Heater Problem

I have a '95 SL2 (150,000mi) with a very strange heater problem.
First this summer the temp gauge was not going above 1/4 scale even tho I
knew it's normal operating position was 1/2.
I knew the air temp coming from the dash ducts was not as warm as it used to
be. (85-90deg) But winter was not here yet.

So, last month I cleaned & flushed the system and replaced the Anti-freeze.
Installed a new thermostat 190deg.

Yea, the temp gauge came back to it's normal operating position of 1/2 scale
and air duct temp was restored to about 120-130 deg.
All was well I thought and was set for the winter.

Suddenly yesterday morning the air duct temp. was back to being only
85-90deg. even tho the Temp gauge showed the normal 1/2 scale reading.
Thought to myself what?
Checked the coolant level and it was fine.
The top radiator hose was hot, but the bottom hose was cold and the hose
going to the heater was only warm.

Not really expecting any change I replaced the thermostat again. And there
wasn't any change.
Opened the expansion tank and started the engine. Yes the coolant is
circulating through the tank. Squeezed the top & bottom radiator hoses and
again in just a few seconds the air duct temp shot up to 120deg. again. The
bottom hose was then warm. ( The temp gauge still was at it's normal 1/2
scale) Thought to myself that there must to have been an air pocket in the
system. This also told me that the heater core is not plugged up as it is
capable of producing hot air transfer.
Replaced the cap and in less than 10min. of driving the air duct temp was
back down to 85-90 deg. again even tho temp gauge was still at 1/2 scale.
( Yes the temp gauge is working normally as it goes from 0 cold to redline
if I leave the expansion cap off and allow the engine temp to rise to that
point and yes the fan does come on just before the redline and brings the
temp back down.)
Repeated the experiment by again taking the expansion cap off and squeezing
the hoses and the air duct temp again immediately shot back up to 120deg.
Replaced the cap and air duct temp again went back down to 85-90 deg, in a
few Min.
It is almost like the water pump has lost "prime" and is not working and
when I squeeze the hose it starts pumping.
That doesn't make sense to me either as the engine hovers at its normal 1/2
scale all the time. (I drive the car aprox 100mi/day with several hours of
driving with no overheating problems. Is that possible?
I am lost as what to do now to restore proper heater operation.

Anyone have any thoughts or suggestions?
Jerry

 

Jerry, I do not mean to alarm you... but my company owns a fleet of Corsica 4
bangers. When we get the 'no heat' problem in the winter after all the common
items have been replaced, I replace the head gasket. I know the engines are not
the same as Saturn, but the head gasket on the Corsicas are allowing
compression into the coolant system causing air pockets in the heater core.
I hope this is not your case, but do not rule it out.
James1549

 

I can understand how that could cause air pockets.
I have had head gaskets on two other vehicles fail in the past. One was
slowly leaking coolant into the cyl and burning it.
The other had a bad leak into the cyl and was blowing coolant out of the
radiator cap.
I don't seem to be loosing any coolant this time but if the piston is
blowing air into the water jacket, that could cause it.



Today everything was just fine, normal air duct temp (120-130 deg.)
Drove about 120miles over a 8 hour period with a lot of stop & start. No
problems.

Definitely something to keep in mind as it could be a very small air only
leak.
Thanks
Jerry


Jerry, I do not mean to alarm you... but my company owns a fleet of Corsica
4
bangers. When we get the 'no heat' problem in the winter after all the
common
items have been replaced, I replace the head gasket. I know the engines are
not
the same as Saturn, but the head gasket on the Corsicas are allowing
compression into the coolant system causing air pockets in the heater core.
I hope this is not your case, but do not rule it out.
James1549

 

Jerry

I wish I could give you the answer but I can tell you that I endured a
similar problem with a 92 for many years and miles and never did lose a
drop of coolant so I don't think it was a head gasket in my case. THe
other thing was that when I had little heat, if I stopped for a stop
light or usually even a stop sign, the heat was then OK for that trip
until I shut the engine off. None of the normal things fixed it and the
dealer didn't have a clue either.

Interestingly my 02 seems to be starting to do something similar... Let
us know if you find a fix.

Ken