Cooling system bleeding fault.

[motorhead]

Bongo td came in with dumping coolant and running hot.
Bled system etc etc after fitting new thermostat,no go! air and more air from the bleed tube.
Used the sniffer,showing slight colour change.
Headgasket suspect.
Head removed and sent for hot pressure testing and surface plane etc as the gasket was not seen to be in a total failed state.
Block flushed and checked.
Pump removed and checked.
New rad fitted due to the rusty coolant and weight.
All reasembled and still the same after many bleeds with small amounts of air.
The engine will run all day at temp at eleven oclock.
The bottom hose warms up proving the thermostat and pump are ok.

The moment the revs are taken to 2500rpm for a few minutes the temp rises with the fans starting up.
Taking temp readings across the head they start to rise to over 100c and the the front even more.
Danger
The temp will then not drop so engine is stopped to cool.
Water level stays the same

Question do the bores become porous or am I to think we have a most strange occurance caused by another previous matter with exhaust.

Is it possible for the newly stainless exhaust system if fitted to have more back pressure causing the turbo to force air into the cooling system under higher engine running speeds.
This would be if the tubo was maybe on its way before the exhaust was fitted.
Am I nuts this thing driving me BONGO!
Any thoughts and Hi to all.

[dandywarhol]

I haven't heard of porous bores on them, could be a turbo/turbo cooling system fault airating the system.

[motorhead]

Thanks for reply, will do a bypass of the turbo cooling to-day and see if any change.