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New radiator: Thermostat not opening


SAM_02

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Put a new 320i brass tank radiator in due to car running hot when pulling up freeway hills. Car runs very hot after new rad, 200*+ and thermostat does not open, pretty sure it did before new radiator. Possible air in system still...?

Would thermostat open or radiator burp properly if I have the heater valve off?? Bad heater box (next big project).

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the thermostat is designed to open at it's design temperature. Doesn't matter whether heater valve is on or off because the heater isn't in the primary cooling loop. I prefer to think of the heater loop as a "side loop" not associated with the primary cooling loop.

If you suspect the thermostat isn't opening, remove it and toss into a saucepan with water to cover and heat it up. You'll see it open. If you have a thermometer, that can be helpful.

as for burping, if I think I'm having that problem I remove the radiator cap then set it back on without rotating it fully closed. Then I drive around awhile. If I had a burping problem, it goes away. If I didn't have a burping problem, then I still don't. Win-Win.

as for personal history, a couple of years ago I installed a new radiator and the car still ran hot. Turns out there was some very gooey goop in the head and/or block somewhere, because suddenly it appeared in the top of the radiator where I could see it. I removed the radiator and flushed it out. Haven't had an overtemp problem since and the gauge needle moves from 1/4 to 1/2, no higher.

That gooey goop, without any scientific basis other than a silly wild ass guess, I surmised it had collected at the coolant outlet from the head and was partially blocking coolant flow into the radiator, having collected around the temp sensor that sticks into that fitting ..... and thus also holding some backpressure resulting in reduced coolant flow which kept the temp high. Somehow/something finally dislodged the goop and it went directly downstream into the radiator. I got lucky and saw it before it "melted" and again went elsewhere. Wierd theory, but more evidence included the fact that one day the car temp was "normal," and the next day was running "hot" and never stopped running "hot" until the goop showed up.

Cheers,

Carl

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heater valve DOES matter in bleeding system of air.

i would not suggest driving around with rad cap loose. when coolant gets up to temp the system pressurizes. if you run with cap loose, coolant should spill everywhere when engine gets warm.

use the system bleeding process documented in numerous threads on overheating.

2xM3

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How are you measuring the temperature? Don't trust the car's gauge.

No amount of skill or education will ever replace dumb luck
1971 2002 (much modified rocket),  1987 635CSI (beauty),  

2000 323i,  1996 Silverado Pickup (very useful)

Too many cars.

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re. running with cap loose. Definitely agree: on a general basis don't run with cap loose.

I should have added more info: with the cap loose I only drive around the neighborhood to get the coolant up to running temp. And I take out a small amount so when the coolant expands it doesn't run over.

The intent is to push any air out of the system by driving a couple of miles around the neighborhood. When I get back to the house the cap can be lifted off while the system is hot .... if there is any air to escape, well, I can't see it escaping.

Cheers,

Carl

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I am not sure the thermostat worked before the new radiator but it would only run hot during the freeway up hills, around town was fine. The old radiator was so bad, the fins all pretty much fell out.

I will try to burp with the heater valve on and then replace the thermostat if that doesn't work.

Best way to give the whole system a good flush?

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