just started noticing a single knock noise when accelerating or letting off the pedal after accelerating. It doesn't sound like the engine, but rather coming from behind the glove box or inside the passenger door or fender well. It is not a noise that comes and goes. every time I step on it it makes the sound and every time I let off after stepping on it, it makes it again. If I barely press and slowly accelerate, it doesn't happen.

almost sounds like a knock that an engine makes when it is 'dieseling'

I thought it went away once the car warmed up, but I haven't driven it long enough to make it go away.

Any ideas would be appreciated. Thanks.

 

I would say its an engine mount....

 

if it is an engine mount, then:

1) should it make the noise when not moving, in neutral? I dont believe that it makes the noise when not moving

2) Is it possible to determine if its an engine mount without taking it to the dealer (350 miles away)?

3) if it is an engine mount, should I continue to drive? what are the risks?

Thanks.

 

I had a similar sounding noise. I thought it was something bumping around in the glovebox, but taking everything out didn't make it go away. Mine, however, did occur even when idling, and was happening 90% of the time, but not always. Of course, when I went to the dealer, it wasn't making the noise. However, based on my description, they replaced the engine mount and the noise has not returned since it was fixed a month ago. The SA said they usually don't replace anything unless they can hear the noise, but since I drove so far, they went with my description.

 

the noise seems too loud to me to be an engine mount. If I were to guess, it seems like a creak in the body, but I could be wrong.

Any other ideas?

 

Still looking for other ideas. It really doesn't seem like an engine mount. There is actually a split second delay between when I let off of the pedal and when the knock actually occurs. It seems like the noise occurs when the momentum changes from acceleration to coast or vice versa.

Help?

 

assuming you have an 05 or 06, the right side hydraulic upper mount has failed-open your hood and you should see a black stain underneath it, wherethe oil ran out. broke my 3rd one on thanksgiving day, hav eignored it since but the knocking is driving me nuts-if my local dealer cant change it tomorrow, under warranty, I will just buy one and do it myself.

 

This sounds almost precisely like a motor mount. '04 and up cars switched from a two-mount upper system that had a mount that only carried the vertical load (weight) of the engine and had a longitudinal strut that absorbed the fore-and-aft motion of the engine. This 'old' setup has a large, all-black engine mount. Newer cars switched to an integrated reaction mount which combined the vertical and reactive functions. This mount is larger, and is encased in a silver metal can.

Motor mount failure is common in the later models. This is indicated by a black crusty oil stain on the body below the mount. This oil is used to dampen the engine movements and is encased much like a balloon inside the rubber mount. The fluid leaks, the mount goes 'flat' inside much like a deflated tire, and the internal rubbing begins to sound like a knock as the engine moves back and forth from torque reactions when accelerating and decelerating. In some cases, the upper bracket cracks or the mounting bolts become loose.

 

for the record, it is an 05 MCS

if its the mount, will it do it when in neutral?

 

bump

 

it will

 

OK. It doesn't/won't make the noise in neutral. It almost seems like it couldn't be louder outside the car than it is inside, though I havent tested that theory.

How about if the car was wrecked and there is a cracked door hinge mount or something like that?

I dont know if the car has been wrecked or not.

 

You can also check the control arm bushing, it also makes the same kind of sound when its worn.

 

100% agree. I had the same problem as you explained. I told the dealer it was a motor mount but they felt that wasnt possiable. so after checking EVERYTHING they checked the motor mount and it was broken. this was the right side mount.

 

My '05 MCS motor mount went out very early on...maybe at 5K. As everyone else has said, you have the symptoms. And you may or may not see any "oozing" beneath the mount - mine had none at all. It must have been shipped with little to no fluid from the factory!

 

So, if it is a motor mount, will it make the noise in neutral under revving or sudden letting off of the pedal?

If it is the motor mount, am I at risk for driving the car with it broken? It is 300+ miles to the dealer? Will they retrieve the car under warranty from here?

 

you first posted this on 1/22 and everyone chimed in that it's your mount, 99.99% sure. It's now in the middle of march and you're still asking about it?

1) The mount failure may not be totally binary. It may not go from fine to you hear list X, Y and Z under conditions P, D and Q. So don't expect a complete list of symptoms of which all will always appear.

2) Did you see any oil under the mount?

I think the reason that others may not be chiming in is that until you eliminate the mount as a possibility, most think that "the horse has been led to water, let's see if he'll drink!"

Matt

When it's shot, the engine moves more but won't fall out. As far as will they pick the car up, don't you think a call to them will clear that up?

 

Definitely sounds (described) like the sound of my broken motor mount. Also I could only here the sound from inside the car at idle nothing from the outside either under the car or with the hood up. I'd jsut have them take a look at it anyway wit hall the trouble that we've been having with them.