Steve 935

What are the symptons? Does the car run rough? Can you check it by removing the caps and looking to see if both rotors are turning?

Thanks

Adrian

Dear Steve,
There are often no symptoms which show up for the average 964 owner, especially if the 964 is their first.
If you think it is broken check it. You remove the dizzy cap off the secondary diizy, one closest the rear of the engine bay and furthest from the fan and take a look.
If you remove both caps you will see it working in all its glory or not whatever the case maybe. However remember to keep your fingers and body away from the removed caps. There be sparkies just waiting to jump out at you. I recommend you remove the centre leads first and tie them out of the way. The DME will still try and start the puppy.
Ciao,
Adrian
964C4

Steve 935

After reading some posts about broken belts it made me nervous. My car runs very smooth and has the vent kit, but it would be good to check anyways. I read that some people experienced a miss or roughness. Will it do that when it breaks ?

Adrian

Dear Steve,
I did a huge amount of research on this issue when I first started my book. It led to some heated debates on this forum believe me. However after contacting various experts around the world including quite a few in the USA I discovered that in general the average 964 owner, as I said does not know when the belt is broken. Some people say they can tell the difference and somebody tuned into their 964 would certainly feel the difference.
Every service a full ignition functional check should be carried out. Most people do not bother.
There are simpler ways of checking but it depends how brave you are. I do not like people to do dangerous things though.
For me I just pull the centre lead off the primary distributor cap when the engine is running. If the 964 stops I know the belt is broken. However you can get zapped doing this. So I do not recommend it. I have been zapped so many times I do not care but others might. Loosen the lead first because it is tough to get off when fully seated. You did not hear any of this from me. Our secret okay.
Ciao,
Adrian
964C4

gjvander

It really doens't get any easier than disconnecting the center lead of the primary distributor (closest to fan), then try to start the car. 2 minute job and you have your answer. Then you can confirm by removing the secondary distributer cap - if the the rotor spins freely the belt is broken.

I had the belt fail at about 45k (come to think of it, a lot of things have failed on this little gem). I could feel the car hesitate at 5000 RPM and above, so I suspected it was detonating. $15 repair.

Regards,

Geo

Steve 935

Adrian,
Thanks for the tips. Is the a write up on the replacement procedure somewhere ? It seems like it would be fairly simple.

Adrian

Dear Steve,
It is not a simple job unfortunately. There is a write up on the net at www.porsche964.co.uk and another on its way between two covers.
Ciao,
Adrian
964C4

Jeff Curtis

Another suggestion:

Prior to every weekend at the track, I put a timing light on one of the leads to the secondary dist. start the car and see if it works the timing light. I then shut the car off, move at least two leads away, reconnect the sensor and start the car again to see if the timing light operates.

I do this because sometimes the belt breaks and the rotor may be stuck between two terminals, and firing on one or the other, possibly BOTH!

So that is my "double check" method.

I like Adrian's method better, but while I have been shocked PLENTY of times during my electrical/electronics career, unlike him - I NO LIKE!!

Claude

I had my belt changed at 47K miles. Vent kit was installed 7 years earlier. I'm glad Adrian said it is difficult to replace---my mechanic charged 3 or 4 hours of labor for it. BTW, the old belt looked like a strong wind would have snapped it--very brittle and shredded--no way of knowing until you take apart the distributors.

Adrian

Dear Jeff,
Whilst I have your attention. You are an old 911SC expert. Do you happen to have any images of a totally disassembled 911SC and any crashed or damaged ones. I need them. I am also having trouble trying to make the description of the body/structure of a 911SC sound interesting because it is not really new. Some interesting images might help me out.
Also if Bill Gregory is reading this, you are an old 911SC expert Bill have you anything.
In fact does anyone have anything.
Ciao,
Adrian
964C4

Phil Raby

This reminds me of a friend's 964 which he'd just had serviced by a well-known specialist. He then took it to another specialist who claimed the belt was broken and used the old screwdriver in the plug lead test to prove it. It seems the first company had just done the standard tests with the Bosch hammer and this doesn't identify the broken belt.

No, I won't say what company it was

Adrian

Dear Phil,
The Bosch hammer does not check the ignition system components. Only the hall sensor and it normally tells lies about that as well.
Ciao,
Adrian
964C4

Jeff Curtis

Adrian, I have very little, as I did not own a digital camera at the time.

What I do have is TONS of pics of an engine and trans. rebuild...I became a PRO at that!! ...I had configured a supercharger setup on the engine and that ate up transmissions like no tomorrow.

I will see what I can find.

Randall G.

When my belt broke at ~75k miles, I could tell something was amiss. The car was running sluggish, and was hesitating at lower RPMs. As Adrian suggests, I had owned the car a long time, and knew something wasn't right. Belt replacement made a huge difference, put a big smile on my face. Somewhat analogous to cleaning clogged jets on a carbureted car.

Adrian

Thanks Jeff. The supercharger stuff would be of great interest for chapter 11.

Dear Randall,
I know a 964 owner, still has it who purchased his 964 and drove it around for a year with abroken belt. How we know the belt did not break in his ownership was simple. It was completely missing. The PO had cleaned out the debris that he could see and said nothing. For this owner everything was normal. When the fault was discovered and a new belt installed he also reported a significant increase in smile width.

Ciao,
Adrian
964C4