318i M40 running temperature oddity

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jimbom30cab
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Post Sun Dec 22, 2013 5:26 pm

The car was running cold, never warmed up to the 12 oclock position and took ages to get warm.

So, I the thermostat was changed (CP4L jobbie), flushed the coolant and topped up with new coolant/water mix with a good bleed.

Now it's running too hot ! When up to temp it settles half way between the 12 o'clock and 1 o'clock position and creeps towards the 1 o'clock line when idling. Never goes past this position.

Ideally I guess it should be steady at 12.

I wonder if my new stat is not operating at the right temp. ??
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Post Sun Dec 22, 2013 5:29 pm

still got air in the system?
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Brianmoooore
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Post Sun Dec 22, 2013 5:30 pm

jimbom30cab wrote:
I wonder if my new stat is not operating at the right temp. ??
What temp. is stamped into it? Failing that, what does it say on the box?
jimbom30cab
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Post Sun Dec 22, 2013 5:36 pm

The old one said 88 degrees, the new one is one of these

http://spareto.com/products/th5111-dot- ... at-coolant

which is also 88 degrees.....

Shall I give it another bleed, I did bleed it really well and the heater is tres hot !!

The fan could be a bit old, do you think a new viscous coupling would help ?
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Post Sun Dec 22, 2013 5:43 pm

I Was going to say Viscious Jim, Whats it like when your driving? Does it overheat? Is it only at Idle?
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jimbom30cab
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Post Sun Dec 22, 2013 5:57 pm

It always stays the same about half way between the 12 and 1. Kinda opposite to the m20 which always stayed just below. Thanks for the radiator cowling mate but it made no difference, cheers anyway
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Brianmoooore
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Post Sun Dec 22, 2013 6:00 pm

Temperature should increase very slightly at idle, until the 'hot' water gets down to the middle of the rad. and switches the viscous 'on', but only by a tiny amount. If it runs significantly cooler in normal driving than when idling, then the viscous is probably weak.
Did you actually check what was on the 'stat before you fitted it. Assume nothing.
jimbom30cab
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Post Sun Dec 22, 2013 6:17 pm

No i didn't fit it Brian, i'll check its bleed and change the stat if it is
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Billwill
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Post Mon Dec 23, 2013 9:49 am

The M40 is supposed to have the 88 deg C thermostat as apposed to the 80 deg C stat that the 6 pots use.

To bleed the M40 properly you need to raise the front a bit, on a slope or on jacks.

Then bleed the air out of the metal screw on the stat input and then bleed it via the large black plastic screw on top of the plastic expansion tank....this while hot.

Allow it to cool down overnight...top up the expansion tank to the cold mark and repeat the procedure.

You sure you fitted the new thermostat the right way around? :wink: