Honda Civic 98 - What else to replace while replacing timing belt?

You won't know until you get there, but the tensioner may also need replacement. It isn't a bad idea to replace it on general principles but they are a bit pricey. Personally, I don't replace the seals. The ones Honda uses are remarkably reliable and I'm always concerned about starting a leak where there was none before, but lots of people replace them without problems. The water pump is a definite "do" and I avoid aftermarket pumps like the plague.

Idler pulley (belt tensioner)

That's what we replace at the dealer. The reason its a good idea to replace all of that is because even though they are good today will they be good until the next timing belt replacement probably not. And to replace a leaking seal or water pump after the timing has been replaced would require removal and possibly replacement of the new belt due to oil contamination and of course at your expense. As for the belt tensioner I have only replaced 1 in all my years of working on Honda's and that one failed because the car was in a flood and water got in it and caused the bearing to fail. Good luck with your car sounds like your mechanic is looking after your car with good intentions...oh and I almost forgot replace the 3 outer belts alternator, a/c if equipped, and power steering if equipped.

I'd skip the cam and crank seals, as the timing belt change doesn't really lend access to them and they are generally very reliable. You should only ever change the complete kit and not just the timing belt as the rollers and tensioner (I think yours tensions off the water pump though?) will wear too and could fail. Other than that, you've got the water pump and coolant on there, just make sure you do a coolant flush to be thorough.

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