Coolant Leak

[sander06]

I've had a very slow leak in the coolant system of my 1992 535i that I've never been able to locate. Yesterday, after stopping, the coolant finally came gushing out at the base of the coolant expansion reservoir during an over-heating event. Is that where excess coolant discharges? It looks like it's been doing it for a while because of the old evaporated coolant residue on the firewall under the reservoir. I also checked in the shop manual, and of course, there is almost nothing about the reservoir noted.

Thanks for the help I hope you can provide.

[BoldUlysses]

Sounds like you have at least one bum hose. Do you know the last time they've been replaced? Based on my experience with the M30, I'd recommend replacing all coolant hoses as a matter of course every couple of years or so. Even if you can't see the break/split, it can still be there. The water pump-to-thermostat housing hose was leaking like a sieve on my old M30; when I removed it, there was no evidence it was compromised.

Excess coolant discharges from the hose just underneath the pressure cap.

-Matt

[bmwwheelman]

My original expansion tank had a crack in the bottom of it where it mounts to the fire wall.. check that first...

[sander06]

Yep, considering that the coolant was pouring out near the bottom of the coolant reservoir, I'm going to make the assumption that I need a new reservoir. The cooling system needs a good drain anyways. The hoses are all new on the engine, although some of the clamps may need to be tightened.

Thank-you very much for your comments.