Another e39 M5 question...cooling system
Discussion
Noticed there's been a few lately so here's another.
Had the water pump and thermostat done recently and since having the coolant changed I've had what is either a slight leak or a slight overfill.
I'm starting so suspect a slight overfill as coolant has been coming out of the pressure cap despite it being renewed. After a drive when everything's up to temperature if I remove the pressure cap (releasing the pressure) coolant starts coming out of the right hand side of the radiator (as looking at the car). Is this where the bleed screw is located by any chance?
The thing is, the coolant level is on the mark. That being said, when I had the cooling system overhauled on my 330Ci I had to have the level just below/on the minimum as coolant kept escaping from the (also new) pressure cap if it was any higher.
I think I might extract some coolant and see if it behaves in the meantime.
Had the water pump and thermostat done recently and since having the coolant changed I've had what is either a slight leak or a slight overfill.
I'm starting so suspect a slight overfill as coolant has been coming out of the pressure cap despite it being renewed. After a drive when everything's up to temperature if I remove the pressure cap (releasing the pressure) coolant starts coming out of the right hand side of the radiator (as looking at the car). Is this where the bleed screw is located by any chance?
The thing is, the coolant level is on the mark. That being said, when I had the cooling system overhauled on my 330Ci I had to have the level just below/on the minimum as coolant kept escaping from the (also new) pressure cap if it was any higher.
I think I might extract some coolant and see if it behaves in the meantime.
If the car was overfilled, it should only leak once, and only as it's heating up.
As the coolant expands when the temperature rises, it fills the header tank. If this is initially overfull it'll push the excess from the tank via the vent/drain.
If you get the car stinking hot, and shut down fast, the heat soak effect may actually cause further expansion before cooling contracts the coolant, and the system draws back from the header tank, emptying it.
A full cycle should force any excess out in one go, assuming that it's not created a slow draining pool on top of the engine undertray, which could be draining from a different point to the filling.
The only bit of info I can add is that having changed the stat on mine, I can suggest keeping an eye on the 3 small aluminium pipes behind the thermostat housing in the centre of the V just under the braided hose feeding the vanos units. Each of the 3 pipes has an O ring on the end which is VERY easy to damage when installing a new thermostat.
Good luck!
As the coolant expands when the temperature rises, it fills the header tank. If this is initially overfull it'll push the excess from the tank via the vent/drain.
If you get the car stinking hot, and shut down fast, the heat soak effect may actually cause further expansion before cooling contracts the coolant, and the system draws back from the header tank, emptying it.
A full cycle should force any excess out in one go, assuming that it's not created a slow draining pool on top of the engine undertray, which could be draining from a different point to the filling.
The only bit of info I can add is that having changed the stat on mine, I can suggest keeping an eye on the 3 small aluminium pipes behind the thermostat housing in the centre of the V just under the braided hose feeding the vanos units. Each of the 3 pipes has an O ring on the end which is VERY easy to damage when installing a new thermostat.
Good luck!
More of an issue here. After it being fine for a while I noticed at the weekend just there that the coolant level was down by about 5cm on the expansion tank. Noticed some pooling on the undertray below the radiator area so I topped it up to the level and would see how it behaved (or not).
When the coolant is at the level mark when cold and you unscrew the cap when hot will it spew from the overflow hose connected to the cap? I've always been able to remove the cap when hot and it rises but only to take up the expected remaining volume in the expansion tank. That's twice now after coming back from work that loosening the cap causes coolant to absolutely piss out the overflow hose, once all the pressure has released the coolant is right up to the top of the expansion tank- despite the fact that there has to be less coolant in the system than the previous day.
There was also an intermittent hissing sound coming from somewhere around the engine, like drops of liquid landing on hot metal but I couldn't see anything leaking from anywhere but around the front (radiator area).
Ugh. Shagged head gasket allowing the cooling system to over-pressurise?
When the coolant is at the level mark when cold and you unscrew the cap when hot will it spew from the overflow hose connected to the cap? I've always been able to remove the cap when hot and it rises but only to take up the expected remaining volume in the expansion tank. That's twice now after coming back from work that loosening the cap causes coolant to absolutely piss out the overflow hose, once all the pressure has released the coolant is right up to the top of the expansion tank- despite the fact that there has to be less coolant in the system than the previous day.
There was also an intermittent hissing sound coming from somewhere around the engine, like drops of liquid landing on hot metal but I couldn't see anything leaking from anywhere but around the front (radiator area).
Ugh. Shagged head gasket allowing the cooling system to over-pressurise?
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