When I rebuilt the S4 engine for my '87 I cheaped a little bit and reused all the lifters with out testing them. It bite me llater on with a few collapsed lifters, the engine sounded like a diesel truck! .. I even confirmed it when I pulled out the valve covers and found at least 4 lifters that were collapsed (I could compress them very easily with my finger) .. I was both mentally and financially ready to replace all of them with either new Porsche ones or the cheaper VW ones. then I remembered an old trick that we used to use on old 350 small block chevys, I took out a quart of engine oil and poured back a quart of dexron 3 ATF into the engine then took it for a 15 minutes drive, to my surprise all the lifters seemed to clean out good, the engine went back to be silk smooth! .. I couldn't believe a 5$ worth of ATF would fix my engine in 15 minutes, I think I lucked out this time!

 

The lifters do bleed down with age and lack of use.
My previously owned '87 had this issue but the loud clackity clack would typically go away after a few miles of driving.
I've never tried ATF but makes sense that it would work, based on its viscosity and agents in the formula.

 

what brand of oil are you using and what weight?

 

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Amsoil high zinc 20-W50

 

Did you replace the motor oil after driving around für 15 minutes with ATF?

 

Yes, put a new oil and filter and it has been quiet ever since.

 

Somthing to keep in mind...Modern ATF has powerful solvents, mostly Toluene. This highly aromatic solvent attacks normal rubber and neoprene seals. AFAIK Only Viton is resistant to Toluene and I'm not sure if any of the engine seals on a 928 are viton or not. I wouldn't worry too much unless you left the ATF in there long tern. This should come as no suprise to anyone that has worked on a modern Automatc transmisson, they're clean and mostly varnish free with lost of detroitis in the pan. That detergent power of pressurized ATF laiden oil forced into the lifters cleaned and freed them up. Easy for anyone to do a few moments before a scheduled oil change but know the risks.

 

Actually you didn't need to drive the car (I would not want to put a load on it), just let it idle and gently increase the idle up and down to 1500 rpm, once the oil(not water) comes up to temp it will quiet down.
Just happened to me when bringing an '84 manual that was sitting for 9 years back, I did a full T belt job and also had to cleaned out the tank & flush the lines, she started and I thought it had a rod knock it sounded that bad.

As for the oil, I used a 15w/50 Diesel for it's stronger detergent to clean the internals, then change w/ new filter after driving around for a bit.
Note: the engine also had a miss that cleared once injector cleaner was added

Dave K

 

That's interesting, I always heard ATF had a lot of detergents in it and believed it, until I heard it had less detergents than motor oil. The SDS for Mobil 1 ATF doesn't sound too scary and seems free of solvents and detergents.