BMW E90 overheated - help with diagnosis?
Discussion
Car is a 2006 325i (E91 estate), with the N52 engine.
Sequence of events was:
-cabin heater seemed to take longer to come on than usual
-driving normally up hill, amber overheating warning illuminates on dash, we pulled over and stopped.
-coolant level was very, very slightly below minimum, the dipstick thingy was maybe 2mm below the top of the reservoir
-let car cool down, drove last half mile home
-inspected for leaks, no obvious signs at all
-scanned for codes, nothing found
-topped up coolant
-ran water pump test sequence. Coolant pumping in squirts, is that correct? Or should the flow be continuous?
-went for 20ish minute drive with Torque App running on dash showing coolant temperature. Highest I recorded was 100 degrees C, with aircon blasting cold, but mostly it was nearer 80. Fan seemed to be switching on and off normally with the car stopped, and heater seems to be working fine again.
So... the heater behaviour and overheat suggests to me that the thermostat was stuck closed. Is that plausible? Does that mean it's on the way out?
Or is it more likely the first signs that the (£££) electric water pump is about to cark it?
Or could a very slightly low coolant level be the sole cause?
Thoughts?
Sequence of events was:
-cabin heater seemed to take longer to come on than usual
-driving normally up hill, amber overheating warning illuminates on dash, we pulled over and stopped.
-coolant level was very, very slightly below minimum, the dipstick thingy was maybe 2mm below the top of the reservoir
-let car cool down, drove last half mile home
-inspected for leaks, no obvious signs at all
-scanned for codes, nothing found
-topped up coolant
-ran water pump test sequence. Coolant pumping in squirts, is that correct? Or should the flow be continuous?
-went for 20ish minute drive with Torque App running on dash showing coolant temperature. Highest I recorded was 100 degrees C, with aircon blasting cold, but mostly it was nearer 80. Fan seemed to be switching on and off normally with the car stopped, and heater seems to be working fine again.
So... the heater behaviour and overheat suggests to me that the thermostat was stuck closed. Is that plausible? Does that mean it's on the way out?
Or is it more likely the first signs that the (£££) electric water pump is about to cark it?
Or could a very slightly low coolant level be the sole cause?
Thoughts?
Edited by MajorMantra on Saturday 7th April 21:08
Well I can't see a very slightly low coolant level causing your problem.
Nor a thermostat - if that fails it just means it stays open so the engine takes longer to warm up, but won't cause overheating.
Sadly I think it may be the death of your electric waterpump - when mine went on my E86 with the N52 engine the temperature went from normal to the end of the gauge (120 degrees IIRC) in less than a mile.
But of course in an E91 you don't get a temperature gauge (I still bought an E91 325i a month ago despite that - the N52 is such a great engine).
Anyway after I got my E86 home in limp-mode I tried the bleed function and it sounded like the pump was working, but just to be sure I went to my local BMW Indy and he found a fault code for the water-pump. The problem with an electric pump is it may only fail intermittently - mechanical ones tend to either work or not work!
So I booked it in and the Indy fitted an OEM pump - but he bought it from BMW so it cost £500 inc VAT! OEM are made by Pierburg I believe and can be bought for around £300.
But if you don't have a code it's not easy to be sure - good luck getting it sorted.
Nor a thermostat - if that fails it just means it stays open so the engine takes longer to warm up, but won't cause overheating.
Sadly I think it may be the death of your electric waterpump - when mine went on my E86 with the N52 engine the temperature went from normal to the end of the gauge (120 degrees IIRC) in less than a mile.
But of course in an E91 you don't get a temperature gauge (I still bought an E91 325i a month ago despite that - the N52 is such a great engine).
Anyway after I got my E86 home in limp-mode I tried the bleed function and it sounded like the pump was working, but just to be sure I went to my local BMW Indy and he found a fault code for the water-pump. The problem with an electric pump is it may only fail intermittently - mechanical ones tend to either work or not work!
So I booked it in and the Indy fitted an OEM pump - but he bought it from BMW so it cost £500 inc VAT!
OEM are made by Pierburg I believe and can be bought for around £300.But if you don't have a code it's not easy to be sure - good luck getting it sorted.
Mr Tidy said:
Well I can't see a very slightly low coolant level causing your problem.
Nor a thermostat - if that fails it just means it stays open so the engine takes longer to warm up, but won't cause overheating.
Sadly I think it may be the death of your electric waterpump - when mine went on my E86 with the N52 engine the temperature went from normal to the end of the gauge (120 degrees IIRC) in less than a mile.
But of course in an E91 you don't get a temperature gauge (I still bought an E91 325i a month ago despite that - the N52 is such a great engine).
Anyway after I got my E86 home in limp-mode I tried the bleed function and it sounded like the pump was working, but just to be sure I went to my local BMW Indy and he found a fault code for the water-pump. The problem with an electric pump is it may only fail intermittently - mechanical ones tend to either work or not work!
So I booked it in and the Indy fitted an OEM pump - but he bought it from BMW so it cost £500 inc VAT! OEM are made by Pierburg I believe and can be bought for around £300.
But if you don't have a code it's not easy to be sure - good luck getting it sorted.
Food for thought, thank you.Nor a thermostat - if that fails it just means it stays open so the engine takes longer to warm up, but won't cause overheating.
Sadly I think it may be the death of your electric waterpump - when mine went on my E86 with the N52 engine the temperature went from normal to the end of the gauge (120 degrees IIRC) in less than a mile.
But of course in an E91 you don't get a temperature gauge (I still bought an E91 325i a month ago despite that - the N52 is such a great engine).
Anyway after I got my E86 home in limp-mode I tried the bleed function and it sounded like the pump was working, but just to be sure I went to my local BMW Indy and he found a fault code for the water-pump. The problem with an electric pump is it may only fail intermittently - mechanical ones tend to either work or not work!
So I booked it in and the Indy fitted an OEM pump - but he bought it from BMW so it cost £500 inc VAT!
OEM are made by Pierburg I believe and can be bought for around £300.But if you don't have a code it's not easy to be sure - good luck getting it sorted.
I thought the same about the thermostat but this is what my Haynes manual says:
Given that, isn't it plausible that the thermostat was stuck closed (i.e. in its initial state), which would mean no cooling from the radiator? (And also no heat through the blowers if I'm understanding the layout correctly.)
Having said that, if I need to change the thermostat it probably makes sense to do the pump at the same time.
Edited by MajorMantra on Sunday 8th April 11:26
I had similar with a friends E91 320i Estate N43 engine.
Low coolant warning and low power mode. He topped it up and rang me for help.
Did the bleed/electric pump test procedure and the water was a constant stream so ruled that out.
On the face of it everything seemed fine, no overheating, nice hot air from the heater, the rad fan cutting in and out etc.
Upon very close inspection, something had gone through and broken the lower bumper grille and t
tted the lower part of the rad causing a very small split. Was only apparent with the engine hot and presented as steam coming off the rad, couldn't see the split so only a tiny leak but over time dropped the levels enough to cause a problem.
Fitting a new rad this week and will be doing a sniff test in case it's borked the head gasket.
Low coolant warning and low power mode. He topped it up and rang me for help.
Did the bleed/electric pump test procedure and the water was a constant stream so ruled that out.
On the face of it everything seemed fine, no overheating, nice hot air from the heater, the rad fan cutting in and out etc.
Upon very close inspection, something had gone through and broken the lower bumper grille and t
tted the lower part of the rad causing a very small split. Was only apparent with the engine hot and presented as steam coming off the rad, couldn't see the split so only a tiny leak but over time dropped the levels enough to cause a problem. Fitting a new rad this week and will be doing a sniff test in case it's borked the head gasket.
Hi,
It's very unlikely to be the water pump. I had same issue with my car (not a Bimmer though) and below is what I did and it sorted out the issue:
1. Faulty thermostat - check and replace
2. Coolant intake line to heater core was blocked with air - unclamp both, intake and outlet hoses and feed tap water with a garden hose (with low pressure) and wait till outlet hose gets clear water. Then clamp back the outlet hose and then feed again till you see clear water comes out through the metal pipe where you unclamped the inlet hose from. Once you've got clear water coming out then clamp that hose back again. Then feed water through coolant reservoir tank and then undo the radiator drain plug. Give it a good feed/drain to get rid of all air bubbles.
3. Let the engine run for few mins, then feed water again through the reservoir tank.
I hope this procedure will solve your issue.
Good luck
It's very unlikely to be the water pump. I had same issue with my car (not a Bimmer though) and below is what I did and it sorted out the issue:
1. Faulty thermostat - check and replace
2. Coolant intake line to heater core was blocked with air - unclamp both, intake and outlet hoses and feed tap water with a garden hose (with low pressure) and wait till outlet hose gets clear water. Then clamp back the outlet hose and then feed again till you see clear water comes out through the metal pipe where you unclamped the inlet hose from. Once you've got clear water coming out then clamp that hose back again. Then feed water through coolant reservoir tank and then undo the radiator drain plug. Give it a good feed/drain to get rid of all air bubbles.
3. Let the engine run for few mins, then feed water again through the reservoir tank.
I hope this procedure will solve your issue.
Good luck
Edited by zakmuh on Thursday 12th April 12:32
zakmuh said:
Hi,
It's very unlikely to be the water pump. I had same issue with my car (not a Bimmer though) and below is what I did and it sorted out the issue:
1. Faulty thermostat - check and replace
2. Coolant intake line to heater core was blocked with air - unclamp both, intake and outlet hoses and feed tap water with a garden hose (with low pressure) and wait till outlet hose gets clear water. Then clamp back the outlet hose and then feed again till you see clear water comes out through the metal pipe where you unclamped the inlet hose from. Once you've got clear water coming out then clamp that hose back again. Then feed water through coolant reservoir tank and then undo the radiator drain plug. Give it a good feed/drain to get rid of all air bubbles.
3. Let the engine run for few mins, then feed water again through the reservoir tank.
I hope this procedure will solve your issue.
Good luck
Thanks but the water pumps giving up is a known issue on these cars, I don't think it's particularly unlikely. Also, the heater started working again almost immediately so it's definitely not air-locked now.It's very unlikely to be the water pump. I had same issue with my car (not a Bimmer though) and below is what I did and it sorted out the issue:
1. Faulty thermostat - check and replace
2. Coolant intake line to heater core was blocked with air - unclamp both, intake and outlet hoses and feed tap water with a garden hose (with low pressure) and wait till outlet hose gets clear water. Then clamp back the outlet hose and then feed again till you see clear water comes out through the metal pipe where you unclamped the inlet hose from. Once you've got clear water coming out then clamp that hose back again. Then feed water through coolant reservoir tank and then undo the radiator drain plug. Give it a good feed/drain to get rid of all air bubbles.
3. Let the engine run for few mins, then feed water again through the reservoir tank.
I hope this procedure will solve your issue.
Good luck
Edited by zakmuh on Thursday 12th April 12:32
I'm going to change the pump and thermostat in any case, and in doing so will be replacing the coolant and purging any air.
As it turns out, one of the wires to the pump was badly frayed, so the pump may not have been faulty. As I was already in there and suspect the parts were original, I replaced both pump and thermostat anyway, and repaired the broken wire.
The bleed procedure sounded much more vigorous post repair, and the car appears to be driving fine although I haven't been on a longer journey as yet...
The bleed procedure sounded much more vigorous post repair, and the car appears to be driving fine although I haven't been on a longer journey as yet...
MajorMantra said:
As it turns out, one of the wires to the pump was badly frayed, so the pump may not have been faulty. As I was already in there and suspect the parts were original, I replaced both pump and thermostat anyway, and repaired the broken wire.
The bleed procedure sounded much more vigorous post repair, and the car appears to be driving fine although I haven't been on a longer journey as yet...
As it turns out the 320i I got involved with needed more than the rad. It all seemed fine and was, for about 100 miles when it got too hot and pumped coolant out past the cap.The bleed procedure sounded much more vigorous post repair, and the car appears to be driving fine although I haven't been on a longer journey as yet...
All the signs were that the coolant wasn't circulating, there was nothing else apparent. So fitted a new, well, used, electric pump and thermostat and like yours, the bleed procedure did seem better.
As of now, all seems fine.
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