Heating issues

[AudiChris79]

Afternoon guys and gals

I've got an issue with the Audi's heating. Now with help of a Mechanic friend we have flushed and bled the whole system. Replaced the thermostat and it doesn't look like the pump is at fault, however it's not been completely ruled out at the moment.

The strange thing is, if I give the car a boot it gets hot. What I find strange though is when I'm stopped at the traffic lights the fan slows down. Could I be right in thinking this is the HVAC controls. Could this also stop the warm air getting through and switches it to cold air? Matrix was flushed out and no crud in there.

Has anyone else come across this issue?

One other thing I do have an issue with is the coolant pipe with the bleed nipple on it, how easy is it to pick that pipe up does anyone know the part number?

Thanks
Chris.

 

[Mike B]

Are both the bulkhead pipes hot?If so the coolant is circulating but not getting round the matrix.It seems the fine pipes in it get blocked and its often impossible to flush them clear.Did you backflush?Wont be pump failure cos it would boil even in this weather.I think the fan has a variable speed coupling and if it slows when stopped thats showing the temp has dropped.Really shouldnt be running much if its freezing.I think you can check the fan by putting a rolled up newspaper in the way .It should stop if not the coupling has failed that might be why its running cool.Does the gauge get to 90 quickly and stay there?

 

[AudiChris79]

Are both the bulkhead pipes hot?If so the coolant is circulating but not getting round the matrix.It seems the fine pipes in it get blocked and its often impossible to flush them clear.Did you backflush?Wont be pump failure cos it would boil even in this weather.I think the fan has a variable speed coupling and if it slows when stopped thats showing the temp has dropped.Really shouldnt be running much if its freezing.I think you can check the fan by putting a rolled up newspaper in the way .It should stop if not the coupling has failed that might be why its running cool.Does the gauge get to 90 quickly and stay there?

Hi Mike,

Thanks for the reply.

The lower pipe is warm but the upper pipe is cold, this is one of the reasons why we changed the Thermostat. Cause we thought that coolant was getting round the engine, but not enough to get to the matrix. Another reason why we thought the pump may be at fault after as this was not resolved. Lower pipe to the radiator is also cold again another reason why we are now thinking the pump.

Its strange as when I got it hot, and was driving normally it stayed hot, but I had to give a boot up the backside to get it hot.

Do you happen to know what the metal coolant pipe with the bleed nipple is called or perhaps anyone else that reads this may know or have the part number, as the bleed nipple has broken.

Thanks again for the reply

Chris.

 

[Mike B]

Chris
Ok so could be an airlock then and first you need to change the pipe but I dont know what that involves.You might get any air out by lifting the expansion tank with the cap off but its going to need a working nipple to get somewhere.Did you use a genuine stat?I have been caught out with cheap ones and it would take a lot of air and stat failure would explain why you got it hot.Coolant must be circulating cos it would soon overheat if the pump fails.First sign would be some bubbling in the tank.Also loss of pressure could be caused by the tank cap seal failing and but this seems unlikely if you did get it hot.You could try loosening the cap when its warm to see if any pressure releases.What about the gauge? thats a good indicator of stat failure

 

[AudiChris79]

Chris
Ok so could be an airlock then and first you need to change the pipe but I dont know what that involves.You might get any air out by lifting the expansion tank with the cap off but its going to need a working nipple to get somewhere.Did you use a genuine stat?I have been caught out with cheap ones and it would take a lot of air and stat failure would explain why you got it hot.Coolant must be circulating cos it would soon overheat if the pump fails.First sign would be some bubbling in the tank.Also loss of pressure could be caused by the tank cap seal failing and but this seems unlikely if you did get it hot.You could try loosening the cap when its warm to see if any pressure releases.What about the gauge? thats a good indicator of stat failure

Hi Mike,

Thank you for the reply.

Firstly apologies for missing the temp side of things, it gets to 90 relatively quickly and stays there, doesn't go above and no boiling over or anything.

Stat wasn't OEM. But it was new on Saturday, if I have to replace it with OEM after I have resolved the issues and potentially got the air lock gone.

I've been given a price of £58+vat for the new pipe from TPS. That price was got for me by a mechanic friend of mine. He's been puzzled by this issue and we were going to actually change the belt and pump when the weather got better. However I think I'm going to change that pipe first and bleed it. Hopefully that will fix it.

Again I appreciate your help.

Thanks
Chris.

 

[Mike B]

Chris
The gauge seems to show the stat and the cap working so we are still on an airlock as the cause .Again not the pump cos failure always leads to boiling thats my experience.The pipes should be about equal even if the matrix was blocked cos the coolant would by pass.I have had little trouble with airlocks despite playing with cooling systems for many years but it seems some engines are more prone than others.Whats yours?I seem to recall advice saying raising the tank when filling helps .Perhaps that gives it a bit of pressureto drive air out but I have never needed to try it.

 

[abyrne153]

I had exactly the same symptoms as you. Only blew warm when giving it some stick and under normal conditions bottom hose warm and top hose cold. Heater matrix is likely stuffed with crap. Check by removing the top hose with the engine running. It is likely just dribbling through or not running at all. If it is stuffed then remove the battery. I disconnected both hoses and fitted two old bits of hose to the 2 pipes and blew out the matrix to clear out most of the water. Got a suitable drum to collect from the bottom hose and filled the matrix with radiator flush. Blew into the top hose to agitate the flush (do not get a mouthful of the stuff) and made sure it got into all parts of the matrix. Left for about 1/2 hr. Flushed through using a funnel and boiling water from the kettle. Repeated again using more flush and this time ran the hose through the matrix for about 10 minutes back flushing from the bottom hose to the top. Reconnected everything and bled - there is a tiny hole in the top hose which bleeds it if its not pushed home fully. Tightened all up and its blowing hot since. I had bought a new matrix as I had thought I might need to change it but it I didn't need to in the end. Hope this helps.

 

[AudiChris79]

I'm still having issues with this. Main issue I have at the moment is I need the metal coolant pipe with the bleed nipple. This is now starting to leak. So I'm losing coolant. ****** car is starting to annoy me now.