Overheating

[dubber6 0]

Strange thing this. No CO2 in the water no high pressure feeding into the header tank. No obvious leaks (no tell tale coolant colouration either). Car warms up runs for about 5 minutes and then overheats. Fans are cutting in OK. Main water pump is happily pushing the coolant into the header tank at idle, checked and is ok, plastic impeller still intact. Am suspecting a stuck thermosts or is there an auxilliary pump? that may not be working?

HELP! Am currently tooling around in a 1400 Mk3

[badboyV6 4]

Souns like it could be the thermostat is stuck closed. Temp sensor is ok as your fans are kicking in. I think someone told me theres an auxillary electric pump.....

[andy 0]

There is an auxilliary water pump, its electric and is situated at the rear of the engine on the rhs, just behind where the leads join the coilpack, (if you have one). It slightly under the black plastic tray that the plugs are guided with, its a vertical metal cylinder and should be running all the time the ignition is on, you should be able to feel it vibrating slightly or hear it humming with the engine off but ignition still on. Do a search on for further info mate.

[dubber6 0]

Cheers Guys

So good to have knowledge out there, that incidentally VW should provide on a database, but then again with their knowledge of their own cars I do wonder how useful that would be.

As you can imagine I'm a little bit green on VR6 stuff but have fiddled and tinkered with all manner b4 this beauty arrived with me a year or so ago, no problems until now, sweet.

Have looked and found an electric pump. My understanding is that this circulates water around the head, particularly good when the engine is stopped and the main pump is not rotating, as it prevents heat build up and potential warping of the head. I wonder if this was a modification when VW found out this was a problem - do the earliest engines have it? Is it a fitment that was needed because of poor engine design in the first place? Vorsprung, vorsprung, vorsprung, etc etc. If this pump runs all the time and it has stopped could that cause the overheating? I'll obviously start with the thermostat on a cost effective basis - is it worth buying the aftermarket improved ones that allow cooler running or is it best to stick with the standard - car is totally standard at the mo - but Im getting itchy fingers!!

Cheers

[andy 0]

The auxilliary pump and the twin fans will run on after the engine has stopped to reduce under bonnet temperatures. Don't think its an afterthought as such, its just a big engine in a small space. If that pump is not running it will probably cause problems eventually, mine broke and it was the straw that broke the camels back in my cooling system.

[acf8181 0]

what happened when your water pump failed andy? i've been curious about whether theres a botch solution should my implode again like it did in germany...could it be bypassed enabling the car to keep being driven? any thoughts anyone.

there are aftermarket ones, i've seen them in one of the motorsport catalogues....they look, er, beefy! not much different in price to a brand new o.e. one.

[badboyV6 4]

Does anyone know why two pumps were fitted? If the mechanical pump was not enough why not just make it bigger in the first place? Or is the auxillary only supposed to kick in, in when stuck in traffic on a hot day for instance.

[andy 0]

No, the auxilliary one should run all the time the ignition is on, and when the engine is off to reduce the under-bonnet temperature when necessary. Gonna need an electric pump when the engine's not running.

[acf8181 0]

yep, thats prob the main reason...for when the engine is off.

all mkIV's/beetle's/passats have one as well, at least the proper engines anyway. if it had been an after thought on the vr6 they'd have dropped it on the later cars.

[badboyV6 4]

Ah i see, spose it makes sense....

[dubber6 0]

Thankyou ma Golfing chums. New thermostat and all is running ticketyboo. Lesson learnt for all perhaps - get the bits and bobs to replace the thing, hide under the stairs until you need them -apparently one will at some point!