dr bob

By the time you take off any of the stuff that will make the shop's work "easier", the car won't drive. Plus if there's ever any issue with the work, it will be blamed on the portion that you do. Doing the job yourself lets you evaluate the variable items list that others have shared. You 'll want to look at those things, with an eye towards what will come up in the next 50k or NN years of driving rather than just what's worn already.

So...

tensioner rebuild pieces. That's seals and boot and clamps for the tensioner itself, plus the rollers and the pivot bushing.

Look hard at the cam drive gears. You are statistically at end-of-life so if they haven't been replaced already now's the time.

The Hall sensor behind the passenger's side gear is easier with the backing plate out.

Those little bearings on the bottom bearing console are Rollerblade wheel bearings, press in and out easily at home in a vise.

Coolant hoses. ALL of them, including the heater hoses, vent lines etc. Heater control valve too since it will be out in your hand for the coolant hoses. New thermostat and both seals since all will be drained and apart.

Crank, oil pump and cam seals. For sure do the cam seals now so you won't have to pull the belt when you do the next project, the intake refresh.

ALL the belts.

Power steering hoses, power steering filter/reservoir. The old hoses are crispy, and deserve their own fire safety warning chapter.

Clean everything you can before you lay a wrench on anything. Like spotless-clean, so you can put your sandwich down anywhere in the area without worry. Makes the project immensely easier.

----

My best results have come from calling my favorite parts supplier, the one that's local to you in Socal. The others are undoubtedly just as good. I asked my spiritual and 928 parts adviser to put together a "care package" of everything I'd need for the project. The package included a lot of stuff I wouldn't have thought of, but all stuff I ended up using/needing. Like new water pump bolts, the little clips for the bottom bearing console, etc. Otherwise you'll end up reusing parts that would be sacrificial on any other car. Take advantage of the accumulated knowledge from your trusted vendors. You'll be happier and you'll be done sooner. And save time & money in the long run.

Socal_Tom

Belated thanks for all of the discussion, very helpful.

I have a tensioner belt warning light on, so not going to drive the car until this is addressed, so pulling it apart to a point where it won't run is not an issue. That said, after your input I am going to leave it buttoned up to make the easier for the shop rather then forcing them to use my organization system.

Any money I would of saved by doing that I'll redirect to pressing forward on the '84.

The list of "now is the time" items is pretty daunting but it is what it is....

Thanks!

docmirror

I have to mildly disagree with Bob vis-a-vis the coolant hoses. The hoses from Porsche were ultra tough material, and though it's been 30 years, I have seen many a car with orig cooling hoses on in perfect shape. The new hoses made now are most definitely inferior materials. I've seen 3 YO hoses with a splash of Ethanol laced fuel drooled on it that would bubble and get soft.

Not that you can't get good hoses, but if you are going to do it, investigate what you buy, and where it was made. Further, cooling hoses are typically not a catastrophic failure mode item like belt path, or lubrication. Might make a mess, but in some cases you could take off a perfectly good hose, and replace it with something that may last a couple years. I just bought an 88, and the hoses on it are still in perfect shape. Pretty sure they are orig too.

edit; this does not apply to the little shorty hose between the block and the heater valve. That thing goes tango uniform pretty quick, and it's hard to reach!

dr bob

I agree with docmirror to a point. While the original hoses are certainly robust, they are also at least 30 years since manufacturing. Whether a hose failure is catastrophic or not depends on when and how it fails. In my limited experience, they tend to go in the hottest weather under high loads when coolant is at its hottest. Stranded on the side of the road half-way up Sherwin Grade between Bishop and Mammoth, just a bit north and west of Death Valley on that same map, for instance. To me that's catastrophic. In fact, anywhere I don't plan to stop with spares and tools and time is catastrophic.

To me anyway, the protocol for the car is no different than the one you use for your plane or what most would use on their race car. The only "convenient" or non-catastrophic place for "stuff to happen" is in the workshop on the day I planned to work on that same "stuff". Since I can't predict when bad "stuff" might happen, it's easier to do PM's a little sooner on my own relatively convenient schedule.

My too sense. YMMV, etc.

Landseer

Again, so it doesn't get lost, during the timing belt job you will have to manipulate the thick, positive cable that feeds power to the antilock brakes. Similarly, you may need to navigate the endmost part of the cable up/around the PS reservoir during removal of front fan / oil lines on S4.

Check the insulation condition of that wire. I think it is a potential spark generator that could ignite the PS fluid. Based on the S4 cars I've worked on.

docmirror

Ectually, the FAA has gotten away from the mantra of 'replace on hours' or some such to a 'replace on inspection and condition'.

The reason for this paradigm shift in thinking came about from a few situations where the demanded replacement part was shown to be worse for safety than the part in service. A number of cylinder asm were mandated replaced, and the units that were installed had a significantly higher failure rate, and caused a couple deaths.

In the comm world, there has been a move supported by the mfgs away from 'replace after N cycles' to 'inspect within N cycles by method X', where the method may be visual, metallurgical, or electrical, or chemical. Saves carriers money, and enhances safety. A known good part, working for N cycles may have a life limit of 10*N cycles, where replacement may introduce a less robust part. This was reinforced by a batch of bad hyd assemblies which came from Brazil, and maybe Taiwan back in the early 2000s. There are also cases where replacement is mandated after an unusual event like a hard landing. Some require only an extended inspection, some require replacement of struts, seals, and joints.

Rotary wing - being the odd man out as usual still has many life limited components, and for good reason. Helicopter - 'an assemblage of small, expensive, fast-moving parts all flying in close formation'.

Back to autos, a 'catastrophic' failure does not include a failure which is inconvenient. Since the advent of the cell phone, inconvenient takes on a whole new reduced definition. For autos, I propose that catastrophic be limited to failures which are immediate in nature, and produce high potential of death, injury, or serious costs, up to and including exceeding the hull value of the vehicle(TBF, valve crash both heads, fire, etc).

Adk46

In some departments, the cheapest way to maintain a car is to wait for a part to fail and then replace it. Nearly all cars are maintained, or "maintained", in this manner. You get the full life from every part! In other departments, of course, it is very expensive (e.g., the timing belt system). In between, you have the while-you-are-in-there stuff.

In industrial settings, downtime is very expensive, so folks like Dr. Bob rigorously pursue preventative maintenance. There are safety issues, too. Dr. Bob lives this in his personal life, too, which I admire.

Getting stranded can be a genuine catastrophe on sparsely traveled roads in the winter. It happens around here - I keep blankets in my car. Or if you are on your way to your wedding (long story omitted). But you will usually live through it. Some even view it as an opportunity for adventure (not me, but my father did).

It's not easy to predict that a rubber item will last 20, 30 or 40 years. I'm certain that some advice is expensively simplistic, like the rule that tires should be thrown away after 7 years. If a tire can last 7 years in hot, sunny, ozone-filled Phoenix, it ought to last 14 years in my area.

I do maintain a healthy fear over old parts - but also new parts. A 30-year-old part that is functioning well and still looks good is a comfort to me. A new part is an unknown; for all I know, it might have spent years in a Phoenix warehouse.

dr bob

To Doc's point, I've kept the old hoses that have come off the car, and in fact they did look like they would last another 70k/15-year "cycle" like the experience they had already enjoyed. Visual inspection only, and only at the ends where non-destructive inspection was possible.

And FWIW, one set of radiator hoses was placed back in service on another car for some more service in a pinch. In that case, gathering drivers at our hilltop Glendale bungalow for a mountain-roads tour included a car that puked it's coolant out from a failed radiator hose.

The subject car belonged to a well-known 928 enthusiast, who it turns out believed in the run-to-failure maintenance plan. That car is seven years older than mine, Cali car all its life, always garage-kept, always driven "firmly". Catastrophe was averted when the failure happened in a place (my driveway...) that had the parts on a Sunday afternoon, plus tools time and talent available to get things taken care of. Had it happened half an hour later up in the Angeles Crest drive and out of cellphone range, it would have been more than inconvenient. Having the same resources nearby and the other drivers as support would have mitigated the impact some. Are we always that lucky? [punk?]. I'm not, at least not enough so that I can depend on it. That same car was flat-bedded home more than once late at night for what I consider stoooped stuff. Non-interference timing belt failure was one that crowned a nice weekend night out. I just don't care to have that much excitement.

The couple $hundred PM cost for hoses pales in comparison with the "inconvenience" or catastrophe, whichever word you choose. I know I'm going to have to replace them sometime, so all we are talking about is the cost-of-money for the time between PM and in-service failure.


The subject deserves a separate thread where we can beat this dead horse to death some more, and not completely derail Tom's thread about what color timing belt should go on.

Socal_Tom

Great discussion and considerations all, very much appreciated.

docmirror

What is a 'run-to-failure' maintenance plan? I've never heard of such. Sounds a bit like an oxymoron; failure <> maintenance.

Socal_Tom

Not my approach, but I assume it is a drive it until it breaks then fix it (which is the act of maintenance).

dr bob

It's apparently when you know something has a finite service life, but you determine that a little prophylactic service now is more inconvenient than the flatbed home tomorrow in the middle of the night with the subsequent service. Yes, the same service/PM that was less inconvenient a day or week or a year ago.

It's apparently a common judgment call. It runs today, it drives today, so lets run and drive it today! So long as it doesn't fail until tomorrow, why fix it today? Probably not the car that I'm looking for. It's a cheap way to drive interesting cars for a while. It's also why luxury leasing programs come with included (and mandatory) scheduled maintenance.

FredR

Bob,

It is like that clown I once told you about at work who said that our fleet of turbines did not need to be serviced as per the manufacturers recommendations and that they could be serviced at something like twice the recommended service intervals. He was correct right up to the point when they started falling over at however million $$$'s a pop to replace.

In my mindset [similar to yours but probably not as systematic] I have tried to develop what I perceive to be a service life interval for the various parts that can ultimately fail and should I choose to keep them in the car longer than that interval then I know that I am on borrowed time.

For instance:
Coolant- two years
Oil- two years or 8k km [20w50 mineral oil]
ATF- 30k km
Power steering fluid 5 years or 20k km
Timing belt 5 years or 60k km
Water pump 10 years or 120k km
Coolant hoses 5 years
Fuel pressure regulator/dampers 10 years
Inlet manifold hoses 10 years
Ignition leads/distrib cover 10 years
Power steering hoses 15 years
Fuel hoses 10 years.
CPS 10 years
Knock sensors 10 years
ISV when it croaks
In tank pump hose 5 years
Critical relays 10 years
MAF 15 years or 150k km- then have it tested/refurbed
Cam chains/pads- visual inspection every 5 years
Note: looking for a good number- any offers?
Mine were good 10 years ago when we refurbed the motor and last time I visually inspected 2 years ago.

No great science to the above - just the opinions I have come to form over 18 years of 928 ownership.

Some of those 10 year items are now at their sell by date and I intend to do them during the next cool season when I do my maintenance.

If I go on a long trip to Dubai I carry spare fuel pump, LH, EZ, & MAF units. Touch wood no trailer rides home in the last 17 years but it can still happen.

The beauty of removing items before they fail is that you still have them in case of a fluke failure as happened to me when a locally purchased belt jumped and derailed the others- one of the main cooling hoses was cut - I replaced it with one I had removed until a new item came in with proper belts from Roger.

"Chance favours the prepared mind". For those who rely on random luck Dirty Harry sure rings true in this regard- "Feel lucky punk- well do ya"?

Brett Jenkins

Does the new version of the PKT come with a tension warning system now, or does something need to be added?