Our car has been overheating. Basically, antifreeze has been boiling over in the reservoir. The gauge hasn't worked for a bit now. The gauge had been doing the typical floating around between cold and hot (I heard this is common on these 240's). But now it doesn't do anything.

Do you know what may cause overheating? What do you think the problem could be? Thermostat?

Thanks ahead of time and look forward to hearing from you.

 

Could be: thermostat not opening, radiator clogged, bad head gasket... Be careful overheating it--the biggest reason for engine failure.

 

Thanks. I'll start with the thermostat. The worst of it seems to be when it's in traffic. The fan may not be coming on, I'll check that. If the fan doesn't come on, is it most likely the thermostat?

 

Well, yes, if in traffic, the fan should be coming on... then I'd start with the t/stat.

 

The fan is controlled by a switch in the radiator. Thermostat sits near the water pump and keeps coolant from going to the radiator when the car is cold. I would check to see if you have good heat next time it's running hot: this implies the water pump is working well. Oddly if the thermostat is not letting scalding hot water near the radiator its fan might not come on. Feel the hoses when the car is hot; they should be hot too, if not this condemns the t-stat.

To me it sounds like an air lock; try loosening (stone cold car) the top rad hose clamp where it meets the radiator and pulling the hose off the nipple a little. Coolant should of course come out. If you get a bunch of air, hold that hose up high, put a funnel in it, and back-fill the engine with antifreeze until it spills out the radiator nipple.

 

does your 240 have an electric fan? our 87 only has a centrifugal clutch belt driven fan. my 740s/940s have all had electric fans (the 1991 has both, the 1992 has a 2 speed electric fan only)

 

Yeah, good point. I don't think the '90 has an electric fan...