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Discussion Starter · #1 ·
I have a coolant leak seems to be leaking alot although my level hasn't dropped below “full”.
I drove the car yesterday for about an hour and let it sit for an hour after… no leaks. I started the car til it got to operating temperatures and the thermostat was opened still no leaks none visible. I drove home and when it sat over night it leaked alot but still not below “full”. Only place it seems to be leaking is between the seam of the upper radiator hose between the thermostat. I havent conducted a pressure test yet but i believe im experiencing high pressure and thats why im expriencing a leak over night when its sat long enough to release pressure but im not sure. Any suggestions?

no oil in the coolant
Not leaking from the block or any other hoses (visibly anyways)
Not over heating
Not experiencing any Fluctuations in temperature
No hissing from ET
Seems to be leaking only directly under thermo/ET
Whole cooling system is less than year old
 

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...and you're not overfilling it so that it's venting the excess fluid?

The obvious answer is something's displacing the fluid,
and the obvious thing to do that is compression gasses,
as they're the highest pressure in the engine.

The usual cause for leaks, though, is a failed seal somewhere. BMW's
sealing 'system' is pretty mediocre- given the forces involved, the temperature
fluctuations, and the effects of high heat on plastics, it's a little surprising
that it works at all. Me, I'd be looking for a failed o- ring or at the end cap
on the radiator. Or the seal around the top of the expansion tank.
Lots of formerly good parts are now HellaCrap, so
'new' has to be followed by 'Nissens' or something similar to NOT be suspect.

If you're 'experiencing high pressure' then the pressure regulator's failed,
and that's in the ET cap. So, try a new cap.

t
occam
 

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Discussion Starter · #4 ·
Okay, thanks guys. Im thinking I might've over filled it at some point and that its draining the access i did rebleed it and drain some of it and its still “full” so we’ll see. Im going to do a pressure test here shortly.
 
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