Confirmation of diagnostics

[Ianmc]

Think I need a new thermostat in the 1.9 M44.

Symptoms are:
1. Very slow to warm up and water temperature only reaches just above blue mark on dial.
2. Only gets to normal (mid way) on the dial when run for 15 minutes or so, then sat in slow moving traffic or turn engine off and restart shortly afterwards. Otherwise dial stays just above the blue mark.
3. Drops to just above blue when on the move again at national speed limit type speeds, having reached centre (as 2).

Fairly sure that 1 and 2 indicate thermostat issue, but don't understand the logic of point 3. If the thermostat is stuck open (if closed would overheat), how would this happen? Undertook a 150 mile round trip today and issue remained constant as above.

Any experience of this would be appreciated.

Thanks, Ian

 

[colb]

Sounds like its failed in the open position so takes an age to get any heat into the water, you would notice it rise if in traffic and at a stand as there would be little airflow through the radiator to cool the water. On the move the airflow through the radiator will drop the temperature again, that's what you are seeing on the guage.
If the thermostat is working as it should you should see the guage needle sit rock steady at 12 o'clock or thereabouts. Thermostat is relatively cheap to replace, swap it out for a new one and report back.

 

[Brian H]

Does sound like a bust thermostat, I would not be surprised if the car is running rich and at a reduced MPG as well.

 

[Zeti]

I had exactly the same problem; I thought it stucked open , but it was just too old! After the first opening , it was never closing again until the engine was completely cold.
We were lucky as the alternative of stuck closed is a disaster for any engine , especially for M44.
Replace it.
Dan

 

[Mnbrennan]

Same problem as mine, new thermostat sorted it ian

 

[Ianmc]

Thanks very much guys, will replace the thermostat next week.

 

[Ianmc]

Changed the thermostat today (Sunday), problem solved. Easy job, 4 bolts and two jubilee clips with sufficient easy access.

Just for interest, part came from Eurocarparts (£28 collected this morning). Priced up a BMW part at £86 plus £12 delivery. The new part seemed OK quality (time will tell), the original BMW part had lasted for 20 years though.

 

[Mnbrennan]

Nice one Ian, good job

 

[Faheem]

@Ianmc did the thermostat in two M44s, symptoms were the same as what you have described. I bought from ECP too. I wouldn't expect it to last as long as the OE does though.

My dad had an E36 with the M43 engine and when the thermostat was replaced we bought the replacement from ECP- it only lasted 5 years before failing again!