Header tank not hot !!

[T2Andy]

Been trying to bleed my cooling system and noticed the header tank will not get hot only slightly warm even after 25min on tick over and even after a run
There is no water coming from the small pipe which returns to the tank,I'm sure it used to flow back in,the engine had a new Audi thermostat last year and water pump ,the rad gets hot right to the bottom and all the hoses are hot but this doesn't seem to get to the tank any idears please ,I'm sure all the air is out now unless there is still one big pocket of air somewhere,the heaters blow hot and the temp gauge is 90' or just below .just fitted a new rad which is 1yr old .

[robo]

Audi thermostat last year and water pump , below .just fitted a new rad which is 1yr old .

Do you know if the water pump had plastic blades?
The new design water pumps that audi uses now is sh/t.

[T2Andy]

I think they were metal as it was from my other engine ,do you think the blades have sheared

[robo]

I think they were metal as it was from my other engine ,do you think the blades have sheared

If they are brass that should be ok, but if you not getting any flow from the little return pipe it could be no circulation from water pump.

[Quattro Dan.]

I think they were metal as it was from my other engine ,do you think the blades have sheared

Andy, the water pump i fitted for you had metal blades, i never fit plastic ones as they are c*ap.

[s2driveruk]

is the rad hot? could be a thermostat problem

[JP]

Andy, the water pump i fitted for you had metal blades, i never fit plastic ones as they are c*ap.

Two schools of thought on that one.

The original Audi pumps pre 1996 where metal and these had a habit of seized bearings in them due to the greater conductivity of heat through the shaft. Resulting in interesting valve to piston impact.

The later ones have plastic impellers and have a habit of becoming brittle with age and breaking of causing overheating. However if the timing belt is serviced within it's allotted mileage/time and water pump replaced each time. The correct G12 coolant is run then there shouldn't be any issues with the plastic ones.

Back to the problem in hand though if there is no water coming back from the return pipe then there is definitely a water circulation issue. The more you rev the car the more water should come back through that return pipe once up to temperature. Is the hose coming of the thermostat housing getting warm?

[GazzaG60]

i have similar issues at times.

i think its due to tthe hose off the water rail on mine leaking uoder heat/pressure.

i too replaced my pump with a new one when i did the engine but it aint got the pressure of the old one.

[T2Andy]

Everything is getting hot bar the header tank ,I can remember the water flowing through the return pipe at some point ,but even when you rev the **** off it it wont produce any water into the tank ,i have brimmed the radiator with coolant too.
I think we put all new parts on Dan if I remember

[GazzaG60]

airlock maybe in top of rad.

i did an air clearing excersise on mine yesterday and heating is hot again.

not overly impressed with thewater pump pressure though

[S2central.net]

Gotta wonder is this why Porsche felt the need to make the 5cyl water pump spin faster on the RS2 - with its smaller roller versus S2 and different timing belt as a result.

This one sounds like an airlock as if the pump wasn't pumping then the car would overheat and you'd never get heat in the cabin. They can be a ****** to bleed properly.

[T2Andy]

This has all happened since changing the radiator

[newsh]

Pull the small hose off the top- back of the rad and make sure water comes out, sometimes they're not open on a new rad.

Squeeze the top hose sharply and the water should surge up into the header tank, maybe bring some bubbles with it..

[T2Andy]

Done that ,if I squeeze the top hose some water will squirt into the tank but not much and in spurts