SL1 - Coolant temperature warning

My coworker just bought a clean, low mileage used '99 SL1.
The radiator appears to have been bent in towing, but not too bad.
Coolant seems to be circulating properly, with no leaks.

He says that although the temperature gauge never rises above normal,
the temperature warning light on the dash comes on - almost immediately.
His mechanic replaced the sensor, but the same thing still occurs.

Any suggestions on how to troubleshoot this problem?

TIA,
Chris

 

My '99 SL had a problem like this but I really did have low coolant --
it was getting into the motor oil. You didn't mention it but I'm assuming
your coworker checked the coolant level....

 

My coworker just bought a clean, low mileage used '99 SL1.

If the light is blinking its due to low coolant level......that would be my
first guess....

 

The coolant level is okay per the markings on the overflow reservoir.

Is coolant added in the reservoir? There is no radiator cap (?).

Perhaps there is some air in the system.
Does anyone know where the bleed is located?

TIA,
Chris

 

That is correct. You have a closed radiator system. It was the same
way when I had an '89 cherokee and I had a hell of a time convincing at
least two shops repair shops of this. They kept insisting I had a
radiator cap.

Air in the cooling system is generally not a problem or terribly unusual
UNLESS you get a good sized pocket of air in the water pump, which IIRC
doesn't happen very often in street cars.

How did you determine that the coolant is circulating properly? Have
you been able to pressure test the cooling system?

I'm not sure if Autozone/etc has these you could borrow, but we use a
laser thing to measure the temp of the tires and various parts of the
engine after we bring a car off the race track. You may try just for
curiosity's sake if nothing else, what the engine/coolant temp is by
pointing it at places like the upper radiator hose connect. Compare
your reading to the car's temp gauge reading.

-rj
98SL2

 

The coolant level is okay per the markings on the overflow reservoir.

Again, IF the light is blinking, the level is low. The sensor is set up pretty
sensitive - it can look like its full but still light the low light. I would
add a little water and see if it goes away. IF the light is blinking, it def
means low coolant, so if you add some and it still doesn't stop, suspect
sensor.