A Curious Thing......

[Toby]

I just bought a 2001 TDI NB for a song. It is purported to have had some kind of timing belt issue. There is no belt on it now but the motor mount and balancer have been removed just as you would to change the belt. The cam cover is off and there is absolutely no sign that anything is amiss. No visible trauma to the cam, head, followers, anything. The story that I got was that it quit on the way to work at less than 15 mph. Its an auto. The "mechanic" told him that the IP "seized" and "shredded" the belt. No sign of the belt or parts in the car. No bits of belt anywhere under the hood or inside the cam cover.

Anybody here ever seen a broken cam belt on an ALH that did not grenade the head?

I just had rotator cuff surgery so I won't be able to tear into it for a couple of months. I may just put a cam belt on it and see if it will roll over w/o making crunching noises. If not then run a compression test......

[vanbcguy]

Never heard of any VW diesel having any kind of belt event happen that didn't nail a valve. 

The crank pulley has the fewest number of teeth so it is the one that slips if say the IP were to seize. 

Here's the thing... Since the valves on these engines are directly perpendicular to the pistons they tend to compress their stems slightly when something like this happens.  Since they're still "straight" just squished they'll still seal so a compression check or leakdown check will tend to indicate that everything is fine.  Then about 10,000 miles later the head drops off the valve turning what would have been a relatively cheap fix (replacing a couple of valves at $10-15/ea) into replacing pistons, rods, the head and possibly even the block.

You can certainly button it all up and hope for the best, odds are you'll have a running engine.  The problem is the expected life after that...

[Toby]

I have no illusions about it having to come apart. Just the fact that it might have had a valve crash warrants that. It is just that I have never seen a belt failure that did not grenade the engine unless it was at idle and the PO claims he was going 15 mph. Perhaps the belt had slipped enough to kill the engine before the belt failed completely. Being an automatic, the engine did not get spun until some catastrophic failure. I was curious whether anyone else had seen this kind of failure.

If it turns over and has compression, I will likely try to start it, if only to see if runs w/o other obvious problems. If it billows smoke then the pan must come off and the pistons out.

I am just bummed because I will be laid up for a couple more months.

[Toby]

Upon closer inspection, one of the cam followers has a tiny crack around the lash adjuster contacts the follower. It took a bright flashlight and a very close examination to find it. The head comes off tomorrow, if I can get someone to break the head bolts loose for me.

[air-cooled or diesel]

how an injpump seizes is beyond me, not very likely, any interference engine that has a belt break while running is toast .  turn ip with a wrench, its prob fine. you may be able to find a good head complete; or head and seperate parts. you need everything beside cam; and possibly that head, depending on condition of head and machine work you end up doing on head. once you have the head off you can see a lot. if tops of pistons look ok, you may not have to get in to the bottom end. who knows you may need a cam on further inspection, but i bet you can use head, cam, and bottom end may be ok.

[Toby]

The crack is so small and only on one follower, that I expect there is no visible damage beyond that. It is very unlikely that there will be any piston damage beyond just a "kiss". A piston protrusion check will be the arbiter of whether the bottom end comes apart. I will report back when the head comes off. Probably this week.

[Toby]

Piston protrusion is w/in .003" so I am good to go. The "kiss" marks wiped off with a rag.

The parts are here fro AutohausAZ, so now I need to spend the weekend cleaning a path to my assembly bench so that I can do the head.

I just bought a 68K mile ALH motor and O1M for $275. It lost a turbo and hydrauliced 2 & 3 on the gusher of oil from the broken turbo bending the rods.

The O1M has the typical 2-3 cutloose that the SK VW-O1M is supposed to cure. I need to buy 4 of them now.

I may use this ALH to diesel up my Eurovan MV. I haven't decided whether to go mTDI or add the harness and go fly by wire. With the O1M electronics run it on a non FBW motor?