Technical Coolant leaking from filler cap....why??

[Scudoria]

I've recently bought an 04 plate Scudo 2.0 JTD and am having trouble with the coolant system.... When warm, coolant is forced out of the reservoir filler cap - quite a bit in fact, about 1lt for 50 miles of warm running.

I've flushed the system, fitted a water pump etc and a new filler cap, thinking the cap could have been faulty....but no joy the replacement cap was a £6 job from GSF.

Car doesn't overheat - it holds a steady 70deg - and no evidence of coolant in the oil.

I have a theory of what could be causing this, but really hope I'm wrong.....therefore would like any other suggestions to investigate please...

 

[Scudoria]

To add a bit more detail:

Starting from cold: rad hoses nice and soft.
After 5 mins running at tick over: rad hoses still soft
When up to temp: hoses under pressure: not rock solid, but definitely pressured
When up to temp: coolant level in header tank has dropped
When cap opened: (yes I know, not when hot!) level rises again
When cap opened when still a bit warm, lots of pressure in the reservoir...how much is normal?

You can see where I'm going with this - had an XUD engined Citroen in the past that had a hairline crack in one of the swirl chambers....

Haven't done a combustion gas test...are the self test kits reliable?

 

[r masters]

cylinder head gasket I would say

 

[T14086]

Thermostat ok? does the cabin heater get and stay warm? System bleed correctly?

Start with easy, quick and cheap things first

 

[Scudoria]

Thanks for replies....heater and thermostat are fine. In terms of bleeding okay, how would i tell? Afaik it's normal - reservoir seems to be the highest point so the old trick with the 2lt bottle as a header tank not needed...

If it was HG (as opposed to cracked head) would I not expect to get contaminated oil? Or not always?

I guess I need to get the coolant checked for CO2 and go from there....

 

[T14086]

I assume the van runs ok ?

 

[Scudoria]

Yes it runs well, good temp etc. apart from the fact it's leaking coolant all over the block, no other issues!

 

[MarcusGC]

Hey did you ever get to the bottom of this? Have the same problem on my 2l JTD scudo