jcastle

Rennlisters I need advice.

Purchased this '96 C4S in Oct 2009. It's a gem except for one flaw. It's torn up the belts 4 times. Yikes. We've replaced the alternator and updated the pulleys. This week I heard a squeal and some thrashing and then the dreaded alternator malfunction light.

Here's pics of my belts. The alternator belt is too loose and flipped inside out. Normally all 3 belts break, but I guess I got lucky this time.

I need opinions on whether I should fix this myself. 2 Dealerships have failed so far. Should I install the RS hub to simplify things? Should I replace the crank pulley...is there a chance it has something to do with repeated failures? I've not heard any fan bearing noise. When the engine runs, everything seems good except the alternator belt thrashing around.

Can anyway give detailed info on how to adjust the shims to tighten the belts.

Thanks so much.

jason

NightFlyer

Jason,
Here is a picture of my belts and pulley. Mine look a little different than yours, although my car is a 95 with a build date of 6/94 so I might have an older style pulley. I know if you get the wrong sequence of the pulley halves and such that that can cause issues.

IXLR8

If a dealer has done it, then it should have been done right. OK, so thats pushing it.

Pulleys aligned?

Pulleys in good condition?

Correct belts used?

Proper belt tension?

Installing & adjusting belts.

KriKit V-Belt Tension Gauge Video

ilko

Belt tension is key. Add/remove shims to adjust. I'd check that first.

trophy

I would check the bottom pulley that is on the crank, if the bolt that holds the pulley to the crank comes loose the pulley will wobble and cause the belts to break. I have seen this a number of times.

This can be a difficult one to fix without either removing the engine or removing all the rear of the car.

Keep us informed on what you find.

kjr914

Complete theorizing without any real data to back it up....
<swag>
Quite possibly, its only the middle belt that is mis-adjusted....it flips, then blows up, taking the others out with it...
</swag> (scientific wild *** guess OFF)

NightFlyer has the old style pulley, with the spacer between the pulley and the outer bolt being a separate piece. The "updated" one has the spacer built onto the outer pulley half.

Robin 993DX

Like other have mentioned the tension was probably not set proper.

You already have the updated pulley so it should not be tearing up the belts anymore, unfortunately since you have chewed through some belts the inside surface of the pulley may already be "polished" which will promote belt to easily slip, so I do recommend replacing the pulley halves this time around.

Lorenfb

A common problem for both the 964 & 993 is the failure of the fan bearing, This bearing
will eventually fail, as it's a sealed bearing which does not receive any lubrication. Once
the bearing fails, one of the two belts will break, i.e. Each belt turns at a different RPM.
Also, if this bearing is approaching its failure point and binding, either of the two belts
can be damaged and/or break. Bearing failure can also damage the alternator shaft,
requiring replacement of the alternator and possibly the fan itself.

Bottom line: The fan bearing replacement should be a normal maintenance item on all 964/933
engines with 100K+ miles, and/or an additional replacement item when the alternator is
replaced.

jcastle

Thanks to everyone for their input.

Lorenfb. If I switch to the RS hub, am I changing the fan bearing? Just want to make sure I order all the right parts. What's your thoughts on also changing the crank pulley? Since the crank pulley is more pricey and a more difficult install, I'm hoping I can leave it alone.

jason

Lorenfb

"If I switch to the RS hub, am I changing the fan bearing?"

When switching to the RS hub, the fan bearing is eliminated. Now both the fan & alternator turn
at the same RPM. This mod reduces a bearing failure to just the alternator bearings, i.e. both are
double sealed bearings.

The crank pulley need not be replaced unless it were damaged in some way, e.g. rough edges on the
pulley, bad pulley belt spacing, & etc.

IXLR8

Do you know how the pulley ratios differ with that set-up?

What speeds up or down compared to the dual pulley set-up?

Not doing the mod; just curious.

trophy

The Alternator slows down to fan speed with the RS Pulley update (Underdriving the Alternator)

Cannot remember the ratio

IXLR8

I guess when you're on the track (RS), one does not worry about idle RPM charging.

If they are handy, is the RS pulley smaller or larger than the original fan pulley.

Mike J

The RS pulley update is great for simplicity, since only one belt now drives the fan and alternator. Its very easy to change the belt.

Down side? The alternator cannot keep up to the pull of the electrics at idle, especially if the lights/heat/heated seat/etc. are on. You will see the lights in the dash noticeably dim when idling. I have the RS pulley, and at night I will use the gas to do a higher idle. I also turned up the ISV to idle the car higher to try to get the alternator to provided enough amps to fulfill the demand.

I guess what I am saying is go for the RS pulley if you tend to avoid stop-and-go driving. Long stretches of idling may cause issues.

Cheers,

Mike

trophy

I don't have them hand to do the comparison. sorry.