Radiator leak....help please (especially Shipkiller :o) )

bjorno

Member
Barrow in Furness
I know a couple of people have had and fixed leaks in the coolent system and from Shipkillers write up am pretty confident I could fix my leak if I could find the bloody thing!

My z is loosing coolant, but only seems to do so on long motorway journeys, I've been keeping my eye on the tank levels for a while now and in normal daily driving (couple of miles to work, pottering round the shops and jaunts up into the lake district) it doen't seem to lose any water at all, but after a good run on the motorway (3-4 hours) the level drops. I've had a good look round and can't find any obvious leaks, have the car booked in for an MOT at the stealer next week (£27 bargain) and whilst its in they're going to do a pressure test to see where the leak, will cost £87 for the diagnosis, so this got me thinking..........

I've got access to pressure test gear at work and wondered if I could do the check myself and save a bit of dosh. I assume that the garage will put a test fitting onto the coolant tank filler cap and pump the system up with a tangye pump? couple of questions..

1. is there any reason why this should definately not be done, ie will i ruin something?
2. What pressure does the cooling system get up to during normal healthy running. I assume that the fact the problem only seems to occur on long motorway runs must be due to the system being at its working temperature and pressure for a prolonged period. The temp gauage has never risen above the normal stright up position.
 
Some time ago I had a car that would only leak when up to a certain temperature. So the only way to find the leak was to leave the car running untill it got up to temp then look under the car to see where the leak was coming from. Turned out to be the water pump seals.

Try what I did and leave it running untill you can spot the leak.
 
The first thing I would check is your water pump and thermostat. Normally the water pump impeller goes out but the shaft seal can go also. It is a known issue.
http://www.realoem.com/bmw/showparts.do?model=BT33&mospid=47798&btnr=11_2180&hg=11&fg=35
http://www.realoem.com/bmw/showparts.do?model=BT33&mospid=47798&btnr=11_3421&hg=11&fg=35


The next known issue is the coolant expansion tank.
http://www.realoem.com/bmw/showparts.do?model=BT33&mospid=47798&btnr=17_0141&hg=17&fg=05
http://www.realoem.com/bmw/showparts.do?model=BT33&mospid=47798&btnr=17_0143&hg=17&fg=05

And lastly on each end of the coolant hoses (both of them) is an O-Ring.
http://www.realoem.com/bmw/showparts.do?model=BT33&mospid=47798&btnr=17_0249&hg=17&fg=05

Coolant hoses are wear items in my opinion. I replaced my upper hose a couple of months ago because of a O-ring leak.

I could see a small amount of coolant below the engine but never see it leak. I could also start to see the aluminum engine pieces above the water pump starting to corrode. I assume it was from the steam. That pointed me to the right area.
 
I recently fixed a leak on my lower radiator hose by following Shipkillers instructions which were very thorough. Coolant leaks are notoriously hard to pin down cause like have been said sometimes they leak at diff temps. For instance here in Canada sometimes extreme cold will induce a leak that is not present in the summer. But that aside I suggest that you follow Shipkillers instructions at least to the point of removing the fan, which will give you way better access to view couplings etc. You may be able to pin down the leak and determine if you can fix it yourself. This is what I did and it turned out to be the O ring on the temperature sender. I had thought the hose itself was the culprit before having a closer look. Turned out to be a free fix, Thanx again Ship
 
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