Overheating & Heater Probems - E34

[pipit]

My 1989 E34 525i (with 125K genuine Km) - a Japanese import - overheated and warped the head. No apparent reason, though a stuck thermostat may have been the culprit. Immediately the shop completed the job, the heaters would not turn off - I was told that one of the solenoids which opens and closes the hot water flow had failed. What's the chance of the system not being bled of air, and causing the problem. (The heater worked fine before the overheating incident.)

What is the difference between BMW coolant and other coolant that makes you recommend ONLY BMW coolant?

[Ross]

Air in the system won't cause the solenoids to fail.
Don't get these guys started on coolant.

[genphreak]

The i6 is a long engine and when looked after won't have head gasket problems. However if later in life it gets overheated, it is very very likely.

The cause of overheating is most commonly

a) Neglect (ie lack of maintenance / incorrect servicing)
b) Thermostat/waterpump failiure
d) a burst or leaky hose/connection
c) Main fan clutch failure, fan switch, resistor, thermostat

It is best to make sure your preventative maintenance is up to scratch on any old car or failures will happen (if its an 6 cylinder). Often they will cause other problems in the process.

Hoses, thermostat, water pump and coolant needs to be looked after in a Bimmer as head gaskets are under a lot of heat and physical stress in such long, hot engines.

We use BMW coolant due to its chemical composition being formulated and tested on the cars themselves. No other coolant seems to make any guarantees and there are bad stories abound. This may be because people use some kind of generic coolant which is not phosophate free, or it might be that they never change it, they just top it up. Some coolants break down when they get old, causing o rencouraging corrosion where normally they cannot and may even sludge up within the system so a full flush of the system is needed every 2 years max.

Your heater valves are sticking. Just given them a tap when opening and closing the thermostat knobs a few times, they might come back to life for you. If not it's an easy replacement. Welcome to the nuthouse, btw! nick