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Discussion Starter #1
hi - I think I have an overheating issue with my car - some background:

I've had the car 2 years now and done loads of the usual items you'd expect - first of these was a new thermostat just after purchase as it was never getting above 77 degree's on the motorway. once replaced never below 79c and rarely above 84-5 unless caning it.

A few months back I was stuck in traffic for 15 mins or so during a warm uk day (30 deg c - its warm for us!) and the car was fine - stopped in a shop for 10 mins then gunned car back down road, check coolant level appears, needle in middle. drive another 250 yrds and stop at lights - steam from front lhs of bonnet+needle rising to 60%. then get low coolant alarm, needle heading for red section - check on cluster and its 99c. pull over and switch off before needle goes into red.

open bonnet carefully and rad top hose has come away, pouring all coolant out all over back of headlamp, fan etc - no wonder it said low! Glad at this point i caught it before it got too hot. Clip holding hose had come undone, not failed. clipped it back on, got 4-5 litres of water in it and recovered it back home (1 mile).

I'd previously purchased a new fan clutch and aux fan due to 130k mileage - fan clutch seemed pretty manky so i installed new one - no difference - car ran hotter than previously in traffic (upto 91c) and cooler on m-way - 77c. around town it would run to 90 then down to 87 when aux fan kicked in.

Arranged to have new aux fan fitted by a friend with their own independant garage - also cleaned rubbish from between rads which was not as bad as i expected. At same time cooling system was flushed. Result was still the same.

Today we fitted a new thermostat and sealing ring as i assumed existing stat had failed partially open/closed, causing odd conditions. Sealing ring was tired but in one piece - anyway replaced both, checked for leaks with vac test, all good. Drove home and car still appears to be the same.

My question is what else could be wrong?

My only thought left is the water pump however i'm struggling to see how it could fail like this - bearings only in my experience and this tends not to affect pumping performance. i have a replacement sensor for top of thermostat housing but not fitted it - garage checked obc temps and various system temps with laser temp probe and they seem to tally.

Anyone else have any ideas or thoughts on what to check? Luckily its getting cooler here now - i spend time sat in London traffic so want to get it sorted once and for all before we hit spring next year. performance is still very good - no codes, mpg average 22 (lot of mway). Oil level fine - oil temp seems to stay pretty low.

Simon
 

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hi - I think I have an overheating issue with my car - some background:

I've had the car 2 years now and done loads of the usual items you'd expect - first of these was a new thermostat just after purchase as it was never getting above 77 degree's on the motorway. once replaced never below 79c and rarely above 84-5 unless caning it.

A few months back I was stuck in traffic for 15 mins or so during a warm uk day (30 deg c - its warm for us!) and the car was fine - stopped in a shop for 10 mins then gunned car back down road, check coolant level appears, needle in middle. drive another 250 yrds and stop at lights - steam from front lhs of bonnet+needle rising to 60%. then get low coolant alarm, needle heading for red section - check on cluster and its 99c. pull over and switch off before needle goes into red.

open bonnet carefully and rad top hose has come away, pouring all coolant out all over back of headlamp, fan etc - no wonder it said low! Glad at this point i caught it before it got too hot. Clip holding hose had come undone, not failed. clipped it back on, got 4-5 litres of water in it and recovered it back home (1 mile).

I'd previously purchased a new fan clutch and aux fan due to 130k mileage - fan clutch seemed pretty manky so i installed new one - no difference - car ran hotter than previously in traffic (upto 91c) and cooler on m-way - 77c. around town it would run to 90 then down to 87 when aux fan kicked in.

Arranged to have new aux fan fitted by a friend with their own independant garage - also cleaned rubbish from between rads which was not as bad as i expected. At same time cooling system was flushed. Result was still the same.

Today we fitted a new thermostat and sealing ring as i assumed existing stat had failed partially open/closed, causing odd conditions. Sealing ring was tired but in one piece - anyway replaced both, checked for leaks with vac test, all good. Drove home and car still appears to be the same.

My question is what else could be wrong?

My only thought left is the water pump however i'm struggling to see how it could fail like this - bearings only in my experience and this tends not to affect pumping performance. i have a replacement sensor for top of thermostat housing but not fitted it - garage checked obc temps and various system temps with laser temp probe and they seem to tally.

Anyone else have any ideas or thoughts on what to check? Luckily its getting cooler here now - i spend time sat in London traffic so want to get it sorted once and for all before we hit spring next year. performance is still very good - no codes, mpg average 22 (lot of mway). Oil level fine - oil temp seems to stay pretty low.

Simon
If you are only overheating in traffic, then I would look at the fan setup. If you are having problems on the highway, say 80 kph or better, than it is not the fans. Could be rad blockage internally, debris behind the rad (you already checked and cleaned), bad rad cap (not keeping pressure, but they do not often fail) or remotely, bad head gasket from the last overheat. It could be a water pump, they are robust, but if an impeller breaks, you are not moving enough fluid and even though at highway speeds you have enough airflow, there is not enough water flow through the rad.

You can also sample the coolant to see if any engine contaminants are in there signaling possible head gasket.

BTW, when you did the tstat, did you triple check all the O-rings on the pipes are good? It is VERY easy to tear an O-ring (ask me how I know!) and that could be the source of a water leak. Pressure testing will help pinpoint any leaks.

Regards,
Jerry
 

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Discussion Starter #3
thanks Jerry.

Yes we pressure tested for leaks today with a vacuum / antifreeze filler tool - sucks air out of system and fluid in apparently.

Coolant is very clean - no fluid loss at all or performance loss so hoping no head gasket issues. Temp never got into red at all so reasonably confident.

We flushed rad last time and it was pretty clear - also used airline to blow debris out of the gills of the rad. it was not as bad as i expected it to be - we split the rad + condensor to do this.

Feels like a water pump issue but its a pain to assume based on the cost and hassle to change!

re. o-rings... i suggested to my mechanic friend we re-use all the o-rings as they were less than two years old - we managed to break all three all three the first time! I'd bought new ones and spares so it was no hassle. using vacuum tool to see if system held pressure was most useful.

Tomorrow i'll see if any movement in water pump shaft / release belt tensioner - by spinning should be able to feel/hear some water resistance hopefully...

Simon
 

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thanks Jerry.

Yes we pressure tested for leaks today with a vacuum / antifreeze filler tool - sucks air out of system and fluid in apparently.

Coolant is very clean - no fluid loss at all or performance loss so hoping no head gasket issues. Temp never got into red at all so reasonably confident.

We flushed rad last time and it was pretty clear - also used airline to blow debris out of the gills of the rad. it was not as bad as i expected it to be - we split the rad + condensor to do this.

Feels like a water pump issue but its a pain to assume based on the cost and hassle to change!

re. o-rings... i suggested to my mechanic friend we re-use all the o-rings as they were less than two years old - we managed to break all three all three the first time! I'd bought new ones and spares so it was no hassle. using vacuum tool to see if system held pressure was most useful.

Tomorrow i'll see if any movement in water pump shaft / release belt tensioner - by spinning should be able to feel/hear some water resistance hopefully...

Simon
Miles on the water pump?

They are robust, but they do fail from time to time.

Regards,
Jerry
 

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Belt slip?
 

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Discussion Starter #8
Hmm interesting - did seem to appear one day by surprise. I'll take a look tomorrow and see whats what. Belts need changing at some point but they are not terrible. I have replacements ready for when they start to go.

Simon
Reading loads of other posts re ktemps it seems those in warmer countries are often in ninety degree temps and higher - i just don't remember that being the case in the UK with my car - post first thermostat i used to check ktemp quite a bit to make sure it was working ok. Today was an unseasonably warm 20c and temp still hit 90c in slow traffic - fell back down rapidly when i got onto faster roads 60-70mph).
 

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Although not normal to fail by reading to high, the temp sensor has a very high failure rate, might be worth replacing. You seem to have checked all the normal things which only leaves the water pump. Very low failure rate but they do fail maybe you have the bad luck.
 

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Are you sure the new aux fan is working? Because I have disabled the aux fan on mine and run just the clutch fan and your car is behaving just like mine does. The clutch fan doesn't kick on until KTMP gets up around 95C and then it drops rapidly to 80-85C. DIS has a good test for the aux fan, you can specify various duty cycles and listen to it generating jet engine-type noise levels as it speeds up.

Also, the rad could be plugged because that would not only cause the high temps round town, but also explain why the upper rad hose blew off when you gunned it. How did you know it was clear when you flushed it?

It's not the water pump. Like you said, it's never the water pump. It's got a steel impeller and I had a hell of a job getting it off the shaft when I took one apart. They are tough.

I've never heard of testing for coolant leaks with a vacuum tester. I can't see how that would work. Did you mean a pressure tester?
 

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Are you sure the new aux fan is working? Because I have disabled the aux fan on mine and run just the clutch fan and your car is behaving just like mine does. The clutch fan doesn't kick on until KTMP gets up around 95C and then it drops rapidly to 80-85C. DIS has a good test for the aux fan, you can specify various duty cycles and listen to it generating jet engine-type noise levels as it speeds up.
+ 1 !

In central London traffic you should be in no doubt that there is a loud fan running ! I mean quite loud indeed !

Perhaps after removing and splitting the rad and condenser you haven't plugged or there is loose connection for the AUX fan now.
 

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Discussion Starter #12
Although not normal to fail by reading to high, the temp sensor has a very high failure rate, might be worth replacing. You seem to have checked all the normal things which only leaves the water pump. Very low failure rate but they do fail maybe you have the bad luck.
hi - thanks for reply. I fitted new temp sensor today - really planned ahead as i bought it 2 years ago!

It looks to report lower but weather is cooler today - will have to check when its warmer again.

Simon
 

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Discussion Starter #13
Are you sure the new aux fan is working? Because I have disabled the aux fan on mine and run just the clutch fan and your car is behaving just like mine does. The clutch fan doesn't kick on until KTMP gets up around 95C and then it drops rapidly to 80-85C. DIS has a good test for the aux fan, you can specify various duty cycles and listen to it generating jet engine-type noise levels as it speeds up.

Also, the rad could be plugged because that would not only cause the high temps round town, but also explain why the upper rad hose blew off when you gunned it. How did you know it was clear when you flushed it?

It's not the water pump. Like you said, it's never the water pump. It's got a steel impeller and I had a hell of a job getting it off the shaft when I took one apart. They are tough.

I've never heard of testing for coolant leaks with a vacuum tester. I can't see how that would work. Did you mean a pressure tester?
thanks - fairly sure the aux fan is ok - when it really gets going you can hear it. The old was was also working but creaking, squeaking and groaning as it went, hence replacement. replacement is louder than original but that seems common to. i'll test it with DIS to make sure its doing its thing correctly.

when we cleaned radiator we just pushed loads of water through it with hose - so don't really know its clear to be honest. didnt seem to be much crap in it anyway - is there a better way to flush? I seemto remember you could get some chemical flush you put in - trouble is crap has to end up somewhere if its in the system.

Water pump seems solid - no movement in bearing i can feel and no tell tale leaks around or under it - access is difficult to see however.

re. testing - we used a tool connected to air line to both fill system with coolant and it also pressure tests - you fill until 25 psi or whatever on gauge and see it it holds. i think it uses vacuum as it is designed to evac air from system by pulling coolant in - fits onto water tank using tapered bung. seemed to do the trick and showed up our damaged o rings in seconds. had several taps, air out, coolant in etc.
 

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Discussion Starter #14
+ 1 !

In central London traffic you should be in no doubt that there is a loud fan running ! I mean quite loud indeed !

Perhaps after removing and splitting the rad and condenser you haven't plugged or there is loose connection for the AUX fan now.
thanks for reply - ah the aux fan jet engine noise - i was quite taken aback by level of noise of new fan.... seems to shift a lot of air though. this one has electronics in a seperate box cooled by fan movement (via heatsink) rather than being housed in centre of fan like oem.

better design but fan itself is noiser - just glad to be rid of squeaking and creaking of old one - that used to turn heads on its own!

Simon
 
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