pushing water out of the overflow pipe but not overheating ...

[kastigeer]

Ok let me try get this to make sense ...

Got a 530i that's been progressively getting worse at pushing water out - started needing water once every couple of months and I never thought much of it. A few months ago it started getting worse, and now it's doing it all the time - I get a coolant level warning after almost every journey over 10 miles.

Funny thing is that it doesn't overheat at all - the temp starts at far left and gradually climbs to half way and quite happily stays there.

The water is being pushed out the overflow on the rear resevoir tank and it seems to take a while after the car has stopped to do this (normally). You can almost watch it. Stop the car, wait a few minutes and it starts chucking out water behind the drivers side front wheel.

It seems to be holding pressure ok, as when I release the cap it does hiss and you can feel the pressure. I've tried replacing the cap with no change whatsoever.

I've also watched it with the cap off and it takes a few minutes again (after stopping) and the water starts gushing out the resevoir in bursts, almost like it's vomiting (sorry for the analogy!) - does this for quite a while and the the level drops right down and I have to put in several liters to bring it back up again ...

Can anyone give me any pointers on what the problem could be? blockage? if so can I get any good stuff to put in the water/coolant to try and clear. bleeding? Air pocket??

thanks in advance
Barry

[632 Regal]

no bleeding necessary on the V8 so no air pockets. When you add fluid do you have the car running and the heat on hot/full? Try that, your symptons are an air pocket that expands from heat when circulation is stopped.

[Tiger]

Put a pressure gauge on it... pump it up... if the pressure goes down, you got a leak somewhere... most likely head gasket because it is pushing coolant out... If it is intake gasket, it would drink and consume it.

[632 Regal]

Put a pressure gauge on it... pump it up... if the pressure goes down, you got a leak somewhere... most likely head gasket because it is pushing coolant out... If it is intake gasket, it would drink and consume it.

[winfred]

whats strange is he claims it only does it after he shuts it off.

[Gooch]

I have two clues, one more expensive than the other, both difficult to explain.

I had an Alfa that did that right before the head gasket blew. A pin hole leak in the gasket allowed compression to get into the cooling system until the hole got big enough to finally blow coolant into the cylinder. When the engine was shut down it blew coolant out the radiator cap. My theory was trapped air in the block came from the cylinder and was very hot. Since the coolant wasn't flowing when the car is shut down the trapped air expanded and forced coolant into the radiator and out the cap. A wild ass guess.

My 525 does it now on hot days (> 90 F degrees) only with the AC on. The temp gauge doesn't show any over heating but sometimes when I park the car and come back there's coolant on the ground. It's really strange but I wonder if I have a small gasket leak that only leaks when the engine is running hotter than usual.

I've changed the thermostat and waterpump 3 years ago but still had the problem on hot days with the AC on. This year I changed the fan clutch and haven't had the problem yet. But it hasn't been over 90 since I changed the clutch.

I would first try to change the fan clutch if you haven't yet. If that doesn't help get a compression check.