i have a van nissan serena CD20T diesel engine AT. For the past years, the cooling system was ok. Two weeks ago i observe the water temperature is above the normal operating mode. So, I check leaks at the hose manifold assembly and found leaks at the elbow hose connecting to the discharge hose of the upper radiator inlet. With the water leaks which was eliminated, i replaced also the water pump belt with new one. Test drive showed that the engine still overheating, for a distance tavelled of 5 km. If the cylinder head has a crack, the engine oil should have been mixed with water. However, the oil was still ok with no water in it. Is it possible that a worm out cylinder head gasket affects the the engine cooling system. Please, anybody can give comment on my observation before i have my engine be opened for repair. Thanks!

jos, June 2011

Does the radiator fan come on went it gets hot if not change the thermostat. To check if there is air in the system or the headgasket is leaking cut off the bottom of a coke bottle 2ltr size and put the neck with a couple of rubber gloves around it to make a seal into the neck of the radiator header tank. Half fill the bottle with water and open any bleed screws on the coolant system to force out any air pockets, close off the bleed screws and top up the bottle with water and start the engine with the heater in the hottest position. Leave the engine running and watch for bubbles coming out of the header tank. If you get a constant stream of small bubbles this can indicate that the headgasket is going. If they are largeish bubbles in sperts these are air pocket bubbles leave the engine running until they stop.

arizona kid, June 2011

could also be a blocked radiator,try back flushing the rad by removing hoses and put fill hose on bottom connection,the higher the pressure the better.

MM, June 2011

Could well be the head gasket letting exhaust gases into the water cooling system. This needn't necessarily be letting oil into the cooling system. Depends how and where the gasket has failed.

ChicksFan, June 2011