pi5tolpete

IM looking at a 1989 964 C4. Today I got to drive it and give it a good look over. After a drive, I wanted to see and listen and smell the engine. That's when I saw the crank shaft wobbling a bit at idle. Not much, and seemed to go away at 2k rpm. What level of worry should I have? Engine was rebuilt 2 yrs ago. Can the pulley be on slightly crooked? I'm trying to upload a vid now.

spitz17

I have this same issue, eager to hear feedback.

Steve Weiner-Rennsport Systems

Its a pulley issue and not uncommon.

BHCfarkas

lol if the crankshaft were bent, you wouldn't be driving the car.

RicardoD

Steve,

Can you elaborate, not uncommon and is a precursor to massive engine damage? Or not uncommon and don't worry about it? What's the root cause of this problem.

BHCfarkas

https://rennlist.com/forums/996-foru...ort-video.html

Vandit

Here's a more relevant 964 harmonic balancer crank pulley wobble thread, with video.
https://rennlist.com/forums/964-foru...e-is-okay.html

And you can add me to the wobbly crank pulley list.

pi5tolpete

Now that the engine is back in and passed the break in period, I have had it up to 6+k rpm. If I go through 4500 rpm quickly, I'm fine, but if I go through slowly, I'll get the pulley belt light on the dash. I popped the lid and watched as a friend brought up the revs. The belt seems to go through a harmonic at about 4500 likely due to the pulley wobble and it triggers the belt sensor.

tdiquattro

I seem to recall the pulley can be out of true when torqued up on the crank. The instructions say to remove and re tighten to set it square. I think it can be checked on initial tighten and tapped with a mallet to ensure it is true before fully torqued.

So the answer is remove and re fit.

NineMeister

I doubt it. Furthermore you will not easily remove a crank pulley from the tapered nose of a 964 crank so I cannot recommend attempting it unless you have to.

In my view the issue will be due to deformation, delamination or deterioration of the rubber between the two halves of the harmonic balancer. The correct solution is to buy a new one. The problem with that is the cost.

Goughary

Mine was bent trying to remove it. When it finally popped off, it shot across the room and through a wall opposite. Cost new is insane. Someone needs to make a good aftermarket equivalent. I sourced a straight and true used one, but was worried about that rubber...so far so good...

Amroth

I got a used one on ebay for about 260 USD. Was in decent condition and is working great for the past months. Tiny fraction of the cost of a new one...

Amroth

Old worn out rubber





Used but in far better condition!