LHS overheating

'94 LHS

Twice today, going to and then coming back from a place about 70 miles away
- car starts running hot, warning light on and temp needle all the way up
until I'd gone about ten miles, then it drops back to normal and stays
there the rest of the trip with no problems. Belts and coolant level look
fine.

I'm guessing that the thermostat is sticking shut, then opening up after a
time, but I ain't no mechanic. ;-)

Am I on the right track? Can I just tell the people at the Chrysler place
to replace the thermostat?

 

If the vehicle only overheats when the vehicle is at a stop, in traffic or
slow speeds you may want to check to see if the radiator fan comes on.

Glenn Beasley
Chrysler Tech

 

Thanks for the feedback.

The car was started cold both times today. This is what happened:

Start car, head down the road
After several miles, car reaches operating temperature
Car then gets hotter and hotter - passing normal temp (unusual)
Car stays at hot temp for several miles
Car then abruptly settles back down to normal temp
Car stays at normal temp with no problems indefinitely thereafter

It's not that it gets hot at stop signs, or anything like that.

 

Was antifreeze recently changed? My Intrepid did the same thing and it
started right after I changed a water pump that was leaking. It seems
that letting the thermostat 'dry out' while the antifreeze was drained
was a bad thing.

I ended up replacing the thermostat.

Also, if you had the antifreeze out, did you purge the air from the
top of the block? (That's why there's a little bleeder on the top
of the thermostat housing.) I guess if you didn't do the work,
are you sure whoever did it was competent.

 

The thermostat on that 3.5 engine is easy to get at and fairly cheap as
well. Replace it and let us know if that does the trick. Assuming the
temperature sensor and fan/relay are working properly, it sounds to me as
though it is sticking closed and requires inordinate heat/pressure to open
the first time.

Bob

 

No coolant lost..... possible thermostat problem

 

No, not in a long while.

This is the plan. Thanks!

 

Thank you - this is exactly what I suspected.

I'm not a technician, but I have done minor repairs to cars when
necessary. Is this thermostat job something that can be done with a couple
of simple tools? No sealants or special gaskets or gunk or anything?

I'm a guy who has replaced the starter, alternator, and other things on my
280ZX, so jobs of that nature don't worry me. But this LHS isn't so easy
to work on.

And where is the thing (thermostat)?

Thanks again!

 

heheh... thanks again, Glenn! I guess I'll just replace that sucker.

 

The thermostat housing is held in place by two 13mm (If I recall correctly)
bolts and has one gasket. From memory, I believe if you follow the upper
radiator hose to the engine block, you will see the housing. Get the right
thermostat and make sure you note the orientation and put it in the correct
way! Scrape and wire brush off all the old gasket and retighten the bolts
evenly. It is not a difficult or costly job. Good luck.

Bob

 

Well I guess I got it on ok. I don't know if I got all the old gasket
off, but all I had to scrape it off was a flathead screwdriver and I
didn't want to scratch up the metal. I can't see any leaking, and after
replenishing a little water I drove to the store and back with no
overheating.

I'll ask here if I see any problems. Thanks so much for the advice!

 

Don't forget to bleed the air out of the system! On the top of the
T-stat housing there's a fitting that looks like a brake bleeder. Crack
it open while pouring coolant into the reservoir, and close it when
bubbles stop coming out with the stream of coolant.

 

The car should be running when I do this, right? Hot or cold or doesn't
matter?