Help - Elusive Noise

DSPTurtle · 06-15-2008, 11:25 AM

I hope someone here can help me from losing my mind. I have been chasing a noise for a few weeks now and still can't find it!!!
The noise occurs only in left hand turns while accelerating. Left turn alone - no noise... accelerating alone - no noise... braking/turning right/jumping small monkeys in a side show - no noise... accelerating while turning left - grinding noise.
I can hear it and feel a little vibration.
Background info to help diagnose... never heard the noise before then I changed the motor mounts, replaced the flywheel pickup sensor due to a broken connector and replace the AFM boot. I am not sure any of this is related to the noise, but it seems to me that it was around the same time. However, since the noise started the following efforts have been completed...
1. Had all belts replaced by a professional Porsche shop... noise still exists
2. Had car aligned... noise still exists
3. Had passenger side longitudinal rewelded/replaced after small rust hole noticed... noise still exists
3.5 Took car to Sebring for a Driver's Ed event... noise still exists
4. I had both rotors turned and repacked both front wheel bearings... noise still exists
5. Rebuilt both front control arms... noise still exists
6. Replaced rear passenger wheel bearing... noise still exists
7. Rebuilt passenger rear CV joints (inner and outer)... noise still exists.

I finished with #6 & 7 last night at midnight. Took car for a test drive... heard noise and about lost my lunch. I can't take it any more... someone please help. I have gone through two containers of hand cleaner in the last 7 weeks. Plus, I have my 930 motor and tranny ripped apart and I need to get back focused on putting that together. It seems that the Porsche gods are mad at me right now and I can't figure out why??? Please help........................................

Arizona_928 · 06-15-2008, 11:30 AM

tie rods?

DSPTurtle · 06-15-2008, 12:36 PM

Excellent point... except that they were replaced about six months ago when the steering rack was replaced. Plus there is no play in the front end since rebuilding the A-Arms.
Thanks for the thought though!!! It is an early 10/82 build so if that helps any guesses???
It is a serious vibration/grinding noise... I almost want to guess a loose exhaust shield but I don't think there are any exhaust shields? Any chance the motor mounts moved the motor "over" such that it is torqueing into something somewhere? How the heck coudl you even check for that???

DSPTurtle · 06-15-2008, 12:38 PM

BTW... AZ_porschekid, my 944 was my first car too. That is why I think I still keep it and baby it so much. I have spent more time and monely on it in the last six months then it probably cost new let alone what it is worth nowadays!!!

hpservertech · 06-15-2008, 12:55 PM

When you did the pass. cv though, did you just repack them or did you replace the entire half shaft? That's usually where the cause is during accel. how did they look before you repacked them?

DSPTurtle · 06-15-2008, 01:58 PM

Compared to the ones I have done on a 914 and the ones in my 930 these looked to be in exceptional shape. There was some minor wear in the piece and almost none on the outer piece. In general they looked good.
Is there anything that moves around? Any way to test the trans mounts? I am wondering if after replacing the engine mounts that the trans mounts are starting to show their age? How the heck do you test them?

hpservertech · 06-15-2008, 03:32 PM

Others will correct me if I'm wrong, but I think if the trans mounts were bad you would get some backlash when taking off from a dead stop. And I dont think turning one way or the other would make this go away or come back.

It is a possibility though.

944 boy · 06-15-2008, 03:52 PM

Drivers wheel bearing? Sometimes the noise doesn't always sound like they come from where they are. I broke a cord in a tire and the vibration was awful, everyone who drove or rode was convinced it was a problem with the pass. side. I checked everything, turned out the drivers tire was the culprit and it was only partially bubbled so you could only see it with the tire off the car.

DSPTurtle · 06-15-2008, 04:46 PM

Oh you are killing me

I do have the parts but... I spent nine freaking hours under the car changing the right side wheel bearing and r&r on the CV. I know, I know... don't do it half assed. But, logically, that wheel would be relatively unloaded when turning to the left. Wouldn't it make more sense that the bearing would grind when turning right?
So what happens when I replace the driver's side and the noise is still there? Do I drive directly to the nearest pier and just floor the gas pedal and pop the clutch?

944 boy · 06-15-2008, 05:33 PM

haha, I know how you feel. I have a hesitation that is quite random and I cannot find a cause. This could leave me stranded without notice but I can't find the problem!!!!!! I was suggesting the bearing because it could cause that noise. I also agree with the tranny mount, the trans. could be moving quite a bit and jamming CV's into each other. The exhaust could be moving around and with the combined forces could be rubbing a CV joint. Honestly I couldn't diagnose it without hearing the noise myself. If you are going to drive it off a pier I would suggest a brick on the gas pedal and bail, getting wet sucks.....;-)

What might help is if you look in odd places for wear marks. Make sure nothing is hitting any of the wheels, there might be some loose plastic/bolts/etc that makes contact in a hard turns. This includes rear brake components. Also did you check the tension of the drivers side rear axel nut? It could be loose. Get some more hand cleaner and keep digging. Good luck!

DSPTurtle · 06-17-2008, 02:04 AM

I figured out why my CV joints look so good. They were replaced in 2001 and since then I have only put 20k miles on the car. So they are likely not the reason for the noise. I ended up taking out the drivers side rear wheel bearing last night. It did not feel "bad" but since I have the parts I figure it would be a good thing to do anyway. Almost got it back together but I destroyed the internal snap ring on the inner bearing. I have no clue how anyone could expect that thing to come out smoothly... that is a seriously messed up design. Hopefully I can get one in today and get the hub put back together. Oh well... maybe this noise is supposed to be there

I did end up bending back some of the exhaust shields... especially the one covering the passenger side motor mount. Noise seemed to be less intense but it was still there even after all the bending.

Phantoms · 03:04 AM

Quote:

Originally Posted by DSPTurtle

I hope someone here can help me from losing my mind. I have been chasing a noise for a few weeks now and still can't find it!!!
The noise occurs only in left hand turns while accelerating. Left turn alone - no noise... accelerating alone - no noise... braking/turning right/jumping small monkeys in a side show - no noise... accelerating while turning left - grinding noise.
I can hear it and feel a little vibration.
Background info to help diagnose... never heard the noise before then I changed the motor mounts, replaced the flywheel pickup sensor due to a broken connector and replace the AFM boot. I am not sure any of this is related to the noise, but it seems to me that it was around the same time. However, since the noise started the following efforts have been completed...
1. Had all belts replaced by a professional Porsche shop... noise still exists
2. Had car aligned... noise still exists
3. Had passenger side longitudinal rewelded/replaced after small rust hole noticed... noise still exists
3.5 Took car to Sebring for a Driver's Ed event... noise still exists
4. I had both rotors turned and repacked both front wheel bearings... noise still exists
5. Rebuilt both front control arms... noise still exists
6. Replaced rear passenger wheel bearing... noise still exists
7. Rebuilt passenger rear CV joints (inner and outer)... noise still exists.

I finished with #6 & 7 last night at midnight. Took car for a test drive... heard noise and about lost my lunch. I can't take it any more... someone please help. I have gone through two containers of hand cleaner in the last 7 weeks. Plus, I have my 930 motor and tranny ripped apart and I need to get back focused on putting that together. It seems that the Porsche gods are mad at me right now and I can't figure out why??? Please help........................................

I have just ran into this same exact problem about a week ago. Except the only work I've had done is new motor mounts, and immediately after the mounts I began to hear the grinding noise only when accelerating through left turns. To me it seems like something minor was just not reassembled correctly. Noise seems to be coming from around the passenger side mount. Ideas?

Phantoms · 02-05-2010, 05:05 PM

I had my buddy who works with a Porsche certified tech look at it and he said after installing new motor mounts the car is used to having the engine sit lower and just makes a few creaks, with a few turns his socket wrench he worked the kinks out. No more odd noises on left hand turns.

Lapponia · 02-06-2010, 02:20 AM

!!!!!!!!!!!!!!!! Do I read this right? After changing motor mounts engine should ride higher than before, doesn´t it? According to Clark´s Garage you should now get a hand between crossmember and oil sump which you can´t when motor mounts are shot. In this case I would go through all bolts and nuts and retorque them especially those big ones at the crossmember. Good luck

______________________________
Lapponia 1984 944 NA

mikepellegrini · mikepellegrini's Garage

Same sorta thing happened to me after I changed the trans in my NA. A grinding, nasty noise that happened when I accellerated turning left - and only then.

It turned out to be a combination of a bad motor mount and the fact that the exhaust had shifted slightly when I reinstalled the trans.

What happened was that at rest, the cat was almost touching the heat shield. A combination of gravity - turning left - and engine torque with a bad engine mount - moved the cat to where it touched the heat shield and vibrated - making that nasty, nasty noise.

But it really made me nuts before I figured out what it was.

944 Ecology · 02-06-2010, 05:29 PM

Bad bearing in diff or bad output flange bearing in transaxle.