cooling system problem

[pauter123]

ive got a 325 which has an ongoing problem with the cooling system. the water keeps boiling up and coming out of the expantion tank cap, although the engine never over heats it just stays rock steady at 12 o'clock. also the in car heater is as good as usless. has anyone got any ideas.
thanks

[96_323]

Your putting tooooo much water in the system. Theres no overflow tank on your system and when water heats up it expands. With your engine dead cold the water level should only be 2/3 of the way up the expansion tank. Are you replacing the coolant that comes out of the tank with water or coolant? Also how many times has it happened and how much coolant did you have to put in each time it happened?

The temperature issue could be numerous things but if you answer the questions above it should give a clearer indication as to the cause!

[pauter123]

at the moment im just using water due to the amount of times im having to top the system back up. I do about 70 miles a day and normaly after 2 to 3 days the system needs toping back up, it normaly takes around 1 to 1.5 litres. I have tried to fill it to the correct level but it doesnt seem to make much difference yet i have set the level correctly this time.

[96_323]

You have a pretty big leak somewhere in the system.
Is it the original radiator, pipes, pump and thermostat?
Did you say the water is coming out of the cap on the expansion tank?? That cap is a pressure cap and is ment to come off by itself under high pressure.
If you cant see where the water is leaking out then id start by replacing the old rubber pipes(cheapest option) but if it is entirely an original cooling system then it will need to be replaced. BMW are amazing at making cars but unbelivably crap at making cooling system!!

[pauter123]

thanks for the help. it is coming out of the cap for sure if i do a long run then get stuck in traffic i can smell it boiling over and have seen it coming out of the cap. as far as i know its all standard the problem originaly started when i did overfill the system before i realised were the full level mark was, and since then ive had the problem that was about 6 months ago, just only managed to get time to try and fix it, i geuse i will have to start replacing things but if anyone has any other ideas i would be greatfull for the help
thanks

[96_323]

If you did overfill it and it burst through the pressure cap then you need a new cap
Heres one here for 5euro
http://cgi.ebay.ie/BMW-E36-E30-E31-E46- ... 2a01b142b0
I cant promise that will fix all your problems but it will fix the overflowing problem.
You will need to replace the the radiator at least, without looking i could tell you its at least warped!!
Lets us know how you get on after replacing the cap.