E36 Cooling System problems

From someone who has problems posting to this group, but who can read it ok.
From: Fiacc Larkin Subject: heater problem Date: Sun, 04 Dec 2005 23:15
"I have a BMW 96 316i E36 M42. Ive been having serious overheating problems. My cooling system is somehow accumulating air to the point that the fan wont kick in (presumably because an air lock is blocking the fan sensor) and once that happens it doesn't take long before it overheats. The annoying thing is that if its bled and topped up with coolant she'll run perfectly for another week or so until the same thing happens again. I took it to the dealer who just bled the cooling system and said it wouldn't happen again. needless to say three days later it did. Obviously the air is getting in very slowly so its gonna be very hard to find, right? where should I start looking?"
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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Always pressure test the cap first, then the cooling system. Of course you would need the correct tools...
If the cap is rated at 1.034 Bar (15lbs.) then I would pump it to 1.172-1.241Bar (17-18lbs.) and then watch the guage for several minutes. If it drops then you grab a light and look for escaping coolant as they should be easy to spot now.
But this does not always reveal more serious issues; sometimes cracked heads and leaking headgaskets wont show unless the engine is good and hot. Remove the cap and warm the engine fully. Ideally you should drive it but you could loose you coolant. Using "BLOCK CHECK" tool insert into the cap opening and begin pumping; if there are any combustion gases present the blue fluid will turn to yellow.
If you plan to become proficient in maintaining your autos I encourage all to invest in these tools I have mentioned. Stant makes a nice coolant system pressure tester. There are several adapters available to service your fleet. Bloc Check is a Mr. Gasket product, but I linked an alternative.
http://www.stant.com/index.cfm?location_id 3 http://store.autotoolexpress.com/colete.html
Best Regards, DieInterim
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