running temperature

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angoose
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Mon Apr 15, 2019 7:38 pm

Hey all,

Need to pick your brains again.

A little back story. The car was running fine and then the temp gauge started creeping up to 3/4 and stayed there. Then climbed higher so I pulled into the services. I let it cool and topped up with new coolant then set off, not far down the road I had the same problem. Got picked up by recovery guy he suspected head gasket.

Upon getting delivered back to me I started to try and work out if it could be anything else. No leaking hoses etc. So i swapped out the thermostat and so far so good. Been out on a few short drives and go a bit further each time just to see how we get on.

All seems good done a bit of town and country roads and been out for an hour or so but the car doesnt seem to get up to half way on the temp gauge. Running between 1/4 and half. Is this a problem? I havent done a motorway run yet but a little apprehensive to do that just yet.

Many thanks,

Angus
Cloggy Saint
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Mon Apr 15, 2019 7:43 pm

Between 1/4 and 1/2 is the correct position for the temp' gauge
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angoose
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Mon Apr 15, 2019 7:46 pm

Cloggy Saint,

Thanks for getting back to me so quick on this. Glad to hear that. I figured it should be ok but after it over heating been watching the gauge like a hawk.

Thanks again
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BenHar
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Mon Apr 15, 2019 8:00 pm

Cloggy Saint wrote:
Mon Apr 15, 2019 7:43 pm
Between 1/4 and 1/2 is the correct position for the temp' gauge
True for a 6 cylinder engine which should have an 82 degree 'stat.

If it's a 4 cylinder it should have an 88 degree stat and run at the halfway mark.

Ben
jmc330i
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Mon Apr 15, 2019 8:09 pm

As above, all my 6 pots have run at just over 1/4, my 4 pots have all run at bang on 1/2.
James
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angoose
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Mon Apr 15, 2019 9:06 pm

Its a 6 cylinder. Thank you all for your help. I really appreciate it.
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Brianmoooore
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Tue Apr 16, 2019 8:42 am

The fact that you've asked about the correct gauge position suggests that it wasn't correct before. What's the temp. stamped on the old 'stat? Does it have BMW stamped on it?
The temp. scale of the gauge isn't linear - it's compressed at the low end and at the high end, so as long as the needle didn't go into the red, the car didn't overheat by as much as you might think.
You haven't mentioned the low coolant light in the overhead panel. If the coolant didn't get low enough to switch this on, there was sufficient coolant still in the engine all the time, so this wasn't the cause of the overheating.
M20s (with sufficient coolant in them) overheat for three reasons when they're moving - thermostat troubles, water pump rotor disintegrating or slipping, and an airlock at the back of the head in the heater circuit. The airlock, once the car has been properly bled after work on the cooling system, can only be caused by a slight leak of combustion gasses into the cooling system, either by a failed head gasket or a crack.
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angoose
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Tue Apr 16, 2019 8:55 pm

hi brianmoooore,

Thank you for taking the time to reply to question. I dont recall the coolant light coming on.

As for the temp gauge it went near red but I had pulled over then and as was getting steam from the coolant reservoir.

I asked about what position on the temp gauge as the car is still fairly new to me. When i first had the car the temp gauge ran around halfway. Then on that journey it after a while crept to 3/4.

When we changed the thermostat there was some debris in the thermostat housing. Something that looked like a but of a seal and the other vaguely resembled wax.

The thermostat appeared to have been replaced before and the seal almost appeared glued in and wasnt easy to removed but we removed it carefully and replaced the seal and new thermostat.

I queried the temp gauge position as its now running at 1/4 which it never has since i've owned it. Which is why I wanted to check this was normal.

So far ive done a good few trips and she seems to be running well.
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Brianmoooore
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Tue Apr 16, 2019 9:17 pm

If all is OK, then perhaps it was just a failed thermostat, and possibly the wrong 'stat had been fitted - wouldn't be the first time I've seen it.
BTW, if the airlock at the back of the head occurs, as well as overheating, there will be no heat from the heater, even with the knob turned fully to 'red'.
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angoose
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Wed Apr 17, 2019 6:06 am

Ok i'll check the heater when I next take the car out and let you know wht happens. thanks again
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