Discussion
So I have an issue with my e39 528 overheating.
Took it to a garage they couldn't find fault with it, so flushed the system and all appeared to be fine.
So roll on 1.5k miles later, the heater is not working properly, its taking ages to come on and when it does one minute its hot the next not...
And it seems the temp guage is wandering again, not got into red yet but still moving up and around that half, which is never does when its working properly..
But the heating thing might be a giveaway to someone...
anything I can try, perhaps its an airlock, I could wait for it to get to tempreture and use the bleed valve?
Took it to a garage they couldn't find fault with it, so flushed the system and all appeared to be fine.
So roll on 1.5k miles later, the heater is not working properly, its taking ages to come on and when it does one minute its hot the next not...
And it seems the temp guage is wandering again, not got into red yet but still moving up and around that half, which is never does when its working properly..
But the heating thing might be a giveaway to someone...
anything I can try, perhaps its an airlock, I could wait for it to get to tempreture and use the bleed valve?
I would suggest, like Dave, either an airlock or, if the needle is wandering, the thermostat/water pump/both has gone.
If you've not had remedial work done on the cooling system prior to this happening you've got to wonder how an airlock has developed......unless you have a leak and the coolant had dropped a lot. BMW temp gauges should be rock steady on these cars once up to temp.
Either way, get it looked at, you don't want to cook the engine.
Tried a sniffer test?
If you've not had remedial work done on the cooling system prior to this happening you've got to wonder how an airlock has developed......unless you have a leak and the coolant had dropped a lot. BMW temp gauges should be rock steady on these cars once up to temp.
Either way, get it looked at, you don't want to cook the engine.
Tried a sniffer test?
Edited by Shropshiremike on Friday 15th January 14:34
The cooling system in the E39 is rubbish. Whatever the problem is if you haven't already replaced the entire cooling system (about£400 fitted) then its worth doing it, my radiator went in my 528 and I was lucky not to cook the engine as I caught it before it managed to overheat. Don't wait for it to break is my advice, most of them do and not everyone is lucky to catch it before it causes major damage.
It could be a failing viscous fan, they can make the car start to overheat in traffic etc, or maybe it is a dodgy heater matrix valve, changing the flow, and jumping the temp around, and also not allowing the car to be un-airlocked by having a section of the system cut off.
To avoid airlocks, fill it real slow, squeeze/pump the hoses with your hands periodically too. make sure the ignition is in the run postion with the heaters set on full hot to have the matrix valve fully open.
Run the car with the cap off for a while too, and rev the engine a bit whilst under there if you can to get the pump pumping coolant about. As long as the rads haven't changed too much in design, you should see a little overflow jet just under the rad cap spraying across.
There is a bleed screw next to the rad cap you can slacken off a bit whilst filling, but i've managed to un-airlock cars before without touching it.
Keep an eye out for overflowing when it gets up to temp, that is often a sign of either a rad cap not screwed down enough or an air pocket inside.
let it cool and pump those hoses again, and you might get a gurgle, and see the level drop down as an air pocket works it's way out.
Some general bmw rules of thumb with cooling are-
overheating when sitting/in traffic is the viscous fan
temp dropping below the middle or taking a while to reach the middle is a 'stat stuck open.
temp going above and below the middle could be a few things, low/leaking coolant is one.
stats rarely stick shut, but it can happen, M3's tend to do this, but the regular engines don't very often.
coolant leaking from the bottom corner of the rad is often down to the rad cap, it gets past the threads, runs down the plastics of the rad behind the expansion bottle, and only appears at the bottom corner, hiding the fact the leak is at the top, a few times now i've found people can tighten the cap by twisting alone which makes it bind before actually sealing, giving the appearance it's tight, but that isn't the case. lean down on top of the cap when twisting to push the centre valve bit into the rad neck.
finally, keep an eye on the bottom few bars of the rad, the middle are surrounded so have equal pressure, but the bottom ones can balloon out and crack along their length, making the last 4-5 bars into a big smiley face which leaks.
To avoid airlocks, fill it real slow, squeeze/pump the hoses with your hands periodically too. make sure the ignition is in the run postion with the heaters set on full hot to have the matrix valve fully open.
Run the car with the cap off for a while too, and rev the engine a bit whilst under there if you can to get the pump pumping coolant about. As long as the rads haven't changed too much in design, you should see a little overflow jet just under the rad cap spraying across.
There is a bleed screw next to the rad cap you can slacken off a bit whilst filling, but i've managed to un-airlock cars before without touching it.
Keep an eye out for overflowing when it gets up to temp, that is often a sign of either a rad cap not screwed down enough or an air pocket inside.
let it cool and pump those hoses again, and you might get a gurgle, and see the level drop down as an air pocket works it's way out.
Some general bmw rules of thumb with cooling are-
overheating when sitting/in traffic is the viscous fan
temp dropping below the middle or taking a while to reach the middle is a 'stat stuck open.
temp going above and below the middle could be a few things, low/leaking coolant is one.
stats rarely stick shut, but it can happen, M3's tend to do this, but the regular engines don't very often.
coolant leaking from the bottom corner of the rad is often down to the rad cap, it gets past the threads, runs down the plastics of the rad behind the expansion bottle, and only appears at the bottom corner, hiding the fact the leak is at the top, a few times now i've found people can tighten the cap by twisting alone which makes it bind before actually sealing, giving the appearance it's tight, but that isn't the case. lean down on top of the cap when twisting to push the centre valve bit into the rad neck.
finally, keep an eye on the bottom few bars of the rad, the middle are surrounded so have equal pressure, but the bottom ones can balloon out and crack along their length, making the last 4-5 bars into a big smiley face which leaks.
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