My M42 is over heating! help!

[iamsam]

Here is the situation:

A while ago i noticed my temp gauge doing funny things like bouncing around. I started a thread on it.

Recently, the temp gauge has been much more steady in the high region. I thought it was my thermostat so i took it out. I am now running thermostatless.

Now my car runs super cool on the highway, like at 1/4 position, but if i get into traffic, the temp gauge goes to the half position. If i park and let the car idle, the temp gauge will go all the way to the 3/4 position. If i rev it up parked, the temp gauge doesn't really do anything, just stays at 3/4 and threatens to go higher.

help???

so its obviously not the thermostat, it may be the fan or the water pump. what do you guys think it is?

Thanks so much

[strad]

Have you checked the fan clutch? You should not be able to stop the fan when the car is at at 3/4ths. use a rolled up newspaper for this, not your fingers. And feather it, don't just jam it in there.

Did you ever check the nut on the back of the cluster? To stop the bouncing around I mean. . . the reason I ask is that, without a good ground, the gauge will deflect all the way to hot. And the nut provides ground.

[Massimo]

What happens when you are stationary and you turn the heater on dose the guage go up or down. If it gose down then i would recommend checking the fan clutch.

[iamsam]

Have you checked the fan clutch? You should not be able to stop the fan when the car is at at 3/4ths. use a rolled up newspaper for this, not your fingers. And feather it, don't just jam it in there.

Did you ever check the nut on the back of the cluster? To stop the bouncing around I mean. . . the reason I ask is that, without a good ground, the gauge will deflect all the way to hot. And the nut provides ground.

these things i will do. Thanks for the info.

What happens when you are stationary and you turn the heater on dose the guage go up or down. If it gose down then i would recommend checking the fan clutch.

gauge goes down slightly as the cooler coolant from the heater core enters the motor. But then it doesn't change much after that.

[iamsam]

UPDATE!!!! it is most definitely the fan clutch. Not only can i stop the fan with a rolled up newspaper, i can stop it with my pointer finger. And i can hold the fan still as i rev the engine.

BUT.... the car was warm, but it was just after i power washed the engine, so the engine may have cooled. Would this make the fan do this? should i re-try the test when the engine is fully hot?

[sumyungguy]

I removed the mechanical fan on both of my m42 cars, if your accessory fan is working properly it will kick on at certain temps.

So is your accessory fan working? An easy test is to turn on the a/c..

Do you have coolant disappearing (no leaks but the level is dropping)? When my profile gasket took a shit coolant was seeping out but burning off on the exhaust side so I never had water on the ground.

This is all I can think of off the top of my head, good luck.

[iamsam]

I removed the mechanical fan on both of my m42 cars, if your accessory fan is working properly it will kick on at certain temps.

So is your accessory fan working? An easy test is to turn on the a/c..

Do you have coolant disappearing (no leaks but the level is dropping)? When my profile gasket took a shit coolant was seeping out but burning off on the exhaust side so I never had water on the ground.

This is all I can think of off the top of my head, good luck.

thanks,

i have never had my AC on, because the compressor is seized, and i have never heard the aux fan kick on. i will try this on my way home though.

[iamsam]

ok! it is fucking HOT today. 95 degrees, and no AC, black vinyl seats, and an overheating problem. Not fun.

So anyway my aux fan works i found out, and since i have no AC belt, i am just going to keep my AC button on at all times, so the aux fan will do what it can. I am thinking of yanking all the AC components including the "radiator" behind the aux fan, but keeping the aux fan in.

so anyway, is the consensus on this my fan clutch, water pump, or both?

[romeomike]

Assuming you don't have a clogged/leaking radiator or air in your system, from your first post I'm leaning toward the fan clutch.

Coolant pumps either work or they don't. When they don't, overheating starts and stays with you. I'd ensure its belt is properly tensioned to eliminate that as a cause. I've seen failing coolant pumps leak, make awful noises, or seize outright.

Good luck sorting it out.

[slow e30]

put in the thermostat. its supposed to be there to help the cooling process. its obviously not that. check for blocked rad, do a leakdown/compression test.

its not hard. search your car for problems, then search r3v for answers, then ask in a thread.

[iamsam]

its not hard. search your car for problems, then search r3v for answers, then ask in a thread.

that's what i be doin, mate!

yeah just got the new thermostat today, gonna put it in tomorrow, go from there.

[slow e30]

that's what i be doin, mate!

yeah just got the new thermostat today, gonna put it in tomorrow, go from there.

overheating usually means air is getting into the coolant somehow. it doesnt matter if your using a jet engine to push cold air against the engine bay. water boils and causes the temp to rise.

hot water causes pressure. let car warm up and squeeze hoses for pressure. check all the hoses. go to real oem for a diagram and check it out. you can eliminate some of them and save the hassle.

goodluck.

ps- im nobodys mate.

[iamsam]

overheating usually means air is getting into the coolant somehow. it doesnt matter if your using a jet engine to push cold air against the engine bay. water boils and causes the temp to rise.

hot water causes pressure. let car warm up and squeeze hoses for pressure. check all the hoses. go to real oem for a diagram and check it out. you can eliminate some of them and save the hassle.

goodluck.

ps- im nobodys mate.

actually overheating does not necessarily mean air is getting into the coolant. in fact, air in the coolant does not cause overheating unless there is enough air to render the water pump useless or disallow circulation.

and the engine isn't cooled by air being forced into the engine bay. The engine is cooled by the air passing through the radiator, cooling off the hot coolant in the radiator, and then that cooler coolant enters the engine.

And water boiling doesn't cause the temp to rise. The temp rising causes the water to boil (generally). But in a coolant system, the coolant/water does not boil because it is under high pressure.

but thanks for the input, and i meant "mate" as in "friend" like the Aussies say it.

[iamsam]

So i ran the "rolled up newspaper test" again with my fan when the engine was hot, same result, the fan stopped immediately, had nearly zero resistance.

I also tested my water pump by letting the car idle while hot and blasting the heat at full to see if the heat cooled down over time, and it didn't, hinting that the water pump is working. The heat gauge also goes down a little when i blast the heat.

so i need a fan clutch asap. And an ICV but that's a seperate issue.

[Mr. Antonov]

so i need a fan clutch asap.

I wouldn't go that route, you'll probably find it cheaper to just buy an electrical fan kit that you can just mount onto your radiator..