3.0 with a strange knock

[muddkatt]

I am putting this in the Camry forum looking for a better response. I have had it up in the Avalon forum for a week with only two replies. Thanks in advance for the help.



My girlfriend has a 2000 Avalon that she bought new, it has about 130000 miles now. It has always been serviced at the stealership with a minimum cover charge of about $500.00. The timing belt was replaced at about 115,000 miles along with an O2 sensor( the one closest to the radiator). About 4000 miles ago she said it started making a knocking noise. NOTE: I never drive her car so I have no clue about when it started. I have not noticed it till this week when it was parked in the driveway and I was letting it idle after I had detailed the Interior for her.It only knocks at low RPM with the air conditioner off. I have checked everywhere and it appears to be something inside the exhaust crossover pipe/Y pipe. it is definitely a knock. It is real damn loud too. It is not a lifter type tick, or a rod knock. And it only does it warm. I am stumped. Help please!!

[toyomoho]

The knock goes away with the A/C on? The magnetic A/C clutch can make a knocking noise. A piece of rubber hose used as a stethoscope can help pin point the location.

[muddkatt]

When the A/C is turned on the knock stops. But this is due to the increase in rpm, not an A/C issue. It ONLY knocks at idle with the A/C off and the engine at operating temperature. I stethascoped the engine all over, A/C, all components that I could reach and it sounds like it is inside the exhaust crossover piping. I am lost as to what would cause the exhaust to knock.