replaced clutch, now engine vibrating

[Curt Hayes]

Hi,
I did the clutch on my 87 325is a while back, at the same time replacing the tranny and motor mounts with urethane ones. When I fired it up I found that the engine now vibrates pretty strongly from about 1500 to 3000, then settles out after that. I changed back to stock engine mounts and it's better, but still there.
Thinking it was missing, I've replaced every part of the ignition system (dme, coil, cap/rotor, plugs, wires), but nothing is better.
Power is the same as it was before, so that's not it.
Not having owned an e30 before this, I'm not sure if this should be expected with urethane mounts or not. I'm sure that replacing the clutch shouldn't result in an out-of-balance engine (all stock), and have been racking my brain trying to figure out what it could be. Outside of pulling the tranny back out to see if I left a bolt out or something (99% sure I did not), I'm out of ideas.
This could've been there before with the really spongy 20-year-old engine and tranny mounts, but why would it do it at all?
Any ideas from anybody?
Thanks,
Curt

[jlevie]

Urethane motor and/or transmission mounts will increase noise and vibration. The clutch won't have anything to do with it unless it was improperly re-assembeled.

[Curt Hayes]

Understood. Vibration has the feel of a once-per-rev thing, like something is out of balance, but I can't think of what I could have put together wrong with the clutch to cause this. I had the flywheel resurfaced, and they did the step for the pressure plate. Maybe they did something wrong?
Seems like if I'd done something wacky with the pressure plate then I'd feel a vibration on the clutch pedal, and I don't.
I'm stumped.

[E30Nova]

You said you went back to stock motor mounts, but what about the transmission mounts? Poly motor mounts don't really increase vibrations all that much, but poly transmission mounts will make your car shake like a top fuel dragster.

When I put in poly motor and trans mounts my car vibrated from idle to around 1500-ish and then smoothed out.

I think I've actually gotten used to it as I don't notice it anymore. :p

Matt

[Curt Hayes]

You said you went back to stock motor mounts, but what about the transmission mounts? Poly motor mounts don't really increase vibrations all that much, but poly transmission mounts will make your car shake like a top fuel dragster.

When I put in poly motor and trans mounts my car vibrated from idle to around 1500-ish and then smoothed out.

I think I've actually gotten used to it as I don't notice it anymore. :p

Matt

No shxt, the tranny mounts will do that? I put the engine mounts back to stock but figured the tranny mounts wouldn't have that big of an effect. I guess I'll order up some stock ones and give it a shot. Certainly easy enough to swap and see. I guess if it works out then I could put the motor mounts back in... or just bag it. It's a stock motor with umpteen million miles on it. The most I'm going to do is a chip, so probably no worries about fans and radiators colliding.

I'm getting use to the vibration, but can't shake the "there must be something wrong" feeling, so it drives me nutty.
Thanks for the advice!
Curt

[E30Nova]

Yeah I've got a 69 Nova with solid motor mounts and it's still nice and smooth, but the minute I put a poly trans bushing in it, the whole car wanted to shake itself apart.

The only reason I even used em on my E30 was because my stock ones were disintegrated, and after putting the solid ones on, I was too lazy to crawl under the car and change em out. Doesn't take long to get used to it. ;)

Matt

[Curt Hayes]

That did it! I replaced the transmission mounts with stock ones ($6.50/ea) and it's all gone!
Hard to believe that those mounts mask that much vibration, but clearly they do.

"Doesn't take long to get used to it."
Yes, I could certainly get used to the bouncing, it's just that I was convinced there was something wrong with the engine.

On a related note, I've seen people saying that the stock mounts can result in the fan hitting the radiator under braking. On my car there's a bumper that mounts to the bell-housing and pushes against the back of the front subframe. Seems like that would keep the engine from popping forward, no?

[iignite]

From what I hear, the tranny mounts do the most vibrations. Engine mounts adds a little vibration but its bearable.

[E30Nova]

On a related note, I've seen people saying that the stock mounts can result in the fan hitting the radiator under braking. On my car there's a bumper that mounts to the bell-housing and pushes against the back of the front subframe. Seems like that would keep the engine from popping forward, no?

Glad you got it fixed. Honestly though, I've never seen this "bumper" that pushes on the subframe. That's new to me.

Matt

[Curt Hayes]

Glad you got it fixed. Honestly though, I've never seen this "bumper" that pushes on the subframe. That's new to me.

Matt

#14 and #15 here: http://www.realoem.com/bmw/showparts...73&hg=11&fg=10

Not shown in the pic is the subframe. The mushroom-shaped bumper pushes against the back of the subframe.
Seems to take care of just what people are worried about.
Curt

[Curt Hayes]

From what I hear, the tranny mounts do the most vibrations. Engine mounts adds a little vibration but its bearable.

Wish I would've started looking in this direction to begin with. All new ignition system didn't do diddly-squat, as you might imagine. The vibration felt so much like a miss that I just headed down that road. My superior German car has now made me feel like an idiot.

Thanks for the help, guys, you've made me a happy driver again!
Curt

[E30Nova]

#14 and #15 here: http://www.realoem.com/bmw/showparts...73&hg=11&fg=10

Not shown in the pic is the subframe. The mushroom-shaped bumper pushes against the back of the subframe.
Seems to take care of just what people are worried about.
Curt

wtf I've never seen that before! That seems like something BMW added to fix the problem of fans eating radiators when the motor mounts break.

Matt

[Curt Hayes]

Maybe so, but mine is about as stock as you can get, and it's there. Seems like a pretty good idea. :)

[E30Nova]

Definitely a good idea. Surprised you have one in your 87 when my 88 doesn't.

Matt

[Curt Hayes]

Yeah, well I keep seeing cars with those cool fuel lines that run thru the a/c, and mine doesn't have it. After all, we need to keep that fuel cool on hot days!