Why is my Toyota Camry making a knocking noise when I let off the gas pedal?
Is this noise there when the engine is running in neutral or only when driving or both/all the time?
No it isn't. Just after I let up on the gas pedal. I thought it was only happening at around 65 mile per hour, but I noticed at around 40 mph too. I have had problems with the exhaust too, but had fixed the leaking oil pump and timing belt. When I let up off the gas pedal I hear a "duh duh duh duh" noise, but I have to listen to it closely in order to hear it.
What is the problem with the exhaust?
They said the exhaust will have to replaced, but I'm not sure on the details. They did say it would be a big job because of the rivets they used. Apparently they don't use bolts to hold it together. It seems the low thudding noise I hear aligns with the gas pedal. When I slow down, I can hear it thudding in there.
Toyota doesn't use any rivets on the exhaust, only bolts and nuts. Do you hear this noise under the hood and can you tell where it's coming from? I don't think it's a mechanical problem because the noise would be louder on acceleration.
Yeah, it definitely feels like it's in the engine. Could it be the transmission because of the deceleration?
Ok so you can hear it under the hood without driving the car, is this so?
I do notice that the sound gets louder at higher speeds though. No, it's only when I drive. I don't hear the noise when I accelerate just when I let up off the gas pedal.
Do you mean higher road speed? At what mph is it the loudest?
Yes, higher road speed. I hear it the most exactly between 60-65 mile per hour. It does fade a bit after 65. But, I can really hear the noise when I decelerate.
It's starting sound like there is a wheel bearing problem in the front, it could also be a differential noise, it's hard for me to say without actually hearing the noise.
The mechanic said I have a slight bit of movement in my front left wheel and I need a new boot join. Not sure what that is, but they told me that and that it shouldn't be a big problem. It sounds like a knuckle knocking on wood, like a dull thud. I can feel it a little bit in the steering wheel at times.
What he's talking about sounds like one of the CV joints are bad, usually one of the inner joints can cause this type of noise, since the wheel feels loose it may need to have that axle bearing replaced as well.
Really? So, maybe I cant hear the noise while I'm accelerating and when I let my foot off the pedal I will be able to hear the wheel stressing?
Does the sound change when either turning left or right?
So from what I've described does this sound like a "must fix"? No, I don't hear the sound when I'm turning, just when I'm driving forward. So, basically, if I'm not hearing the noise consistnetly, then it is most likely not in the engine?
In that case you should have the CV drive axles checked especially the one on the left, the inner CV joint may be worn and the axle may have to be replaced. If it was an engine noise you would hear the same noise without driving the car.
Is this a costly repair?
Do you feel any vibration when this noise happens?
I feel a little vibration, yes. I've just been worried about engine trouble because the oil pump just had a gasket blow out and it was leaking oil all over the timing belt. And, now I hear this noise.
A CV axle can be bought aftermarket from most auto parts stores, they are around $250 you can also find them online. Okay, so just to be clear, you CAN hear the noise with the engine running and not driving the car, is this so? This is important.
No I cannot hear the noise when the car is in park. It is only when I am driving the car that I hear the noise.
Just one question. Why would the knocking sound only be audible when I let up on the gas pedal?
The noise is in the drive train as I already mentioned not the engine. I would recommend that you have the axles and bearing checked. By the way, what condition are the tires in? Just checking because this could be a tire noise. When decelerating the load is reduced from rotating parts and any excessive clearance can cause noise, the only other thing I can think of is that this is a differential problem, so you should have it checked by a mechanic that is experienced in these areas.
Ok thanks so much. You have definitely clarified the issue. The tires are ok (the mechanic said), but they have about 6-8 months left in them. The CV joints are definitely loose, but not a lot. That may be the problem. It isn't a huge noise, but I can hear it a little.
Thanks for the reply!