Mechanics

COOLANT SYSTEM PRESSURISING AND LEAKING COOLANT FROM CAP.

2005 Volkswagen Golf • 77,000 miles

Basically if I drive the car fast the coolant system seems to build up so much pressure that the coolant starts coming out of the cap.

i took it to a local garage who done a pressure test on two seperate occasions couldnt find nothing.

he replaced the cap with a new one and I thought the problem was solved, I drove over 1000miles to france and back not a single drop of coolant leaked.

then it started happening again, changed the cap again and it was sorted for a couple of hundred miles and its doing it again, some people have suggested head gasket failure and that the exhaust gasses are entering the coolant system causing it to pressurize.

used one of those kits to test to see if there are exhaust gasses in the coolant and it come back negative.

there are no other signs of headgasket failure either, no oil in coolant, no water in oil, no sweet smelling exhaust fumes. Engine is not overheating there are no other problems at all.

i drained as much coolant out of the system as possible by disconnecting the bottom rad hose and replaced with fresh coolant and bleed the system, there is definetley no air locked.

anyone have any idea what could be causing this?

Golf MK5 1.9 TDI 05 plate
Avatar
Mattgriff88
June 19, 2012.



Broken water pump impeller. There may be no circulation from the pump.

Sorry Joe

Roy

ASEMaster6371
Jun 20, 2012.
You can check the water pump by starting it cold and removing the cap, watching the small hose at the top of the reservior, as it idles and warms up watch for the coolant to flow into the reservior from that hose. This tells you the pump is functioning properly. Do the cooling fans work? While the engine is cool spin the blades by hand, they should turn freely and smooth, and quiet. Otherwise there may be a restriction in the system, kinked hose or something. Check for debris in front of radiator.

Tiny
Vwscott
Jul 7, 2012.