I have purchased the entire kit to replace all the tensioners and guides with the third generation metal tensioners and guides. I am debating whether to just replace the secondary tensioners myself or send it to the dealer to place everything. It comes down to one question. When I took the covers off I had a look. The guides had hairline cracks in them. Is that just the outer plastic covering on the guides or are the guides themselves at risk of splitting apart? When I reviewed most of the previous posts I could not find a definitive answer. If there is a coating that will fall off the guides, I am not concerned if the underlying guide stays in place. If the guides are at risk of breaking apart then I am going to get everything done.

 

Yes they are shot if they develop hairline cracks. If the cover breaks off the guide it will jam in your chain. I was able to pull one of my covers off by hand when I replaced mine. You'll most likely find cracks in the bodies once they're out of the car and you can get a closer look. Remember, when they break, your engine breaks. $$$$$$$

 

The Plastic Body of the Tensioner can crack and the Metal Part can separate with the following results:



Also, the wear surfaces or "Shoes" of the Tensioners can shrink and detach from the Metal part and cause a Metal-to-Metal contact between the Tensioner and the Chain. And (as mike66 says, jam in the Chain).

The lower (Primary Chain) Guides can crack although they are not known to cause a catastrophic failure.

 

Just re-read your post. If it's the primary guides that have hairline cracks, you may be okay. As Paul says, you don't read much about an engine failure from cracked primary guides. Secondary tensioners are the main issue. My decision was to do the secondaries only because it is alot more time and effort to do the complete job. Your cost/benefit decision.

 

Thanks guys. I am aware of the slippers on the secondary tensionsers detaching and causing the metal on metal chain wear. The second generation tensioners look to be okay in my car but I am not taking a chance on those. If the guides themselves can crack off in pieces then I think my decision is made. I don’t want to take a chance on those hairline cracks lasting forever. I did see cracks on all four guides.