tracking down a hum and a grind


Jun 9, 2003
Mesa, Arizona
My wifes 80 just started humming, for lack of a better word. 93 FJZ80 with 135k miles. It is a medium pitched hum, and it sounds like it is coming from the area lower front of the engine, around the water pump/AC compressor area.

When the AC compressor turns on, the sound appears to go away--although the AC compressor going on revs the engine and may just be covering up the noise. It is hard to tell.

Any idea what this could be? Could an AC clutch hum when it is not engaged, and then stop when it is turned on? How can I narrow down the possibilities?

BTW, the belts are only a couple of years old

And one more thing-- when I was trying to track down the noise I asked my wife to briefly rev the engine. When she let of the gas, and the engine started to slow, there was a very noticable, but brief grinding-like sound coming from some thing called the "PAIR reed valve" on the front passenger side of the engine. What is up with that? I don't have a clue as to what the PAIR reed valve is, or if it should be making a noise like that. Can anyone help me?

I should also mention that there appears to be more oil on the engine in the front, and around this PAIR thing then is normal. But that could be my imagination.


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