Oil pump: is change REALLY ALWAYS necessary?

[Weezl436]

Much has been said and written about the superiority of the gear-driven oil pump/balance shaft design, and as an engineer I am among the first to recognize this. However... many well- and properly-maintained engines with the chain-driven system have gone well into the 300,000 mile range without any catastrophic failure. So I have the following question: absent any signs of imminent failure of the oil pump unit and with all else being as it should be in the engine, and with no undue visible wear on the sprockets, would it not be to an owner’s financial advantage to replace just the chain and tensioner at the time of a timing belt/water pump, etc. change? Especially if this is just the first timing belt change? Any comments and/or observations would be welcome.

[chittychittybangbang]

It would be to the owner's financial advantage to load fine art into the trunk, push it off a cliff and pocket the insurance money!

Some comments: It's not possible to inspect for wear without being 3/4 into the job. You may see wear on chain tensioner guides but sprockets won't really wear much until it's already too loose. No noise until it's too loose as well. Even if tensioner guide is OK, tensioner likes to snap at a weak point which means sudden failure, no warning.

So if you're having the TB done and car is still on chain, if it were my car I'd do the gear conversion. The parts seem to be back ordered often so you have to plan ahead for this one.

[YMZ]

Originally Posted by Weezl436

... many well- and properly-maintained engines with the chain-driven system have gone well into the 300,000 mile range without any catastrophic failure.

Do you know of many BHW engines with oil pump chains that have gone 300,000 miles problem-free? (It's like the old joke: there are 2 kinds of computer users... those who have had a hard disk crash, and those who will... a good friend just found out the truth to that... lost 2 weeks' worth of work...)

Originally Posted by Weezl436

absent any signs of imminent failure of the oil pump unit and with all else being as it should be in the engine, and with no undue visible wear on the sprockets, would it not be to an owner’s financial advantage to replace just the chain and tensioner at the time of a timing belt/water pump, etc. change?

For starters, I'm not sure you can even purchase new chains and tensioners... I'm pretty certain that you can't purchase new crankshaft sprockets, so... if you don't drive much (the proverbial little-old-lady-who-drives-only-to-church-on-Sundays), I suppose you can skip it, but since these cars are meant to be driven, I'd get them running properly...

Yuri

[Weezl436]

OK, but again, we're talking about the chain, the tensioner, the tensioner guide, etc., not the pump itself. All this stuff is accessible at the front of the engine at the time of a timing belt change. Replacing the pump unit requires a lot more surgery.

[chittychittybangbang]

Supposedly, the slop in the chain lets the allen key drive for the oil pump get worn too. You can buy these separately but would I? No since a new module comes with it

[Weezl436]

Thanks, C2B2 and Yuri for sharing your thoughts on this. For the time being, at 117K mi, it still sounds like a new engine with no rattle or clatter, so I'm going to hold off on the gear-job for a while.