Temp troubleshooting

[Henn28]

Changed my coolant level sensor and now the coolant wont get hotter than 99 deg. Can’t imagine how these could be related, but a very BMW-like coincidence at any rate.

Any thought on troubleshooting this? Basically the car warms up, a little slowly perhaps, but gets to 99 degrees and hold it there, rock solid in fact. My experience with the OE 105 tstat (which is in the car) is that the temp will vary say, -10 degrees to +5 degrees from 105c/221F. Current my m62 is hardwired at 99 deg after it warms up. The oil temp is slightly low too…3 or 4 degrees or so.

The radiator outlet temp does vary significantly still under load, so seemingly the tstat is still working at some level. My foxwell indicates that MAP cooling is not active either.

Tstat failing or maybe a heater valve failure? My uneducated thoughts are that the heater valve has failed open, since it is 22 yers old, while the tstat is only 3 years old. Wouldn’t I feel a failed heater valve at the vents thou…hotter air?

I wish it would have gotten stuck at 90 deg so I could see if that triggers an SES light. I have a 90 deg map tstat I want to install, but don’t want to deal with a possible SES light so I’ve been procrastinating. Maybe I’ll pop it in along with a new heater valve.

[80stech]

Maybe this partly is due to you paying more attention after changing the coolant sensor??Heater valve is open by default and should close when you select the lowest temp. Map cooling is only active when the DME wants it for emissions. Otherwise I think if the engine really isn't warming up to where it should be, the thermostat is probably number one suspect.

[Henn28]

Originally Posted by 80stech

Maybe this partly is due to you paying more attention after changing the coolant sensor??Heater valve is open by default and should close when you select the lowest temp. Map cooling is only active when the DME wants it for emissions. Otherwise I think if the engine really isn't warming up to where it should be, the thermostat is probably number one suspect.

Normally I’d say you were correct, that I only noticed it because I just worked on the system. But after my self induced overheat, near catastrophe after the motor swap I actually watch the temps quite often.

Good info on how the valve works, I didn’t realize it was open under normal ops and sending coolant into the heater core. So my failed valve theory doesn’t make sense. T-stat change in order it seems.

[X5chemist]

I've seen mine run from 90-105C. While moving, 90C seems to be its ideal temp with a stock thermostat. I think it would have to way lower than 90C to set a code.

[Henn28]

Drive it home from the airport last night and decided that it took a long time to get up to temp, and once again, never got above 99 deg. Who knows, maybe the tstat has developed a mind of its own, but it’s definitely behaving differently from the last 3 years it’s been in the x5.

So today I popped the 90 deg tstat in and took it for a test drive with the dogs. So far so good. 93 deg what’s where it settled out, plus or minus a couple, regardless of outlet temp. Outlet temp varied from about 110 up to 150 or so in stop and go traffic with the AC on “Max”.

Anyone know at what temp the fan clutch kicks in? I’ll be interested to see how the system performs in the summer.

The Zerex g48 coolant had been in the motor for about 20k and looked a bit dark. I drained it via the lower hose connection at the radiator and got out about 1 gal. Perfect for the tstat job, but with 2 gal left in the system, including the bottom of the radiator, not a good way to do a full drain. The OE tstat, looked like new, for what it’s worth.

No need to take the fan or its housing out for this job, as it turns out. There is plenty of room to work with the intake and boot out. An extension with a universal on it is needed to get 3 of the 4 housing bolts off.

[haigha]

Interesting... I recently flushed the coolant and added the same Zerex G48. On the initial 14 mile test loop, I monitored KTEMP on the OBC hidden menu 7. The highest I saw was 101 C, '04 4.4i N62.

Mine is stock and all original parts in the cooling system. The last flush was at least a decade ago. My mechanic friend, RIP, (BMW master tech) would check the coolant every year and say it was still good.

I got ~1.25 gallons out using my modified radiator flush method. I'll post more on that on my original thread.

[Themoog]

I'm having a new thermostat installed in my m62 next week as mine is running too cold and it's only doing 15mpg..