M62TU timing chain tensioner - which is best?

[andrewwynn]

Plastic not rubber. There is virtually zero wear at 160-180,000 miles on the plastic guide parts on the two m62tu I rebuilt. The only problem was the plastic shattered because it's stupendously brittle. Until there is an impact from chain slap there is virtually zero wear because oil pressure sets up an oil film layer.

If you have a better theory than mine based on post mortem disection of a couple different high miles M62tu I'm all ears.

Facts:

1) Some m62tu have gone > 400,000 miles on original guides

2) the plastic is stupendously brittle probably before 100,000 miles

3) most common symptom of shit hitting the fan is startup rattle that goes away; this in every case I'm aware of preceded destruction

4) in 3 cases that I've helped with the startup sound happens, fiber-optic camera confirmed guides not broken, replaced tensioner and rattle went away 100%. (120-180,000 miles)

When I took out the old guides, every piece of plastic was brittle like dried mud; I could easily crumble, but the pieces that didn't shatter yet were still 100% complete until I took them off and crumbled in my hands.

Dimensionally they were nearly identical to new, there was no wear save a couple 1/10000 of an inch where the edge of the chain rubs a little bit during the start and no oil pressure to generate the oil film.

It's no guarantee that regular replacement of the tensioner will prevent the chain slap; you may hit a big enough pot hole to overcome the chain tension.