Bill Ball

Nicole:

Great job! I'm back, so I can help you button it up after you get the bearing.

Had my 89S4 up to a trap measured 164.4MPH (speedo indicated 168) at approx. 6,000 foot altitude at the Bonneville 100 open road race. Averaged 140 for the distance. Not bad for a bone stock S4 with 128K miles.

Nicole

Wow, Bill, that is awesome!!! Did you win anything?

I went under the car with the digital camera to take two more pictures: The front of the disassembled compressor, and the label. It is, in fact, the Nippon-Denso, but instead of 10PA 20C I read 10PA 20 "S"!

Since I have a hectic week ahead of me and might not have time to shop for the bearing, I ordered it online from the place borland had suggested. It should be here by Wednesday. This way, the car should be up and running again before the weekend - even if I have don't have a new belly pan by then.

But I don't think I'll get much underbody detailing done by then...

SharkSkin

VU, you're right... it IS better to design the system as seen on the AC units we've been discussing. However, not all electromagnetic clutches are built the same way. I can't remember where I've seen the bearing riding on the shaft in automotive applications... some old unit in a forgotten car. I have definitely seen the "bearing on shaft only turns with clutch released" configuration in industrial applications, especially where the EM clutch is sold as a retrofit for existing systems.

Things are not always done the best way, not even by Porsche. On my AC page I point out two flaws... well, one definite flaw in the wiring, and one stupid idea re: belt routing. Nothing is perfect.

Nicole:
Excessive belt tension may have played a part. The bearing may have been dropped or pressed in improperly, resulting in microscopic irregularities in the bearing race or *****. The grease inside of the bearing may have simply migrated away from the contact surfaces over the last 13-14 years. Maybe it's a combination of all 3.

You said that your compressor seemed to turn smoothly; you made no mention of oil around the front seal. Like wine, every bearing has its time... your bearing's time is up. That's all... try not to worry, just get it put back together with the proper air gap, and if it makes no strange noises forget about it.

One more thing... a thin coat of Anti-Seize on the compressor housing before you install the bearing would be a good idea. I know you didn't have trouble taking it off this time, but it's cheap insurance...

Bill:
Awesome! Sounds like you had a great time! Any pics/vids?

Bill Ball

Don't know about awards yet. I think I was a couple of seconds off and that's not good enough for an award. George Suennen is the event photographer and takes so many pics I decided not to take any. We should have results and pics in a few days. BTW, we had FOUR white 928s running in the event!

ColinB

Great job Nicole. I'm most impressed. Given the same symptoms I suspect I would probably have removed the compressor and sent it for overhaul. Obviously not the right approach in this instance.

Colin89 GT

BTW, don,t you have a 928 Intl belly pan? I ordered one on the strength of your description but I haven't received it yet. Surely it can't be that one that's falling apart already?

Nicole

Hi Colin:

No, I have a standard Porsche plastic belly pan, and the aluminnum piece behind it. It's the brackets on the aluminum piece that came lose. I have seen both the DEVEK and 928 International belly pans and find them superior to the factory version - especially because they can't crack or break. The DEVEK pan has the air vents almost exactly like the factory pan. The 928 International pan seems a little sturdier (not sure, if ttat's an advantage, if you hit something - maybe it is supposed to flex?), and also has a nice black finish. I think they are both good, and sooner or later I'll have one of them.

It would be an easier decision, if one of them would offer the additional benefit of easier removal/replacement, or an access door for oil changes.

Bill Ball

Nicole. We can fix those brackets. If the belly pan is still intact, you shouldn't need to change anything. I can come by and look things over on the way home tonight if you will be around. Let me know.

jayc67

Nicole, does your original plastic pan still have the air deflectors that connect to the duct vents? If so could you take a pic of that while it's apart?

All of the aftermarket metal pans have the ducts but no duct work and I would like to reproduce the original duct work. I understand it aims air towards the motor mounts.

Thanks a million!!!

Jay

Nicole

Hi Jay: Will take the pics later. If I were you I'd call the supplier of your aluminum belly pan of choice and ask them for used ducts. They often have banged up belly pans from which they can remove the ducts - then you have the right stuff and don't have to worry about it. I don't think the cost for used ducts is worth the time trying to recreate them. They are actually pretty complicated in thier shapes...

Nicole

New bearing arrived today. Now the next phase of the adventure can begin...

Below are some (not so good) pictures of the belly pan vents, first the drivers side, then passenger side.

jayc67

Thanks Nicole. Well I asked all of the Big 3 and no one has the duct work, used or not. So, I guess I will do without until someone has a set for sale somewhere.

Thanks anyway!

borland

Nicole,

There are two belly pan screws that attach at each air duct. Those holes in you pictures are for driving these screws in, and the tabs on yours look bent over so it doesn't look they were being attached.

That could be a source of noise/rattle.

Nicole

Good catch! More screws to put on or take off - exactly what I've been looking for... But here is another possible source for that mysterious 2900 rpm vibration noise.

The good news is that the new bearing is in the pulley now, and we'll be trying to finish things up on the AC tomorrow.

I might leave the belly pan off temporarily for some more cleaning. It's unlikely I'm going to encounter any rain or 100mph+ runs in the next few days... We'll see tomorrow.

Nicole

Well... It's all done and wonderful. Just came back from my first test drive. Now I know that this problem has been developing for a while. Bill and I suspect that the belt might have been over-tensioned...

Putting things back together went pretty quickly tonight. and upon starting the engine we were delighted to hear no scratching or clicking noise from the AC compressor anymore. There is a slight whistle coming from the air tube that attaches to the back of the alternator, but I could not figure out how to take the tube off for inspection.

I had already cleaned the belly pans. With Bill's help we were able to straighten the aluminum part pretty well and reattach the broken bracket with pop rivets. I repainted the black rear bracktes and put everyting back together.

Looking at all the gunk under the car, I realized that I will not be able to clean this up in the next week or two, so I went ahead and reattached the belly pan as well. What an ordeal that is! I kept thinking of Beth's forehead trick, and used a variation of it.

I'm glad everything is back together and the car runs sooo much smoother than before. Now all it needs is a bath, and it'll be ready for DEVEK days!

Thanks, Bill, for giving me a hand, and Ron and Dave for your telephone support. Also thanks borland for posting the source for the bearing - that saved me a lot of time shopping for it!

Total cost was about $43 for the bearing and two-day shipping, plus a bunch of nitrite glvoes, brake cleaner, and this magic spray to losen sticky nuts. Even if I factor in the jack stands (I already had a jack) and the wrench I bought I was not even close to spending $100.

I believe that ponentially many 928s have a similar bearing problem. Once you have determined that you have a scratching/clicking noise from the front of the compressor (use a shop vac hose to locate the source), you need to determine what type of compressor is in your car, then get the appropriate bearing. Tools needed are wrenches and nuts in metric sizes 8, 10, 13, 14 and 17 as well as circlip pliers (very important!).

To remove the old bearing from the pulley, you need a large nut and a sledge hammer, or some other suitable tool. It sure helps to cool the bearing and warm up the pulley for doing this. We had put the new bearing in the freezer before carefully pressing it into the pulley.

Hope this helps someone in the future. Maybe Greg Nichols will pick up a condensed version of this for his famous resource website...

SharkSkin

Awesome Nicole! < $100.... how satisfying is that? I have to say that I think this was an admirable undertaking on your part. Most of us can do more than we think we can. I imagine that there are people who never have turned a wrench on their shark and never will... but you may find that this is addictive, fixing minor problems yourself and "getting off easy".

BTW, I have my AC done, blowing nice and cold. Now the weather is nice, and I don't need it, even with a black/black car... Now I just need to fix my windshield washers before winter's over.