High coolant temp. Help please (sitting on the side of the road content)

Hey guys. On a mountain run with some friends and my coolant started to approach red. Pulled over as soon as I could.

Got up to 114 degrees and is currently at 113. The fan isn't on so I think that's screwed or a faulty connection or something.

Any tips on what I should do? Wait for it to cool down? Just drive it easy?

What temp can it get up to? My oil only hit 110

Any help is really appreciated. Thanks guys!

Currently at 105.

If fan isn't working that could be the cause. Have you checked the fuse? I think it is Fuse 37.

Any water around ... split expansion tank? Yellow Low Water light?

If all is OK, I would wait until the temp got down to normal and drive easy making sure you still have air passing over the radiator. Turn the engine off while stationary in traffic.

Good Luck

turn the heater on full blast, that will help cool it down

whats the normal coolant temp?

Normal temp is 89-96°C

OP are you using the cluster
(menu 7)? If so, good.
Obviously, do not drive it hot!!

Thanks Gents.

I waited on the side of the road and turned the heat on full with the engine off. Seemed to extract some of the heat from the engine bay (right into the cabin). Waited until it got to 88 then continued to drive home with full heat on. Coolant temp remained at 84/85 the whole way home..

32 degree aircon + 37 degrees outside for 50 minutes.. Think I might need some water! What an uncomfortable trip home.. Got some weird looks driving around in my jocks sweating my arse off!

Was using Intravee II to monitor the temps. Not the cluster menus.

Originally Posted by DeclanM3

Was using Intravee II to monitor the temps. Not the cluster menus.

Use Distilled water when you go to top it off (engine cold)

Good luck.

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Just noticed you're also in Brisbane. Which mountain were you on? It was a pretty hot day today, that's for sure... sorry to hear the M3 almost overheated!

Originally Posted by Alpine

Just noticed you're also in Brisbane. Which mountain were you on? It was a pretty hot day today, that's for sure... sorry to hear the M3 almost overheated!

Was out at Mt Tambourine with some really nice cars. So annoyed I had issues

So I thought that my radiator fan was screwed as it wasn't on when I turned the car off today. I thought they were suppose to run after you turned the car off to ensure they cooled the engine to a certain point. It even wasn't running when I had the key in position 2 which I would've thought it would.

Checked the fan tonight and it was working fine when the ignition was on.

This therefore leaves me in a bit of a pickle in terms of trying to figure out what happened today. Should the radiator fan have been running when the coolant was at 113 and the car was off? If so then any suggestions on what might cause this to fail but still allow for the radiator the run normally when the ignition is on?

I have checked the coolant and it is at a normal height but it hasn't been flushed since I bought the car (i've only had it 6 months). Was done just before hand but for good measure I'm going to do a flush.

Could the coolant have just gotten so high because it was 37 degrees outside, I had the aircon on 16 at full fan, windows down and was driving spiritedly? I wasn't driving really hard but it was constantly between 4,000-6,000 revs for a few minutes straight. Not really abnormal for an M3 though?

Start by bleeding the coolant? Would have thought you'd have issues by now though...
I'd say coolant temp sensor, but you were monitoring them which means the sensor itself can't be bad....?

Originally Posted by Jall

Start by bleeding the coolant? Would have thought you'd have issues by now though...
I'd say coolant temp sensor, but you were monitoring them which means the sensor itself can't be bad....?

The way in which I was monitoring the temps was from the Intravee II unit which I believe hooks into DME and the cluster. Perhaps it's a different system that actually controls the radiator fan due to coolant temp than what the car uses to display the temp to the driver?

Edit: also, not sure if this makes a difference but the coolant remained at 84/85 the whole way home. Mind you I was driving very cautiously and was at speed for most of the time but even when I got into the city and was driving up my multi-storey car park it stayed at 85.

Check thermostat

Is 114 degrees that bad? I've seen my car get up to 100 degrees and that was just in a hot day, normal highway driving.

Originally Posted by Davconelectric

Check thermostat

Is the thermostat the same thing that reports the temp to the computer, cluster etc.?

Originally Posted by ating

Is 114 degrees that bad? I've seen my car get up to 100 degrees and that was just in a hot day, normal highway driving.

We're talking coolant here, not oil. 114 for oil is fine, it's pretty warm for coolant though.

Originally Posted by DeclanM3

Is the thermostat the same thing that reports the temp to the computer, cluster etc.?

Coolant temp sensor is on the lower radiator hose, on a non m at least.
If t.stat's not opening that could explain it...



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^ agreed with Jall. Might have been a stuck thermostat.... cheap and easy to replace.

As already pointed out, check for signs of leaks and a good idea to do a coolant flush.

Good luck and well caught!



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Well assuming that your coolant is fresh than most likely its your fan clutch is starting to go.