Captain_Slow

Group,
There appears to be near universal agreement that a pre-S4 VDO odometer cannot be trusted. This lead me to ponder proxy indicators for mileage. I have seen a lot of examples of intakes in photos and in person at a local shop (particularly "organ pipe" 85-86 and S4) and notice the paint/coating flaking of the magnesium is inevitable. However, there does appear to be a progressive worsening of the flaking. But for a long time I've wondered if it is more related to age or to mileage (engine hours), or other variables.

Condition of driver seat, gas and brake pedals, steering wheel, worn off icons on the switches and control stalks all give hints to the true mileage. Is there a consensus on what one can or cannot infer from the extent of flaking present on an intake? Or, are there too many environmental or other contributing factors?

Thanks,
Jon

worf928

IMO, flaking of intake and cam cover coating is directly proportional to the number and intensity of heat cycles. Or, in other words, the coating on a 928 driven lots of times for only an hour in a hot climate and perhaps also with the engine running a bit too warm will deteriorate far earlier than a car driven occasionally but for long duration in a cold climate.

I've seen 100k-mile S4s with almost perfect coating and 22k-mile GTSs with deteriorating coating. And the reverse.

And, harsh cleaners will cause the coating to deteriorate faster.

Bilal928S4

Power washers.

LeRox

[QUOTE=worf928;9025010]I've seen 100k-mile S4s with almost perfect coating QUOTE]

125K + and still no chips... i hear it is discolored as compaired to factory original color

Glenn Evans

Actually the alkaline wash solution which is usually used. This rapidly causes the silver paint to yellow.

Captain_Slow

All of these replies are very interesting. Dave C described a thought I'd had but could not articulate. Pressure washers would sure help accelerate the flaking.
Jon

NoVector

Jon - I'd add brown windshield washer fill tube and radiator overflow tank to the list too of things that show the miles rather than the age. I used to think they just yellowed/browned with age/UV and not so much the heat. But based on some of the low milage OBs showing up on ebay and the almost new condition of the tube and overflow tank, I think it's definitely the heat that makes them look like crap. Actually, I think it's the heat that releases the browmine in the plastic...

worf928

That may be true. There is, also, a steel insert in both the filler neck and overflow tank that rusts. The rust gets circulated and gets 'into' the plastic and viola! brown plastic. The insert is to keep the plastic from cracking when gorillas tighten hose clamps to 1.02e12 ft-lbs.