Got the S70 torn apart, replaced the timing belt with a racing spec Gates belt, and put in a new idler and tensioner pulley, along with new water pump, because I couldn’t find record of when these were last replaced.
Oddly enough, the original belt, tensioner, idler and pump were in very good shape. They all spin pretty much exactly like the brand new parts, though the water pump did feel like it had a single grain of sand in it when spun (just a tiny little bit of grit or something). Original belt pic below.
The tensioner was set pretty loose though, so I’m glad I caught that. The timing belt itself was honestly very easy to replace. If I wasn’t doing the water pump with it, putting on a new idler/tensioner/belt would probably take me under 2 hours now from start to finish. The water pump adds about an hour, maybe 90 minutes due to the time and care needed to drain/refill coolant, and properly clean the mating surface before installing new pump and gasket.
Anyway, I also pulled the coils and plugs and replaced them all. Someone put aftermarket 4-electrode bosch plugs in at some point, they looked OK but were worn.
In with new OEM plugs!
The plug wells were actually pretty clean, considering there was some oily gunk collecting around them. Thanks for those double O-rings molded into the coil on plug boots, Bosch!
Car runs great, and with the known-good timing belt on, I finally worked up the nerve to take the engine to redline, and the car loved it. Pulled strong and smooth all the way to 6500.
I’ll see it again at 400k!