Piston Slap: Ronnie Schreiber Gets Piston Slapped

TTAC’s analyst extraordinaire, Ronnie Schreiber writes:

My daughter has a Volvo 940. The local Volvo mechanic said that the noise it’s making is the #1 piston hitting the head because of a sloppy big end bearing, which explains the low oil pressure at idle. I was thinking that 60 or 70 years ago, a mechanic might have fixed just the bad bearing, without rebuilding the engine. I was thinking just to do a quick fix, I could drop the oil pan, take off the offending rod cap, mic the crankshaft journal, buy the best fitting bearing per the crank measurement, and bolt everything together with the new bearing. So, Sajeev, with this true piston slap question, is it worth it to try a cheap engine repair like this?

Sajeev replies:

I’d run with that plan, though a small part of me insists on pulling the motor and replacing all bearings. And gaskets, since you’re going in there. Or, conversely, getting another motor if you have over 200k on the clock. That said, let’s bring in TTAC’s resident Volvo-guru, Alex Dykes:

Alex replies:

Ronnie, sounds like you’re on the right track to me. Given the age of the 940 I’m assuming you’ve probably put on more than 100,000 miles already? Since it sounds like you’re a handy guy, I’d give this fix a try before I did anything else. If this doesn’t fix it, then I’d just run out and grab an engine of the same displacement from any Volvo 740, 780, 940 or 960. The 700 and 900 series are often considered the last of the “bullet proof” Volvos so overall I’d say this fix, or even a used engine would be a worthwhile repair. Be sure to check out prices on used 940s, 960s and S90s before you explore a used engine, with the recent trends in used car values, you might be able to pick up a whole car cheaper.

[Send your queries to mehta@ttac.com]