knocking in engine on 1999 Chrysler Town & Country

my 3.8l engine is making a knocking noise at idle when the engine is cold. When i hit the gas or once it warms up the noise goes away but then when i turn on the A/C the knocking noise returns. My oil level is fine. Any ideas?

by in Worcester, MA on September 26, 2009
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1 answer 1 comment
ANSWER by , September 26, 2009
Knocking sounds are never good. It could be a sign of present or past oil starvation internally in the engine which has cause crankshaft bearing or connecting rod bearing failure. As the engine runs and builds up oil pressure and that pressure gets out to all the internal rotating engine components combined with components in the engine expanding with heat, the noise may go away. When you turn the air conditioning on the compressor puts aditional load on the engine which could mean an engine problem or a problem with the compressor which would be a much better problem to hava as it would not be an internal engine problem. Without being able to drive your car and listen to the problem, and do some basic diagnostic tests first hand it is difficult to speculate as to the cause of the noise, but get a trained ear to listen as it could be something serious. You may have to leave the vehicle over night so the engine can be started from cold.
COMMENT by , August 29, 2010
I have the same issue. What is the worst case, engine rebuild? Or is there a repair? Van is only worth, $2,300 so no need to spend more than its worth. What does a compressor repair run?