Cooling System chronic problem

[BigBill62629]

On my 1993 E34 M50 525i

I have had a constant cooling system problem over the last two years. The coolant light would go on intermittantly. I would replace the small amount of coolant and go. Many days and hundreds of miles with no problems then it would repeat.

Then, 3 weeks ago the car overheated about 7 miles from home with all warning lights going. I stopped and waited 20 mins. and used some snow to place on the radiator. I limped home 1 mile at a time.

I replaced the expansion tank (attached to the radiator) and the O-rings. Now, I see coolant leaking at the low end of the junction between the expansion tank and the radiator. I removed and replaced the tank and still have a leak

Where is it coming from?

[Dr. evil]

try and us some RTV to help the seal

[scott 4991]

This happened to me also - I thought I had a head gasket seal leak - my problem turned out to be the radiator cap - as you know, which did not occur to me, the coolant system is under pressure, and you blead the air out. This of course means you will have pressure at the radiator cap all the time, unless it's leaking - but the cap has a valve in it, allowing fluid to excape should to much pressure build up OR, as in my case, if the cap is bad, and it allows fluid to escape, via the over flow hoses (2). My cap would allow water out of the radiator while driving - as I never saw it while the car was parked. 2 weeks ago, I saw water gushing out from under the car, "Great, now what?" the water was coming from the overflow. I looked into this and was told it was the radiator cap, which had never been replaced. I replaced it, problem solved, and now I HEAR a 'pissss' as pressure is released when I undo the cap. A cleaver little system actually as you would not want the radiator itself to blow, or other hoses - the cap release works great.

sc

[Kalevera]

RTV is useful as a temporary patch at best, and typically does more harm than good because people goober it on. Worst case scenario is clogging internal engine coolant passages and cooking the motor, best case is a set of new phantom overheating issues to resolve (a la clogging the return line on late M30s).

Replace plastic cooling system parts. If it's leaking, it's ready to explode. An overheated thermostat should also be replaced. What kind of water pump is in the car and how many miles are on it? The symptoms of loss of coolant and overheating...really don't tell us that much -- need more details.

BMW issued a radiator cap recall years ago. If the car hasn't had the recall performed, take it to the dealer and have them deal with it. Give a dealer the VIN and they can check over the phone. Funny thing about that particular recall is that some suggest it was a ruse to mine customer information after a computer system switch, and that the original caps are fine. Either way, it's a free cap.

[s2 airflow]

I had similar problems with my '92 525 Tourer.My garage changed the heater
matrix to begin with as it was weeping slightly but it continued(130,000m)I got the rad. cap recall;changed the @stat & water pump;bled the system as per BMW staff instructions;(not happy @ this point as I had changed the head gasket on my prev.E28-245,000miles);had info re failing radiators so changed that;Problem now getting out of hand and with 145,000m on the clock & the car not warranting the expense of having major work done by a garage with BMW expertise I did the head gasket myself.Sod's law being what it is,this was in January in an unheated garage,but I'd been like an ostrich not wanting to think of the obvious but awkward problem that BM's seem to have suffered from for years.I used the Bentley Manual from the States as Haynes didnt seem to cover it too well.The head was only just within skimming tolerances but had never been off before.,& when re-assembling ,the new stretch bolts worried me a bit-no torque settings but angles instead.I didnt use special tools but used mainly ordinary ones Anyway I must have done something right as its now 231,000 miles now LPG fuel.a