Chain tensioner failure after rebuild

[ninelevenick]

I'm frustrated right now because one of the non pressure fed tensioners that I rebuilt failed just two days after I installed it. The piston seemed to be nice and stiff before I inserted it back into the housing. I drove the car on Monday without incident. Yesterday evening, I took the car out again, and within a 1/4 mile from home, I heard the awful sound of the left side chain slapping the ramps and whatever else inside the housing. I quickly doubled back for home and proceeded to investigate. After removing the cover, I found the piston totally compressed and sticking. I proceeded to dismantle the tensioner. The upper chamber (for lack of better words) was holding oil just fine. I then disassembled the lower chamber. I inspected the parts as they came off. There appears to be no defects, and the parts were installed the correct way. I then assembled the lower chamber again by putting the parts back where they should, and I submerge the whole tensioner in oil when I introduce the oil while purging it of air. Them I tested it. Here's the failure: I can compress the cylinder with my own hands because oil is somehow seeping out as I compress it. I disassembled and reassembled using the old parts, and still the same results. I should also mention that before I rebuilt this tensioner, it appeared to be working fine. It was the right side tensioner that really needed to be serviced. I just rebuilt both for the sake of being thorough. Can someone who has a better understanding of the mechanism please enlighten me about what could be causing this failure?

[john walker's workshop]

If you can compress it by hand, the check ball is not seating properly, or the lower chamber has air in it. To bleed the lower chamber, you fill the upper chamber with oil, insert a key tag wire into one of two holes in the piston to dislodge the check ball and slowly pump the piston so oil gets sucked into the lower chamber. Pull out the wire and test for squishyness. Should have none. Fill the upper chamber, open the bleed screw a bit, tilt the tensioner so the screw is angled upward, squeeze in the top aluminum disc until air bubbles stop coming out the bleeder screw, but don't bottom it out. Close the screw. Assemble the tin cap, spring and clip.

[ninelevenick]

Thanks, John. I will try bleeding the lower chamber using your method. Fingers crossed that it works and that my chains didn't jump the sprockets...

[eastbay]

Also make sure there are no defects in the housing bore. O-rings need a perfect bore to seal. I had one with rust pitting and had to replace it before rebuilding. Luckily non p fed used tensioners are cheap and plentiful on the forum here.

[Trackrash]

Safety collars?

[ninelevenick]

Thanks for your input, eastbay. I checked the housing bore, and it was as smooth as silk with no rust. Well, I think I have success. When I rebuilt the right side tensioner, I distinctly remember filling the lower chamber with oil and then bleeding the chamber after. However, for the left tensioner, I did the bleeding procedure followed by filling the chamber with oil. This resulted, presumably, with air trapped in the chamber. I have since redone the procedure with the tensioner, installed it, buttoned up the various items that go back in their places, and the car runs well. Given that the tensioner totally failed, think I dodged a bullet. Hopefully further tests prove that it will hold in the long run.

[ninelevenick]

Hey Gordon, no collars. I did some research before I started the project, and some suggested to not use them. However, now I'm thinking that there are more benefits to having them than the potential hazards.

[Jack Stands]

I think that the use of safety collars and the later idler arms with the larger bearing area make the system pretty foolproof. Luckily, it sounds like you dodged a bullet this time.