Hi, I recently re-installed a re-built head on a VR6 in a '93 Passat. Engine started and ran smoothly, but valves seemed a bit noisy. After a few minutes of running the engine started running roughly and eventually quit with a rather unhealthy sound. Today I got around to taking it back apart and found the cams seriously mis-timed. I'm well aware of the implications of this and the potential that I'm taking this head off again for a second re-build. However, I was very careful with the cam timing when I put it together. I removed the timing chain tensioner bolt and found the small hole that allows oil-presure to charge the bolt plugged with a small bit of rubber, sorta o-ring material. Not sure at all where this bit came from but it sure has caused a problem. My main question is: Why is there no spring in this tensioiner bolt, relying on oil pressure is great when the engine runs, but why doesn't this tension relax when the engine is stopped. Perhaps there's a check valve somewhere, but that would still leave the initial start-up after rebuild a bit dodgy. Does anyone have experience with that bolt, is it supposed to have an inherent "springiness" independent of oil pressure? (it's the earlier design, with a nipple that fits into a grove in the metal tensioner itself, what a horrible design that piece is, but anyway...). Thanks in advance for any help, my current plan is to re-time, re-assemble and compression test to see if I can figure out the state of the valves before I remove the head. -- andy hamilton
Sounds like your chain skipped, causing the cams to be mis-timed. The newer style chain tensioner (from mid-97 and up ) do contain a spring, and hold the chain in place even when there is no oil pressure. I would change my upper tensioner bolt and rail to the newer style. the newer motors only have a single row upper chain, but don't worry about that. This setup will work fine with your double chain setup. the newer style upper rails also last a lot longer that the older ones. Many people have done it with no problems.
Bolt has a check valve built into it. Therefore, it can ONLY extend, never compress. Once oil pressure extends it, it will not retract (unless you put a very small wire into the body of it to release the check valve, then you can push it back in. When installing it, you must first bleed that bolt, by engaging the check valve with small wire, and submerging the bolt in tub of oil. Then, extend and retract bolt tensioner a few times. Set tensioner on bolt to provide "a little" tension on chains. Once engine fires, it will build pressure and tension itself. As long as there isnt peice of rubber in the oil port
The rail and bolt are designed to work together. You need both.
Gary
Gary
Now: '99.5 Jetta GLS VR6 (281,000 miles and counting! ) - Stupid CEL Then: '90 Passat GL 16v - (RIP - i.e., Rest in Pain!!! in a junkyard somewhere you LEMON POS - still loved her though )
I had similar problems with my other '93 passat aswell...I rebuilt the motor and re-used the tensionner thinking it was good(and keeping rebuild costs down ) and whenever I started the motor after sitting for more than an haour, the chains would make this gawd awful noise, but after it ran for like 5 seconds it would be perfect(didn't know what the problem was at first), Come to find out the tensionner was f'ed and was draining oil pressure when the car was shut off. it ended up missaligning one of the cams by one tooth and causing loss of power (but still running). In your case, if the motor ran ALL that time with no oil pressure going there, and no tension on the chain, your probly looking at bent valves.
2004 Infiniti G35 Premium 6MT Navigation. 1997 Jetta VRT (solded) Some people are like slinkies... Not really good for anything, but they still bring a smile to your face when you push them down a flight of stairs.
) - Stupid CEL 
(RIP - i.e., Rest in Pain!!! in a junkyard somewhere you LEMON POS - still loved her though 
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