E39 540 - temperature gauge goes beyond red
Discussion
A disaster of the lower radiator hose coming off my wife's 2000 E39 540 whilst the car was being driven has left the temperature gauge faulty. On switching on the ignition, it goes hard over to the red and stays there, even if the engine has not been started for a day! The full contents of the coolant system was dumped, and i don't know how long the car was driven before she stopped.
I have taken this opportunity to replace the expansion tank, radiator and thermostat. I have now correctly connected the hose, and filled and bled the system.
When i turn the ignition on, the temp gaugue, which is correctly positioned to the left of blue with ignition off, moves to blue with ignition on, but after a couple of seconds shoots hard over past the red.
On running up the engine, the heater correctly blows warm air, the top rad hose gets hot, but the bottom one remains cold.
Is there a temperature sensor, other than the one on the thermostat housing, that i should replace? and would this cure the problem.
Any other ideas, as i am at a loss.
Many thanks
I have taken this opportunity to replace the expansion tank, radiator and thermostat. I have now correctly connected the hose, and filled and bled the system.
When i turn the ignition on, the temp gaugue, which is correctly positioned to the left of blue with ignition off, moves to blue with ignition on, but after a couple of seconds shoots hard over past the red.
On running up the engine, the heater correctly blows warm air, the top rad hose gets hot, but the bottom one remains cold.
Is there a temperature sensor, other than the one on the thermostat housing, that i should replace? and would this cure the problem.
Any other ideas, as i am at a loss.
Many thanks
I can't answer your questions, but do know the temp gauge in the E39 is stabilised so it sits in the middle of its dial over quite a range of temperatures.
My 540i has twice had electrical problems which fooled the temp gauge into shooting over to the far right and staying there, even after a day of sitting still with the engine off. Finally traced the second time to a short circuit where the temp sensor in the top of the radiator had melted (I think that's right, my independent chap found it and I just paid the bill). However, I am certain mine didn't actually overheat, so it's possible there's some residual problem as a result of your dropped coolant.
ETA: are you sure you've bled it correctly? An airlock might be the cause of your gauge starting off in the blue then going to red. Mine went hard into the red as soon as you turned the ignition key, no period of sitting in the blue at all.
My 540i has twice had electrical problems which fooled the temp gauge into shooting over to the far right and staying there, even after a day of sitting still with the engine off. Finally traced the second time to a short circuit where the temp sensor in the top of the radiator had melted (I think that's right, my independent chap found it and I just paid the bill). However, I am certain mine didn't actually overheat, so it's possible there's some residual problem as a result of your dropped coolant.
ETA: are you sure you've bled it correctly? An airlock might be the cause of your gauge starting off in the blue then going to red. Mine went hard into the red as soon as you turned the ignition key, no period of sitting in the blue at all.
Edited by SJobson on Wednesday 17th December 12:21
Thansk for your replies chaps.
Its funny how things never turn out as you expect.
I ruled out the thermostat by fitting a new one.
I ruled out the water pump by watching it pump water out of the space left by the removed thremostat, and previously by checking that the heating was working fine.
One of the temp senders was favourite in my book, but i was prompted on another forum to try the "hard reset". So i disconnected the battery for about 10 minutes, reconnected, and voila! Temperature gauge back to normal.
I have just finished putting everything back together, filled the cooling system with water, and done a test run - all ok, everything runs up to temperature, the fans kick in OK .
So, now to drain the system and refill with correct coolant... fingers crossed
Its funny how things never turn out as you expect.
I ruled out the thermostat by fitting a new one.
I ruled out the water pump by watching it pump water out of the space left by the removed thremostat, and previously by checking that the heating was working fine.
One of the temp senders was favourite in my book, but i was prompted on another forum to try the "hard reset". So i disconnected the battery for about 10 minutes, reconnected, and voila! Temperature gauge back to normal.
I have just finished putting everything back together, filled the cooling system with water, and done a test run - all ok, everything runs up to temperature, the fans kick in OK .
So, now to drain the system and refill with correct coolant... fingers crossed
Edited by Blues on Wednesday 17th December 19:21
Blues said:
I ruled out the water pump by watching it pump water out of the space left by the removed thremostat, and previously by checking that the heating was working fine.
The pump could still have some propeller blades detached so not working fully?I'm not sure on the E39 but the E36's I've owned have an electric heated coil next to the heater matrix so help warm up the air being blown onto the screen on cold mornings so maybe that's why the heater appears to be working fine. Have you checked how hot the pipes get going to and from the rad and matrix?
I can virtually guarantee it's doing it for none of those reasons!
Try disconnecting the battery for 20 minutes and then reconnecting and see if that cures it! I bet it will!
My 540i Touring did EXACTLY that after I did a precautionary water pump change.
Doing the above sorted it out straight-away.
Try disconnecting the battery for 20 minutes and then reconnecting and see if that cures it! I bet it will!
My 540i Touring did EXACTLY that after I did a precautionary water pump change.
Doing the above sorted it out straight-away.
derin100 said:
I can virtually guarantee it's doing it for none of those reasons!
Try disconnecting the battery for 20 minutes and then reconnecting and see if that cures it! I bet it will!
My 540i Touring did EXACTLY that after I did a precautionary water pump change.
Doing the above sorted it out straight-away.
Try disconnecting the battery for 20 minutes and then reconnecting and see if that cures it! I bet it will!
My 540i Touring did EXACTLY that after I did a precautionary water pump change.
Doing the above sorted it out straight-away.
See my post above:
Blues said:
but i was prompted on another forum to try the "hard reset". So i disconnected the battery for about 10 minutes, reconnected, and voila! Temperature gauge back to normal.
Thanks again to all for your interest and replies
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