E39 running cold
Discussion
Hi guys,
Last week I noticed the temp guage on my 530i was dipping below the half way mark. I plugged the laptop in and found that the car was idling at about 83c and dipping to low 70's high 60's when driving. My understanding is that the guage reads dead centre if the temp is between 75c and 116c, hence it dipping towards cold because of the lower temp reading.
Picked up a Wahler thermostat from ECP and its now been changed. However...
...the problem remains. Infact on the way home the problem seemed to have become even more pronounced. It's losely based on road speed but sometimes it'll dip into cold in traffic, it seems to cycle between mid 60's and 83ish.
Up until last week it would sit at between 90c and 93c whether I was crawling through traffic in 37c heat or sitting at 70mph when it was -3 outside.
I'm a bit at a loss now. Everything points to thermostat but... it now has a new thermostat. Where do I go from here? There are no fault codes showing.
Ta!
Last week I noticed the temp guage on my 530i was dipping below the half way mark. I plugged the laptop in and found that the car was idling at about 83c and dipping to low 70's high 60's when driving. My understanding is that the guage reads dead centre if the temp is between 75c and 116c, hence it dipping towards cold because of the lower temp reading.
Picked up a Wahler thermostat from ECP and its now been changed. However...
...the problem remains. Infact on the way home the problem seemed to have become even more pronounced. It's losely based on road speed but sometimes it'll dip into cold in traffic, it seems to cycle between mid 60's and 83ish.
Up until last week it would sit at between 90c and 93c whether I was crawling through traffic in 37c heat or sitting at 70mph when it was -3 outside.
I'm a bit at a loss now. Everything points to thermostat but... it now has a new thermostat. Where do I go from here? There are no fault codes showing.
Ta!
Fox,
Have you tried testing the thermostat? It's really simple:
Get a saucepan of water on the hob, stick the thermostat in it, and gradually heat it up while measuring the temperature. You should see it open and at what temperature. I would test the one you have removed to see if it is within spec.
I wouldn't rule out a brand new thermostat not functioning correctly.
It sounds very strange, and aside from some sort of fault in the climate system adjusting the heater valve randomly (which you would probably know about as a non-functioning climate system), I would say it is the fault of the water temp sensor reading incorrectly.
Have you tried testing the thermostat? It's really simple:
Get a saucepan of water on the hob, stick the thermostat in it, and gradually heat it up while measuring the temperature. You should see it open and at what temperature. I would test the one you have removed to see if it is within spec.
I wouldn't rule out a brand new thermostat not functioning correctly.
It sounds very strange, and aside from some sort of fault in the climate system adjusting the heater valve randomly (which you would probably know about as a non-functioning climate system), I would say it is the fault of the water temp sensor reading incorrectly.
Fairly sure Wahler were OEM supplier at least at one point during production of the M54 engine.
I've now worked out whats happening I've just no idea why. Basically, sometimes the Thermostat opens at 70ish rather than the 95+ it's supposed to open at. Once this happens, obviously, the engine then runs cool. Weirdly if I shut the engine off and then restart it, it works fine.
Thinking its some sort of electrical issue - something is sending a signal to the MAP controlled thermostat to allow it to open early. But what and why?
I've now worked out whats happening I've just no idea why. Basically, sometimes the Thermostat opens at 70ish rather than the 95+ it's supposed to open at. Once this happens, obviously, the engine then runs cool. Weirdly if I shut the engine off and then restart it, it works fine.
Thinking its some sort of electrical issue - something is sending a signal to the MAP controlled thermostat to allow it to open early. But what and why?
It is a MAP controlled thermostat - it has a wax core but it also has a heating element controlled by the ECU which artificially lowers the point at which the thermostat operates if the ECU deems it neccesary.
The idea being they can run hotter at lower load levels for emissions and economy reasons, but the ECU can intervene to reduce the operating temp under heavier load.
Which is great when it works....
The idea being they can run hotter at lower load levels for emissions and economy reasons, but the ECU can intervene to reduce the operating temp under heavier load.
Which is great when it works....
roofer said:
Try bridging the temp sensor on the bottom hose...
I replaced that a few years back - when that failed it went open circuit and triggered the aux fan to run all the time. I think it's working ok as I've been using its readings to work out when the thermostat is opening and closing. But if you still think its worth a go...?Gassing Station | BMW General | Top of Page | What's New | My Stuff