busted distributor belt!

[91C2wrencher]

Drat, and double Drat!, Any body got advice for the broken belted?

[Drew_K]

Yikes, sorry to hear about that. I know some people have replaced the belt themselves. Others have mailed theirs off to Steve at Rennsport in Oregon (Portland?) with success. $150 as I recall. I had my belt replaced last week by my dealer ($300). You could simply replace the entire distributor, but that's definitely the most expensive route.

How did you notice the belt was broken? Any harm done?

[jmiles1]

If you are really good with that Wrench then you can do it yourself. Check out my Technical page (John's 964 Web) and click the dizzy vent kit link. You will find a link to Louis Guerra's instructions. Tricky procedure though.
J

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John Miles, 964 C4 1990
John's 964 Web
The Porsche 964 Group

[dsentel]

Steve at Rennsport is a good option in my opinion, quick turnaround, and relatively low cost. Mine is still working from a rebuild this spring. Be careful when packaging the rotors if you want to reuse them. It's very easy to remove the dist, much harder to rebuild.

[kr911]

We have nice instructions, but is there anyone who've actually done the rebuild by himself ? Any suggestions ?
I'd like to do it by myself next weekend...

[J Richard]

Bummer. For those of us who have yet to get belt-wipped, how quickly were you able to recognize the problem? As soon as you got a light did you know it or did you have to figure it out?

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93RS

[91C2wrencher]

Richard, What light? I'm under the impression that there is no idiot light for the dist.belt. I had taken her out for an evening spin, at the turn around (10 miles?) I heard a strange weezing sound along with a definite "miss" on accel. My first reaction was to think of the dist belt. I eased it home and parked her

[J Richard]

I had always assumed you would get a check engine light if the distributor belt went. I would think it would wreak havoc with the DME...(?) I'm going to get pretty ticked if the dang thing can monitor just about every system in the car including the brakes and not tell me if the distributor is all wonkey...

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93RSA

[Bill Wagner]

The DME won't tell you if the distributor belt is broken. If the guys programming it had been aware that it could be a problem, they probably would have put some code in to at least check (or make some assumptions) that would set the light off. The fact is, they didn't do it. How the DME will react probably depends on where the rotor stops on the secondary distributor. If it's in between rotor contacts, the distributor will likely not fire on a spark and the DME will likely end up doing nothing more than a slight timing adjustment. If it's stuck on top or near a spark, I suspect it might actually set off a Check Engine light since they're would be a lot of misfiring, but I don't know. I didn't program it.

Bill Wagner

[J Richard]

Well F*%$#!, with all of the idiot (sorry annunciator..) lights on this thing it looks like a christmas tree. You would think at least one of those pocket protector wearing engineers would have thought of monitoring the distributor output. Oh well I gotta go out and inspect my distributor belt now...

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93RSA

[91C2wrencher]

Well here's the update for all you 964'ers. I've taken out the distbutor, this process is not very hard:
1. diconnect battery
2. take out blower tube
3. remove and tag coil wires
4. remove top cap
5. remove the wire guide that goes over the fan(for extra wire play)
6. remove plug wires 4,5,6 from top rotor(tag'em)
7. remove lower cap
8. hand crank engine TDC #1
9. Undo hold down bolt on distbutor
10. gently lift out dist.

I'm hoping the re-install goes as smoothly won't know for a week or so 'till Steve gets my dist fixed.

Note 1: The lower rotor did stop very near the #1 cyl. post and apparently did "crossfire" ouit of sequence(melted rotor) but an inspection of the #1 plug showed no unusual signs(nice and gray)

Note 2: There is no idiot light and Steve reccomends this repair every 50,000 miles, wanna take a guess as to my mileage? yep!

[964Cab]

If you get stuck on the road due to a broken twin distributor drive belt would it be wise (?) to disconnect the lower's cap's coil feed (to the lower cap's center electrode) and thus at least be able to limp home without further damage to the car ?? If the lower distributor's cap is not getting juice from the coil than it wouldn't matter where it's rotor got stuck at, right ?

[J Richard]

Anybody have a response to 964cab's idea?sounds pretty solid if you could ground the wire to keep from frying the CD, Any thoughts? My belt looks ok but I'm going to be due in a bit...

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93RSA

[91C2wrencher]

Don't know about cab's idea. I thought breifly about doing just that when mine broke and then decided to just ease it on home. LISTEN UP! the condition of my dist belt was HORRID!!! very dried up and brittle, it looks like it sort disentgrated, perhaps over time. maybe even running on the "threads" before breaking, don't know but I think this could result in un-syncronizing the rotors..BAD! Anyway I suggest that if havvn't looked at your belt recently you should just get it replaced, mine was really gone.

[91C2wrencher]

bought a new lock nut and washer for the distributor hold down. As I suspected the nut is a "one use" locking nut: you can not reliably reuse it.

p/n 999-084-095-02 locking nut 8mm $.65
p/n 900-025-007-03 washer(new part#) $.26

Does anybody know the proper torque for this nut?

[Bill Wagner]

964Cab:

In my opinion, that's DEFINITELY a good idea. However, you probably won't really limp home. Many of the people that end up having this problem are unaware of it because most of the time the rotor will settle far enough away from any contacts in the secondary distributor to generate a current path to the spark plugs. I've read a lot of posts where people were informed that their belt had broken and they were completely unaware of it, and very few where it was actually causing the pinging, knocking, and misfiring that occurs when the rotor settles right on top of a contact.

An interesting experiment would be to dino a car with the secondary distributor removed just to see how much power was lost.

Good Luck,

Bill Wagner

[Roland Kunz]

Hello

The DME will not detect a broken belt, it only will react on pinging trough missfires and retard the ignition to the lowest level.

The dangerous situation is when the belt losses one or two thoots and runs asynchron or when the belt spin off at high speeds with free rotating secound distributor shooting randomly pre ignitions.

Grüsse

[J Richard]

Wrencher, did you have the dist vent kit on the car? Or how long did you go without it?

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93RSA

[This message has been edited by J Richard (edited 08-17-2001).]

[Bill Wagner]

Roland:

The idea of teeth busting off is one I've never heard of. I can certainly appreciate how that would certainly cause a problem, but I've never heard of it happening before...not that it couldn't...as these cars age I suppose this may be yet something else to worry about.

About the "free wheeling" rotor, considering how cramped that area is, I find it hard to believe such a situation could exist. I'm not saying it couldn't exist. I just think it would be extremely rare for a distributor rotor to be free wheeling. From what I've heard, when the belt busts, the driven rotor virtually forces the remnants of the belt to surround the secondary distributor.

Have you or someone you've known come across the conditions you're describing, or are these theoretical (yet entirely possible) situations?

Best Wishes, and it's good to hear from you,

Bill Wagner

[This message has been edited by Bill Wagner (edited 08-18-2001).]

[This message has been edited by Bill Wagner (edited 08-18-2001).]

[91C2wrencher]

J, I put in the vent kit just over a year ago, so the car went nine years w/o it. Do I think it mattered? NO, like any rubber belt its gonna break sooner or later. Hopefully the new belt will last at least this long, but I won't hesitate to change it next time before it breaks as part of the 30,000 mile check up.