Thump/pop from front half of car w/ turn - PeachParts Mercedes-Benz Forum

JDmills · #1 07-14-2006, 12:16 PM

I have been hearing a noise comming from the engine room recently... it occurs most often when turning to the left, durring a 90 degree turn. (turning into a drive way, or parking lot at 10-15 MPH)

Originally I thought it was the right guide rod mount.. which MAY be making noise as well.... but last night I heard the thump/pop noise just at the shut down induced final shake. So now I am wondering what else might be the cause. It has new motor mounts, it does not sound like an exhaust rattle, and I can not get the guide rod mount to rattle when the front wheel is jacked up... any suggestions on where to look?

rrgrassi · #2 07-14-2006, 12:59 PM

When you jack up the car, do so that the suspension is "relaxed" by lifting the entire front end using the frame lift points. Check tie rod ends, ball joints, control arm and sway bar bushings, idler and pitman arms, and also check the all engine and transmission mounts again. Also check the "anti-vibration" shock on the engine.

JDmills · #3 07-14-2006, 01:04 PM

how would one check the engine shock? Prybar method?

rrgrassi · #4 07-14-2006, 03:55 PM

That I do not know, since it is a shock absorber. Can't do the bounce test on the engine ones like you can the suspension. I do know that the steering damper in 4x4 pickups are usually just replaced every 30,000 miles or so.

no-blue-screen · #5 07-20-2006, 02:10 PM

hey JD, did you ever figure out what this was? I have the exact same thing on mine.

Rusty Cullens · #6 07-20-2006, 03:39 PM

Generally, the guide rod mounts "clunk" right under your feet when slowing down like at at Stop Sign or Traffic Light.

JDmills · #7 07-23-2006, 03:37 PM

Not as of yet... gonna have another look at it this week.... will report then.

deniss · #8 07-23-2006, 04:08 PM

when i had busted guide rod mounts, they would clunk/clatter/thump over uneven road surfaces, like a series of closely spaced small bumps, whether driving straight or turning.

i initially thought those were balljoints, but dealer said that balljoints would only clunk during turns... go figure.

maybe it's one of the front wheel bearings worn or sitting loose?

JDmills · #9 07-23-2006, 04:18 PM

My first hunch is that it is related to the engine mounts... Not sure how it can be, but it seems to clunk just before the apex of the turn to the left... may be guide rods. I have yet to figure out how to "test" them, they dont seem to allow any movement..

deniss · #10 07-23-2006, 06:40 PM

pick a really bad road surface or gravel surface with lots of bumps and little dips - if they rattle/knock then they are definitely bad

JDmills · #11 07-23-2006, 07:22 PM

I have three seprate rattles in some where in front of the footwell's... only two guide rod mounts. Also the right one is new, and it is the side that is making noise...

sixto · #12 07-23-2006, 07:46 PM

The guide rods have bushings at the front and rear attach points. If this is the SDL, the guide rod mounts have two bushings each into the frame.

The car puts a lot of force on the guide rods during braking and turning. The bushings will clunk long before you can feel slop by tugging on the guide rod.

Sixto

JDmills · #13 07-23-2006, 09:49 PM

Sixto,

It is the 300TDT.. that is making all the front end racket... So Is the only way to "check" a guide rod mount that appears to make noise, is to replace it?? (that means it was junk when it came out of the box!!)

sixto · #14 07-23-2006, 09:57 PM

The typical symptoms of a loose guide rod balljoint is clunking when you apply the brakes or hit an abrupt change in pavement elevation. Basically anything that will move the weight of the car forward relative to the front axle.

I replaced both guide rod balljoints in my SDL. One was very loose, the other was quite firm -- I mean I couldn't feel longitudinal play. Firm meaning difficult to move. The new one was impossible to move. That got rid of the clunks left and right.

Sixto