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interminttent engine noise

1204 Views 5 Replies 3 Participants Last post by  Brother James
Hi all, my tdi is an 05 pd with 133000 miles on it. The problem is this; suddenly and without warning when starting to drive from a standing stop the car apruptly sounded as though the exhaust at the cat just let go. Really loud, right under my seat, the vibrations were moving stuff around on the dash. I shut the car off and looked under expecting to see the all too familar exhaust hanging loose and broken only to find all as it should be. Next got back in, pulled over to the side,and this time left the car running so as to lsten for the leak. It was quieter outside the car, under the hood did sound louder and rougher. I shut it down again, waited , check the oil, down 1qt. (but I knew that, I had planned to change the oil next weekend) , added 1qt. of oil to make sure the dip stick was reading right, it was, it was now at full. I decided to drive on, its now about an hour nice the onset, and the car is sounding less bad. Drove for 2 mi. stoped, waited, checked everthing one can check while on the side of the road, and then drove on. The noise and vibration were gone, as if it never happened.
I drove around town the next day, no problems but I had a feeling that something just isn't right. I drove 45 min. to work , all still alright, untill the last 1/4 mile, a hard right up a steep hill in first gear, and there it was again that phantom noise, back again. It was gone when I check 15 min. later. Any thoughts any one ?
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I would say that if it didn't get worse or better, it was a loose driveshaft. If it were the winter, it could be a chunk of ice stuck in the wheelwell fell onto the tire and was grinding away (scared the bejeesus out of me because in addition to the noise it acted like a brake and made the car pull to one side, I thought I blew a tire).

There is nothing under your seat that should vibrate so the next guess is a loose dogbone mount. This is the engine mount that attaches to the subframe in the middle underneath the car. Another possibility is something related to the clutch. Is there any soot sprayed around the engine bay? All of these should be constant, not coming and going.

Because you said it was exhaust noise, maybe a component related to the EGR blew open? Check for soot spray on the firewall.
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thanks for the reply. The noise is there while driving and at idle. The reference to it coming from under my seat was to suguest that the source of the noise was neither up frount nor in the rear but near the cat.(Ive had one or two other cars that had exhaust issues). I hope to be able to make time today to get the car up on ramps, drop the skid pl8 and see wat I can see.
I forgot to mention that on my ride home from work this morning the noise started to come back with in 1 min. of driving, though much milder then on day 1. It did not fully manifest itself, and the engine/exhuast noise subsided, so as to sound just a little courser then normal for the rest of the trip (60 min./45 mi.) . Hope this makes things a little clearer. TY
There's a shield around the CV boot, maybe it's broken and dangling loose and occasionally hitting the axle.

Just to verify, it's not related to speed? Does it change with engine rpm?
OK wo wants to hear a story with a happy ending? Well ChittyCittyBangBang was so close, if I had mentioned that I had a skid pl and was driving on a dirt road he would have been right on. A rock was wedged between the small black bracket that connects the dogbone mount to the trani and the skid pl8! The rock of course fell out when I removed the skid pl8 but I could see the wear marks on the bracket and the pl8. And by pulling several measurements found that these two wear marks did match up. So there it is. I feared the worst, cam failure, and panicked. thanks all it was good to have some morral support.
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