Weird flushing sound after heater matrix replacement

[Wilfcrook]

You may have some trapped air. It's normal after a matrix change. The system is designed to self bleed but it can take a few weeks. Keep checking your coolant in the morning when it's cold. If it drops a bit keep topping up. Mine `gurgled` a bit until it finally burped its way clear. Took about 3 weeks and I topped it up about 4 times. I think some people also put the heating on max to encourage the car to circulate the coolant.

Yeh it definitely seems that way. What did the gurgling noise sound like (like area where the sound comes from etc) because I do here a weird noise which sounds to the left of my engine when in high revs at third gear. Also, do you know why the level would drop if the coolant weren’t to be leaking? Thanks for your help too.

 

[Wilfcrook]

You may have some trapped air. It's normal after a matrix change. The system is designed to self bleed but it can take a few weeks. Keep checking your coolant in the morning when it's cold. If it drops a bit keep topping up. Mine `gurgled` a bit until it finally burped its way clear. Took about 3 weeks and I topped it up about 4 times. I think some people also put the heating on max to encourage the car to circulate the coolant.

Also any signs of coolant being higher than usual after driving(borderline overflowing)?

 

[BillyCool]

Yeh it definitely seems that way. What did the gurgling noise sound like (like area where the sound comes from etc) because I do here a weird noise which sounds to the left of my engine when in high revs at third gear. Also, do you know why the level would drop if the coolant weren’t to be leaking? Thanks for your help too.

The sound I heard was almost as if it were behind the dash - possibly where the heater matrix hoses come in via the bulkhead. Can't be precise but I could only hear it when the car was turned off after a journey, certainly not when driving. If you have air trapped in the system, it slowly gets bled out and that air gets replaced by coolant. So your coolant level will drop a little but it's not a leak - just replacing air.

 

[BillyCool]

Also any signs of coolant being higher than usual after driving(borderline overflowing)?

The coolant system pressurises when the engine is running, so the coolant level in the expansion tank will increase. It's shouldn't really overflow, unless you have trapped air that is now warm trapped air (which expands when warm) and the air is trying to escape. I can't say for sure.

You can always try squeezing the main radiator pipe between the rad and expansion tank. It's the old school way to try and purge air our of the system.

I can't properly diagnose it, so keep an eye on it. Also check oil is clean (no water contamination) as there could be other reasons over pressurising the coolant such as head gasket leak or charge cooler leak.

Hopefully - it's just some trapped air. When you replaced the matrix, how much coolant did you remove and then replace?

 

[brightWYFR]

I have this noise. Its been there for weeks. Funny because i changed the heater matrix in my previous Audi A3 2014 and didnt have this problem with that.

 

[Compo1]

I have this noise. Its been there for weeks. Funny because i changed the heater matrix in my previous Audi A3 2014 and didnt have this problem with that.

If you have VCDS

Bleed the low temperature circuit, basically it will activate the egr/matrix electric pump dispelling the air.

 

[Wilfcrook]

The coolant system pressurises when the engine is running, so the coolant level in the expansion tank will increase. It's shouldn't really overflow, unless you have trapped air that is now warm trapped air (which expands when warm) and the air is trying to escape. I can't say for sure.

You can always try squeezing the main radiator pipe between the rad and expansion tank. It's the old school way to try and purge air our of the system.

I can't properly diagnose it, so keep an eye on it. Also check oil is clean (no water contamination) as there could be other reasons over pressurising the coolant such as head gasket leak or charge cooler leak.

Hopefully - it's just some trapped air. When you replaced the matrix, how much coolant did you remove and then replace?

Completely forgot about this thread , my bad! But you were right my friend, it was due to very bad air pockets int eh cooling system. Coolant was also not flushed after my heater matrix change(great). But now I’ve had a few flushes and a new expansion tank. But I went in the motorway and the coolant has dropped below min-empty. I remembered you said this was due to coolant replacing air, do you reckon I should just keep topping up? Or should I say soemthing to the garage (as they charged me a fair bit).

 

[Compo1]

Completely forgot about this thread , my bad! But you were right my friend, it was due to very bad air pockets int eh cooling system. Coolant was also not flushed after my heater matrix change(great). But now I’ve had a few flushes and a new expansion tank. But I went in the motorway and the coolant has dropped below min-empty. I remembered you said this was due to coolant replacing air, do you reckon I should just keep topping up? Or should I say soemthing to the garage (as they charged me a fair bit).

It is their problem but it does sound as though you have it almost there, id just top up as it gets rid of air. That is as long as the heat comes through the vents as it does.

Bad practice in my opinion, not flushing before fitting a new Matrix.

 

[Wilfcrook]

It is their problem but it does sound as though you have it almost there, id just top up as it gets rid of air. That is as long as the heat comes through the vents as it does.

Bad practice in my opinion, not flushing before fitting a new Matrix.

Okay I will leave it and see how it goes in the next week.
the guy that did the heater matrix was an independent(very independent). He hadn’t a clue about heater matrix issues on VAGs and I basically had to run him through everything. He charged me £120 to change it, I asked if he had flushed it but it was clear that he hadn’t, when he gave me my bottle of coolant back, that had gone down about 200ml….

 

[BillyCool]

Okay I will leave it and see how it goes in the next week.
the guy that did the heater matrix was an independent(very independent). He hadn’t a clue about heater matrix issues on VAGs and I basically had to run him through everything. He charged me £120 to change it, I asked if he had flushed it but it was clear that he hadn’t, when he gave me my bottle of coolant back, that had gone down about 200ml….

I'd top it up and see how you go. Keep an eye out for leaks and give it 3 or 4 weeks.