Chrysler Repair: 1992 LeBaron - no heat/bubbling over, head gasket leak, coolant system

Question
QUESTION: Recently my LeBaron has begun to not produce heat for the inside of the car...and the engine is overheating at the same time.  Today I noticed that the overflow tank in the coolant system seems to be spewing coolant under the hood.  I am wondering if this could be the fault of a bad thermostat or something worse!?

Something else that may be related....for a while now when I travel a low speeds for any distance the engine will sometimes begin to overheat - if I rev the engine to over 3grand the temp will drop back to normal range!

Thanx for any help....
 K

ANSWER: Hi Katie,
All of the symptoms point to a coolant system malfunction, of course. It could be a thermostat stuck closed issue. But it depends upon the state of the system when you start the engine. If the system is not low on coolant due to previous overflow and as well does not have any air pockets in the system, then if it were the thermostat it would simply warmup as if normal but just keep going up to H and then boil over.
On the other hand, when you start the engine from cold, take a look at the tailpipe and observe for how long the usual white smoke comes out, and does it disappear reasonable quickly. If not, and it continues to bellow white smoke and the smoke when allowed to condense on the palm of your hand smells like anti-freeze then you have a worse situation: a head gasket leak in the engine.
The other thing to observe is whether the overflow from the coolant bottle start to appear before the temp gauge read hot. That would be a second indication that you have a head gasket leak. Also listen for the sound of bubbling inside the engine during that early warm-up period, which would also be a head gasket leak symptom. The last symptom would be milky engine oil on the dip stick.
If you have none of those then I would suspect the thermostat or the alternative to that which would be an obstructed radiator core.
If you have the 2.5L 4 cyl engine (rather than the V-6) then you might have a simple issue of air trapped in the thermostat housing. If the coolant system was drained recently it could be that it was not refilled properly. So let me know if you have the 4 cyl engine and I can tell you how to refill it.
Roland

---------- FOLLOW-UP ----------

QUESTION: Thanx for the response, Roland.

Yes, it is the 2.5 4cyl engine.

Not the head gasket...went down that road with this vehicle about 8 years ago and the 'symptoms' are not the same!  But to be sure I performed the tests you recommended. No problem there.

I did discover not long ago that my radiator fluid was low (have no clue why!) and added antifreeze to it and to the overflow tank - bringing both up to "normal" levels.  I just checked the overflow tank is still too full (but not to the overflowing point) even though the engine is cool.

Any help will be much appreciated!

K

Answer
Hi Katie,
It seems like the system is not sucking the fluid back into the engine from the overflow bottle, when it cools, which does say you have an internal leak of air/liquid some place. How about the radiator cap being worn out? Is the rubber dried/cracked.
How about the bubbling sounds/milky oil?
To deal with the air in the thermostat housing possibility, lower the level in the engine by draining the radiator about 2 qts, saving for refill. Then take the plug out of the top of the thermostat housing (8 mm hex wrench, located between spark plug 3 and 4), then add coolant back into radiator until coolant level rises to the top of the thermostat housing, then put back in plug, then refill the system the rest of the way.
Check to see if both side manifolds of the radiator feel hot after driving it a bit. If one side is cold and the other hot then you have plugged up radiator.
Roland