3.0 TDI CRCA – Air in cooling system after driving, no coolant loss

[Skula]

Hi everyone,
I'm new here and hoping to get advice from someone who's been through this before.

I have a 2011 VW Touareg with the 3.0 TDI CRCA engine. The car runs great — no overheating, stable temperature, strong heat from the HVAC, and no external leaks. Coolant level has been stable for months. However, I’m noticing something odd and repeatable:

• After intensive driving (long highway trip or spirited driving),
• The coolant level in the expansion tank drops by about 200–300 ml,
• After the car cools down overnight, I open the cap — there’s a clear release of air pressure,
• And then the coolant level returns to normal.
• No bubbles in the tank, no loss of coolant over time, no oil contamination.

So basically, it seems like air is entering the cooling system during load, but not escaping or mixing. I have already replaced the water pump, thermostat, expansion tank cap, and oil cooler gasket — all with OEM parts.

My suspicion is the EGR cooler — maybe exhaust gases are pushing into the coolant side during load, without actually causing a leak. It seems too clean and consistent to be a head gasket failure, but I’m open to all ideas.

Has anyone experienced air accumulation in the coolant system without coolant loss like this?
Could a hairline crack in the EGR cooler cause this kind of behavior under load?

Any input or similar stories would be much appreciated. Thank you!

 

[oilhammer]

The combustion pressure could be finding a way into the cooling system under those conditions, that would be much greater than the exhaust pressure the EGR cooler would have. And it may be so slight, it isn't really carrying much of any actual combustion with it, so you are not getting any soot finding its way in.

And any added pressure/air/volume could be just getting vented out the cap as normal. I'd say at this point, unless you've really got time and money to burn, leave it be. It sounds like you'd never know unless you were looking.

But I have no first-hand experience with this engine, as they didn't sell them here. But I assume it is similar to the CATA V6.

 

[TurboABA]

But I have no first-hand experience with this engine, as they didn't sell them here. But I assume it is similar to the CATA V6.

CRCA is a gen2 engine... more similar to the our CNRB

 

[TurboABA]

I have already replaced the water pump, thermostat, expansion tank cap, and oil cooler gasket

Since all that was done, was the coolant system correctly refilled, using the vacuum method?

 

[GravyTDI]

Hi everyone,
I'm new here and hoping to get advice from someone who's been through this before.

I have a 2011 VW Touareg with the 3.0 TDI CRCA engine. The car runs great — no overheating, stable temperature, strong heat from the HVAC, and no external leaks. Coolant level has been stable for months. However, I’m noticing something odd and repeatable

Have pretty much the same issue. No coolant loss, oil looks good. I put a clear piece of tubing on the return line to the expansion tank and have never ending bubbles returning, minimal at idle more with throttle and test positive for exhaust gas. I also do not have soot noir does it smell like exhaust, has never overheated and runs well.

in process of deleting both EGR coolers before accepting its a head gasket. Wondering if you ever found anything more?

2012 Touareg TDI CATA 140k miles.

 

[TurboABA]

Answer what I asked the OP in #4

 

[GravyTDI]

Yeah I vacuum filled with just water, brought to temp and cracked the bleeder. Still was getting air.
Currently have it tore down waiting on parts to delete both egrs and reseal the valley while I'm in it, even though it was dry.

 

[TurboABA]

So your belief is that you have a leaky EGR system that somehow still manages to hold vacuum during the refill procedure?
Or are you saying that you just pulled some vacuum, but didn't actually pull sufficient as per FSM procedure or checked to see if it held?

 

[GravyTDI]

That's a good point.. truth be told it was a half hearted attempt because I knew I was getting air in the system and did not expect it to hold and didn't allow to hold vacuum for long. Especially after the combustion gas test came back positive. Deleting was something I had planned to do for a while so figured I would start with the EGR's.

My real hope is I haven't found much for evidence the 3.0 TDI has head gasket issues. OP's is pretty spot on to mine and the only other case I have found that was not also loosing coolant which appears common when an EGR cooler fails. Had hope he had figured something out, lol.