1997 Cadillac Deville Overheating

57630 Views 14 Replies 8 Participants Last post by Playdrv4me, Jun 1, 2007

BladeBC97

Discussion Starter · May 31, 2007

Hi guys,

I've been reading through the forum but haven't been able to determine any clear answers on my problem. I have a 97 Deville with 127,000 miles on it. It's been having some strange overheating problems lately and everything I've been reading points to a head gasket since they are so common to fail, although I'm always up for some second opinions.

Here are the symptoms:
*Temperature is within the normal range when driving around town - about 195-205
*Temperature stays fairly low when cruising on the highway - about 220
*When accelerating on the highway and traveling at faster speeds the temperature shoots up to approx 240-255 but then eventually falls back down
*There are no warning messages or check engine lights
*All overheating stops when the heater is turned on, regardless of city or highway driving and speed

I just topped off the coolant, but I've been unable to determine if I'm losing it or if it is just getting rid of excess. Whenever I turn the car off I seem to smell coolant around the engine but never see it, and it never has leaks or puddles underneath. I've also never seen any white smoke or coolant smell from the exhaust. I guess the thing thats stumping me is that the coolant temperature is fine when the heater is left on, this would normally point to a bad thermostat right? Anything else I should try, short of getting a pressure test and hydrocarbon test?

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Playdrv4me

· #2 · May 31, 2007 (Edited)

Check the carpet behind the instrument panel, if its wet or moist, you could have a heater core problem.

Monitor the coolant, if your losing any consistently, and theres no clear indication of WHERE its going, thats the biggest sign of a HG failure.

chubbyranger

· #3 · May 31, 2007

When you topped off the coolant: how much did you add and how long has it been since you added any? Do the engine cooling fans run alot? Another possiblility is a plugged radiator - it seems like if you add cooling using the heater (and thereby increase cooling capacity) everything is OK, so you may have some pluggage impairing the radiator. Do the t-stat for sport and track how much coolant it uses. This isn't to say its not early HG symptoms, but there are some other alternatives.

pnj2108

· #4 · May 31, 2007

I also have 1997 Deville and i had a problem a while back where i would smell coolant but i wouldn't see it leaking and it turned out to be that my reserve tank had a slow and very small leak and when it would leak it was landing on the serpentine belt so it would evaporate before you could see it but after a while the whole in the reserve tank grew bigger because obviously the coolant is hot i replace the tank and flush the coolant so problems since. Now your temperature from most of the cadillacs i have seen i would say the temperatures you were describing are higher than the normal or average. My 97 is always 187 - 205 when driving around town and when driving on the highway it stays at 188- 196 i have never seen it higher on the highway.

Well good luck i hope it's nothing big

misfit6794

· #5 · May 31, 2007

It could be early signs of your headgaskets failing, the smell of coolant but no leak is a bad sign. Usually though the coolant being dumped in the exhaust will ruin a o2 sensor and trip a check engine light. Check the heater core and thermostat. Also put your finger in the tailpipe (when its cooled down) and wipe the side, if there's coolant in there, youve got a headgasket problem. You definetly should not let the car get past 220, if the hg's aren't bad now, they will be if you let it overheated.

Ranger

· #6 · May 31, 2007

I think the fact that you are smelling coolant is a good thing. That leads me to think external leak. Many times a small leak will evaporate before it becomes evident. My '97 had a small leak at the bottom side of the pump cover. I could smell coolant when I pulled in the garage and walked past the front fender. Took forever to locate it. Radiator side tanks are another common leak point that are hard to discover. Your best bet is to have a cooling system pressure check done. They will pressurize the cooling system and let it set. Eventually the leak will show itself.

BTW, dried Dex will leave a whitish telltale residue.

chubbyranger

· #7 · May 31, 2007

Check the water pump, water pump belt and tensioner. I could smell coolant on my STS and eventually found it dripping out the bottom of the pump housing. If the belt or tensioner is slipping that might also cause high speed overheat. If they haven't been done at 128K it might not hurt anyway.

BladeBC97

Discussion Starter · #8 · May 31, 2007

Thanks for all the tips guys, I'll check everything out that was suggested. Seems awfully strange, but now a day after I wrote the post...I put in some Lucas Fuel Injector Cleaner, and I've been driving it nonstop with the A/C on, off, and the heat on...and now there doesn't seem to be any coolant smell or temperature gain at any point in time. Extremely strange, but I'll definitely check for leaks in case.

I keep getting varying answers on this one thing though, what temperature should these engines run at? What is the normal range? Some say 195-205, others say even 240 is O.K. Normally mine is around 205 or so, then about 220 on the highway. Is that even normal or another sign of a possible problem?

Ranger

· #9 · May 31, 2007

My '97 Deville (digidash) ran a consistent 206 (summer) and 213 (winter), highway, city or traffic jams. 220 is a tad higher than normal, but nothing to worry about. 240 is. Have you ever cleaned the bugs out of the condenser fins?

BladeBC97

Discussion Starter · #10 · Jun 1, 2007

That I have not, I'll give that a shot as well. In other news it came up with a check engine light....pulled a check engine code of P0155 HO2S Heater Performance Bank 2 Sensor 1

Could this be part of the problem? What does that error mean, the sensor is going bad and needs to be replaced?

z06bigbird

· #11 · Jun 1, 2007

Stuff some cotton balls in your nostrils. No more smell. Problem solved????

LOL

z06bigbird

· #12 · Jun 1, 2007

Climb under car (maybe at night) with FLASHLIGHT or drop cord). Check the bottom of every hose and look closely at bottom of overflow tank for tiny leaks. Also, there is about a 1 inch hose at the bottom of the overflow tank. You need to pull the tank out to see it.

Otherwise, have someone do a pressure check for several hours.

lenny lincoln

· #13 · Jun 1, 2007 (Edited)

HO2 bank ? what ever, I am no obd2 code expert but it sounds as if your O2 on your leaking headgasket bank is going bad. leak down test is in order.

Misfit6974 "Also put your finger in the tailpipe (when its cooled down) and wipe the side, if there's coolant in there, youve got a headgasket problem"

How do you determine regular exhaust condensation from a leaky headgasket? do you taste the mositure for the sweetness of antifreeze? Coming from a car guy, Dont do that or tell others to do that.

the best way to determine headgasket leakage is to smell the exhaust and visually look at it. White smoke and sweet smell is antifreeze. Foamy bubbles in the radiator or foamy oil on the dipstick is another indicator.

misfit6794

· #14 · Jun 1, 2007

How do you determine regular exhaust condensation from a leaky headgasket? do you taste the mositure for the sweetness of antifreeze? Coming from a car guy, Dont do that or tell others to do that.

Its extremely easy to tell the difference between water and coolant, especially for a car guy. Normal exhaust condensation won't smell sweet, like coolant, it won't be slimey like coolant, and an extremely reliable mechanic told me about that trick.

Chances are your O2 sensor went from coolant being dumped onto it. Coolant won't let the sensor heat up and cause it to fail.

Playdrv4me

· #15 · Jun 1, 2007

misfit6794 said:
Its extremely easy to tell the difference between water and coolant, especially for a car guy. Normal exhaust condensation won't smell sweet, like coolant, it won't be slimey like coolant

:werd:

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