Losing coolant with no visible leaks.

[Siani 0]

My '91 525i has been running a bit rough and it is losing coolant, but there don't seem to be any leaks. The oil appears ok with no milkyness, or residue. The coolant is only disappearing after running, there was no loss when it had been parked up for a week.

The temperature remains ok. It is chewing through fuel, and pinks and almost back-fires occasionally with acceleration.

I had it tuned not long ago, for similar symptoms, and they checked the hoses as I had not long had the radiator replaced. At that time they said the spark plugs were pretty dirty.

And that's about all I know about it.

Any suggestions?

And some recommendations for BMW servicing/repairs in the Chch/Ashburton area would be great too.

Thanks.

[cainchapman 0]

The heater pump (LHS near firewall) was leaking in the 540. Changed it and the problem was gone.

Cheap enough to buy a new one and easy for a non-mechanical person like me to replace.

DCH Motorsport in Sockburn or Graeme Clyde's, GAC something, off memory.

[SpidersWeb 0]

Sorry I can't help too much, but I will say that all 3 of my BMWs lose coolant.

325i M50 chews threw coolant, no leaks etc, so I suspect its the heater pump/pipework as above.

535i SE M30 I haven't owned long enough to find where it going, probably heater pump/pipework, nothing visiable once again.

535i M30 auto is at the mechanics at the moment because the water I was losing was being mixed with ATF in the trans cooler (oh *joy*). Water looked the normal green, but trans fluid was milky white which lead to its dimise.

[pureboiracer 0]

check head gasket mate. common to loose coolant through a fried gasket. should be able to pick up in a cylinder leakage test

[Steve K-B 51]

Im dog tired but these things come to mind::

If it is a head gasket, it would explain the pinking with higher compression due to the water leaking in but i would have assumed the computer would compensate for that, also im guessing it would have to be leaking a lot for this to be possable.

Pull your plugs out and see if any one or more are extreamly clean - another sign of water.

Is it steaming out the exhaust at all? - another sign.

Ahh, good luck

[Siani 0]

Thanks for your suggestions.

It takes about 500ml top-up after about 30km travelling (to work and back and a bit of round town)

It only disappears after running, not when parked.

There is some exhaust smoke as it warms up, more white than blue coloured.

I am leaning towards head gasket, with my limited knnowledge, and a bit of googling.

I am going to appropriate my husband's explorer, and book the beemer in for some tests.

Thanks again.

[Siani 0]

If it is the head gasket, how much should I expect to pay for repair?

[pureboiracer 0]

depends on labour prices where you go etc. rule of thumb is the garage will send the head away to get crack tested pressure tested and plained. that will cost you about 200 to 250 plus say 6 hours labour could be around 500 to 700 as a rough estimate.

[Siani 0]

Thanks, that's about what they quoted me.

[Siani 0]

Ok, was a head gasket that was causing the running problems. Replaced and running nicely, but I'm still losing coolant.

Have to top it up a quarter to half a litre or so every couple of days.

[pureboiracer 0]

hmmm ok. so still no external leaks? is the car putting out abit of white smoke?

[parriehunter 0]

Hey my e30 had a problem with it leaking out of the heater matrix in behind the dash.only noticed it with the coolant sittong under the passenger seat and the smell. but i would suspect that if it was that you would be able be the coolant.

[Siani 0]

hmmm ok. so still no external leaks? is the car putting out abit of white smoke?

A little bit of white smoke on acceleration for the first block or so. No leaks under the car; I've got plastic down just in case, but none there. No smell of coolant from the heater.

Had the radiator replaced at the beginning of the year and it maybe is related? A small hole in a hose somewhere perhaps?

[pureboiracer 0]

run the car on your drive or something for 20 to 30 min or so. go have a cuppa while you wait. with some clean plastic underneath. then check for any water on it. also check your oil. undo sump plug just enough to let a few drips out. see if its water or oil or both that drip out. do you know if the garage machined and tested your cylinder head when they replaced the gasket?

[Siani 0]

I asked, and no they didn't.

[pureboiracer 0]

take it back to the garage. ask them to test the headgasket again. i am suspecting that your head warped slightly when you overheated it so the new headgasket blew again almost straight away. the garage should have sent the head away. if the garage says that its the headgasket. complain to them and try and get them to do a propper job free of charge (there work should be under warranty) failing that go somewhere else