: 1998 Cadillac STS overheating

02-22-11, 12:58 PM
98 sts overheating loosing coolant, no coolant in oil, no white smoke, runs great until it overheats. when it starts to overheat and looses heat i race engine up to circulate the coolant and it helps. what could be the issue i believe a blown head gasket??

02-22-11, 01:02 PM
best way to tell if the HG is blown is to do an exhaust gas test ...
That thread is pretty long but has a lot of good info in it

this post has a link to the tool you will want to test with

02-22-11, 01:23 PM
Headgasket is toast.

Just went through the EXACT same symptoms with a 3.0 taurus. Car ran fine, slight miss at idle, run over 70-80 mph, there goes the temp needle.

Kept cruising around until I received a check engine light P0305, cylinder number 5 misfire. Tore it apart, the computer didn't lie. The head gasket disinergerated at one of the coolant passages at cylinder number 5. The compression was being blown straight into the cooling system.

Fix it before it gets worse.....

Mark C
02-22-11, 01:34 PM
If you increase RPMs and the temperature comes down then your problem is with water circulation, either your water pump is shot, the drive belt is loose, or you have alot of air in the system causing the pump to cavitate and not move water at the lower revolutions. As with any over heating check your purge line and ensure you have a nice steady stream of water passing thru it, that increases with RPMs. Then check your water pump belt and tensioner condition.

02-22-11, 01:53 PM
Do you smell coolant after you drive the car?

Are you adding coolant on a regular basis?

Is there a rough idle at times and it goes away when the vehicle warms up a bit?

When you turn on the heat in the vehicle do you get cool air at times and heat sometimes?

After you have driven the car, let it cool down a bit, have you tryed to remove the radiator cap only to hear, (a) water starting to boil over or (b) a very large hissing sound?

Cars can have a bad headgasket and still function for the most part. The cars will run until the headgasket isn't strong enough to keep enough compression, spews coolant all over place everytime it gets hot, or you look like a locomotive going down the street.

If the car has been somehwat maintained and most of the "obvious" things check out. It's the headgasket.

You are in the early stages of failure......

02-22-11, 07:51 PM
how long have you had car? you should know its habits if you owned for awhile. if you just got it and it has a new radiator, than thats a clue.