhost.com/index.php?showtopic=13440

[JimD]

Is the water pump belt and belt tensioner in good condition?

Your coolant is going somewhere; dried Dex-Cool will leave a chalky white residue on metal parts. As the temperature goes up the pressure goes up; possibly the coolant aroma is from the top of the reservoir when the pressure cap relieves at 16 psi.

Be sure the air purge line is not clogged. Remove the rubber hose from the top of the reservoir; with the engine at idle, there should be a small steady stream of coolant from the end of the rubber hose.

My '98 temperature gauge corresponds to numbers like these http://i70.photobucket.com/albums/i101/Jim...withnumbers.jpg

Also, my '98 fans operate like this:

"Engine idling, A/C OFF, no airflow over radiator (inside garage), ambient temp.

~~ 80 degrees. Coolant temp. as reported to the OBDII connector was 223 degrees

when both fans came ON at low speed and 212 degrees when the fans turned OFF.

Not possible to "hear" the fans at low speed.

I let the PCM cycle the fans 6 times for confirmation.

Forced the temp. up with blocked airflow and 1,500 RPM brake torque.

Fans go to high speed at 234 degrees. Appear to stay on high speed until temp. drops

to 212 where they are shut off."

[triplekey]

Is the water pump belt and belt tensioner in good condition?

Your coolant is going somewhere; dried Dex-Cool will leave a chalky white residue on metal parts. As the temperature goes up the pressure goes up; possibly the coolant aroma is from the top of the reservoir when the pressure cap relieves at 16 psi.

Be sure the air purge line is not clogged. Remove the rubber hose from the top of the reservoir; with the engine at idle, there should be a small steady stream of coolant from the end of the rubber hose.

My '98 temperature gauge corresponds to numbers like these http://i70.photobucket.com/albums/i101/Jim...withnumbers.jpg

Also, my '98 fans operate like this:

"Engine idling, A/C OFF, no airflow over radiator (inside garage), ambient temp.

~~ 80 degrees. Coolant temp. as reported to the OBDII connector was 223 degrees

when both fans came ON at low speed and 212 degrees when the fans turned OFF.

Not possible to "hear" the fans at low speed.

I let the PCM cycle the fans 6 times for confirmation.

Forced the temp. up with blocked airflow and 1,500 RPM brake torque.

Fans go to high speed at 234 degrees. Appear to stay on high speed until temp. drops

to 212 where they are shut off."

Thanks for the reply went to mechanic today and he tested the coolant in the reservoir and it showed combustion gases the color changed to light green in the test kit.. is that the end of the head gasket ?

[JimD]

Thanks for the reply went to mechanic today and he tested the coolant in the reservoir and it showed combustion gases the color changed to light green in the test kit.. is that the end of the head gasket ?

I have no experience with testing coolant for combustion gas.

A definitive head gasket test would be to rotate a cylinder to TDC and apply 100 psi shop air via a spark plug adapter. If air bubbles are seen or heard in the cooling system, the head gasket is failed at that cylinder. If no evidence of air, move on to next cylinder.

[BodybyFisher]

I would pressurize the cylinders as Jim notes. These engines have so many places that can leak coolant. I have a coolant smell right now and I believe its the cross-over gaskets. You can leak from the radiator side tanks, the heater pipes at the rear of the engine, the heater core, hoses, etc.

Are you getting a coolant smell at the exhaust? How reputible is your mechanic? With the engine cool start it, with the cap off the resevior and see if you get any bubbles there. DO NOT let it get warm, this is just a quick test. Coolant with no pressure can and explode all over the place and scald you and ruin your paint, so just run the engine for 30 seconds or so while the engine is cold and see if you can see bubbles with a flashlight.

[Stealth]

where the question is: is it the head gasket ?

i be doing a CO2 test on the coolant.

you would have the answer cheap and fast.

I am not sure what to check. My 98 STS northstar engine red lined for the 1st time since this problem has started. The OBD told me to turn off the a/c and idle engine I did that and coasted to the side of the highway, by the time the car had stopped on its own the tempeture started going down to the middle again.

Just some history:

Car usually runs in middle of temp gauge under normal driving but when driving for a while and then get in traffic the gauge moves up. Most of the time to the next line past the middle then will work its way down towards the middle. but when the window is open after a warmed up engine i do smell coolant. My mechanic feels it may be a head gasket because of the things we tried below but i do not want to believe him as of yet. This is what we did so far....

changed the water pump, was leaking thought that was my smell.. no change.

losing coolant but none on floor

pressure tested the radiator holds good pressure.

tested the fans both do work at allotted time. never saw them on high speed though?

put diagnostic tool to check what temps the fans come on and off car doesn't seem to overheat much past the middle usually gets to 230 at the hight and then cools down to 198 i believe.

Any suggestions on what should be checked would be greatly appreciated.

Steve

[zonie77]

You probably have a leaking head gasket. The pressure test will determine which cylinders but from experience and time spent on the board you should change both. It is a major job but a fairly experienced DIYer can do it at home. It takes some perseverence.

[BigCat83]

Your car is exhibiting exactly the same symptoms mine did when I blew all of the rear headbolts out of the block last fall.

Take my advice - please- first confirm exhaust gas in the coolant, if it's present AND you are not a very experienced mechanic to Timesert the block yourself (and even if you are...) have a reman motor put in it. Tampa Caddy dealer quoted me 5 large for a timesert job. You can install a reman motor for the same or less.

[Stealth]

sorry .. i missed this being in a hurry. THAT was the CO2 test.

now, you got few choices here.

do a gasket replacement or do a temp resin fix.

resin fix ($150+) for a car that may not be a long term keeper,

gasket replacement ($1,500+) for a car that is a gem.

once you tear down the top end, might as well

do anything else that may need replacement.

now many miles on the car?

after you are done, make sure you maintain a

2 year schedule on coolant changes .. it will help you

conserve gaskets for the next 20 years or even longer.

regardless of opinions and defense of GM's methods,

contraversial topic or not, the gaskets go for one of two reasons ..

coolant depletion resulting in oxidation or overheating.

your mechanic did the CO2 test? ask him ..

i bet he agrees if he thought of doing the CO2 test.

those that dont agree with the coolant issue tend to avoid the

CO2 test ..... go figure.

in the future, avoid both coolant depletion or overheating at any cost.

keep us posted?

lol

note:

if you are a car guy, tool box and parts on hand, it is a weekend job.

if not, read how to do before you start, have right tools avail, take lots

of pictures of what goes where. two or three weekends ought to do it IF

you know how to use tools well. if you dont, an alum engine is probably

not the place to learn, IMO.

Thanks for the reply went to mechanic today and he tested the coolant in the reservoir and it showed combustion gases the color changed to light green in the test kit.. is that the end of the head gasket ?

[tommysls]

I had the exact same symtoms with my 98 sls.

I had head gaskets replaced and time serted at a cost of approx $3000.

That was 40,000 miles ago. Glad I did what I did.

Find a trustworthy mechanic that has northstar experience and will work by the book.

Exactly by the book (repair manual).

Where else are you going to get a car like this for $3000.

Repair it and repair it right and you will be a happy driver.

Good Luck

tommy