Help Please! Coolant problems following water pump and thermostat change

[Fat Audi 80]

Gents,

Some advice please.

I have recently completed the cambelt change, which included a waterpump and thermostat.

I have the car back together and it runs, but the coolant is not flowing correctly. I have filled cooling system back up from the expansion tank, and tried to bleed it. However, my symptoms are as follows:

The engine warms up to an indicated 90+ degress after 5 - 10 minutes. The fan is NOT kicking in. The TOP of the radiator is HOT, the bottom is cold - hence the fan not kicking in. The coolant in tne expansion tank is COLD. The hoses out of the back of the thermostat are COLD. The engine is obviously very HOT!

I am 95% sure I have the thermostat in facing the correct way. I have read a post about it having to be at a certain rotational position.

Is all this pointing to a thermostat fault or installation mistake? Should I try anything else before I strip the thermostat out again to check its orientation and function?

All parts were genuine brand new ones and the car was perfect before I took it apart!

Thanks,

Steve

[A80Avant]

How about the radiator being blocked?

We had to do this once upon a time on my car. It had stayed in the garage for 2 weeks stationary and when the engine rebuild was complete we got the same symptoms and the radiator was 95% blocked.

[Rusty]

Sounds like you need to bleed it properly. Have you lifted the expansion tank up and bled the rad? How did you bleed the.matrix?

[s2driveruk]

airlock by the sounds of it Steve....they can be a pain to bleed or there is crud in the radiator and you need to reverse flush it - mine had a bit of scale in it

[Fat Audi 80]

I have "lifted" the expansion tank, but have NOT turned the heater controls to HOT. I must admit, I have been quite relaxed over this last bit. Just threw the coolant in it and expected it work!

I can unscrew the bleed screw at the top of the rad, there is a tiny bit of water seeping out. The system is NOT pressurising as far as I can tell...

It has taken the satisfaction out of (I hope) a job well done.

[Fat Audi 80]

Sounds like you need to bleed it properly. Have you lifted the expansion tank up and bled the rad? How did you bleed the.matrix?

I haven't bled the matrix at all.

[4WheelDrifter]

Don't worry Steve. These little problems can happen to anyone. Don't let it put you off.

TBH I can't remember on the S2, but there is often a small hole in the top of the thermostat, to let air bubbles escape. Air-locks can be a PITA.
I think I would run a hose pipe through the radiator to check that is clear. Then bleed the matrix hoses. Have you got original hoses on yours, Steve?

[Fat Audi 80]

Hi Stu,

Yes all original hoses. I need to investigate a bit more. I only got it back on it's wheels today and have run out of time to look at it this weekend.

I want to work out my plan of attack for the next chance I have to work on it.

I will have a go at bleeding the heater matrix next then check the rad. It was perfectly fine before I took it apart. I either have an air lock or I cocked up the installation of the new thermostat (or it's faulty - unlikely but not unknown)...

Cheers,

Steve

[s2_bo]

Carful losing the nuts on the matrix hoses, they are fragile to say the least!
Good luck!

[4WheelDrifter]

Carful losing the nuts on the matrix hoses, they are fragile to say the least!
Good luck!

Yes. That was what I was getting to. Go careful!

You are right, Steve, just because the stat is new doesn't mean it works.

[Fat Audi 80]

How about the radiator being blocked?

We had to do this once upon a time on my car. It had stayed in the garage for 2 weeks stationary and when the engine rebuild was complete we got the same symptoms and the radiator was 95% blocked.

Sorry, missed this yesterday. I am not ruling out the rad, but I don't suspect it yet. The coolant that came out was very clean and pink. The rad is relatively new (5 years old) and the car was perfect before I drained the coolant...

Cheers,

Steve

[Fat Audi 80]

Anyone got a good diagram of the cooling system to hand please? I want to start at first principles....

Cheers

[Pirvu Eugen]

If you lifted the tank when filling the coolant...the thermostat is dead or improper fitted.
The cold low side hose means the thermostat is not opening.
I know is a big job...but i think you should check that.
Goodluck!

[Fat Audi 80]

If you lifted the tank when filling the coolant...the thermostat is dead or improper fitted.
The cold low side hose means the thermostat is not opening.
I know is a big job...but i think you should check that.
Goodluck!

This is what I suspect. I am going to have to bite the bullet and lift the PAS pump out the way and try and strip the Thermostat out again.

Unless I have a air lock in front of the thermostat (if that is possible?) which is preventing it from opening.


First I will double check I don't have an air lock, then do the thermostat. The whole point of changing the thermostat was it was easier while I was doing the cambelt. I wish I hadn't bothered now, my car has always behaved perfectly from a cooling point of view.

Thanks.

[pixsaudisex2]

I always leave the lid of the tank. Fill it up via the radiator hole. Run engine untill the bubbles start flowing an fill up with warm kettle water. And anti freeze.


But like you say if the thermostat is wrong way I imagine it would cause a few problems..