Coolant leak - The Unofficial BMW M5 Messageboard (m5board.com)

ian hall · 8th September 2002, 23:37

My car is leaking coolant from somewhere at the back of the engine.It is really hard to see where from,water appears on the sound deadening and then runs everywhere!!
I thought it might be the heater matrix,this is usually confirmed by a smell from the heater-which i do not have.The leak did seem to get worse when the heater was on.Is this a coincidence or is there some sort of valve that lets coolant into the heater when it is turned on?
Apart from this the car has been very reliable!

Ian

P.S Car is a 94 3.8

M5 powered · 9th September 2002, 00:21

I can tell you exactly what this is as it happened to me three weeks ago! It's the aux water pump seal (used on startup before the main one kicks in) which has failed. For some stupid reason (only known to BMW) they put a bleed valve on this which tends to fail when the rubber perishes over time. It's located by the matrix and hence why some think this £1000 part has failed. As the water system is under pressure the coolant goes everywhere and makes it difficult to locate.

The cost for the pump is around 60-80 pounds and is a generic 5 series part. Also check all the pipes around that area and look for cracks.

Regards

M5 powered

dronfieldm · 9th September 2002, 12:02

Sounds like the culprit. I had the same problem on my E32 735i some years ago. I did have the inside of the windscreen misting up more often as well.............my M5 has not been affected yet !!!!

All the best