Cooling Issues (fanpack/radiator)

[golfglos]

Hi all,

I have a mk5 golf GTI stage2+ and noticed after a spirited drive and standing in traffic, or idling back on my drive the temperature has for the 1st time ever started to creep over 90c on the dial. Looking via obd I have confirmed it says around the same temperature for coolant. When it gets to around 116c or so I'd expect the fans to turn on.. but they don't. Before they would come on with the temp on the dashboard staying at a steady 90c as I'd sit on the drive waiting for them to stop spinning before turning the car off.

Stuff done so far

- Checked and swapped fuse F38
- Replaced the fanpack (twice)
- Fans spin on fanpack when connected directly to 12v

The car doesn't have AC, so I don't think the small fan turning on via pressing the AC cabin button will work.
It wasn't VCDS but sending Engine output test the fans don't spin
Coolant level seems fine, pipes to the res and to/from the radiator appear to be hot

Any ideas?

Thanks in advance

[LC5F]

coolant sensors? both of them.

[pudding]

90 on the dash could be anywhere between 80 - 110 degrees.  They've engineered it to stay in the middle like that, because.....Coolant temp for dummies.  It keeps paranoid people out of the dealers.

Where did you apply 12V directly to the fans? At the main connector on the fan casing?

Did you check the big chunky fuses in the engine bay fuse/relay box? 

[golfglos]

Hey thanks both for the replies

Yeah I understand the dial itself, so I have been checking with an OBD scanner as my first thoughts were the main thermostat was playing up again. still 'runaway' coolant temp shown there.

Yes, 12v directly to the fanpack and fuses/relays checked but I will do so again, I think it was fuse f38 I swapped/checked.

From other reading the next best thing would be the coolant sensor - I think there are two.. going to swap the easier one first.

Thanks for your help

[pudding]

The scan tool output test bypasses all external controls, and the fact that didn't work points to a problem elsewhere.  Wouldn't hurt to replace the sensors anyway if you think they're misreading/not functioning.

Have you scanned the HVAC controller as that is also tied into the fan control?  You say it doesn't have AC....as in you've removed it, or it was never fitted at the factory?

[exodus_ste]

I've had almost exactly the same issue for a couple of years now! So frustrating. I've also changed the fan pack, both sensors, all fuses are intact but i can get the fans to run full whack during output tests in VCDS.

My AC is not functioning at the mo, think there might be a leak in the system somewhere. Had it re-gassed at AKS a couple of years back and it was icey cold for 3/4 months. For a week or two after having the re-gas my cooling fans worked but not every time it got hot 

Genuinely given up with it, just suffer with running the climate at full hot when ever stood in traffic for a period.

Toyed with just fitting a switch under the dash to turn the fans on.

[golfglos]

I got this fixed. On the fuse box there are the in-line fuses. 3rd one in is the 50 for the rad control. Testing that there wasn't any voltage. Swapped it out and the fans are now working as they should. HTH!

[GVK]

Thanks for updating the thread with your fix!   

[exodus_ste]

Agreed, thanks for posting a fix. Unfortunately not helped my case but i've since made a discovery i think. When my temps were over 95 or so, if i switched the engine off the fans would kick in.

Ran some tests in VCDS and you can see the temp of both sensors. G62 engine outlet is the one above the gearbox and G83 radiator outlet is the one just before the t'stat on the block. I think i worked out that when the engine is running it uses the signal from the radiator outlet to kick the fans up - which makes perfect sense. I think when the engine is switched off and the aux pump runs that it uses the engine outlet sensor to trigger the fans. My readings when the engine was super hot and running were:

G83 radiator outlet @ 22deg
G62 engine outlet @ 102deg

Explains why the fans don't come on when the engine is running, then fire up when switched off. Purchased a new genuine sensor so will swap it out this weekend and hopefully this fixes it!