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

7K views 58 replies 20 participants last post by  Alpine 
#1 ·
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!
 
#3 ·
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
 
#7 ·
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!
 
#12 · (Edited)
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?
 
#14 · (Edited)
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.
 
#24 ·
How much cooling does the fan provide at speed though. Once moving wouldn't the majority of cooling be from outside air moving through the radiator?

Unless I read wrong, it started heating while driving, not stopped?

Sent from my GT-I9300 using Bimmer App
 
#29 · (Edited)
You're correct, it was whilst running and at 60+k's when it started to rise. It continued to rise despite me only doing low revs until I found a safe place to pull over.

The AC was still on 16 and full fan as it didn't cross my mind to turn that off at the time.

Could it have been a case of hot day, AC being overloaded and possibly some pretty shiet coolant?

What's weird is I have driven at the track doing 10 minute stints of high revs with AC on (mind you not 16 full fan and such a hot day. Was probably 30 degs outside temp) and the coolant never got above 94. Just seems strange it got to 114 yesterday.

It has got me stumped! I can't think of a logical explanation although I'm not overly familiar with the cooling systems in general so it's likely there's something I don't know about.

Probably cracked radiator bottle..why wont BMW go back to regular radiators....money always wins

Sent from my HTC eVo using Bimmer App
Coolant reservoir was still full after letting the car sit for 4 hours after I got home.

Roll up some newspaper into a long tube and stick it in the fan, if you can stop it then it's ur fan clutch.

Only do this once your engine is at full operating temp.

Sent from my GT-I9305T using Bimmer App
Won't I risk snapping the fan blades?
 
#26 ·
Roll up some newspaper into a long tube and stick it in the fan, if you can stop it then it's ur fan clutch.

Only do this once your engine is at full operating temp.

Sent from my GT-I9305T using Bimmer App
 
#30 · (Edited)
You're actually better off revving the crap out of it if it tries to overheat. Reason being that you're spinning the water pump and the clutch fan much faster.

When my 535i tried to overheat on the last BMW club run it was worst under load (up hills) at low revs. I just made sure to keep the revs sky high for the rest of the trip and it behaved itself.


And a clutch fan will mostly only affect your cooling at low speeds. If you were on the run I highly doubt it's the fan. The auxillary fan won't be the be-all-and-end-all of this either so I wouldn't look at that.



How long since you've done a full system overhaul? Possibly slightly busted water pump or malfunctioning thermostat?

I don't believe that a hot day and any sort of load should have any sort of effect on a car with a functioning coolants system. If any of those things affect the ability of the car to keep the temperature constant, it's because something isn't functioning.


You're not having much luck with this car are you.
 
#32 · (Edited)
I was going up a hill but had plenty of revs before this started to happen. I was driving with a GTR, 430, 360, GT3 RS, 996 Turbo etc.

I guess the waterpump could explain it if it decided to stop working momentarily.

What's the easiest way to check the waterpump?

Time to sell up Dec and cut your loses.
Yeah, time to bin it and get a 116d.
 
#33 ·
The water pump will work or it won't - there is no intermittent.

It could simply have been the weather conditions and being in a bit of "bad" air following the other cars up a long climb. Mind you, I've been up and down Tamborine and Nebo/Glorious heaps of times in all weather behind other cars with no issues at all.

If your engine driven fan (if an auto) and your electric fan are working and your coolant level is OK when cold then it was probably just a one off. I think you said the coolant level was OK and that the coolant was changed not so long ago anyway. Maybe it just needed to bleed out an air bubble from the last time it was flushed.

Just keep a close eye on it and see how it goes. Check the fans work properly (check their operation from time to time) and that your serpentine belt isn't slipping - which it shouldn't if your belt tensioners are working OK.
 
#34 ·
Cheers. I'll double check the belts but they all seem ok.

I'm thinking it could've been the thermostat jammed close for whatever reason and then when I restarted the car it reopened. I think I'm going to replace that and do a coolant flush for my own peace of mind and then keep an eye on everything else. If the belts / tensioners seem worn I'll do them whilst I'm at it.
 
#35 · (Edited)
I'm not sure I agree with the thermostat theory. Once the car has driven about 1 or 2 km in current Brisbane conditions, the thermostat will/should be open. Thermostats (engine) rarely just fail and then close mid drive. It's more a case of them never opening fully or jamming open or closed. If jammed closed from the start, you'd be overheating everywhere. Of course, if that pesky auto transmission thermostat has failed then all bets are off.

It wouldn't hurt (except your wallet) to replace it. I'm fairly paranoid about coolant temps, but I'd be closely monitoring it for the time being to see what happens - especially if you have a monitoring system better than just the dash temp gauge.
 
#37 ·
I totally agree with you but nothing else is logical. For the coolant temp to rise substantially like that whilst traveling at 60+ks an hour it can really only mean that the engine isn't getting coolant circulating though it. Be it from the water pump not being driven, thermostat failing to open or the coolant leaking at a high speed.

Considering I've got full coolant and the water pump hasn't shown signs of failure / wouldn't generally stop working intermittently the thermostat seems to be the next logical step for me.

Having said this. I've only got what I've read in the last 48 hours to base my opinion on. Considering the thermostat was $50 and some new coolant is also cheap I'm going to start there then if I still have problems I guess it's likely to be the pump itself.
 
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