Does your water temp move at all on track?

[funtime]

Just come back from the ring, had a good time but worried about a possible temperature issue...

Here's what it did.. - bare in mind it was 25-27 degrees whilst doing this:

I was running most of the time with the aircon off and the heating fans set to around 20 degrees at about half power.

The temp gauge towards the end of the lap would be around the 2/3rds marker and oil around 125.

Then on Monday they opened the F1 circuit aswell so each lap was just over 15 miles. My mate drove the CSL as he knows the track very well and when he drove we had the aircon on all the way round with the fans on nearly full power blowing cold, by about 2/3rds of the way round i noticed the water temp was almost in the red, and by the end of the lap it was just in the red, but after going under the gantry on the back straight and coming off the power coasting to the exit of the track it had already returned to half way on the water temp.

This got me worried, although the only thing that made me feel slightly better about it is that his M3 was doing exactly the same, so I put it down the the hot weather and longer track, although i was still surprised it got as high as it did.

The next time we went out, I put the heaters on full chat at 32 degrees, and had the windows open a touch to stop us melting, and by doing this the temp never went above the 2/3rds marker.

I did some reading yesterday and saw Shimmys troubles and a few others on here and instantly feared the worst so I did a compression check this morning.

Results are fine and don't show any signs of a HG failure which is a relief, but im just worried now about what else it could be.

I'm guessing you boys don't do all hot track days with the windows open and the heaters pumping at 32 degrees!

Any help and suggestions much appreciated :)

Another thing to note - my temp gauge never seems to sit bang in the middle either, normal driving it sits just under the half way marker and then a spout of hard driving you can actually see it move to just over the half way.

Could this all just point to a dodgy thermostat?! :hahaha:

[shimmy]

My guess would be that if oil is going over 2/3 followed by water going over 3/4 towards red then HG is favourite. I'll be surprised if its not even if yo have checked it.

Very common on high mileage cars, Dunc, Rob, me, Daz, and a few other have had HG changed.

I think early symptom if high temps on track on hot days first.

Get compression test asap (cylinders 5/6 will be worse) to rule it out before you start, like I did, rafting around with stats, rads, water, fans, oil coolers,

My car used to do hot days with a/c running no temp issues the slowly on hot days on track it started creeping up. Since HG changed no issues

[funtime]

My guess would be that if oil is going over 2/3 followed by water going over 3/4 towards red then HG is favourite. I'll be surprised if its not even if yo have checked it.

Very common on high mileage cars, Dunc, Rob, me, Daz, and a few other have had HG changed.

I think early symptom if high temps on track on hot days first.

Get compression test asap (cylinders 5/6 will be worse) to rule it out before you start, like I did, rafting around with stats, rads, water, fans, oil coolers,

My car used to do hot days with a/c running no temp issues the slowly on hot days on track it started creeping up. Since HG changed no issues

Well like I said i did fear the worst and so got the compression test done this morning - results are as follows (bare in mind the engine was not red hot so readings are a little low across the board)

1 - 149
2 - 154
3 - 155
4 - 157
5 - 159
6 - 151

So whilst I appreciate what your saying I wouldn't have thought the above results would suggest a HG?

Any other thoughts?

Also whilst doing the compression check we couldn't help notice the pollen filter had not been replaced for a very long time... but it's just had an Inspection 2 :smt083

[shimmy]

Shouldn't compression tests be done hot?

I couldn't replicate my overheating anywhere but on track, warm day, full power.

Cleaned rads, replaced stats and sensors, viscous fans, etc etc. US forums have loads of this and if you think about it if you only get it at full chat, warm day, so plenty of air and fan is not an issue. Temp of oil ruses first followed by water so it seems to be engine caused not water cooling system.

I narrowed it down to injectors, map or fuel related. Removed Map and still happened then HG failed proper and after fixed it never happened again

[funtime]

Shouldn't compression tests be done hot?

I couldn't replicate my overheating anywhere but on track, warm day, full power.

Cleaned rads, replaced stats and sensors, viscous fans, etc etc. US forums have loads of this and if you think about it if you only get it at full chat, warm day, so plenty of air and fan is not an issue. Temp of oil ruses first followed by water so it seems to be engine caused not water cooling system.

I narrowed it down to injectors, map or fuel related. Removed Map and still happened then HG failed proper and after fixed it never happened again

Yes ideally - it wasn't done cold, just not as hot as it should have been. Was rushing and the engine had cooled for an hour or so because i realised i didn't have the right adapter to reach down the thin spark plug access holes and connect the compression tester.

Anyway, for a HG check it doesn't matter too much if the car is not red hot, as your looking for anomalies between the cylinders. Hot readings would just show around 15psi higher on each cylinder.

It does make sense what you say with regard to oil temp rising first causing the water temp to budge, although the other M3 that was with us had the same sort of oil temps 125/130 but his water temp didn't budge at all. :smt102

I'll give Simpson's a ring on Tuesday and see what they think...

Didn't you end up replacing your engine shortly after the headgasket Shimmy? was that the result of damage caused by the failed headgasket in the first place?

[shimmy]

No, bottom end, spun a shell.



If you look at the gasket the spaces between cylinders are very small and my belief is that when engine gets warm/ hot the compressions between the two cylinders drop very slightly when at full whack and you get overheating at 100% throttle.

My original throughts Were that the occasional near overheating caused the HG failure but as I never found a reason for the overheating and it went away at that time, I can only conclude the reverse.

As you car is higher than average mileage and you get E46 with 60-80k miles ith HG failures pretty commonly now days that have never been on track, i personally would do a thorough check first.




http://i401.photobucket.com/albums/pp97/shimmylasco/CSL/september2009005-1.jpg

[shimmy]

Just an aside - in all the reading I've done about this on UK and US forums, it never seems to be replicated on road but only on track in warm weather. Obviously high numbers in Southern American states.

I think road going cars don't ever get this syptom and go straight to misfire and pinking on HG failure at a later time.

(oh and I changed the water pump on mine, cleaned out rads, inside and out as well and no joy)

Yours could be a differet thing but tbh a 110k miles might be worth HG change anyway!

[magnust]

[slightly OT]
With my M3 E36 3.2 I had problems with oil temps going too high the last two - three years (on track only), it got slightly worse each year. It was a damaged oil cooler thermostat. With it changed all went back to perfect.
[/slightly OT]

In my CSL I have a problem with the water temp going high sometimes on track. Dropping back the driving tempo slightly just half a lap makes the water temp go back to totally normal (normal = not 100% straight up but thereabouts). Oil temps go up a bit on track but just a bit and never more than that. I had no idea where to start, but checking the comp sounds like something I should do then?

[glendog74]

So James, remind me what it was you were saying about your car being a safer/more reliable bet than one which had been tracked in the past? You've had a few issues now... :whistle: ;)

On a thread related note, I have never had any overheating issues on my car; not even before my HG went recently.

[shimmy]

On a thread related note, I have never had any overheating issues on my car; not even before my HG went recently.

Sorry Rob, I thought. Said above you have to drive it flat out and at full throttle to get it......:whistle:

[alexk]

We had this discussion in another thread.

The water temperature should never move higher, on track full speed or not.
You car has a problem (radiator, water pump, head gasket / 1 or more..).
Get it checked.

[northernjim]

Sorry Rob, I thought. Said above you have to drive it flat out and at full throttle to get it......:whistle:

is it not also the case on high mileage cars like robs....:blalalala:

We had this discussion in another thread.

The water temperature should never move higher, on track full speed or not.
You car has a problem (radiator, water pump, head gasket / 1 or more..).
Get it checked.

be told James;)

[funtime]

I have a feeling... (and I'm hopeful I'm right) that it could just be the thermostat.

Reason being is I was driving it this evening and kept an eye on the temp, it got up to the middle but then went down and sat just a bit to the left of bang in the middle 'where it should stay all the time'. When I hit some B roads the temp went to half way and then maybe 1mm to the right of half way and when I backed off it came down to below the half way point.

This leads me to believe its the stat as it's actually overcooling at some points and not cooling enough at others. If the HG had gone or anything like injectors or water pump it would surely ALWAYS run too hot and never too cold like its doing?

Anyway, i'll get it checked out, but less worried about it now, we'll see what a thermostat does :smokin:

Thanks for the replies though boys :thumbs:

And Rob - yes I did say that, but mine hasn't had a HG yet and yours along with a few others on here that have done half the miles have so that's all I was getting at. Never made it would be problem free... ;)

[monkeycsl]

My temp gauge can be slightly to the left but never goes higher than half way could well be thermostat, but would prob do head gasket change on yours due to mileage and that you will be tracking her.:thumbs:

[shane@mbtech]

You should have bought bealos with ap and warranty :whistle:

[grumps]

My temp gauge started to read just below half a few months back so i replaced the thermostat (gen) which made no difference,Oil temp is just as before! Any ideas?
Regards Pete

[alexk]

My temp gauge started to read just below half a few months back so i replaced the thermostat (gen) which made no difference,Oil temp is just as before! Any ideas?
Regards Pete

I think your fan coupling has an issue and is always engaged (part number 2) and cools down the engine constantly.
Do you hear a "noise" .. .fan noise when you drive slowly with open windows ?

http://bmwfans.info/parts/catalog/E46/Coupe/Europe/M3_CSL-S54/LHD/N/2003/september/browse/engine/cooling_system_fan_fan_coupling/

[shane@mbtech]

My temp gauge started to read just below half a few months back so i replaced the thermostat (gen) which made no difference,Oil temp is just as before! Any ideas?
Regards Pete

I think your fan coupling has an issue and is always engaged (part number 2) and cools down the engine constantly.
Do you hear a "noise" .. .fan noise when you drive slowly with open windows ?

http://bmwfans.info/parts/catalog/E46/Coupe/Europe/M3_CSL-S54/LHD/N/2003/september/browse/engine/cooling_system_fan_fan_coupling/

As Alex says it is possibly your fans, but could also be faulty temp sender, so many possibilities. Better to read a tad low than too high;)

[grumps]

I had a new viscous coupling fitted late last year under warranty! as lawsy suggested i think its probably down to the sensor as it makes no difference if the weather is hot or cold and if the ac is on or off ;)

[alexk]

I had the same high temp problem today on track. Almost touched the beggining of red.

It was quite hot @ 30 degrees.

As soon as I backed off the throttle, it immediately dropped.
Then, I continued revving up to 5500 and didn't have a problem.
I suspect it's the viscous fan as with the engine hot, it doesn't engage properly (lawsy knows the check I am sure).
Also, for a year now when I would slow down from high speeds in germany, the temp would drop a bit.
I will start with the viscous coupling of the fan.

shimmy, how do you explain that the HG problem results to increased temperature, when there is no impact in the water or oil flow ?
I am just trying to understand why there would be a temp issue.

[shimmy]

I don't know, I'm no mechanic but I replaced viscous fan and no change (exactly same symptoms as you)

Don't forget HG leak is cylinder to cylinder, not water or oil related.

It can only be found on track at full throttle then 2 secs of the throttle and water temp drops (but oil temps stay higher). Therefore logic says the enine is affecting oil temps not water initially so I can't be fan, water radiator, pump, pipes, thermostat.

It must be oil related so engine is affecting it via timing, fuel, coils, injectors or oil cooling is affected by blocked rad or dodgy sensor.

When I replaced my HG i also changed coilpacks, refurbed injectors, oil filter and it went

Shimmy

I had the same high temp problem today on track. Almost touched the beggining of red.

It was quite hot @ 30 degrees.

As soon as I backed off the throttle, it immediately dropped.
Then, I continued revving up to 5500 and didn't have a problem.
I suspect it's the viscous fan as with the engine hot, it doesn't engage properly (lawsy knows the check I am sure).
Also, for a year now when I would slow down from high speeds in germany, the temp would drop a bit.
I will start with the viscous coupling of the fan.

shimmy, how do you explain that the HG problem results to increased temperature, when there is no impact in the water or oil flow ?
I am just trying to understand why there would be a temp issue.

[shimmy]

Ok the facts as I see them...

1. Oil temp rises to 2/3
2. Then water temp rises to 3/4 and then on to red slowly
3. Only happens at full throttle,
4. Initially happens only on warmer days
5 Only on Trackdays (presume this coz 100%throttle uncommon on road)
6 Off full throttle temp of water drops quickly

Mine happened last at Snett, then started to run badly at higher revs, then diagnosed as failed HG between cylinders 5/6 worse and others.

Now question is does the HG failing and leakage between cylinders cause the engine oil temps to rise OR does something else cause the oil to rise and then result in a failed HG cause of raised engine temps?

Now as Oil temps rise first noticably I think this means that the engine is getting hotter before the water temps are, so therefore the water cooling system can't be at fault.

[shane@mbtech]

I had the same high temp problem today on track. Almost touched the beggining of red.

It was quite hot @ 30 degrees.

As soon as I backed off the throttle, it immediately dropped.
Then, I continued revving up to 5500 and didn't have a problem.
I suspect it's the viscous fan as with the engine hot, it doesn't engage properly (lawsy knows the check I am sure).
Also, for a year now when I would slow down from high speeds in germany, the temp would drop a bit.
I will start with the viscous coupling of the fan.

shimmy, how do you explain that the HG problem results to increased temperature, when there is no impact in the water or oil flow ?
I am just trying to understand why there would be a temp issue.


Its not the viscous as the viscous is only effective below say 10-15mph. It might still spin but its efforts are wasted as the speed you are travelling pushes more air through the rad than the viscous could ever pull through it.


In most cars overheating can cause the headgasket to fail.

The hg can fail between the 2 cylinders which increases cylinder temps, which in turn will increase water temps. Which in turn can then cause the HG to fail more so, its a viscious circle.

There are varying factors.

First thing to check is cooling system, if all is ok, then onto engine side.

Fuel pump, fuel injectors, engine timing faults, remaps can all cause det, if not perfect. When det occurs, cyl temps increase, cyl temps increase which causes more det- see where its going.


Or it could simply be an inherent fault due to the nature of the beast. The s54 engine has very small gaps between cylinders. Over a prolonged period of time with extreme operating conditions (track), and with a few miles, the gasket can fail, which results in overheating which accelerates HG failure. LOSE LOSE.

I have noticed over the last 12 months a big rise in /HG failures on both M3 and CSL.

I believe it is just the nature of the beast.

[shane@mbtech]

If I had another CSL, without doubt I would fit a motorsport thermostat.
Esp if it was on track.

[DuncanR]

Anyway, for a HG check it doesn't matter too much if the car is not red hot, as your looking for anomalies between the cylinders. Hot readings would just show around 15psi higher on each cylinder. I dont go along with this, it should be remembered that with any temp increase ALL dimensions get BIGGER ! ... and that includes clearances and any gaps or cracks.

My temp gauge usually sits just past halfway or 100 during Ring or track day work, and falls back to just below half after about a minute, at which point I consider switching engine off, I never switch off if reading is above 100.

If I had another CSL, without doubt I would fit a motorsport thermostat.
Esp if it was on track.Part no and supplier Lawsy, good shout that man !

[alexk]

Ok the facts as I see them...

1. Oil temp rises to 2/3
2. Then water temp rises to 3/4 and then on to red slowly
3. Only happens at full throttle,
4. Initially happens only on warmer days
5 Only on Trackdays (presume this coz 100%throttle uncommon on road)
6 Off full throttle temp of water drops quickly

Mine happened last at Snett, then started to run badly at higher revs, then diagnosed as failed HG between cylinders 5/6 worse and others.

Now question is does the HG failing and leakage between cylinders cause the engine oil temps to rise OR does something else cause the oil to rise and then result in a failed HG cause of raised engine temps?

Now as Oil temps rise first noticably I think this means that the engine is getting hotter before the water temps are, so therefore the water cooling system can't be at fault.

shimmy, I am no pro but the family biz is bmw cars.
I have seen in the past many issues in BMWs that started with the viscus fan or water pump.
As lawsy said, then it's a chain.

I don't want to doubt what you are saying, but I find this strange.

Lawsy says :
>>
The hg can fail between the 2 cylinders which increases cylinder temps, which in turn will increase water temps. Which in turn can then cause the HG to fail more so, its a viscious circle.
<<

Why if we have compression loss between 2 cylinders, the temp rises ?
I would expect the knocking sensors will detect this and adjust the ignition and injection.
The car would run very poorly etc.

I will take out my spark plugs today and also run the diagnostic to see for any strange knocking/compression values between the cylinders and update you.

PS : I am not rulling out the HG but at 84k km and always using good fuel, low env temperatures, never had a knocking failure and the water temp decreasing after stops from the autobahn, I find it unlikely that my car has a HG issue

[alexk]

I dont go along with this, it should be remembered that with any temp increase ALL dimensions get BIGGER ! ... and that includes clearances and any gaps or cracks.

My temp gauge usually sits just past halfway or 100 during Ring or track day work, and falls back to just below half after about a minute, at which point I consider switching engine off, I never switch off if reading is above 100.

Part no and supplier Lawsy, good shout that man !

It's this one -> 11531417215

http://www.turnermotorsport.com/p-3-e46-m3-motorsport-thermostat-55-degree-c.aspx

[shane@mbtech]

shimmy, I am no pro but the family biz is bmw cars.
I have seen in the past many issues in BMWs that started with the viscus fan or water pump.
As lawsy said, then it's a chain.

I don't want to doubt what you are saying, but I find this strange.

Lawsy says :
>>
The hg can fail between the 2 cylinders which increases cylinder temps, which in turn will increase water temps. Which in turn can then cause the HG to fail more so, its a viscious circle.
<<

Why if we have compression loss between 2 cylinders, the temp rises ?
I would expect the knocking sensors will detect this and adjust the ignition and injection.
The car would run very poorly etc.

I will take out my spark plugs today and also run the diagnostic to see for any strange knocking/compression values between the cylinders and update you.

PS : I am not rulling out the HG but at 84k km and always using good fuel, low env temperatures, never had a knocking failure and the water temp decreasing after stops from the autobahn, I find it unlikely that my car has a HG issue

Try the stat first Alex

Simple and cheap, try the motorsport or tropical one

[shimmy]

Try the stat first Alex

Simple and cheap, try the motorsport or tropical one


Hmmmm agree, cheap check.

But if water temps are good until oil temps rise, can't see it helping

I think it's an engine issue. Timing, map, fuel, injectors Or HG on its way out.

Don't forget its ONLY at full throttle (and on track this tends to be when air flow at its best) and its not when standing.

[AlexGTT]

Any unexpected high temps on track at WOT always points to HG failure between cylinders if said temps then fall quickly when slowing. Most HG failures blow into coolant or oil system which is easy to diagnose. E46 M nearly always between cylinders. Less easy to spot and can remain minor until complete fire ring failure shows itself with a noteable miss-fire.

Any problems like this an I'd have a cylinder leak down test, NOT compression test.

[shimmy]

Any unexpected high temps on track at WOT always points to HG failure between cylinders if said temps then fall quickly when slowing. Most HG failures blow into coolant or oil system which is easy to diagnose. E46 M nearly always between cylinders. Less easy to spot and can remain minor until complete fire ring failure shows itself with a noteable miss-fire.

Any problems like this an I'd have a cylinder leak down test, NOT compression test.


Alex, why does cylinder to cylinder leak cause higher temps at full throttle then?

[shane@mbtech]

Alex, why does cylinder to cylinder leak cause higher temps at full throttle then?

Full wot will create more heat, the heat and subsequent Movement/expansion of the head/block IMO then highlights the hg slight failure, the increase in cyl temps due to the cyl to cyl then IMO accelerates the issue further

These are all just theories, Each part only has to be minute to create overheating issues

Once it's got too hot once then I feel damage is already done, ticking timebomb then.

Try the basics first, forget your fan, it's got fuck all to do with it, unless it overheated whilst stationary at an earlier date.

We had a similar problem on a big powered Evo
It left us and several big tuners scratching our heads.
We looked at it from a very basic angle, tried a thermostat as it was basic diagnosis and it fixed it.

Said tuner had done all kinds of things to remedy it, as they built the engine from scratch, the problems started soon after. They even wire rung the head
A preventative measure that masked rather than cured.
Same fault happened again.

We replaced stat and problem fixed.

[funtime]

Lawsy & Shimmy - agree with your theories, not sure about Alex's case, but my fluctuation in water temp does not follow high oil temp. My water temp is moving about without the oil going over 100, (only 1-2mm left and right of the centre of the gauge in normal driving) so I've been advised to change the thermostat first.

As soon as I have done so i'll report back - good thing is I'll know as soon as I've done it whether it's fixed the problem as it shouldn't move at all. (or so I've been told)

Fingers crossed ;)

[shane@mbtech]

Lawsy & Shimmy - agree with your theories, not sure about Alex's case, but my fluctuation in water temp does not follow high oil temp. My water temp is moving about without the oil going over 100, (only 1-2mm left and right of the centre of the gauge in normal driving) so I've been advised to change the thermostat first.

As soon as I have done so i'll report back - good thing is I'll know as soon as I've done it whether it's fixed the problem as it shouldn't move at all. (or so I've been told)

Fingers crossed ;)

Yours dropping below also, does sound like a stat issue

Hope it's a simple fix for you.

[AlexGTT]

Lawsy & Shimmy - agree with your theories, not sure about Alex's case, but my fluctuation in water temp does not follow high oil temp. My water temp is moving about without the oil going over 100, (only 1-2mm left and right of the centre of the gauge in normal driving) so I've been advised to change the thermostat first.

As soon as I have done so i'll report back - good thing is I'll know as soon as I've done it whether it's fixed the problem as it shouldn't move at all. (or so I've been told)

Fingers crossed ;)

Mine wasn't a case. Not had HG probs with mine..................yet!

Shim, any transfer of compression to another cylinder before it's ready for that particular cycle will cause heat issues. Then add combustion to that other cylinder as well (ignition from the cylinder that's lost the compression across the gasket) and you are effectively getting pre-ignition. If that is happening durring the up stroke of the next door piston.......................well, you can imagine the rest:bigcry: with the engine turning at 133 revs/second @ WOT.

[glendog74]

Mine wasn't a case. Not had HG probs with mine..................yet!


Do pay attention Alex - Funtime is referring to 'alexk' who has posted earlier in this very thread... :whistle:

Clearly you haven't been spending enough time on this forum lately! :hahaha:

[AlexGTT]

Do pay attention Alex - Funtime is referring to 'alexk' who has posted earlier in this very thread... :whistle:

Clearly you haven't been spending enough time on this forum lately! :hahaha:

Sorry Sir. Must try harder.:smt075 Feckin' hell, sounds like every school report I ever got.:hahaha: Things never change.

[alexk]

Today I found the time to remove my thermostat and do a comparison to the new one.
I am reminding that I had an overheating problem at the track.
I was also experiencing a drop in water temp after a fast run (i.e. highway with 200km/h and then backing off, the water temp would drop... and then after a while will go back to the middle).

I changed the viscus fan sometime ago as mine was dead.
This solved the overheating problem but clearly the thermostat was faulty too.

I ran a few tests using the traditional method of a an old pot and hot water.

1st test, put boiling water inside.
The new thermostat is on the right on all pics.
It opened faster but also opened wider.
You can see there is a difference of 2mm.
http://clubcsl.com/CSL/thermostat/CSL-thermostat-hotwater1.jpg

Then I quickly pulled them out for a pic.
Again the difference is massive.
http://clubcsl.com/CSL/thermostat/CSL-thermostat-hotair.jpg

I let them cool down and then did a 2nd test.
The result was similar.
http://clubcsl.com/CSL/thermostat/CSL-thermostat-hotwater2.jpg

3rd test
I started putting cold water inside.
The old thermostat didn't close fast enough (that explains my water temp dropping when backing off).
http://clubcsl.com/CSL/thermostat/CSL-thermostat-coldwater.jpg

I am confident my temp issues will be totally resolved with the new thermostat.
My recommendation is if someone has overheating issues to change the viscus fan and thermostat.

Last but not least, a picture of my helper 'Pipis'.
http://clubcsl.com/CSL/thermostat/CSL-thermostat-pipis.jpg

[shimmy]

Very interesting Alex, great test and nice pussy :thumbs:


I have my M stat fitted now so my temps are rising slower than before but no test yet of overheating issue, need 23oC + for that

[Bounce]

I bet you can boil an egg to perfection Alex.:thumbs::thumbs::hahaha:

[magnust]

...
I am reminding that I had an overheating problem at the track.

...

I changed the viscus fan sometime ago as mine was dead.
This solved the overheating problem but clearly the thermostat was faulty too.


VERY interested on how it was behaving at the track before and after changing the fan "thingy"! A bit surprised the fan would be involved in cooling the engine at speed on the track.

[alexk]

VERY interested on how it was behaving at the track before and after changing the fan "thingy"! A bit surprised the fan would be involved in cooling the engine at speed on the track.

It is a very tight track where you do 5 corners doing 60-65 (2nd gear).

[magnust]

It is a very tight track where you do 5 corners doing 60-65 (2nd gear).
Ah! Thx!

[shane@mbtech]

It is a very tight track where you do 5 corners doing 60-65 (2nd gear).

The Viscous pulls air through the rad from outside the car. When you are travelling at say 15mph, the air pushing through the rad is far greater than your viscous can pull it through.

Viscous only works when stationary or crawling in traffic.

[alexk]

The Viscous pulls air through the rad from outside the car. When you are travelling at say 15mph, the air pushing through the rad is far greater than your viscous can pull it through.

Viscous only works when stationary or crawling in traffic.

You theory is correct mate.
However, I have seen many times in Greece (with temps above 40C) BMWs having overheating issues when driving up a hill/mountain on 2nd or 3rd gear (40-80km/h) which were caused only by the faulty viscus fan.

You will notice the sound of the fan on a very hot day when accelerating on 2nd gear for example.

[shane@mbtech]

You theory is correct mate.
However, I have seen many times in Greece (with temps above 40C) BMWs having overheating issues when driving up a hill/mountain on 2nd or 3rd gear (40-80km/h) which were caused only by the faulty viscus fan.

You will notice the sound of the fan on a very hot day when accelerating on 2nd gear for example.

Yes, but it does not mean its doing anything. It just means the temp in the block is enough to kick off the viscous.

How can a viscous fan, which is only pulling outside air (40*c) through the rad exceed the effect of the air rushing through at 50mph? And stop it overheating?