Engine overheats but temp is normal

r2romero · #1 (**permalink**) 05-15-07, 12:27 AM

I got 99 SLS 102k mi. and the the engine overheats. I have changed the water pump, thermostat, coolant tank, coolant tank cap, the radiator is 8 months old, fans works properly, and has no leaks. Anybody have any suggestions?

**Playdrv4me** · #2 (**permalink**) 05-15-07, 12:31 AM

Quote:

Originally Posted by r2romero

I got 99 SLS 102k mi. and the the engine overheats. I have changed the water pump, thermostat, coolant tank, coolant tank cap, the radiator is 8 months old, fans works properly, and has no leaks. Anybody have any suggestions?

Have your coolant checked for exhaust gases and do a search for "headgaskets" and "overheating". It sounds like your headgaskets are gone, this test will confirm. Also look for bubblies in the coolant tank, white steam from the exhaust with a sweet smell, and just a general odor of coolant that lingers.

Man we are seeing like 1 or 2 of these a day lately.

Welcome to the forum... Wish it were under better circumstances

r2romero · #3 (**permalink**) 05-15-07, 12:53 AM

Thanks

JimHare · #4 (**permalink**) 05-15-07, 06:59 AM

Quote:

Originally Posted by r2romero

I got 99 SLS 102k mi. and the the engine overheats. I have changed the water pump, thermostat, coolant tank, coolant tank cap, the radiator is 8 months old, fans works properly, and has no leaks. Anybody have any suggestions?

Ummm...I have a question - how can it overheat if, as you say in your title, the temp is normal?

blunted · #5 (**permalink**) 05-15-07, 05:11 PM

Quote:

Originally Posted by JimHare

Ummm...I have a question - how can it overheat if, as you say in your title, the temp is normal?

If your temps are normal but are seeing a "Engine Hot" message that could mean your PCM or a sensor is shot.

TheGlassMan · #6 (**permalink**) 05-15-07, 05:54 PM

What are the first signs of a headgasket going?

would you lost fuel economy as the first sign...or is it more like bamo, its gone and your smelling coolant like mad from the exhaust??

**Playdrv4me** · #7 (**permalink**) 05-15-07, 06:37 PM

Quote:

Originally Posted by TheGlassMan

What are the first signs of a headgasket going?

would you lost fuel economy as the first sign...or is it more like bamo, its gone and your smelling coolant like mad from the exhaust??

It can vary from car to car... its just like a serious disease or something... each vehicle exhibits different symptoms. Alot of the guys here noticed as the very first symptom, the fact that they slowly have to begin adding coolant to the system... first every couple of months... then every month, then every couple of weeks and so on. The system basically begins using coolant at a high rate.

Youll also start to get a faint whisp of coolant odor here and there and eventually youll start to get all of the symptoms one right after the other, in no particular order of course... White steam from the exhaust, overheating etc.

Overheating that is consistent is usually actually a later sign.

**Ranger** · #8 (**permalink**) 05-15-07, 09:40 PM

Poor fuel economy is not a symptom of a failed head gasket.

jholland · #9 (**permalink**) 05-16-07, 12:09 PM

It doesn't sound like the air bleeder line to the coolant tank has been checked.

TGrits10 · #10 (**permalink**) 02-25-09, 01:27 AM

Quote:

Originally Posted by jholland

It doesn't sound like the air bleeder line to the coolant tank has been checked.

Could you/someone tell me more about this air bleeder line and its possible role in overheating?

Forgive me for reviving an old thread, but the OP's problem sounds a lot like mine

-99 STS, ~115k miles
-Car overheating
-Not leaking coolant
-Not consuming coolant
-Exhaust looks/smells normal
-Radiator popped a leak (as a result of overheating?), replaced/brand new
-WP & belt replaced, tensioner checked & OK
-System flushed
-Fans working
-System holds pressure (even cold after sitting overnight, opening the cap releases pressure)
-Thermostat replaced/brand new AND I dumped it in a pot of boiling water to make sure just now. It works.
-Owner at end of rope, doesn't think symptoms fit head gasket (not eating coolant, not smelling/seeing coolant in exhaust)

So...as far as I can tell, everything is in place for the cooling system to be working great, yet the car stubbornly and massively overheats any time I drive a good distance or get on the highway. I am running out of possibilities to investigate and rule out.

-Head gasket failure?
----Doesn't fit because coolant doesn't seem to be getting into the cylinders, oil level is fine, exhaust seems normal, engine runs fine....

-Kooky water temp sensor?
----Doesn't fit because a bad sensor would give wacky readings, or read consistently high or low. Everything is normal as the car warms up, then levels off at 12 o'clock on the temp guage. It then stays there for quite some time, indefinitely if it's just idling in the driveway with the filler cap off. Drive long enough or get on the highway though, and the temp starrrrrrrrts a'climbin

and doesn't seem to care what you do after that. Sitting at idle seems to help some, as does coasting in gear...but gas pedal = temp up.

What am I missing?

97EldoCoupe · #11 (**permalink**) 02-25-09, 01:53 AM

Quote:

-System holds pressure (even cold after sitting overnight, opening the cap releases pressure)

Unfortunately, your HG's are in need of replacement. I can pretty much tell from what you've described.

TGrits10 · #12 (**permalink**) 02-25-09, 12:21 PM

Quote:

Originally Posted by 97EldoCoupe

Unfortunately, your HG's are in need of replacement. I can pretty much tell from what you've described.

Well...that's certainly not what I wanted to hear, but it makes some sense and at least it's an answer.

What are my chances of limping it along for a little while with some leak sealing product and short drives? The death of this car would be a lot less inconvenient if it could wait until the summer

**Ranger** · #13 (**permalink**) 02-25-09, 05:28 PM

Forget the snake oil, it won't work. From what you say it does not sound like it will limp along any further.

TGrits10 · #14 (**permalink**) 02-25-09, 11:30 PM

Quote:

Originally Posted by Ranger

Forget the snake oil, it won't work. From what you say it does not sound like it will limp along any further.

In that case, what's the cost of parts and how long would it take me to do, if that's even realistic? Special tools required? I could set aside a weekend and just go at it for 12 hours a day if need be, and I have a lot of experience wrenching on my own cars over the years, including some pretty complex/extensive jobs.

I'm ignoring the option of having someone else do it because I understand the cost to be $2-3k+ which is more than the car's worth as a trade in at this point, so why bother. If snake oil doesn't work (not getting my hopes up) and I can't replace 'em myself, I guess I'll have to sell it to a junkyard or give it away for a tax writeoff...then it'd be time for some hurried car shopping

**Ranger** · #15 (**permalink**) 02-25-09, 11:45 PM

I would not put the snake oil in there. It may clog your radiator or heater core. You have to drop the drivetrain to do it. There are a few good posts on doing it. Zonie and Tateos have done it and will give you an idea on the length of time, cost and special tool. I think there is a tutorial in the Tech Tips section.