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dodgydd · 09-11-2007, 08:44 AM

I was reading about this on carbibles the other day...
Car Bibles : The Engine Oil Bible

"When it's an oil and water emulsion from a leaking or blown head gasket. If this happens, you get a whitish cream coloured sludge on the inside of the oil filler cap. The filler cap is typically cooler than the rest of the cam case and so the oil/water mix tends to condense there. So if you take the oil filler cap off and it looks like it's covered in vanilla yoghurt or mayonnaise, you've got a blown head gasket. A surefire way to confirm this is if your oil level is going up and your coolant level is going down. The coolant is getting through the breaks in the head gasket and mixing with the oil. When it gets to the sump it separates out and the oil floats on top. A slightly more accurate way to check for this condition is to use a combustion leak tester, or block tester. If you're in America, NAPA sell them for about $45 (part #BK 7001006). If you're in England, Sealey sell them for about £70 (model number VS0061). Combustion leak testers are basically a turkey baster filled with PH liquid, with a non-return valve at the bottom. To use one, run your engine for a few minutes until its warm (not hot) then turn it off. Use a protective glove (like an oven glove) and take the radiator or reservoir cap off. Plug the bottom of the combustion leak tester into the hole and squeeze the rubber bulb on top. It will suck air from the top of the coolant through the non-return valve and bubble it through the PH liquid. If the liquid changes colour (normally blue to yellow), it means there is combustion gas in the coolant, which means a head gasket leak.
There is one other possible cause for this yellow goop : a blocked scavenger hose. Most engines have a hose which comes off the cam cover and returns to the engine block somewhere via a vacuum line. This is the scavenger hose which scavenges oil vapour and gasses that build up in the cam cover. If it's blocked you can end up with a buildup of condensation inside the cam cover, which can manifest itself as the yellow goop inside the filler cap. "

09-11-2007, 08:44 AM	#4 (permalink)
dodgydd Newbie Join Date: Sep 2007 Posts: 6 Gallery: (0)	I was reading about this on carbibles the other day... Car Bibles : The Engine Oil Bible "When it's an oil and water emulsion from a leaking or blown head gasket. If this happens, you get a whitish cream coloured sludge on the inside of the oil filler cap. The filler cap is typically cooler than the rest of the cam case and so the oil/water mix tends to condense there. So if you take the oil filler cap off and it looks like it's covered in vanilla yoghurt or mayonnaise, you've got a blown head gasket. A surefire way to confirm this is if your oil level is going up and your coolant level is going down. The coolant is getting through the breaks in the head gasket and mixing with the oil. When it gets to the sump it separates out and the oil floats on top. A slightly more accurate way to check for this condition is to use a combustion leak tester, or block tester. If you're in America, NAPA sell them for about $45 (part #BK 7001006). If you're in England, Sealey sell them for about £70 (model number VS0061). Combustion leak testers are basically a turkey baster filled with PH liquid, with a non-return valve at the bottom. To use one, run your engine for a few minutes until its warm (not hot) then turn it off. Use a protective glove (like an oven glove) and take the radiator or reservoir cap off. Plug the bottom of the combustion leak tester into the hole and squeeze the rubber bulb on top. It will suck air from the top of the coolant through the non-return valve and bubble it through the PH liquid. If the liquid changes colour (normally blue to yellow), it means there is combustion gas in the coolant, which means a head gasket leak. There is one other possible cause for this yellow goop : a blocked scavenger hose. Most engines have a hose which comes off the cam cover and returns to the engine block somewhere via a vacuum line. This is the scavenger hose which scavenges oil vapour and gasses that build up in the cam cover. If it's blocked you can end up with a buildup of condensation inside the cam cover, which can manifest itself as the yellow goop inside the filler cap. "