Body Vibration & Intermittently Soft Clutch

[imgolden]

Hi folks,

It's been a while since I posted here, but I recently got a new project that has a few stumpers. It's an 82' 240D manual that sat for a long time (in a garage, gratefully) so I am getting back on the road.

#1: After replacing the transmission mount and motor mounts, it still has a harshness in the cabin that isn't normal. It's RPM specific, and does not change by speed. In other words, it's the same when driving or revving in nuetral while parked. It doesn't move the whole car, but rather is a very harsh vibration. From outside the car, the engine moves a little but looks and sounds normal. I have also changed all the fluids and filters, as well as did a valve adjustment.

#2: The clutch is intermittently soft. Most of the time it's ok, but sometimes it won't go in gear and I have to pump the pedal a few times to be able to shift. Otherwise, no grinding, no fluid loss, clutch slave and master are both dry. I have tried to bleed it a few times, but it's possible there's trapped air I'm not getting?

Thanks in advance for your help! It's a nice car, and I'm excited to get it back on the road where it deserves to be.

[Frank Reiner]

There's a fair chance that the vibration and the non-release are related.
The vibration is likely a flywheel/clutch out-of-balance situation. It could be as simple as a portion of the friction disc loose, or as serious as a cracked & separating pressure plate.
If the original trans was an automatic, the manual flywheel may not have been match-balanced to the autobox flywheel.

[imgolden]

Originally Posted by Frank Reiner

There's a fair chance that the vibration and the non-release are related.
The vibration is likely a flywheel/clutch out-of-balance situation. It could be as simple as a portion of the friction disc loose, or as serious as a cracked & separating pressure plate.
If the original trans was an automatic, the manual flywheel may not have been match-balanced to the autobox flywheel.

Thanks Frank, I was also wondering about the flywheel and clutch. This was always a manual car, so no swap. However, I need to go through the service records and see if the clutch was replaced and when. They serviced at what seems like a reputable shop.

I should say though, the clutch issue feels hydraulic to me. And, the vibration doesn't ramp up with vibration like an out of balance flywheel. It does smooth out at certain RPMs

[vwnate1]

The '82's (and some others) had a third 'motor mount' under the center of the engine *just* in front of the transmission ~ it needs to be adjusted or it will telegraph nasty engine vibrations directly into the body by the tranny hump .

Quite often the rear tranny mount gets oil / ATF soaked and goes soft and allows the tranny's tail shaft to transmit vibration .

The correct fix here is to replace the two engine side mounts and rear tranny mount _then_ jack the car up and located the 17MM ATF bolt on the center engine mount and loosen it until you can lower or raise the "L" shaped center part until it's dead centered in the hole it passes through .

I was shocked when a M-B dealer trained Mechanic didn't do this after installing my tranny ~ the vibration was -so- hash my Sweet asked if I needed a new muffler or something .

Those that couldn't figure this simple thing out usually removed it, a bad idea .

[imgolden]

Originally Posted by vwnate1

The '82's (and some others) had a third 'motor mount' under the center of the engine *just* in front of the transmission ~ it needs to be adjusted or it will telegraph nasty engine vibrations directly into the body by the tranny hump .

Quite often the rear tranny mount gets oil / ATF soaked and goes soft and allows the tranny's tail shaft to transmit vibration .

The correct fix here is to replace the two engine side mounts and rear tranny mount _then_ jack the car up and located the 17MM ATF bolt on the center engine mount and loosen it until you can lower or raise the "L" shaped center part until it's dead centered in the hole it passes through .

I was shocked when a M-B dealer trained Mechanic didn't do this after installing my tranny ~ the vibration was -so- hash my Sweet asked if I needed a new muffler or something .

Those that couldn't figure this simple thing out usually removed it, a bad idea .

''

Thanks Nate! I belive I know the mount you're talking about, it's the 2 13mm bolts I had to remove in order to lift the engine to do the motor mounts.
It's hard to believe that such a flimsy little piece of rubber could transmit so much vibrations. But, I really hope you're right. It would be such an easy cheap fix...

[vwnate1]

Let us know how it goes please .

That simple little mount caused me so much grief, I couldn't listen to the radio, talk to my Sweet and so on .

The "L" needs to be dead centered in the hole it passes through .

[imgolden]

Folks, reporting back here with more info on this issue. Your opinions are much appreciated.

I disconnected the t-mount as Nate suggested, and there was no change. I then went for a drive and obverved some facts:

#1: When I bleed the clutch, it will work fine for about 10 minutes. Then the pedal will get soft, fluid in the master cyclinder goes down, but every system is bone dry (brake pedal stays firm). This leads me to believe the slave is leaking into the transmisson.

#2: the harsh vibration is present and unchaging regardless of motion, clutch postion, or gear selected. It ebbs and flows with RPMs.

#3: When the car is coasting, with the clutch pedal depressed, and I select gears, I observe a rattling noise coming from the transmission. I took a video of this sound, and you can hear it very clearly about 17 seconds in: https://youtube.com/shorts/S0jTuFyUV14

Here's what I'm thinking is happening. Brake fluid has seeped into the clutch, damaging it and throwing everything out of balance.
In regards to that sound, hopefully it's a pilot or throwout bearing? If not, something internal to the transmission, which wouldn't be connected to the other issue. This issue is concerning because it only happens when gears are selected.

What do you all think? This is obviosuly a big setback so I'm trying not to be bummed about the whole thing.

[Shern]

I had the leaky slave cylinder issue. Have you checked the bottom of the bell housing for drips?

It's a long shot, but there's also the possibility of the master cylinder leaking fluid and draining behind the firewall.

Maybe you have two separate issues, but I'd deal with that slave cylinder first.

[imgolden]

Originally Posted by Shern

I had the leaky slave cylinder issue. Have you checked the bottom of the bell housing for drips?

It's a long shot, but there's also the possibility of the master cylinder leaking fluid and draining behind the firewall.

Maybe you have two separate issues, but I'd deal with that slave cylinder first.

Thanks Shern. I did observe some fluid on the bottom of the bell housing, but not the side, which is another reason why I suspect the slave is leaking by the pin, into the bell housing.
I am curious your thoughts on the sounds in my video, do those sound anything like your car? I know you drive yours a lot.
I will be ordering a slave cylinder, and some redline today to start there.

[vwnate1]

I hope you didn't remove the center mount ! .

Does it make this noise in all gears ? .

Will it make the noise coasting in neutral ? .

When was the last time you changed the tranny oil ? .

[Shern]

Originally Posted by imgolden

Thanks Shern. I did observe some fluid on the bottom of the bell housing, but not the side, which is another reason why I suspect the slave is leaking by the pin, into the bell housing.
I am curious your thoughts on the sounds in my video, do those sound anything like your car? I know you drive yours a lot.
I will be ordering a slave cylinder, and some redline today to start there.

Yeah, dude I have no idea what that sound is… it sounds a bit like a friction slap. Like an rpm thud, but I certainly wouldn’t go to the mat for that. I do get the odd vibration from time to time. Typically it’s higher pitched and metallic, which lets me know something needs tightening. Let us know what happens after you swap that slave out.

Originally Posted by vwnate1

I hope you didn't remove the center mount ! .

.

He loosened the T-mount, the mount you suggested inspecting. I believe it started appearing on 240s from 82, and I’m surprised it had any effect whatsoever for you. It’s a pretty flimsy piece of rubber!

[vwnate1]

The reason it can (not does) transmit nasty vibrations is : it needs to be properly adjusted every time it's touched / loosened .

I don't think the noise I hear is external to the transmission ~ it sounds internal to me .

[imgolden]

Originally Posted by vwnate1

I hope you didn't remove the center mount ! .

Does it make this noise in all gears ? .

Will it make the noise coasting in neutral ? .

When was the last time you changed the tranny oil ? .

Hi Nate,

Yes, I disconnected the t-mount briefly to test your theory before I take the time to adjust it.

It does indeed make this noise in all gears, especially 2nd. No, it doesn't when in nuetral. Additonally, if I am in park with the engine running, it sometimes makes that sound noise until I push the clutch in.

Tranny oil is an unknown, since I just bought this car. I plan to inspect and replace this weekend.

At this point, I'm thinking that the throwout bearing and/or some part of the clutch assembly is the issue. Hopefully it's not the transmisson itself, because it shifts nicely with no grinding ot popping out of gear.
I may drop the transmission this weekend just to get a good look at the clutch.

[imgolden]

Originally Posted by Shern

Yeah, dude I have no idea what that sound is… it sounds a bit like a friction slap. Like an rpm thud, but I certainly wouldn’t go to the mat for that. I do get the odd vibration from time to time. Typically it’s higher pitched and metallic, which lets me know something needs tightening. Let us know what happens after you swap that slave out.




He loosened the T-mount, the mount you suggested inspecting. I believe it started appearing on 240s from 82, and I’m surprised it had any effect whatsoever for you. It’s a pretty flimsy piece of rubber!

Yeah, to me it sounds like a bad bearing or damaged pressure plate perhaps. I'll report back for sure!

[vwnate1]

Well ;

If it's the throw out bearing it'll make noise when you step on the clutch, even in neutral .

That it makes noise in every gear says *maybe* the cluster shaft bearings are kaput .

Don't be in a hurry to yank it out, drain it into a super clean pan and see what's in the oil .

Golden colored glittery stuff or silt is the synchronizer rings, unless they break they rarely make noise .

Steel colored SWARF or silt means the tranny is or is close to the end .

I have never done one of these trannies but in general I find manual trannies to be very straight forward in repair .

If there's just one bad bearing (what I *think* it sounds like) probably caused by the bad hydraulic clutch it may well be an easy repair : change every single bearing in it and new synchro rings, set the lash / end float and even if it whines it should be good to go .

Of course you're going to add a small magnet to the fill and drain plugs no matter what you find .

Sadly I see more than a few 240D's with the manual box still in them being crushed for scrap after the lazy owner makes it like a pig sty inside them junks it when it fails to start .

Point being there should be an affordable used tranny out there for you or, what I'd do : make one good one out of at least two plus new bearings and synchros .

Keep us posted please .