Nasty Knock... likely timing belt?

[Greeno]

Hey, so I'll try to give you guys the rundown from the start. Bought a 92 TsI AWD (with a 6-bolt) on which the timing belt had broke and bent all 16 valves, one rebuilt head and some belts later, (glossing over the occasional newbie mistake) we had her running, timed and everything seemed great... I was driving home from the shop at my old man's place, and about 20 miles into the 30 mile trip, slowing down because of an upcoming speed zone when I got a loud nasty knock, I slowed down hard and fast in 5th gear, and when engine hit about 1200 RPMs, she stalled, it will still start and run, but it is making one ugly sound... as best as we could tell at 3 am on a dark road, the cam gears and crank gear seem to be in time. I am currently waiting on a tow truck to get her back here to the shop, and I have been searching, but most knock issues seem to go to TB or spun bearings.

Any ideas on other possibilities?

My dad said it may be possible that someone gave us a 2g TB instead of a 1g TB? are they slightly larger? causing an easy TB skip? the tensioner seemed nice and strong, and the belt was tight and timed, like I said, she ran quite nicely for... almost an hour before this happened.

Any thoughts and suggestions would be greatly appreciated, I've had this girl in the shop for months while I got parts collected and money saved, I just want this baby on the road, but I think if I have to tear the head off again, I may just build an engine on the rack, I dunno

 

[ekanddsm]

did you shave the head when you did the valve job.
There is a mark on the head surface for mininum machine to, kinda like a brake rotor thickness, but for a head.
But if you shave too far, when they get warm, or driven hard for a mile or two, the head will super heat(best way to describe) and close up clearence that were borderline when measured.

Did you do the headwork yourself?
Did you replace valve guide?
or simply is the timing belt still tight between the cams, if your lucky.

 

[Greeno]

the head was shaved 8 thou when it was rebuilt, all 16 valves and guides were replaced, I'm not sure about the springs. In the daylight we were able to see that the timing has not in fact skipped *whew* but once we ripped the valve cover off, one of the rocker arms is out of place and one of the intake valves on the #2 cylinder is jammed about 1/4inch down, so I'm definately removing the head again... at least I'll be well practiced

I'm happy its only going to be 1 valve/guide/lifter to be replaced this time, as that isn't too costly... but my bigger fear now is, what caused this?

if we get the head off and see debris jammed in the valve, that will be a definate answer, but if there is nothing jamming the valve, I don't know if we'll ever be able to tell if the rocker arm just came out, allowing the cam to whack the valve, and bend it, jamming it down... or if the valve jammed first, allowing the rocker arm to come free

maybe I'm missing something completely, this is my first DSM, but if anyone has thoughts, comments, previous experiences... I'd love to hear em

ps. one other thought I had was if the spring wasn't replaced, is it possible for just one valve to float?

 

[pedrick1]

check the lifter on the valve where the rocker arm came off, the ball joint on it will be lower than all the rest if it's bad. If a lifter goes bad it basically doesnt lift anymore because it cant hold pressure. This happened to me after putting a new head on my car but fortunately i saw the loose rocker arm and put in a new lifter before any damage was done.

 

[Greeno]

Thanks, I will check that when I get home. (out of town for work) I'm assuming by "ball joint" you mean the rounded top portion where one end of the rocker arm rests, correct? Should I replace all 16 lifters and valve springs once I get the head removed again? Will a lifter be noticeably lower if its bad or are we talking a matter of 1 or 2 mm?

 

[pedrick1]

Yes that is what i mean by ball joint and it will definately be noticeable. The easiest way to check is try and shake each rocker arm by hand and if one is lose then you may have found the culprit. You can replace a rocker arm without taking the cams off. Depending on which piston it's on just rotate your engine so you know that piston is down and you can use a prybar to pop the rocker arm off, take out the lifter, and replace it.