Volvo D12 pressure in expansion tank. I checked for exhaust Gas, its fine.

I am building pressure in cooling system in the expansion tank. At idle it looks like its bubbling. I checked for leaks in EGR cooler. EGR cooler is not leaking. Checked for exhasust gas. No Exhaust Gas. Checked compessor air while cap off and no coolant shooting out when air building up. When it cools down pressure build up and expands on all hoses creating excessive pressure. When cool, I remove cap and get air pressure. It is forcing coolant out of the odd hose. When I run the truck, temperature is normal, fan comes on when it should. Compressor seems to be functioning preoperly. Changes both caps on expansion tank. I am stumped.

 

yes but if it was injector cups there would be exhaust in the tank, but I tested with die kit. No exhaust.

 

I appreciate the response. I had my injector cups done a while back, but they dont use good parts anymore, so I gues they could need to be done.

 

I ordered a compressor. I will instrall tomorrow and post the results. A volvo mechanic said it was the compressor. But it was charging the system with air overnight when truck was cooling down. How does air work back from air tanks??

 

A volvo mechanic told me it was the compressor likely with my symtoms. I forgot to ask him how does air work back from tanks while at rest not running. It seems to charge the cooling system overnight while cooling down. I thought there were check valve to stop air returning from tanks. How does a bad head push air if it has stopped running. Once I run the truck I leave it over night and the system starts to pressurize, by morning its pushing coolant out of hoses that normally never leak with enormous pressure on the hoses.