With a new short block, crankcase and sensor, why is my car still overheating?

Dear Car Talk

Dear Car Talk | Jul 01, 1997

Dear Tom and Ray:

I have an '89 Olds Cutlass Ciera with 40,000 miles on it, and it has been a
great little car. To make a long story short, I was having a problem with
overheating, and my GM dealer examined the car and told me I had a cracked
engine block. I had a new short block and a crankshaft installed, but when I
got the car back, I was still having problems with the temperature.

After 30 or 40 miles of driving, the temperature gauge started creeping up past
the halfway point. I took it back and they replaced a thermostat sensor. I
drove it again, and after 30 miles or so the temperature started going up
again. Now I'm afraid to drive the car any distance. Could it be that the fan
motor isn't kicking on? Gentlemen, I'm 82 years old, and I need wheels because
I'm not too good on roller skates. Thanks for your suggestions. -- Hy

RAY: Hi, Hy. Sorry, I couldn't resist that one. Let's consider the best- and
worst-case scenarios first, since it's probably neither of those.

TOM: The best-case scenario is that everything is fine. You say that the
temperature gauge creeps up past the halfway mark, but you don't say whether it
KEEPS going. If it stops just above the halfway point and stays there, that may
just be the result of the new block breaking in and running a little hotter
than normal right now. And that would be nothing to worry about.

RAY: The worst-case scenario is that your dealership made a mistake and failed
to notice that the cylinder head, and not the block, was cracked. Or that the
head was cracked in addition to the block.

TOM: But let's not be alarmists. There are several other good possibilities
here. It could be a faulty fan, as you suggest, and that's very easy to check.
Your mechanic can simply run the car in his shop. Even at idle, the fan ought
to cycle on and off as the engine temperature rises and falls. And if it's
working, sooner or later you'll see it (and hear it) come on.

RAY: But the most likely culprit, in my opinion, is the radiator. Overheating
problems that occur when the car is under load (i.e., when you're asking the
engine to do a lot of work, like when you climb hills or drive 30 or 40 miles
on the highway), are more often than not due to plugged-up radiators.

TOM: The dealership probably assumed that the cracked block was the cause of
the overheating problem. But it may be that the plugged radiator caused both
the overheating AND the cracked block. And if you don't fix the radiator, you
could end up cracking another block, so you're right to be afraid to drive the
car any distance.

RAY: Have the dealership remove the radiator and flow test it. If it IS plugged
up, and I suspect it is, once you fix or replace it, the problem should
disappear, and this car should easily go another eight years for you (or until
you're ready to buy your Corvette, Hy). Good luck.

* * *
TOM: Hey, do you think you're taking good care of your car? Are you sure?

RAY: If you're like many of our customers, you may be ruining your car without
even knowing it. Yes, even you! Find out how. Send for your copy of our
informative pamphlet, "Ten Ways You May Be Ruining Your Car Without Even
Knowing It!"

TOM: Send $3 and a stamped (55 cents), self-addressed No.10 envelope to Ruin
No.1, PO Box 6420, Riverton, NJ 08077-6420.

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