voo51 0 Posted May 26, 2013 Hi all, I'm finally getting round to sorting my water pump issue. When the fan starts the water pumps stops working, pressure builds up and coolant is expelled under the pressure. The head gasket is fine, that has been tested. Does the round black plug in the picture have an electrical link between the fan and pump? I ask as it appears at some point the wiring has been played with and the plug is not connected properly. Unless anyone has any other ideas? Thanks http://i32.photobucket.com/albums/d14/voo51/Ice%20violet%20vr6%20Corrado/Engine%20pics%20during%20detailing/20130525_122047_zpsf62832dc.jpg Quote Share this post Link to post Share on other sites
nrc 0 Posted May 26, 2013 That plug is on the stage 1 + 2 fan switch and is used when the ignition is on, via the fan controller/relay box. Do you mean the auxiliary water pump stops when the fans come on? That's not so much of an issue as you should still have the main water pump driven by the serpentine belt. Nothing electrical is going to stop that! Quote Share this post Link to post Share on other sites
Dox 23 Posted May 26, 2013 Make sure the earth to the fan control relay is connected and clean. Check all other earths for the coolant system too. When the fans come on check to see which side of the aux pump power is being switched off, the pos side or the neg ---------- Post added at 10:19 AM ---------- Previous post was at 10:14 AM ---------- Make sure the earth to the fan control relay is connected and clean. Check all other earths for the coolant system too. When the fans come on check to see which side of the aux pump power is being switched off, the pos side or the neg Quote Share this post Link to post Share on other sites
voo51 0 Posted May 26, 2013 Dox - thankyou I will check those. NRC - I didn't think it would be such an issue either as people remove them and run fine but apparently that is what the overheating is down to. The radiator and various other sensors and coolant tank have already been replaced but I'm debating buying another expansion cap to see if the new one was a dud. Other than what's been suggested the only things I can think of are: An air lock in the system Faulty aux water pump Faulty main water pump Faulty temp sensor Faulty fan switch Faulty thermostat or fuse I'm getting a bit worried about testing things though as I don't want it to keep loosing all of its coolant. Quote Share this post Link to post Share on other sites
nrc 0 Posted May 27, 2013 Is the coolant coming out of the expansion tank cap or the relief valve on the side of the tank? The relief valve on mine gave up recently when waiting in traffic on a hot day and the fan controller failed, spraying the engine bay with coolant. I've a new one on the way but currently it starts to weep from the valve when the coolant hits ~100 C. Not sure if they're single-use or whether it's just an old part. Quote Share this post Link to post Share on other sites
Stonejag 10 Posted May 27, 2013 (edited) You can run it on plain water if you're just testing, no need to keep pouring away tons of G12... My aux pump's not been running for ages now and I don't see overheating like you describe. The plug shown is for the fan switch, however turning the fans on obviously won't help if no coolant's circulating through the radiator. Are both top and bottom radiator hoses getting hot? (if not: thermostat). When running there should be a steady trickle of coolant being pumped through the small-bore return hose into the expansion tank - you can run it with the cap off to see. If not, you might have some vanes broken off your main water pump - this is supposedly quite common with the plastic-impeller ones they got from the factory. You can eliminate an airlock quite easily by running the engine with the expansion tank cap off and the interior heater turned up to full heat until coolant is about to bubble out of the top of the tank. If you don't turn the heater up first then the air bubble can hide in the heater matrix. The fan controllers have a couple of relays in them which can go bad - cheap to replace from scrapyards (look in Mk4 Polos or Mk3 Golfs and other similar-era cars, I found one in a Sharan once) but be aware there are four types depending on model so make sure you get the right one! Expensive from VW though, I was quoted £150ish 25 1H0919506 electric fan control unit / to be used for: / also use: / F >> 50-P-020 000 1H0 919 506 A N 017 125 2 / ABV,KR,9A,PG (25) 3A0919506 electric fan control unit / to be used for: / also use: / F 50-R-000 001>> 357 919 506 A N 017 125 2 / ABV air condit.: 2E (25) 357919506E electronic control unit / electric fan / for models with radiator fan run-on / F 50-R-000 001>> / 9A,2E (25) 3A0919506B electric fan control unit / for models with towing facility / and/or / for vehicles with automatic / for vehicle use in warm climates / F 50-R-000 001>> / 9A,2E I'd personally be gunning for your thermostat being stuck shut (not allowing hot coolant into the radiator to cool down) or your main water pump being duff. Hopefully that gives you some ideas though, I had a very frustrating few months with slow leaks everywhere, broken senders and a stuck-open 'stat so I know what it's like! Stone Edited May 27, 2013 by Stonejag Quote Share this post Link to post Share on other sites
