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

Originally Posted by [SeN]

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

Are there any ways to check this?

Originally Posted by DeclanM3

32 degree aircon + 37 degrees outside for 50 minutes..

Good on you. So you warped your own head to prevent warp the engine head

Originally Posted by TonyJ

Good on you. So you warped you head to prevent warp the engine head

It wasn't all bad. Stripped down to my underwear, had the windows down and put the AC on the middle vents, passenger side only, aimed away from me.

Did get some weird looks from people in 4WDs..

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?

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^ this.

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.

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You have two fans sometimes one attached to water pump or electrical fan if manual tranny...other is forward of water pump fan this one will continue to run when vehicle is off if temp to high

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

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Originally Posted by Jall

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?

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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.

Originally Posted by KKB-BMW

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

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Coolant reservoir was still full after letting the car sit for 4 hours after I got home.

Originally Posted by [SeN]

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.

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Won't I risk snapping the fan blades?

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.

Time to sell up Dec and cut your loses.

Originally Posted by trive2

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.

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?

Originally Posted by rossim3

Time to sell up Dec and cut your loses.

Yeah, time to bin it and get a 116d.

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.

Originally Posted by Brissyjohn

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.

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.

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.

Originally Posted by DeclanM3

Are there any ways to check this?

Once youve removed the thermostat, and replaced it with a fresh.
Put the old one in a pot full of water on the stove with a thermometer in there with it. Once the temperature gets to that labelled on thermostat it should open.

Originally Posted by Brissyjohn

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.

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.

Originally Posted by DeclanM3

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.

Is your car an auto? If so, have a look here too http://forum.e46fanatics.com/showthread.php?t=960980.

I'm more inclined to go with intermittent electric fan operation - dodgy connector or something - especially if the problem occurred at low speed on a long climb at high ambient temps. The electric fan is designed to kick in when there isn't enough cooling air flow from forward speed or the engine driven fan (if fitted).

Anyway, time will tell. Good luck with the fix. A visit to RX Automotive may be helpful.

With what Brissyjohn said it made me think - get the codes read. There maybe something there to help identify the actual issue, perhaps in the shadow codes (event occurred but symptom no longer present).



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Originally Posted by Brissyjohn

Is your car an auto? If so, have a look here too http://forum.e46fanatics.com/showthread.php?t=960980.

I'm more inclined to go with intermittent electric fan operation - dodgy connector or something - especially if the problem occurred at low speed on a long climb at high ambient temps. The electric fan is designed to kick in when there isn't enough cooling air flow from forward speed or the engine driven fan (if fitted).

Anyway, time will tell. Good luck with the fix. A visit to RX Automotive may be helpful.

It's SMG and I'm pretty sure M's have different setups to non Ms.

It was at speeds between 60-80 when it occurred. I could be wrong but don't think a fan failure would make that much of a difference at those speeds?

I'll try get the codes read though.