Funola? Really? No thermostat will cause the car to overheat? How is that possible?

The car overheat even when I had the tstat in. It overheats now but much slower.

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1984 300td euro turbo

yep the bypass design requires a T stat installed to work correctly. is your belt on tight? you should not be able to turn the water pump pulley.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

I'll go check my water pump pulley now

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1984 300td euro turbo

squeeze hose test requires engine running, fully warmed up.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

The car was at 90c and running when I checked the hose.

I pulled on the belt. It did not budge. I did happen to see that the belt is cracked. trying to get a picture up.

Picture is attached. Hard to see. It's not a big crack.

Attached Thumbnails

 

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1984 300td euro turbo

I agree that that engine needs a good working thermostat. You should check your old one before putting it back in or buy a new one.

If you guys are 100% sure that the car will overheat without a thermostat (even though it didn't overheat in the winter with it out) then I'll put it back in. I don't want to put it in and then later have doubts it's working properly then have to remove it all over again. Even if I check it before putting it in, it still leaves doubt since you can't see it.

I've seen posts where people drill holes in their thermostat and achieved cooler temps. Also read posts where people who live in the desert completely remove the tstat. So I'm still trying to understand the logic.

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1984 300td euro turbo

Absolutely. If your radiator is plugged up, or if your water pump is bad, then your engine will overheat with or without a thermostat.

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'79 240D

No no Left Coast. They're telling me that maybe the reason that the car is overheating is because the t-stat is missing. I don't see that as possible.

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1984 300td euro turbo

I had all these heating problems you describe and tried all the suggested cures. In the end I replaced the fan clutch and the heating problem went away.

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1984 300SD turbo 126
"My true love"

God made me an atheist and who am I to question His wisdom

When you tested the fan clutch, did it spin freely when you spun it or did it have resistance? Mine feels ok but who knows.

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1984 300td euro turbo

Neither do I, unless you are really giving the car a workout in serious hot weather. The thermostat is basically a tempering valve. When it is open, it allows coolant to bypass the radiator, and the majority of the coolant circulates directly back to the engine. That happens at 80c, more or less, on a normal thermostat But the thermostat should close again when coolant temp gets to 94c, forcing all of the coolant to circulate through the radiator. So a thermostat that opens at 80c is not necessarily working correctly, as that is only half of the test. The thing is, unless it is really hot outside or you are really working the engine, you should never see temps much higher than 90c, unless you have some other deficiency in your cooling system, regardless of what the thermostat is doing.

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'79 240D

Just in my opinion. With a thermostat installed all the coolant will see the radiator. Once operational temperature is arrived at. No thermostat some is going to go through the bypass circuit as well. Thus avoiding the radiator. This will reduce total flow through the radiator.

In a strange way your car being able to run without the thermostat and not get really hotter than with one installed means there is some signifigant flow through the rad or the fluid would use the bypass circuit more. Path of least resistance I suppose.

Most times when I have to engage the heater to pull down the temperature on a car it has turned out to be a poor radiator. If that small heater core area actually pulls the temperature down.

Of course it can be other things but one has to keep in mind just how old some of these radiators are as well.

Test for fluid fan clutch is to kill engine when at normal operating temperature or above. Blades should stop fairly fast and not freewheel much. You really should consider geting the test strips to verify there are no exhaust gas components in the coolant. It is perhaps the cheapest thing to do as well as may save money in finding the cause.

You have looked for any bubbling present in the container with the engine warm and cool? Because of the age and milage on some of these buggies a cooling system bath with citric may or may not help.

If it comes to it a decent looking rad from a wreckers if it looks good may be worth a chance. Few cars there are scrapped because they overheat.

please describe in detail symptoms of your overheat, how long it takes, how fast you were going etc.

I have a combustion gas "block tester" if you want to check. how's the engine running otherwise?

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

This may help.
Cooling System:


.

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