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Discussion Starter #1
Hello,
Does anyone have an idea of why my clutch would give a (fairly significant) vibration when engaging only when it is hot? It really only happens from a standing start as shifting at speed is too fast to allow the shake? This only seems to happen when the motor is at temperature and it is reasonably warm outside. Other tidbits: the clutch is virtually new (7000kms), the problem seemed to appear a year or so after the clutch replacement (say 4000 kms ago). The guibo is brand new, motor mounts aren't new, but seem to be in good shape visually (but can't rule this out). One suspicion is oil from the rear main seal. My motor used to leak no oil (really!) and now over the winter I have a few drops on the floor (minor for an Alfa in my opinion), but the leak seems to be the rear main. Could it be oil working it's way into the clutch?
Also it is very doubtful that oil could come from the tranny, as I just switched them and there was no leak on the last one, and the new one does the same. The clutch assy looks dry, new and shiny, but I didn't disassemble it for inspection during the tranny swap (I guess I should have....)
Any insight would be greatly appreciated!!
cheers
 

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1966-2013
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*When the friction disc was replaced, was the flywheel turned?
(bedding issue)

*If so, was the shoulder of the flywheel turned to an equal amount as the face?
(pressure issue)

*What happens if you are moving at like 20mph and engage 4th then mash the throttle to try and accelerate away?
(if there's slip, that'll show it)

*Was the pressure plate replaced at the same time as the friction disc, or the old one re~used?
(heat can effect the spring fingers over time)

*Was the pilot bushing replaced, or at least measured to be sure it was in~spec?
(if its on the too loose side of things it could allow trans input shaft wobble as it warms up)

*Do you ride the clutch to keep the car in place while sitting at slight uphill grade stoplight instead of holding the brake?
(if yes, then you deserve what you get as a result :))

I'm sure there's other things it could possibly be as opposed to that above, but its a place to start anyway and will get some of the usual questions out of the way first thing.
 

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Darren covered my ideas.
 

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I've had issues similar to this (though not with an Alfa) and the culprit was a cracked flywheel...
 

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Discussion Starter #6
Thanks for the quick feedback. Everything on the clutch was replaced (pressure plate, throw out bearing, and disc). In fact the reason for the clutch replacement was a "lazy" pressure plate that allowed slipping under full load. The flywheel was turned, but I'm not sure about the shoulder as you mentioned Darren.. There is no slipping now. The problem did not show up immediately after the clutch replacement, but after some time (a year or so) and several kms (maybe 2000 or 3000km). Since then, I've put on about 4000kms. I just swapped transmissions, but this clutch shudder is exactly the same before and after the switch (not surprising...). I really hope the flywheel is not cracked, it has crank degree marks all the way around and a handy little pointer in the bellhousing which is very nice for setting the ignition/cam timing....
Oh, and no, I'm not a clutch rider :)
 

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Discussion Starter #7
The thing I find a bit puzzling is that it only shows this behaviour when it is hot (engine).

Maybe important also is that the car sits over the winters (rust on the flywheel?), but I guess the vast majority of our Alfa's take the winters off...
 

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Discussion Starter #9
The engine mounts are about 10 years old. tranny mount - the same. I actually bought a new tranny mount when i did the swap, but when I felt the old one compared to the new, I really could't feel a difference by twisting the metal bushing around. Additionally the other transmission (with it's mount) did not seem to have any affect on this problem. But the motor mounts I really couldn't rule out (even if they "look" good). Is there any kind of rule of thumb to be able to say if the motor mounts are good or not? for info, I do have the fan shround mounted, and the fan doesn't hit the shroud...
 

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clutch judder

I had an Austin Marina years ago that had pretty bad clutch vibration on engagement. I always assumed it was getting oil on it or had oil soaked into the lining to cause the judder. Well I had to lend the car to my mother for a week while her 80s V6 Camaro was getting its 3rd worn out clutch replaced in 4 years. She rode the clutch continually, and this was the last manual transmission car we let her buy. Anyway when I got my Marina back from her no more clutch judder. I assume she rode the clutch as usual and burned off the oil and cleaned off the lining fairly well.
 

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If the clutch engages at too-high rpm for some time you can end up with this symptom. I had a VW on which the idle would not kick down well; clutch engagement got steadily more juddery over time, til I replaced the disk. My sense is the disk gets hot and develops burned or nasty spots as a result from too much friction on engagement. Maybe your has developed similar symptoms through some overheating.
Hydraulic clutch cars are not known for clutch judder to the same extent as mechanical clutch cars, but it certainly can happen.
Andrew
Andrew
 

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I believe you mentioned the flywheel had been surfaced. I have several examples of racing flywheels with actual divots cut into them by bouncing discs. sometimes the pressure plate also has similar divots.
Hydraulic clutches will bounce and judder like mechanical, it is just harder to feel, being damped out by the mechanical advantage of the two different sized cylinders in the hydraulic system. A friends racing '87 BMW 325is, had a clutch pressure plate and flywheel full of divots, yet other than slipping as the disc was worn out, it felt fine!
 

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Discussion Starter #13
The curious thing is that when the car is cold (taking off first thing in the morning, and for that matter regular driving on a sub 20°C day) the clutch behaves fine. This leads me to beleive that it couldn't be a "permanent" problem like a cracked flywheel or divots (but certainly won't rule this out).
Is there actually a path for the oil to run from the rear of the engine into to the clutch or is this false trail that I'm on?
thanks / andrew
 

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It can come out of the rear main or cigarette seals then find its way into the clutch friction area as oil that got slung onto the bellhousing interior drips.

Still, an oiled clutch is an oiled clutch: pretty much full time screwed up, not something that would be temperature related or even intermitant for that matter. Strictly 'bad' to 'worse'.

Are other things dealing with the system in good order and properly set up?
'Other things' being pretty much from the clutch pedal proper all the way to the throwout fork.
 

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Discussion Starter #16
I won't have a chance to drive it again for a couple of weeks, but to answer the question, I beleive that everything else is in good shape;hydraulic system, fork, etc.
When I pulled the last tranny off the guard plate on the bottom of the bell housing was pretty oily, so it is probably the cigarette seals as you mentioned that are leaking. rats.
 

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Was is engine or gearbox oil on the guard plate? The front seal on the gearbox can weep a bit (mine did for years) without getting on the clutch - it just dribbles down the bell housing.
 

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Discussion Starter #18
It was engine oil, the inside of the bell housing was surprisingly clean considering the gaurd plate was pretty grimy.
On the note of the front gearbox seal, I had to reassemble the bell housing onto the transmission, which means sliding the seal over the transmission shaft. I was told to put a bit of grease on the seal, then slide bell housing over the shaft and fix to the transmission. Is this the correct way? Any other tips to ensure the seal doesn't leak?
 

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That is the way to treat most seals on installation. Gearbox lubricant, engine oil, or something like that. On the bellhousing seal you must be very careful not to cut the seal edges with the splines on the transmission input shaft. Also, for a number of reasons, this seal is most often installed backwards. I've seen several. Just remember, the lips always go toward the oil retaining side.
 

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Discussion Starter #20
Well I think that I have found the cause (or at least a good culprit) for this problem. As mentioned there was certainly some oil on the guard plate (but don't all Alfa's have oily guard plates?), but as I had the car on the hoist yesterday, i found some drops of coolant hanging from the bottom of the bell housing also. The coolant drain plug on the engine block seems to be leaking a bit, as there is always a green wet spot below the plug (dry above the plug, so it doesn't seem to be the head gasket (yes, I am touching wood now!)). This seems to be the only coolant leak as far as I can tell (the coolant level in the expansion bottle has been very gradually going down also). For extra info, I changed the oil yesterday too, and there is no evidence of coolant in the oil. The path for the coolant to go from the block drain into the clutch does seem a bit fantastic to me, but, the fact is that there is coolant drops on the bottom of the bellhousing...
I will flush the coolant, and reset the block drain plug and see if this cure the problem (hopefully!) I'll keep you posted.
 
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