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I have to replace the water pump on my 98 Mazda 626 2L and would like to know how I can evaluate if I need to replace the timing components as well?

I know the conventional wisdom is to do the timing as well, however the belt looks to be in good condition, I suspect it may have been done in the past few years, and I don't want to spend more than I have to as the timing components are quite expensive.

The belt itself looks like it's in very good condition. I've only put about 5k kilometers on the car myself, it has 245k kilometers on it total. I have no idea at the moment when the timing was last done, although now that I think about it there may be some indication in the pile of paperwork the previous owner gave me.

EDIT

After looking through the paperwork, I see that the timing was last done 80k kilometers ago, so technically I've still got another 20k till I have to change the belt.

  • The rule I follow is do it while you're there. The most time consuming task is stripping everything down. I always take it as an opportunity and apply the rule where I can. The only time I would deviate would be when the parts to be stripped down had only recently been done. – Mark Oct 6 '16 at 13:15
  • I found a nice tutorial here: mazda626.net/topic/… – Robert S. Barnes Oct 6 '16 at 18:33
  • There's also a video tutorial: youtube.com/watch?v=aEfEmqJDYzs – Robert S. Barnes Oct 6 '16 at 21:10
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Given that the water pump is in such a bad condition it could be that rest of the timing related parts (idler, tensioner, something else?) is in the same condition. I suspect the previous owner did (if he did) only the belt itself, and not the other parts. I would recommend you to apply the full kit.

Should you decide to estimate the condition your timing components I would recommend you the following:

  • Look for visible cracks/wear on the belt (don't forget the inside)
  • See if the rollers of the idler and tensioner have feel-able play or excessive friction
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I would say you should replace the belt and tensioner while you are in there and everything is apart. If you really want to put the old belt back on I would consider:
How close the vehicle is to the recommended service interval
Dry rot (flip it over and bend it. Look for cracks)
physical damage (chipped teeth)
Wear in the back of the belt
Tensioner bearings and spring

If this all looks good, you should be able to get away with running the same belt.

  • How would I check the tensioner bearings, idler and spring? – Robert S. Barnes Oct 6 '16 at 13:32
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    I would just be sure it spins freely, but doesn't feel too loose (wobble). Make sure the spring has good tension and doesn't seem worn out. Not sure how exactly your tensioner is set up, some rely almost completely on a spring, others just bolt down in place. – rpmerf Oct 6 '16 at 13:40
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It it was my car, I'd do the timing gear whilst it was apart. I'm not a fan of reusing timing belts if they have to be disturbed plus it's a good opportunity to do it whilst everything is already in pieces. If you don't do it now and the belt fails, you'll only be angry with yourself.

  • Would you replace just the belt or the whole kit? – Robert S. Barnes Oct 6 '16 at 13:33
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    On my own car? The whole kit without a doubt. Gives you peace of mind. I've had a cambelt let go on a car I was driving some years ago and it's not a very nice place to be (especially as I was 300 miles from home). Any measures you can easily take to avoid that situation; take them. – Steve Matthews Oct 6 '16 at 13:34
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The 98 Mazda 626 owners manual states the timing belt should be replaced every 105k miles, or every 60k miles if you drive in extremely cold weather (indirect source https://mazda626.net/topic/31256-timing-belt-change-interval/). (Note: I'm using miles not km)

Given the vehicles age I'm betting its safe to say you're over 105k. So if you havent had the belt replaced before then yes it is time to replace it anyways.

If you're close to a 105k interval you might as well just do it.

The thing is almost all of the cost of the timing belt change is in labor taking everything apart. The parts themselves are generally not too expensive. So if you're pulling the water pump, assuming it's on the timing belt (not sure about the 626), you can potentially save yourself a decent amount of money by doing it now even if you're not at an interval yet.

On the up side, at least according to https://mazda626.net/topic/43000-626-20-l-engines-interferencenon-interference/, the 2000 626 has a non-interference engine (the pistons and valve heads never cross into the same space). Assuming that forum thread is correct and applies to the 98, that means the risk of serious engine damage after a timing belt failure is significantly reduced. So that's something to take into account.

But really you just have to make the call based on maintenance intervals and how much money it will save you (if youre not at an interval yet just figure out the pricing on everything and make the call - ask the shop what the cost of doing both at once vs two separate jobs would be). If you're doing it yourself replace money with time.

  • I don't know when the belt was changed. I've personally only put about 5k on this car, but it's at 245k total. The belt looks like it's in really good condition, so I don't want to be changing parts without a good reason. The parts are about $150 - $200 including import taxes. – Robert S. Barnes Oct 6 '16 at 13:27
  • Theoretically, the next time the belt should be changed is 315k, so at 245k, you have 70K left on that belt. If it looks somewhat new, it might had been changed at the recommended service interval of 220k. – rpmerf Oct 6 '16 at 13:49
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    @Robert Oh wait. You know according to mazda626.net/topic/… it looks like the 626 has a non interference engine (the pistons and the valve heads never cross into the same space). You might want to verify that but if that's true the risk of heavy damage with a failed timing belt basically goes away, which pretty much negates my personal "insurance" worries. – Jason C Oct 6 '16 at 15:35
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    @JasonC Kilometers, I live in the part of the world that's not the USA ;-) – Robert S. Barnes Oct 6 '16 at 18:00
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    Don't forget that non-interference engines can turn into interference engines if there is a lot of carbon build up, somebody warped the head through overheating the engine and had it skimmed, somebody replaced the valve gear with the "wrong" parts, etc, etc. It all depends how confident you are that you really have the "full" service history! – alephzero Oct 6 '16 at 19:27

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