Coolant leak, failed block test

[swb]

My van (T6, 150) is losing coolant. VW suggested I keep an eye on it. I have done - it's got a bit worse.

I did a block test today - liquid changed colour. So there are exhaust gases getting in there somehow.

I don't understand the ramifications though - esp whether this definitely points to the head gasket or whether EGR failure can lead to this. (or indeed whether other culprits are possible from here)

Any recommendations for a garage (around N Manchester) familiar with diagnosing and fixing this would be very welcome!

 

[Dellmassive]

If your referring to a snif test....

Where the green liquid goes blue... That's normally attached to the coolant expansion tank and engine running...

Is normally a sign of a leaking head gasket or cracked head.

Allowing combustion gasses into the coolant, and drawing coolant into the combustion chamber.

..

Signs are :

loosing coolant.
Expansion tank under high pressure.
Coolant smells of exhaust.


Confirm the sniff test, then get the cylinders compression tested, and engine/coolant smoked tested.

Which should show and leaks

 

[DXX]

I don't understand the ramifications though - esp whether this definitely points to the head gasket or whether EGR failure

How many miles has the EGR done? If it’s more than 60K miles I’d just renew it anyway as apart from being the most likely cause it will also be fouled with carbon.
If less than 60K remove and pressure test the EGR water circuit, isolated from the engine circuit.
You haven't mentioned the consumption rate mL / miles?
When a repair is eventually made and proven good ensure the coolant is drained 100% and renewed or you could get a false hydrocarbon positive in a future coolant test.
The worst case scenario is a hydrolocked engine, ensure you check the coolant level before starting engine, if it has dropped more than 100mL since the last cold check I would not try and start the engine.