Arrgh! I've literally done everything and can't figure out why my temp gauge is running high. I have a pre-1985 water temperature gauge, so the temperature compensation board is not an issue.

Until two weeks ago, my temp gauge pointed to the bottom of the "N." Now it's half-way between the top of the "N" and the red zone, regardless of how and where I drive.

I've changed: coolant (50/50), radiator, thermostat, fan clutch (that was fun).
There are no leaks and I hear pressure when I try to loosen the coolant overflow cap. The water pump is not leaking and does not make any noises. I cleaned the water temperature sender terminal.

As a member of the "Cheap and Easy" approach, I would consider all the things that can give you the symptoms, and check things out.

1) The gauge lies. Other posts have this well covered.

2) Not enough coolant flow.
a. Low coolant lavel.
b. Thermostat failed in closed position.
c. Water pump not moving anough coolant.
d. Clogged hoses.
e. Clogged radiator.

3) Something else, like a bad head gasket. BTDT

My vote for quick and easy is the check for clogged radiator.

Add more cooling area. Do this by running the car heater at full hot full fan, all windows open if necessary, and watching the temp gauge. If it drops, it's a clogged radiator. Sorry.

Check for head gasket problem not otherwise apparent. Cold start, first thing in morning. Open hood, remove coolant reservoir cap, leave hood up. Watch the coolant reservoir opening while starting the engine. If coolant wells up and overflows out of reservoir, it's the head gasket. BTW I ran like that some years. As long as gauge stays OUT of the red.

Hope it's something cheap.

Good Luck,

Bob

:>)

Bob wrote:
Add more cooling area. Do this by running the car heater at full hot full fan, all windows open if necessary, and watching the temp gauge. If it drops, it's a clogged radiator. Sorry.
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My 245 used to do that - it worsened at the end of last summer.

I'd put the heater on and it would "solve" the problem. Only happened in hot summer weather in stop and go traffic or idling for 10 min in hot summer weather. Near the end of the summer the "heater trick" wasn't as effective and the car would heat up sooner. I also noticed that anti-freeze would begin to very slowly leak out of the coolant reservoir when the needle was still in the safe zone - this mainly occured when I stopped and shut the car off.

The car is stored for the winter and in the spring I'm planning on installing a new rad.

Could it be a combo of the head gasket and the rad? I've never run the car into the hot area / had a boil-over.


Any info will be appreciated.

Thanks,

Jaak

Had similar problem but only at idle and low speeds. I changed everything including a three row radiator and water pump twice (GMB, Volvo). Then did some experiments. Tied fan blades (7 blade w/ thermostatic clutch) to pump shaft with nylon cable ties to make turn at full engine speed. No diff. Then inspected air flow around fan at idle with a strip of paper, dangerous! Turns out there is virtually no flow through the radiator, air just circulated around the tips of the fan. Finally fixed with aux fan in front of a/c condenser. Wired to come on with compressor.

having needlessly replaced cooling system parts myself try...
http://www.ipdusa.com/ProductsCat.aspx?CategoryID=475&NodeID=4439&RootID=629
or something similar. good luck-it's almost always the gauge.

My first suspicion would still be your water pump. A failing pump will not necessarily leak or make noises that will be audible above the sound of the engine. Do you know how old it is? Especially if it's more than a five years old, I'd swap it out before I worried about anything else.

When you replaced the thermostat, did you make sure the jiggle valve was at the top?

If you finally rule out errors in the temp gauge, try adding a "water wetter" to the coolant. I was very skeptical myself but it helped us lower the temp significantly on our ProRally car. This product supposedly breaks down the surface tension of the coolant and allows better transfer of heat from the block to coolant and from the coolant to the radiator.

Skip
'93 850GLT
'83 242TI Flathood

You might try cleaning the fins in the radiator by blasting a hose from the back to forward.

You could replace the temp gauge sender on the side of the head below the intake manifold. They are pretty cheap. Maybe yours has gone bad.
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Thanks to everyone for the help, Doug C. 81 242 Brick Off Blocks, stock, M46; 86 244, 140k , auto.

Sounds like you have covered everything but two.

Check your return hose from the radiator when the car is warm and see if the it is cool. If not, need a new radiator.

More likely, take out your insturment cluster and take it apart until you have the gas and temp cluster out. See the little pins where the electrical contacts are? See all that black crud on the pins? Clean all of that off and also run a small pipe cleaner through the holes on the cluster which make contact on those pins. (Be careful of the cluster to not bend the red indicator wires, they are VERY fragile!)

Put it all back togeather. Let us know how it works out.

Gambit...

Is it possible that the water pump is not working effectively? The fan belt could be a little bit loose. I wish there was a way to test the water pump without taking it out (major pain in the neck). Plus, this model uses an unusual water pump that's special order (like a left-handed water pump where most other 240 water pumps are right-handed; the red hose is positioned differently on this particular car/model year for whatever reason and it took three orders to get it right).