Ok, so I've got an old 240 that has had a rough life. I wanted to take it on a 1000 mile trip. I took it to a shop that my friend works at. They did a few different things, none of which were related to the cooling system. I drove her 1000 miles, no problem.
Two days after I get home, I notice the temp gauge start rising. I turned the heat on and made it home. There's plenty of coolant, I would just like to get an idea of where to start.
I've done repairs to cars I've had in the past, but I'm pretty bad at trouble shooting. Any help would be super appreciated.

Sean

 

start the car when its cold, wait for the temp gauge to come up to normal, and feel the big radiator hose hose between the thermostat (top front of engine) and radiator, is it hot? if not, the engine thermostat isn't opening.

otherwise, could be a clogged up radiator (replace radiator), or clogged up engine block cooling passageways (ugh). has this car had radiator flushes every few years? you really should do that every 2-3 years, or at most every 5. old coolant looses its anti-corrosion stuff, and the block and radiator start to crud up.

of course, the engine temp could be fine, your problem might be the stupid 'temp compensator board' on the back of the instrument panel... these are known to go flakey, and result in the dashboard temp gauge giving wild readings. IPD has a kit to replace it with a simple jumper wire. the compensator board's function is to keep the needle exactly in the middle if the temp is anywhere near normal, this to prevent excess service calls from neurotic owners freaking out that their car is running cold/hot as appropriate. Me, I'd much rather have an actual indication of the engine temp even if its within 'normal' range.

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Well, I know that I occasionally have to hit the to hit the top of the dash to get the speedo to act right, but the temp gauge doesn't seem to have the same problem. I'll try out your advice tomorrow if i can. Thank you.

Sean

 

if the engine is overheating, you'd probably smell it, and if you turned on the heater, it would have been a lot hotter than normal.

 

Piercer!

Thanks again for your poignant resposes. Ok. So, how hot is hot? When it gets up to temp, that hose is warm, but not hot. I can grab it no problem. I would call it loosely warm, not hot at all.

(P.S. the 240 wagon is no speed racer.)

 

what matters is how hot the engine actually is when the gauge goes up to the top.

next time that happens, pop the hood and check it out, if the engine no hotter than it normally is when its been driven, then its probably fine. if its too hot, it should be pretty obvious.