Piston Slap: A rude awakening after a Roller’s hibernation

Art writes:

I have a 1979 Rolls-Royce Silver Shadow II with 58,000 kilometers (36,040 miles). It’s in good condition; it’s even been a class winner! Last spring, after coming out of storage, there’s been a sudden introduction of tappet-like noise when I started it up. All fluids had been changed earlier; it is synthetic oil and it’s as clean as water. The noise goes away when the engine warms up, but under load I can hear it coming back. Any ideas?

Sajeev answers:

The mileage, condition, and excellent maintenance of this Rolls-Royce notwithstanding, we have two likely causes: a lifter/tappet noise from the L-series V-8’s valvetrain, or a leaky exhaust manifold. My money’s usually on a bad manifold gasket, as leaks seal themselves as the motor heats up and tolerances get tighter, except this scenario feels special: The problem happened after coming out of storage.

Sticky lifters are likely after a deep hibernation, while gaskets/manifolds rarely (never?) fail during that period. But since the exhaust is far easier to inspect, check the manifolds for leaks or cracks. Start with a visual inspection for cracks and sooty residue, perhaps with a cheap endoscope to aid in inspection. If the system isn’t cracked, run a slip of newspaper around the manifolds with the engine running, looking for errant exhaust gases making the paper flop around. (Temporarily shielding this area from engine fan airflow is mandatory.)

If the exhaust system checks out, try to un-stick a sticky lifter before tearing apart the motor for replacement: run a light oil additive (like Marvel Mystery Oil) in the crankcase, performed in accordance to the instructions on the bottle. Drive the Rolls-Royce so that the motor gets high oil pressure for sustained periods, like at highway speeds and under moderate loads (like going uphill) so that it has a fighting chance against a stuck lifter. Perform an oil change shortly afterwards, using 100 percent “normal” motor oil of your choice. Did it fix the problem?

If not, it’s time to figure out which lifters are bad and replace them. Replacements for the L-series are not readily available new, but used parts are easy to find. Not fun and anything but free, but odds are the noise is bad enough to warrant all this work. Best of luck!

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