The definitive VR6 cooling guide

[ziderapple 0]

Great thread, been thinking for ages someone with the knowledge should do a decent write up on the subject. So thank you. :salute:

 

Also would it be worth copy and pasting the first post into a wiki guide?

[dinkus 10]

Just added the pumps section :lol:

 

Also would it be worth copy and pasting the first post into a wiki guide?

 

And yup, if the wiki would let us edit it at the moment :( (it's on the to-do list)

[Kevin Bacon 5]

So if you pull up after a journey and the fans don't run, that is a good thing, not a bad thing :wink:

 

Glad to hear that. Thanks Mr Cheesewire :D

 

Forgot to say...... it's a good thing providing the dash gauge isn't reading 100+ :D

 

If temperature is normal i.e. ~ 90 degs when you stop, there's a good chance the 95 deg Stage 1 won't be triggered. It may kick in randomly as the after run pump circulates the hotter water out of the matrix and block/head into the radiator. All normal stuff.

 

If the fans do nothing when the gauge reads 100 (middle), the rad switch is probably knack'd.

 

If the fans do nothing past 105, the rad switch *or* fan controller is borked.

 

If the fans do nothing past 110, run!! :D

Nah, stage 3 switch is borked or missing in action, presumed dead....or the controller.

 

I've had to replace the controller and it's an eye watering experience, £110+VAT IIRC!

[ziderapple 0]

Is this being added to the knowledge bank?

[biggerbigneil 0]

Can we have a 'cooling trouble shooters guide for dummies' please as this makes absolutely no sense to me....

 

I've just bought an M red VR6 on 69k and the water temp reading is going up to 110, whereas the oil temp on the maf says 108 at most. The coolant is the colour of rust and the oil is black as the car has sat in a garage for 3 years - will be serviced on Saturday!

 

The fans only turn on after I turn the ignition off and even at 110 degrees do not kick in until the engine is turned off?

 

Any thoughts before I go and buy a 5 speed setting fan with AC????

 

Biggerbigben thinks I need a new fan switch but after calling up VW they say there are several - so I said I'd find out on the C forum!

 

Cheers

 

Neil

[dinkus 10]

First of all, I'd get it plugged into VAG-COM and see if the coolant temperature that it reports (Blue temp sensor) matches what the gauge on the dash says (yellow sensor).

 

If they're hugely different numbers (i.e. the ECU one is reading much lower) then I'd wager the yellow sensor is kaputt and lying about the temps being too hot.

[biggerbigneil 0]

Thanks chap, i'll try that!

 

The other issue is that the fan won't run whilst the engine is running but it will kick in as soon as the engine is turned off?

 

Switch below where the battery is?

[dinkus 10]

Err tricky one - if you don't know whether the temp gauge on the dash is lying or not, then it's hard to say whether the fans should be on or not while the engine is running...

[oxfordpaul 0]

Mine goes up to nearly 110 too before the fans cut in. Also I've just noticed that when I turn the engine off when hot and the fan was on with the engine running, the fan stays running but then cuts off and then on for say 5 seconds, then off and on at least 10 times for 5-10 second intervals. It's like its become really sensitive and thinks it's cooled but then the heat quickly returns triggering the fan again - any ideas?

 

Also I'm convinced a lot of Corrados show nearly 110 before the fans cut in as I see a lot of posts about this but mine didn't used to until I changed the rad switch and I wonder if there's a common fault no-one has got to the bottom of?

 

Surely they should stay around the 90 mark as all other cars I've had generally stick around the centre?

 

About the only part I've not changed is the water pump - could this be weak therefore not pumping water through the radiator and around the thermoswitch quickly enough to trigger it - i.e. the water in the engine block is much hotter?

[steve @ 0]

Mine does pretty much the same as yours Paul. The cooling system on mine is all pretty much new (rad, ally crack pipe, water pump thermostat etc etc). I dont think its a problem so long as the fans keep the temp at 110

[dinkus 10]

The VRs run hot. Sounds like you're a bit too paranoid :lol:

[biggerbigneil 0]

Okay, just had my car serviced - oil, plugs, filters, coolant (all the proper VW stuff).

The oil temp goes up to 114 and water to 110 - mfa and clocks.

The fan does kick in at 110 I'm told but not before unless the engine is turned off.

I've had two previous VR6 Corrado's and the water tep never went up to 110.

There is no loss of performance or any warning lights at 110 and it does not go any hotter but it should be around 95-100 at most as I was cruising at 77 mph only.

 

The switch can't be buggered as the fan comes on, the sensors are correct and other than hooking up to VAG-COM I'm unsure what to do, except possibly an oil cooler.

 

Thoughts?

[pete_griff 0]

any chance this thread could be stickied - some very useful info on here

 

thanks very much for your efforts dom - top man :thumb right:

[fla 9]

I've got two spal fans wired into mine (i have aircon plus a mocal so its quite congested!) At stndstill the fan trips in at 78 degrees oil, for about 5 seconds and then turns off again. The oil temp rises to about 82 although the fan still exhibits this behaviour. I havenet driven it too far yet as i'm trying to burn off some oil on the exhaust downpipe, but notwithstanding that point, any suggestions on this?

[Kevin Bacon 5]

Also I'm convinced a lot of Corrados show nearly 110 before the fans cut in as

 

Shouldn't be the case.

 

Speed 1 kicks in at 95 degrees, speed 2 - 105 degs and Speed 3 - 120 deg.

 

You can check if for yourself if you like.

 

The blue water sender in the stat housing should give the following :-

 

935mV at 90 deg C

781mV at 100 deg C

620mV at 110 deg C

495mV at 120 deg C

 

If these are correct and the fans come on at their designated temps, then you know the dash guage is lying.

[fla 9]

I've got two spal fans wired into mine (i have aircon plus a mocal so its quite congested!) At stndstill the fan trips in at 78 degrees oil, for about 5 seconds and then turns off again. The oil temp rises to about 82 although the fan still exhibits this behaviour. I havenet driven it too far yet as i'm trying to burn off some oil on the exhaust downpipe, but notwithstanding that point, any suggestions on this?

 

Just an update on this - i took my car for a bit of a blast yesterday, the water took ages to get up to 70-80C, but the oil rose quite well to about 94C (water still at about 70) I initially thought the water gauge was faulty it was taking so long. Mine is an auto so there is a slightly greater heat load due to cooling the auto tranny fluid too. But i've also got a mocal with the heat exchanger sitting on the front rad panel. Coming back home, the drive was at about 10mph (due to loads of speed bumps) and oil went up to 104/106, with water at about 95. I would ahve though oil would have been a bit less? As above, i have 2 spals and the mocal with an 80C sandwich plate. I also have aircon so its quite congested. Any thoughts? The standard oil/water heat exchanger has been deleted.

[markrtw 0]

I have been having the same problem recently. I have replaced the matrix, rad, both water pumps, the thermostat, the fan controller unit and a number of pipes, but the cooling fan only kicks in (on fan speed 3) when it is very hot. Fan speed 1 & 2 never seem to work unless I switch the engine off when its quite hot. (Switch the ignition on again and it stops again).

I was talking to Keith at ACEngineering recently about an ongoing Davia issue I have, and mentioned this to him and he said that it sounds like a broken resistor (or broken wire leading to/from). I asked what resistor as I did not know of one and he said that he could not remember the exact location on the corrado, but somewhere behind the front bumper area. I have not yet had time to investige this, but I know there is one behind the front near side headlamp, but I thought that was for the lighting. Apparently the control system when the car is off does not use this circuit as it's driven from the ECU, but when the ignition is on, the feed via the radiator thermoswitch does.

Can anyone confirm/deny or expand upon this??

[oxfordpaul 0]

Mmmm, this sounds like an interesting line of enquiry. All I can say is that when these cars were new I'm sure people would have been straight back to the dealers if their guages were showing nearly 110 before the fans cut in and I'm sure the guage should stay around 90. The fact that mine is dead on 90 when moving suggests to me my guage is fine. It's since I had a new thermoswitch in the rad that my temps are up and I wonder whether later batches of these are incorrectly manufactured and have a higher opening temp for the fans to kick in? Or this resistor theory or broken wire makes sense as mine too will put the fans on when I turn the ignition off as this circuit seems to work correctly and knows the engine is too hot. It's very frustrating and a bit concerning that the engine is so hot.

[biggerbigneil 0]

markrtw

 

That's exactly what mine did, however the water temp has not gone over 108 for the past few weeks. The car I bought was in storage for 3 years and i've only done 500 miles in it since July so maybe it just needed a good hooning! All stages of the fans are now working so god knows, either it fixed itself or the mechanic did it and didn't tell me about it.

[markrtw 0]

OK. I have finally fixed my problem. I replaced all 3 thermostat sensors as they were the only devices in the cooling circuit that I had not replaced and there was no difference (except the dash readouts are more accurate now), so I took some time out testing the wiring. Into the thermoswitch on the radiator there are the 3 wires to trigger the fan, so I switched on the ignition and did the age old test of bridging the Red (main live feed) and the Red/White (earth) wires and nothing happened (yet it has done previously). So I got out the multimeter and continuity tested the earth circuit to the battery which was fine.

I then (after some forum searching) pulled out the fusebox, checked its fuse (19) and located the other end of the wire which (with the fuse box in place) is located (most conveniently) on the left hand side 3rd from the bottom and is quite obvious as its a thickish red wire. About 10cm from the fusebox it has a connector where 2 wires go in (from the fuse box) and 1 comes out (the thin wire is terminated here and connects to nothing). I pulled the connector apart and continuity tested the Red cable back to the radiator thermoswitch and got nothing. So I then traced the wires path through the dash and bulk head into the engine bay. When I pulled up the wiring (after removing the battery and washer fluid bottle) I found a tiny nick out of the wire's insulation where it passed by the suspension turret (just where the wrap of wires has a junction off to the fan controller). It was only a tiny nick in it and the fuse had not blown so I was a little unsure, but looking at it the copper was a bit green. What had happened was moisture had been getting in there for probably years and corroded a cm or so of the wire away. I cut out 2 cm and then soldered it back together and then continuity tested it again - OK. Then the fan test worked after I had rebuilt the car and remembered to put the connector back on the fan and replace the No 19 fuse!

I can only guess that as the wire finally croaked it's last it would sometimes make a connection so when I tested it before it showed up fine. I hate electrics! Still, at least the cooling system is brand new/tiptop now!

[fla 9]

Just had a really stop - start drive around London this evening. It was getting a bit chilly outside (MFA showed 8C) but oil was constantly at 110 at a few points it went up to 114. Water however only went up to 90-92. I am usually more concerned with the oil temp, especailly as i have a mocal and 13 plate cooler. First time i have noticed the cooling fans stay on for more than about 5 minutes after we parked up. Is it worith fitting a larger cooler? Or any other suggestions for keeping the oil down at around 100-104C?

[SamG40 0]

Sorry if I'm being a bit thick but my aux water pump comes on with the ignition but stops as soon as the ignition is turned off. Everything else seems fine and I've replaced every sender within the last few months. Should I be looking at the fan controller relays as the aux pump is defo working.

[dr_mat 0]

Oil temps oh 110 - 114 are perfectly normal for a healthy VR6. Change the oil a few times - costs less than an oil cooler.

[fla 9]

Oil temps oh 110 - 114 are perfectly normal for a healthy VR6. Change the oil a few times - costs less than an oil cooler.

 

But i have a mocal also fitted, so this should be lower, around 100-104 or so, or not?

[andy35554 0]

Sorry if I'm being a bit thick but my aux water pump comes on with the ignition but stops as soon as the ignition is turned off. Everything else seems fine and I've replaced every sender within the last few months. Should I be looking at the fan controller relays as the aux pump is defo working.

 

mine does exactly the same!

and when the fan kicks in its only on for a few seconds (15 or so) then goes off

dont think I have ever heard the other "stages" to the fan - i will have to do a bit of testing off this thread to find out though, time to make a few shorting straps and get the multimeter out!