V6 TDI Head Gasket Failure

Hi.
This is probably a silly question, but how can I tell which side of a V6 TDI engine is faulty?
Immediately after starting, the engine builds up pressure, or, if the expansion tank is open, it bubbles out of the rear connection that comes from the center of the engine block. It's hard to explain, but I can take some pictures tomorrow.
The engine is a BAU.
Best regards,
Dirk

Hello there,
I would like to try it out.
- the idle speed control.
- the compression.
There might be a cylinder exposed, which could also reveal the head.
hg
Herbert.

I would definitely remove both cylinder heads. Otherwise, there's a risk that the second cylinder head or its gasket might fail after a certain amount of time. And then having to disassemble everything again, essentially starting from scratch, is very time-consuming.

Hi.
Okay, I've removed both of them, and it was the one on the right side, so numbers 1, 2, and 3.
She easily won from 1 to 2 and went straight into the water.
I'm going to make everything look really flashy and put it all back together.
Best regards,
Dirk