Thread: 300tdi intermittently oveheating

I have heard of aiming a jet of water from a hose pipe at the fan, which might be safer.

Originally Posted by AK83

just on the off chance, and only mention this because it could be done .. are the fan blades facing the right way around?

If you guys, or someone previously did work and changed the viscous hub, the fan can be unbolted from the viscous and could potentially be fitted wrong way around.


I remember first time I tried to remove the viscous hub, and didn't realise it's turning the 'wrong way'. That is, to remove it you have to 'do it up'. So with that in mind and engine running(at idle of course) check that the fan is pulling air to the back of the engine.

Has the viscous hub been ruled out as a dud too?
Couple of ways you can test it:

Easiest is if you have a heat gun. heat the front of it gently, and it won't take long. the coiled up spring should slowly move. This opens the valve to allow the silicon to move about within and lock it up(kind'a).

What I do now is to pop the nut end into a vise and spin the fan by hand. It could be a bit stiff to start with when cold(normal) then start to free up and spin freely. Then use heat gun on the coil, and it should be obvious when it winds itself.
I think it only needs to be about 80-90° ish and it will open the internal valve. Then while its still hot, try to spin fan again whilst on the vise. it may still start off a bit free, but then begin to offer resistance. if it never has any resistance while it warm, it's dud.

The other, dangerous, method is while still on the car, and engine got hot and motor off, hold fan with thick gloves or lots of cushioning and get someone to start engine and hold onto fan. at first it may feel free, but with a small amount of time it will start to spin on you.

That bleed valve thingy is important. Was on mine anyhow. I had same issue where it was leaking and I put a normal t-junction too. but then I had overheating issues and someone mentioned this little device. The mod I was suggested was to squeeze a small tube into the port coming from the thermostat in the T-juntion, but make sure that the small tube doesn't get sucked through too, so open up one end of the tube to shape it like a funnel. Was a bit of mucking about and I had the vacuum line that fit perfectly. Otherwise everyone recommends to use a Y junction, and not a T.
Anyhow, if new proper part is fitted shouldn't be a problem.

One last question about this issue. Does it happen on a highway drive only? does it happen around town driving too?

Thanks Arthur,

We have replaced the Viscous fan hub recently, however this improved cooling dramatically over the old hub when the motor was in the other car. I also checked the fan orientation and it is on the right way around.

The issue happens around town as well, the last few times the car hasn't actually gotten hot, I just check the coolant levels after each drive and the expansion bottle is full and the thermostat housing is empty.

I have ordered a new overflow bottle cap as a last small fix attempt.

Are there any other good ways to properly determine of this is a leaking headgasket?

Thanks again,
Riley