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Old 10-12-2012, 10:14 PM
robertobaggio20 robertobaggio20 is offline
Location: earth
Join Date: Oct 2009
Posts: 3,403
Mein Auto: car
Originally Posted by My525iT View Post
M50s are not that tough to bleed. No doubt you did it properly. If the car overheats your best bet would be to replace the thermostat - even if it is not the original problem. Make sure you drill a bleed hole at 12oclock on the new one. Makes bleeding a cinch.

I believe the fluid should travel from the upper to the lower rad hose. Therefore if the tstat and water pump are working properly the rad should cool it down towards the lower hose. From everything I read not sure I could rule out water pump/fan clutch/aux. fan/rad blockage.

You can run a head gasket test pretty easy. Go to autozone or other and borrow their fluid reservoir. By a bottle of HG fluid, stick it on the rad and it will change colors if gas is in the coolant. Great for peace of mind.

Also, you can jump the aux fan with a paper clip and leave it on high when you drive to keep the engine cool. (No it is not a fix).

Well, here we are, something old that's actually new to me and no doubt many others. The HG colour change fluid test. Brilliant ! Larrick please do that right away sir.

And I'd like to say, with respect to 525it, that drilling holes in the thermostat is completely unnecessary. I've never done it and it has never made anything difficult. You don't have to be worried if you don't do it. Its another myth for the modern age, that may have had a relevance in an earlier era.

I agree that you should change your thermostat and water pump. Oreilly's sells a composite impeller thermostat for around $50, with a lifetime warranty. If the HG fluid test checks out and your HG is ok, then please change both the thermostat and the water pump. They both have approximately the same life span, if I'm not mistaken.

Just remembered. Another way to check for HG problems is via the compression test.
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