Expansion Tank Problem? Leaking

[av8r]

I have been trying to chase down a coolant leak problem and noticed that there is a drip coming down what appears to be a plastic flange under the expansion tank. Could the tank be cracked? Is there an easy way to check this? Could this be the reason that the coolant level light comes on when the engine is stopped and then reappears only to disappear when you start driving. Any help would be appreciated.
Chris
95 530i, 1975 C-172 M

[Espen]

I have the same problem, a small drip from the expansiontank... I just bought this car and havent had time to check this out yet.

Let me know if you find it out.

[Dave M]

Try a search if you haven't. The M50 rads are known to leak at the bottom end of the expansion tank. If you can get your hands on a pressure tester (or bring it to your indy), try checking it under pressure while cold.

Been a while, but I recall aan O-ring in the M50 rad that like to leak. It maybe a matter ofreplacing the expansion tank only, not a tough job.

Dave M

[av8r]

thanks for the reply dave. it is an m60 with the expansion tank mounted on the firewall. i have searched and searched and found alot about overheating but nothing on how to troubleshoot a leak like this.
I have also read about the lower radiator hose needing to be warm. Well the top hose is hot, the bottom is cold but when i run my hand along the face of the radiator it is consistant in its heat distribution.
Chris

[Alexlind123]

My expansion tank is mounted to the firewall, like yours. It has had a leak for awhile (was going to order one the other day from bmw but they were out of the other part i needed and shipping is free over $50) but it doesnt leak once its down past a certain level. Its really odd though, the cooling system works flawlessly nevertheless.

[av8r]

same here. i believe the smell i get is from the fluid dripping onto the bell housing. But the cooling system is running one tick over center. i have a new fan clutch coming today and will install it over the weekend. i was thinking of making one without the clutch(i own a machine shop) because they seem to be a weak link in this system. i definately do not want to run when anything is leaking.
Chris

[calmloki]

My '83 533i expansion tank - mounted away from the radiator - split just above the seam joining the upper and lower parts together. Tricky to spot until it was filled above the split and I checked while it was hot and under pressure. Wiping the wet spot with a rag and seeing where it got wet first told the tale. Patching didn't fix it, replacing did.
Tom Walrod

[mystical_wings]

same here. i believe the smell i get is from the fluid dripping onto the bell housing. But the cooling system is running one tick over center. i have a new fan clutch coming today and will install it over the weekend. i was thinking of making one without the clutch(i own a machine shop) because they seem to be a weak link in this system. i definately do not want to run when anything is leaking.
Chris

DO NOT REMOVE CLUTCH.I did that before on a 300zx and paid the price.The clutch is there so the fan isnt always ,if ever spinning top speed .removing the clutch will strain your engine and severely lessen engine power.Trust me its not a good Idea.

[av8r]

got a new tank from the stealer. will install and advise.
chris
95 530i, 1975 C172m

[Karl]

Your radiator is different than mine (525i) In mine the expansion tank is built into the end of the radiator. It developed a leak in the gasket between the expansion tank and the radiator end.