My truck has developed a tapping sound that changes in speed with acceleration,also there is a coolant leak that I can't find with pressure testing.Could my engine be burning the water.The truck runs great and the mileage is 28 mpg and the spark plugs are clean.I have maintained the truck well and it has 160,000 miles on it.had the timing tensioner replaced at 130,000 and am on the second radiator and 4th starter motor.
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1995 Toyota Pickup Question: loud tapping noise,disapearing coolant
Answer #1patrick mannion from Greg Solow's Engine Room, October 24, 2009, 10:05Master
The 22RE engine is a great engine. I would remove the valve cover and adjust the valve clearances and with the valve cover off I would carefully inspect the timing chain guides, they get brittle and brake. I have seen the guide brake, and the slackness in the chain wear a hole allowing coolant and oil to mix, at that point the chain cover has to be removed. The coolant loss I would pressurize the cooling system using a pressure tester and look for external coolant loss if no loss is found do what is called a block check. The most accurate way to test for a blown head gasket on a gasoline engine is to test for the presence of carbon monoxide in the cooling system. Snap-On, Matco (part # CO 2000), and Napa sell a tool to check to carry out this test. Another link to a supplier of this tool is http://www.etoolcart.com/combustion-leak-detector-lis7550.... Carbon Monoxide is only present if there is a blown head gasket or cracked cylinder head. http://www.arrowheadradiator.com/head_gasket_or_combustio... I think the napa part number 700-1006. http://www.blockchek.com/instructions.htm . Signs of a blown head gasket are coolant loss (frequently have to top up the coolant level of the engine without seeing an obvious leak), experiencing over heating or rough engine running or the presence of white sweet smelling steam from the exhaust. A badly blown head gasket may allow engine coolant and oil to mix.
A last thought on the engine tapping sound, with the engine running slacken the valve cover hold down bolts I have seen some aftermarket V/Cover gaskets allow the rockers to contact the inside baffle in the valve cover, with the valve cover off look for indentations on the oil baffle in the valve cover, after that inspect for rocker wear..Love to hear what you find it may help someone else!
Replyjhnbelli, October 24, 2009, 11:21Rookie
Thank you for the information,I hope I haven't done too much damage to my engine,and I now know that the mystery coolant leak could be serious.I will stop driving it until I can get it in the shop....Thank yo !