Piston Slap: The Truth About "Throwaway" Motors

Dear Sajeev,

A recent post on the CX-9 users forum (at www.mazdas247.com) caught my eye. An stalwart owner tore down his 3.5 (Ford) engine to clean up a sludging problem and broke a rod bolt in the process. He then discovered much to his dismay that replacement rod bolts are not considered “serviceable parts” by Mazda. In fact, it turns out that most of the internal engine components you would want to replace in a rebuild are not available from Mazda. (This is true for both the 3.5 and the more recent 3.7 litre versions.) Unavailable items include pistons, rings, bearings, etc. Searching on-line one can find the typical factory exploded parts diagrams with all these internal components listed, but in lieu of part numbers there is the notation, “This part is not serviced.” ( Here’s an example)

These parts also don’t seem to be available from Ford for the Ford versions of the same 3.5 or 3.7 litre (Duratec) engines. Equally strange, there don’t seem to be any after-market sources either. How is that possible? Have we finally entered the era of the sealed-for-life, black box engine, with no serviceable parts inside? Is engine rebuilding going to go the way of lamp-lighting, blacksmithing, doctor house calls and the like? Fortunately long and short blocks are available from Mazda, but at the kind of prices ($2800 and $6400 respectively) that always made rebuilding an attractive alternative. I know many independent mechanics often prefer to use salvage engines, but some problems still require actually tearing into an engine. How can you rebuild an engine if you can’t get the parts?

Sajeev answers:

Two things: torque-to-yield bolts and other replacement parts nightmares are a sad new reality, but engine building is here to stay. It just won’t be for everyone.

Actually, who in their right mind wants to do it now? Thanks to advances in Inventory Management and the Internet, you can easily throw away your old motor and get a replacement with a warranty from a host of on-line junkyards. For the price of replacing those torque-to-yield bolts, you’ll cover the shipping on a junkyard motor. Actually probably more than just the shipping. And while the motor is used, today’s engines are far more trustworthy than they were 20-30+ years ago. If the junkyard motor is bad, the warranty will cover it. So who cares about actually rebuilding a motor?

For the nut jobs that want to build one, you can get the parts. Not from a manufacturer, but from places that cater to engine builders. Then engine builders like Nautilus Performance can go above and beyond**…if that’s what you really want. And that’s just for the Ford Duratec V6: there is a late-model performance engine builder for damn near any make out there. I suspect the Duratec gets such love because of the Noble M12 supercar.

**This is not an endorsement for that engine builder, or any aftermarket builder. I just Googled this to prove the point: you can rebuild an engine with readily available parts, but you don’t really want to. Unless you are nuts enough to be a modern-day hot rodder.

Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry.