8 years and 3k mi, timing belt change?

[gmendo]

I found a very clean 928 S4 with 90k mi for sale that was in a private collection and not driven very much in the last 10 years. Records show the timing belts/accessory belts/water pump/plugs/wires were changed less than 3k miles ago but it was 8 years ago.

Should I be concerned? Would you guys change the timing belts again?

Thanks

[Landseer]

I treat them all as requiring tear-down inspection.

Too few mechanics, dealers included, get it right.

If not a dealer, chances are high that a rebuilt pump was used. One rebuilt pump failure mode is impeller sliding slightly toward block, acting like a machine tool on it. (New-casting, plastic impeller "Laso" replacement pump is a recent development by enthusiasts to combat this issue -- It wasn't around 8 years ago). Porsche new pump was the better option back then, and still is, but is cost prohibitive now for most of us.



(Most uber-enthusiasts will say 8 years is too long on a rubber timing belt. Assuming thats a legitimate fear, you sure don't want a tracking issue or sharply worn gear to be hidden under those covers at the same time).

I'd also insist on new fuel lines!


Further, I'd check crankshaft endplay on a PPI if automatic car. Crucial check for automatic S4 & GTS. Thrust bearing failure is terminal and the 928 has a design flaw that can silently increase preload force on the crankshaft, resulting in contact wear of thrust bearing.

[stepson]

Originally Posted by gmendo

I found a very clean 928 S4 with 90k mi for sale that was in a private collection and not driven very much in the last 10 years. Records show the timing belts/accessory belts/water pump/plugs/wires were changed less than 3k miles ago but it was 8 years ago.

Should I be concerned? Would you guys change the timing belts again?

Thanks

Since it is an interference engine, I would make that one of the first things I did. If it was a non-interference engine, I wouldn't have worried about it. 6 years is the new Porsche mandate for changing timing belts.

[gmendo]

Thanks guys, flexplate preload and crankshaft endplay will be checked tomorrow. This car has been the best driving S4 i've driven so far but it was #2 interms of power, i've driven 5 total. Today was very hot though; about 109* according to the display.

Does ambient temp have a big effect on performance in a S4? Are there any maint items or adjustments that can affect performance but cause no driveability issues if not correct?

Lastly, are there any aftermarket ECU/chips to increase performance. If so, maybe the other car that felt faster to me may have had one considering the other appearance mods that car had. Then again, I did drive that car on a cooler day at sea level too but even with more apperant power, the other car did not drive nor shift as good as this one.

[Landseer]

Yep. Throttle cable and bowden cable adjustment for transmission kickdown makes a huge difference. Aged/cracked knock sensors dial-out the timing to ensure no knocks, but degrade performance. Aged/broken/maladjusted throttle position sensor (switches on at about 70% throttle) will modify timing to make it scream under heavy throttle.

Vac leaks also have impact.

Computers can be reprogrammed using special software aka "sharktuning".

These cars are so old, regardless of miles, that they almost always need electrical cleaning, intake refresh and timing belt system refurb to run right, reliable and safe. Budget $3K or so minimum, DIY.


How is the AC, btw?

[gmendo]

AC appears to need a recharge and fan controls only work on high. It'll be inspected tomorrow also.

Is there a way to check the condition of the knock sensor? If the trans downshifts to 1st, is it safe to assume the TPS is working? If not, how do you check for that?

As for the $3k budget for a DIY service, what does that include?

[Landseer]

Not sure how to check them without bosch hammer or sharktuner.

TPS has nothing to do with downshift. Its simply a switch. If throttle goes deeper than approx 66%, timing shift is made by computer.

Downshift happens twice. Once due to cable running from throttle linkage to trans. Then, with electric switch on floor under gas pedal makes contact (foot to floor). Both need to be set properly. Sluggish like grandma's 6 cyl Buick otherwise.

$1000 nominal for parts, timing belt service.
$2000 parts for intake refresh, cam cover seals, O-rings. (no cosmetics/paint)


Also, MAF platinum wires degrade over time. Rebuild $350. (MAF condition or calibration can both affect running/power)
LH computer has a component that degrades, so if not already rebuilt, another $300. Just budget for this stuff

PPI would have to be by somebody like Greg Brown for this stuff to be caught I expect.

You are basically buying a project car, unless somebody like him maintained it with an open checkbook. Part of the beauty of the 928 is the fact it takes the deepest pockets to maintain one. They come into hands of enthusiasts very inexpensively.

Usually, the "maintained" status and pile of receipts is a bit of a smokescreen. Some stuff was done. Not all. And what was done, especially w/in last year of ownership, was often shaved.

Still a great value. But you know all this hidden maint stuff from your signature line.

[gmendo]

Oh yeah, like any other used exotic, price of admission (purchase price) is just a small fraction of true cost of ownership. lol

Thanks for your advise

[Danglerb]

I think different years get a bit different gear ratios? That can feel very different, but not a good idea to put a lot of weight in "how well it pulls, feels etc." its not that easy to judge seat of the pants.

8 years and 3k miles will take time and money to catch up on.

[gmendo]

The stronger feeling car was an 87. This one:
http://orangecounty.craigslist.org/ctd/2550380469.html

The one I'm considering now is an 89

[Landseer]

89, like DanglerB says, has a different rear end ratio, & sporty modifications to valve body.
It really should outperform from an acceleration feel perspective when you hit the gas. I shoehorned one into a 16V 84 car and it transformed the car.

[Landseer]

You might want to contact SeanR down in DFW area. He seems to be in the heart of a very active 928 community and has offered some customer cars for sale recently. Networking within the 928 freak community, rennlist too, might be the way to shop right now. Lots of periphial enthusiasts, those not involved day to day, seem to pop-up lately, ready to turn-loose of well maintained cars.

Its just one other place / way to pursue the buy and gain knowledge. Many of us here are more early / mid-year enthusiasts. Except Stepson I think who crosses deep into S4.

Another source is the pro high-end car reseller Michael Wilhoit. He deals in the Fabrege egg cars with 15K miles on them, but seems to turn-up 70 to 100K mi cars from time to time.


I'm not a fan of the type of internet-based, professionally photographed (low resolution) display methods used to make 9K cars look like 17K cars.

[stepson]

Final Drive ratios from 928 Specialists web site:
87-88 S4 - 4-Speed Automatic (US) 2.20
87-88 S4 - 5-Speed Manual (US) 2.20
87-88 S4 - 4-Speed Automatic (Euro) 2.54
87-88 S4 - 5-Speed Manual (Euro) 2.64
89 S4 - 4-Speed Automatic 2.54
89 S4 - 5-Speed Manual 2.64
89 GT - 5-Speed Manual 2.73 Limited-Slip - 40% (Standard)
90-91 S4 - 4-Speed Automatic 2.54 Limited-Slip - PSD (Standard)
90-91 GT - 5-Speed Manual 2.73 Limited-Slip - PSD (Standard)
92-95 GTS - 4-Speed Automatic 2.54 Limited-Slip - PSD (Standard)
92-95 GTS - 5-Speed Manual 2.73 Limited-Slip - PSD (Standard)

[gmendo]

Thanks for the info!