I am mostly with you, but preferring a timing chain to a timing belt is... interesting. Virtually every engine I know with a chain ends up either regularly failing early, or requiring early (and labor intensive, and thus expensive) unscheduled replacement off all the tensioners, etc.
Timing chains used to be a non-service item. Robust metal chain that runs well-oiled inside clean conditions inside the engine: there's not much wear that happens there in the first place.
Then they started reducing the amount of material they could minimally require in order to still produce something resembling a chain. Newer chains are narrower, made of thinner steel, lighter in all aspects, you name it -- all in the name of reducing drag and friction, and thus the relative load on the chain increases and the strength of the links and pins decrease. Add in chain tensioners adhering to the same philosophy. Bang! We have timing chain failures.
If you want ultimate resilience, get a car with non-interference valvetrain. Doesn't matter if the timing breaks up, you'll just install a new chain/belt and continue.
Care to share some? Because that's the exact opposite of my experience. I've never heard of a chain itself failing, but the plastic guides can get brittle and break. I think BMW and some Fords are bad at that.
I've owned several high mileage vehicles (over 300k) including Toyota 22RE, 3RZ, and Chevy LS with their original timing chain. Now that I think about it, does the LS even have a tensioner or chain guide?
Belts tend to fail abruptly and catastrophically, but generally only if they're neglected and used well beyond their design life. Chains fail more insidiously, because they get longer over time. The pins eat away at the plates, increasing the spacing between the rollers. This isn't immediately noticeable, because the timing sprockets will wear to match the altered dimensions of the chain. Worn chains cause all sorts of subtle timing problems and the lifespan of a chain is much less predictable, because it's highly dependent on lubrication; missed oil changes or poor oil quality will drastically accelerate chain wear.
From an enthusiast's perspective, a chain is probably preferable, because it tends to give you some warning before it fails - you might hear a rattle at idle, you might have problems with starting or misfires, you might get a check engine light and an EBD-II code from the timing sensors. That's a much less scary prospect than the potential for a sudden and catastrophic failure of a timing belt.
From a manufacturer or dealership's perspective, belts have some clear advantages. Unless there was a manufacturing defect in the belt, they'll almost never cause trouble if replaced according to schedule. That has obvious liability implications - it's not their fault if the customer ignores the specified replacement interval, but it potentially is their fault if a chain wears faster than expected. BMW, VAG and Jaguar Land Rover have all recently settled class action lawsuits related to the premature failure of timing chains.
I'm more of a hobby bicycle mechanic. Isn't there some similar tool for the meassuring of the chain as you get for bicycles? Just push it down and you directly see if it's time to change the chain. If not done early enough you have to change all the sprockets too because of wear. If done in time, you might not have to change all the sprockets.
You can measure it with an ordinary caliper, but the problem is getting access. The timing chain needs to be continuously supplied with oil, so it is in rather than on the engine and can rarely be accessed without pulling the engine from the car. It takes several hours just to access the chain for inspection, so it's not something you'd periodically check - if you suspect a timing chain problem, you might as well replace it.
VW had a few years making cars with chains that would catastrophically fail. Lots of destroyed engines. It was the EA888 put in Golf GTIs from 2010 and on. After like 5 or something revisions they finally improved the tensioner that caused the failure.
Previous gen GTI was a belt. Garage told me they preferred belts because people know they need to replace those. People aren't expecting to be told your chain needs to be replaced plus it's much more expensive and labour intensive.
Never heard of Honda having problems with chains, though. Some of their motorbikes even had gear driven cams! (VFR I think).
Can confirm, have a 2012 GTI, replaced the stretched chain on it about 10 days ago. The problem is that they provided no service interval for the timing chain when it really needs replacement every 80K miles. It’s an enthusiast car so there are a ton of aftermarket parts that are of good quality and VAG cars share so many parts (the 2.0T e888 engine is in a ton of vehicles from 2008 through today). My car has 211K and I intend to take it well over 300K.
Oh, the chains themselves can fail, in a quite a dramatic fashion, flying through your engine hood.. But that tends to happen well after the mileage they were designed for.
They are by no means immortal, but, by design, should have a much longer lifespan than belts.
> Virtually every engine I know with a chain ends up either regularly failing early [..]
But I have no idea which early-failing models OP is referring to, as the engines I know about where quite reliable. (As in 1e6+ km reliable, with chain maintenance per manufacturer guidelines.)
For example, on BMW Minis, which all have timing chains:
- 1st gens Minis (2002 -> 2006 roughly), with Chrysler engines, have a bulletproof engine, and replacing the timing chain is a rare occurrence
- 2nd gens Mini (2007 -> 2013 roughly) with PSA engines modified by BMW have a suicidal engines, especially the pre-LCI (2007 -> 2009) engines, that are known to often break timing chain guides. The symptom for that is named "death rattle", which is chain slap.
- 3nd gens Mini (2014 -> 2022 roughly) with BMW engines are so far known to be pretty bulletproof. Note that some of them now have high mileage with no large-scale issues.
So a well-designed engine with a timing chain is preferable to a timing belt. But a timing belt is preferable to a problematic engine with a timing chain, which will break at the most inconvenient time and leave you with an unexpected large bill.
I've had two bmw e39's with a m57 engines, and these chains last literally forever. One of my engines has over 500k clocked on it, no chain rattle still.
Buuuuut, there's also modern Opel engines where timing chain is guaranteed to kill the engine if not replaced every 100k km.
So it really depends on the engine rather being simple chain vs belt.
It's a general rule, and it's mostly because I can tell when the chain's wearing down. If the belt is accessible, it's also not as big a deal.
As with all things, the build quality and overall design will overrule single atomized design decisions. GM iron dukes have geared cams, which should be frickin' bulletproof, but they use a nylon spindle that tends to blow apart under variable load or just using weird fluids.
Chains usually have no service interval, so at the outset they seem cheaper and more reliable. But the unfortunate reality is they still fail, or something related to keeping them on fails, you just live in a false sense of security for a few 10's of thousands of km more
And since they're not meant to be serviced on a regular interval, they're designed that way too. A timing chain might be over four times the expense to replace when compared to a timing belt, but possibly without actually lasting over four times long.
