Cameron

I have never been overly concerned about the 928 timing belt issue. I guess that I view it as a maintenance item and if properly cared for, I believe that this issue will not present itself to me. Of course, I have not suffered a failed timing belt with no warning, for no previously apparant reason as some on this board have. I do believe that the reputation of a great engine, the 928 engine, has suffered as a result of this design and issue.

Our flat six bretheren are going through something now that draws my interest. In the same way that BMW M3 engine issues were exposed (via messge boards), the 986 and 996 appear to have a high number of RMS failures. In the case of BMW, they dicked around for a good 9 months in denial, before they stepped up to the plate and admitted that they have a problem. Even then, they managed the issue, telling some people that their cars were not affected, only to come back to them a year later telling them to come in and replace the bearings.

I believe that the M3 as well as the BMW reputation suffered as a result of the way an obvious problem developed and was handled. I hope that Porsche is more responsible and proactive, comes clean on the issue and then stands behind the product in an appropriate manner. The only reason that Porsche can charge a premium for its product is because of its reputation in the broadest sense of the word. If they screw this one up, used P car prices will drop and new P car prices may be next.

.....Cameron
'91 Euro GT

MikeN

I feel the same way about the timing belt issue. My first 928 ('87 S4 auto) went 78k miles and 10 years with the original belt......not my choice, but original owners oversight. The only reason the belt was changed was after the water pump seized. So I can say that maybe Porsches original recommendation of a 60K mile belt change was not insane.......if everything is kept up to snuff and not worked on by an unknowing mechanic......these things are pretty reliable.

As far as the RMS issue goes, it's almost treated as a maintenance item now and is really not the same type of problem a broken 928 belt is. It's more of a nuisance for Porsche rather than a major
engine breaking issue. It's a leak.....that's about it. If the leak cannot be repaired sucessfully, a rebuilt motor is swapped in. Pretty common for dealers to work on a couple a week, and from what I hear Porsche is making good on most if not all of them when it happens......even when it is out of warranty. Should Porsche be let off the hook......absolutely not!, is it pissing a few owners off.......yes, but I don't think Porsche views it as a show-stopping event at this point.......but an ongoing problem that they have and will keep addressing.

sharkmeister85

Ok stupid question time. What is "RMS"?
Glenn

MikeN

Rear Main Seal. Basically on many 986 Boxsters and version 996 911s the
rear main seal for the engine is prone to leak. In most cases it doesn't cause any damage at all.....just leaks. Porsche has tried to fix with newly designed seals, new installation tools and techniques, etc. Some cars have had it fixed several times. To fix you basically unbolt and remove the tranny, replace the seal and bolt the trans back. Most dealers can do it easily within a day or less.

Sometimes the crank is too far out of spec with the block mounting points for the seal and if this is the case the engine is swapped out.

Jim R.

I have owned a car with the M96 block (200 Boxster), and had the RMS leak. The dealer repaired it, it failed again, and repaired again. When I traded it in, it was not leaking from the RMS, but from elswhere. I don't know that I would want to have one that needed a engine replacement for an unfixable oil leak out of warranty. Between the Boxster, 996, and 997 there are a lot of these blocks out there.

When I purchased my 928, I was aware of the inteference engine and timing belt. I don't think it is any less reliable than most inteference engines with a timing belt. Obvoiusly, a chain would probably be safer, but I feel good about my chances. I did my TB service, and replaced all gears, rollers, WP, rebuilt the tensioner, and properly tensioned the belt. I think with regular tension checks and preventative maintenance, it is a relatively reliable system. The occasional catastrophic failure will happen, and I hope not to me or any of us. All in all, having owned both, I'll take our engine over the M96 type for long term reliability.


Jim R.

Jim bailey - 928 International

rear main seal ...the seal on the crankshaft near the flywheel it seals the engine case which should not move to the crankshaft which does move . When they can not get it to stop leaking they put in a new (rebuilt) engine because the case (engine block) probably HAS moved !!

heinrich

If someone came out with a workable chain system for the 928 I would buy it, even at huge prices.

PorKen

I believe one of the problems with our tensioner is inconsistent tension and the lack of damping (shock absorption). Both causing premature wear on the belt. Newer style belt timed engines with active tensioner/dampers have much longer belt service intervals.

Our tensioner is not much better than the prototype manual tensioner:

click pic for larger

When I get some time, I'm hoping I can fit an AUDI V8 auto tensioner/damper (4.2 A6,A8,S8, VW Phaeton,Touareg), in place of the factory tensioner. The belt should be much happier; but the parts are close to $300, unfortunately.

The 4.2 tensioner is similar to the 2.8 tensioner:


I have a hidden agenda, however, which requires an automatic tensioner. I want to make a variable cam advance, using belt length.

Sharkbait

So can our timing belts go 60k miles with proper checking of tension? Or are people changing them every 30k or 45k miles?

MikeN

I think if you started with a "new" 928 or a fully rehabbed timing belt system
and drove 60k miles in less then 4 years you would be fine. However most 928s are not driven that way and time also plays a factor here. Thats why I think most dig into it a little earlier.

heinrich

Ken .... I like it. How about a chain?

moon928

Interesting topic. My belt has at least 10k left on it, but the tensioner was shot. Apparently, it was not rebuilt the last time the T/B was done.

drnick

i agree, the 928 engine is reliable and belt service is simply routine maintenance. if you had an engine that repeatedly let go on its timing belt then that would constitute a design/manufacture issue.

i dont agree that porsche is making good on its recent engine probs.

rob rossitto

from what I've seen, a TB if done w/tensioner is ok till about 100k miles - after that it's gear time...if you keep the system up, the rubber band is fine... but I've heard a lot about R&Ring a failing belt, and using the old gears on a high milage (over 100k) car only to be followed by a catastrophic failure...

problem seems to be that sometimes the gears get sharp edges and cut the belt, bearings freeze up, or gears will be so worn the new belt won't seat properly, shreds teeth, slips and it's "Big Dave" time...OEM and mileage may vary a bit, depends on environment, overtensioning/undertensioning, etc...but anything over 100k and it seems like it's time to get critical on the gears/rollers/etc...they just wear out...

IIRC, belts do generally have less drag and are quieter... IMO they need LESS maint than an exposed motorcyle style chain...did kinda like the internal chain a la early V8's...they seemed to last as long as the rest of the motor - about 65k-85K miles in a big block...guess as motor life went up, the chains didn't - so "easy to replace" rubber bands it was...internal chains were also hard to ck, impossible to adjust when buried inside (although sharks aren't exactly trivial TB task nomines)

according to some 928 pro's there IS a difference in belts - some stretch more than others...could easily lead to issues if left alone too long...overall, I think the piston coatings seem to go long before properly maintained belts or gears do...

would be interesting to create a Mean Time Between Failure database - the FAA does it w/planes...when a part seems prone to failure at X hrs, a bulleton goes out to owners/operators and depending on severity, planes get grounded till it's fixed...PITA when I had to pay to replace parts that looked fine, but it was for a good cause - although the newsies love it, we just couldn't be spilling beer all the time on those improvised landing strips - or worse yet, sometimes we'd run dry while waiting on the ground in remote (far from a liquor store anyway) locations...

a shark part MTBF DB could be really usefull for us though (call it BITE- Before It Turns Expensive) if we just recorded part, miles and MY of shark, it'd be a real eye opener on when to expect stuff to explode...of course it'd just provide a stastical analysis (not a crystal ball), but IMO it could be increasingly useful over time if enough folks put stuff in...

just my 2 cents...regards to all!

goliver

Mercedes big V-8s have issues with chain failures. I used to have a 560SEC and was on a board in re: to those cars much like the rennlist and it is quite common. On the other hand, have owned numerous BMWs with chains and they seem bullet proof. Very simple tensioner. Basically a spring pushing a pistion against the chain rails. My old 6 series went 280,000 miles on the stock chain and rails w/o issue. My wife's 7 series saw almost the same mileage before we sold it with basically the same engine design. So it is doable. I do think the belt if properly maintained (bad w/p rebuild notwithstanding as I got bit by that one once and totalled an S4 engine) they seem to be pretty reliable.

Regards,