Weird flushing sound after heater matrix replacement

[Aero843]

I'm having problems with my coolant system after replacing the Heater Matrix. dropped the rad hose and everything and drained, left the cap on heat full on till it got up in temps to 90 to get air out, topped up with coolant as the coolant went around the system but now I'm getting noises as seen in the video? any help appreciated
https://www.youtube.com/shorts/ATZ8mmkf85c

 

[RUM4MO]

I'd think that you still have air trapped within the coolant system, I bought a Draper Coolant Vacuum Refill Kit not because I wanted to, but because I thought that I would need that when I replaced the coolant after fixing a slight leak in my old S4, that worked okay, or at least I probably ended up with less air trapped initially, when I dump the G13 out of my wife's 2015 VW Polo I'll probably need to use that to minimise the chances of ending up with air trapped in its coolant system.
Eventually your system might end up purging itself of all trapped air, some earlier cars with the old 1.4 16V 86PS petrol engine were tricky to get rid of trapped air, I ended up finding out that the only or best way to refill that engine's cooling system was to remove the engine coolant sensor and refill the system with that out and continuing to refill once only coolant was coming out while refitting that sensor, a bit tricky doing that yourself, but it worked first time after failing to get rid of the trapped air by driving it a few times!

Edit:- maybe tell us which engine is fitted to that car, it does sound a lot like it is a TDI though!

 

[Aero843]

I'd think that you still have air trapped within the coolant system, I bought a Draper Coolant Vacuum Refill Kit not because I wanted to, but because I thought that I would need that when I replaced the coolant after fixing a slight leak in my old S4, that worked okay, or at least I probably ended up with less air trapped initially, when I dump the G13 out of my wife's 2015 VW Polo I'll probably need to use that to minimise the chances of ending up with air trapped in its coolant system.
Eventually your system might end up purging itself of all trapped air, some earlier cars with the old 1.4 16V 86PS petrol engine were tricky to get rid of trapped air, I ended up finding out that the only or best way to refill that engine's cooling system was to remove the engine coolant sensor and refill the system with that out and continuing to refill once only coolant was coming out while refitting that sensor, a bit tricky doing that yourself, but it worked first time after failing to get rid of the trapped air by driving it a few times!

Edit:- maybe tell us which engine is fitted to that car, it does sound a lot like it is a TDI though!

Oh ye forgot to mention, its a 2.0 tdi 184, I am just paranoid the coolant is getting around all the system and somewhere is getting no coolant and is just gonna burn out or something

 

[RUM4MO]

Oh ye forgot to mention, its a 2.0 tdi 184, I am just paranoid the coolant is getting around all the system and somewhere is getting no coolant and is just gonna burn out or something

A wise way of thinking about this!

 

[BigJase88]

When you were bleeding it with the cap off did you also have the heating set to max?

Also check coolant hoses as they head through the bulkhead and make sure both flow and return are hot.

Squeezing / pumping these hoses here with the cap off is also a good way to force trapped air out

 

[RUM4MO]

@BigJase88, do these cars not just use "air blending" to control the air temperature, ie they just use flaps to direct/divert the incoming air?

The generic instruction to "set heating to max" in this situation is only relevant to cars that have a thermostatic valve controlling coolant flow through the heater matrix.

 

[BigJase88]

@BigJase88, do these cars not just use "air blending" to control the air temperature, ie they just use flaps to direct/divert the incoming air?

The generic instruction to "set heating to max" in this situation is only relevant to cars that have a thermostatic valve controlling coolant flow through the heater matrix.

No idea.

It's just something i have always done on every car.



Probs stuck in the past

 

[Yern]

(Set heating to max) Ah the old days, just a piano wire cable was all you needed for heat...

 

[SuperV8]

@BigJase88, do these cars not just use "air blending" to control the air temperature, ie they just use flaps to direct/divert the incoming air?

The generic instruction to "set heating to max" in this situation is only relevant to cars that have a thermostatic valve controlling coolant flow through the heater matrix.

They do - but it actually says to set heating to max in the workshop manual (from memory)
There is a separate electronic pump for the micro circuit - (heater matrix & EGR cooler circuit) which I may be activated when heating demand is requested.

 

[RUM4MO]

They do - but it actually says to set heating to max in the workshop manual (from memory)
There is a separate electronic pump for the micro circuit - (heater matrix & EGR cooler circuit) which I may be activated when heating demand is requested.

I agree about the comments still being included in the official workshop manuals, but like a few other of similar comments/instruction, I think that this is just legacy stuff, being copied and pasted by lazy or not quite technical enough technical authors.

 

[mykro]

I'd think that you still have air trapped within the coolant system, I bought a Draper Coolant Vacuum Refill Kit not because I wanted to, but because I thought that I would need that when I replaced the coolant after fixing a slight leak in my old S4, that worked okay, or at least I probably ended up with less air trapped initially, when I dump the G13 out of my wife's 2015 VW Polo I'll probably need to use that to minimise the chances of ending up with air trapped in its coolant system.
Eventually your system might end up purging itself of all trapped air, some earlier cars with the old 1.4 16V 86PS petrol engine were tricky to get rid of trapped air, I ended up finding out that the only or best way to refill that engine's cooling system was to remove the engine coolant sensor and refill the system with that out and continuing to refill once only coolant was coming out while refitting that sensor, a bit tricky doing that yourself, but it worked first time after failing to get rid of the trapped air by driving it a few times!

Edit:- maybe tell us which engine is fitted to that car, it does sound a lot like it is a TDI though!

Do you mean coolant temperature sensor at engine block ? Because when I pull off sensor attached to radiator, it will bleed only cca 3.5l from entire 10l. 1.8tsi 2015

 

[RUM4MO]

Do you mean coolant temperature sensor at engine block ? Because when I pull off sensor attached to radiator, it will bleed only cca 3.5l from entire 10l. 1.8tsi 2015

That comment I made was concerning an older engine that was known to be difficult to refill, even although its cooling system was basic, and that is mainly the problem with newer engines, their cooling systems are getting quite complicated - well at least when it comes to refilling the cooling system. So, with some models, you do need the manufacturer's diagnostic tool to enable electric coolant pumps and open any electric isolation valves in the system, as well as using a vacuum re-filling system.

All very annoying for the home car mechanic DIYer.

 

[martin j.]

They don’t want DIYers, they want yer money!

 

[Aero843]

When you were bleeding it with the cap off did you also have the heating set to max?

Also check coolant hoses as they head through the bulkhead and make sure both flow and return are hot.

Squeezing / pumping these hoses here with the cap off is also a good way to force trapped air out

Ya I took the cap off and put the heating on max and let it run for about 30 minutes, Noise is still there everytime engine is turned off so not sure

 

[brightWYFR]

I'm having problems with my coolant system after replacing the Heater Matrix. dropped the rad hose and everything and drained, left the cap on heat full on till it got up in temps to 90 to get air out, topped up with coolant as the coolant went around the system but now I'm getting noises as seen in the video? any help appreciated
https://www.youtube.com/shorts/ATZ8mmkf85c

Did you ever get to the bottom of this ? I have this too

 

[Aero843]

Did you ever get to the bottom of this ? I have this too

Yes ended up being a cracked coolant hose, not sure exactly which one but one of them had a crack and was replaced for 20 quid

 

[brightWYFR]

Did you have water loss with the cracked hose ?

 

[Aero843]

Did you have water loss with the cracked hose ?

No, made this noise for 3 months without any coolant loss

 

[Wilfcrook]

No, made this noise for 3 months without any coolant loss

Hi, was the cracked hose allowing air in or something? Or was it not a case of trapped air. Replaced my heater matrix yesterday and the exact same noise is happening.

 

[BillyCool]

Hi, was the cracked hose allowing air in or something? Or was it not a case of trapped air. Replaced my heater matrix yesterday and the exact same noise is happening.

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.