Coolant Temperature, Auxiliary Water Pump and Fans, it's all gone Pete Tong!

[rickdonald 10]

Hi All, know this is a bit of a common one, but I have tried searching for the last few days and poking around under the bonnet, and all its doing is getting me more worried!

 

My coolant temperature started getting quite high while sat in traffic a few weeks ago, and from the sounds of it, my fans only come on at stage 1 when the temperature on the gauge reads 110. Then it just sits around there till i start moving again and it will sink back down to 90. I have tried checking the fans, by bridging the relevant pins to make sure I get stages 1, 2 and 3, and that seems to work fine.

 

But on checking that I have now noticed my aux coolant pump is a bit temperamental and appears to only really work when it feels like it, i.e. sometimes it comes on, but mostly it just doesn’t bother. I have recently changed the rad, the rad thermo switch and the header tank, so I don’t know whether it could be something to do with the rad thermostatic switch? I was considering changing it back the on in my old rad.

 

When I turn the ignition off sometimes the fan will run on when needed, but I’m not sure auxiliary pump does. When I try bridging the terminals of the 'yellow lead' to check the pump and fan run on, the fan runs, but I don’t think the pump does.

 

Not expecting an answer but if anyone has any advice or suggestions would be great. Going to have a go at checking all the connections tonight, I had a look at the fan control module yesterday to see if anything was loose, but it was fine.

 

Cheers

 

Rick

 

---------- Post added at 05:40 PM ---------- Previous post was at 03:47 PM ----------

 

just had a look at the feed for the aux pump, and it's showing 12v when the ignition is on, so I'm guessing I have a bad pump. Anyone any ideas why it's hitting 110 before the stage 1 fan turns on? Or if it could be related to the six pump? I can't see how it is, just wishful thinking I guess.

[floppyman 0]

It does look like you have two problems... Aux pump and the fans not kicking in.

Have you checked all the fuses? Including the ones on top of the fan controller?(right side of engine compartment by the coolant tank).

If not fuses then problably one of the sensors

[floppyman 0]

There is a tread around here that talks alot about cooling... Maybe some one can put a link

Here

 

http://the-corrado.net/showthread.php?t=38925

[rickdonald 10]

Yer, had a good long look through there last night, been having another play, I've noticed if I bend the top of the connection over on the aux pump it works, doesn't sound too health, sounds like there is a bad connection inside. And I tried the test on my fan again and both stages seem to work fine, so I think it might be the rad switch that's causing it to only switch on at 110

[floppyman 0]

On the aux pump then it might be the plug... On mine I had to replace the plug aswell.

Did you check the fuses? Try bridging the wires on the thermoswitcch 3 wires?

If the fans work then its the thermoswitch

[floppyman 0]

A little stupid but.... Is the plug on the rad switch the right way around?

[rickdonald 10]

Ha that would be abit embarrassing wouldn't it, I thought it would be like the other plugs and only go on one way but I will check just incase, yer bridging the wires and the fans work fine, so looking like the switch. Will try replacing it. How hard is it to replace the pump connection? Tempted to try that, really don't want to have to buy a whole pump if it's just the connection. Cheers pal

Edited July 27, 2011 by rickdonald

[floppyman 0]

Its not hard to replace the plug... Maybe is just easyer with some crimp connectors

[rickdonald 10]

Ah do you mean the plug or the socket? I think mine is the socket on the actual motor that's gone. So it will mean taking it apart I think and seeing if I can rewire it. Cheers

[floppyman 0]

I see.... I was thinking it was the plug, in that case you will probably need one new pump.

Its not easy to open it and fix it

[Kevin Bacon 5]

But on checking that I have now noticed my aux coolant pump is a bit temperamental and appears to only really work when it feels like it, i.e. sometimes it comes on, but mostly it just doesn’t bother.

 

Bear in mind the Yellow temp sender turns on the fans and pump at 100 deg C and off at 95 deg C, so you won't always hear the fans running when you switch the car off. Whilst the engine is running, all 3 speeds are available and the pump runs permanently. It's just a booster pump for the heater matrix, so I wouldn't worry too much about that. Pins 1 & 4.

 

Pins 2 & 3 are for the temp guage on the dash. It's quite common for the yellow sender to go on the after run side.

 

As the pump is a brushless motor design, you can actually take it apart and clear out any metallic crud that's built up and stops the impeller from turning smoothly. You can also test it in a bucket of water and a battery.

 

If your fans aren't coming on until an indicated 110 degrees with the engine running, it could be the radiator sender, which triggers speeds 1 and 2.

[rickdonald 10]

Cheers for that, I will try taking the back off the motor tonight and see how it looks inside.

 

I think I’m leaning towards it being the rad sender that’s causing the temperature to rise to 110 before the fans come on. As the fans do run on sometimes when I park, but only if the coolant is still 100-110, usually I have had a good run before I pull up and the coolant temp is around 90, and they stay off. So that makes me think the yellow sender seems ok?

 

Also because I can get the fans, and coolant pump (when it feels like working) to switch on when I bridge the two relevant terminals in the yellow sender plug. Am I right in thinking points to the yellow sender working ok?

 

I also tried plugging it into VAG-COM the other night and the temperature shown on there from the ECU seems to match the gauge, so I'm guessing I cant really blame that either

 

Thanks

[rickdonald 10]

Update, I've been playing around with the car for a few days now trying to get to the bottom of this. I took the pump apart and gave it a good clean and its now working. So I now have the pump whenever the ignition is on, and if the after run is triggered (i.e. >100 degrees). Which I think is how it should work on the later VR?

 

However if the fans and pump run on after I switch the ignition off, then it means that the yellow sender is reading the coolant temp is >100 degrees, therefore you would expect for stage 1 fan be on pretty much constantly when the engine is still running? but its not, it will come on for like 10 seconds, then go off, then after another 30 seconds it will come back on again, and off...... as if the temperature cools really quick, so the fans go off, then it heats up again, fans come on, then cools again. But the temp gauge and the VAG COM readout both say the temp is just over 100 when this is happening. Does anyone else know if this sounds about right and I am just being soft?

 

Initially I thought it might be the temp switch in the rad, but I have replaced that and it’s still the same, even checked the old one to check it opened stage 1 at 90 odd degrees by putting it in near boiling water, and it seems fine! As I said before if I bridge the connections on the plugs then the fans work exactly as they should on all 3 stages.

 

I think my last thing I can think to do is to replace both yellow and blue thermostat temperature sensors, as I think they are both reading too hot, does this sound logical to anyone else? Or can anyone offer any more advice?

 

Sorry for the long winded explanation, just wanted to try and get everything in.

 

Cheers