: (Pressing gas) CLUNK.. What the heck?



georgeluis
01-21-04, 02:48 AM
Not sure what's going on here. I just purchased a "pre-owned" '98 Deville about 2 weeks ago. It has around 58k miles on it. When accelerating briskly from a stop, there is an abnormal amount of engine/exhaust vibration felt and heard through the body. This only occurs under near wide open throttle conditions from a stop, and only happens for 3-5 seconds, after which the normal amount of engine noise is heard (nearly none). I'm guessing that the problem might be a failed engine/transmission mount. Any ideas?

BeelzeBob
01-21-04, 02:58 PM
Failed engine/trans mount or possibly just a misaligned exhaust system. The exhaust "moves' quite a bit even with a properly funcitoning mount so if the system is bent or misaligned it can contact the body and ground out under heavy load.

Try putting the car in gear and holding the brakes and "power braking" it at various throttle openings in drive and reverse. If you limit the power braking to 20-30 seconds at a time you cannot hurt anything even doing WOT maneuvers against the brakes....Just hold the brakes firmly. The engine rocks different directions when you do this in drive or reverse so it makes a big difference in how the engine moves and the exhaust clearance required. Have the hood open when you do this so you can observe the engine motion. If it moves smoothly then the mounts are likely ok. If it suddenly jumps a lot in a jerky motion then you may have a mount that is failing.

The most common problem with the exhaust alignment and grounding is someone backing into a parking curb stone and catching the exhaust pipe tip....that drives the entire exhaust forward and bending it making it easy to ground out. If you can get it on a hoist at a muffler shop and do the power brake maneuver on the hoist in the air it will be very easy to see where the exhaust is grounding out and whether a mount needs to be replaced or not.

powerglide
01-21-04, 06:26 PM
Not sure what's going on here. I just purchased a "pre-owned" '98 Deville about 2 weeks ago. It has around 58k miles on it. When accelerating briskly from a stop, there is an abnormal amount of engine/exhaust vibration felt and heard through the body. This only occurs under near wide open throttle conditions from a stop, and only happens for 3-5 seconds, after which the normal amount of engine noise is heard (nearly none). I'm guessing that the problem might be a failed engine/transmission mount. Any ideas?


sounds like the torque struts.
Same clunk heard on my deville 98 72K miles.
look at the two dog-bone's connecting your engine to the front of the car near the radiator (these are called torque STRUTS)....are the bushings worn, cracked or even totally gone? (the dog bone shouldn't be loose enough to jiggle around by hand)
about 34 bucks per side (left and right) at gmpartsdirect.com

good luck