Camshaft carnage(Audi/VW content)!!!

Hey guys,

So I am a generator technician among other things at work. This past Wednesday I was at one of out locations that uses a odd genset that consists of a Audi/VW 6-cylinder turbo diesel mounted vertically and driving a generator at the bottom of the set. We have maybe 4 of these gensets left in our footprint, and I hate them with a passion! Leaky,loud, terribly conceived, high-revving lumps. Did I mention I hate them?

Well I had this genset running for a routine like I do every month, and it had been running with the building load for about 30-40 minutes. While working on another part of the building I heard so really loud noises coming from the area of the generator. By the time I got over to it (about 30 seconds) the noise got worse, and before I could do anything it made a really loud bang, and stopped really quickly.

The generator sits in a housing about the size of a Sub-zero refrigerator. I opened the door and was expecting to see really bad things. To my surprise it didn't look too bad at first glance. I noticed the serpentine belt I had just replaced about three weeks prior when we performed a full service on the engine was now half as wide as it was when new, and the cover over the cam gear was in a few pieces. No oil or other foreign fluids however. Upon further inspection I noticed the cam gear was not sitting horizontal like it should be but rather at maybe a 25 degree angle from horizontal, but the timing belt was still on it, and tight (well mostly tight), but not broken.

I got on the horn to get some help to hook up a portable genset that I was either going to go tow to the site or have a co-worker tow to me. In the meantime I was looking it over with another co-worker, and we noticed the bolt that holds the cam gear in place was still tight. He said " I bet the cam is broken!!". I agreed, and then I took off the valve cover which made a pretty good mess in itself due to the orientation. Here is what we found.

That's right, the cam is broken in two places!! No idea how, but my co-worker thinks the timing belt skipped a few teeth, and then the piston to valve contact broke the cam, but I think that would just hole a piston, or bend a valve, but I could be wrong. Anyway at least the cam is toast, and maybe the head, and the rest of the engine. There was a job in place to replace this genset anyway, so now the engineering department is expediting it.

Note we had just changed the oil,coolant,belts (not timing), hoses, and filters about three weeks ago. This is unlike our other gensets in that is spins at 3600 rpm instead of the normal 1800, and it had about 50kw of load on it at the time. I didn;t see the oil pressure as it was making noise but prior to it the oil pressure was around 45psi, and the engine was at 180 degrees.

Any ideas as to what happened?

Mazdax605 wrote: Any ideas as to what happened?

Hitler's ghost. They're going to win eventually.

check the bearing under that cap. I bet it's welded.

Cam belt on an industrial engine? Who thought that was a good idea?

Your assumptions would be correct, on a gas engine. SOHC diesel with the valves straight up like that is a touch different. Check out the timing failures on benz OM617 engines, often times the cam bearing towers get broken off the head, cams snap, etc.

I raise you a broken inline 6 VW cam, with a broken almost inline 6 VW cam.

@#)($* happens is the cause.

Yeah, I can't see a skipped timing belt doing that. Usually, like you said, a piston or two gets ventilated. Like this

Yeah I know, I've posted these a few times before. But carnage like that deserves this deserves to be hot-linked.

In reply to DrBoost:

Valves in that engine were angled relative to the piston, in OPs case they are going straight down, on pistons that are built to handle a engine that actually runs by knocking. There is zero inclination for the valves to bend short of loading to a point of exceeding the compressive strength of steel.

Are any of the lifters cracked? That would be a sign of valve to piston contact if so.

Wow. I work around generators quite a bit, mainly monthly load tests. But ours are big Cummins and Cats mainly.

I just can't imagine a VW/Audi engine in that role. Bad idea!!! (obviously)

My experience (on the older versions of VW diesels)would suggest that if the belt skipped, the cam would be broken in many more pieces than that.

I'm gonna go with 'cam seized, jumped time, cam stopped with valves open in wrong spot, piston hit valves, valves broke camshaft' for $800, Alex. But here's the really big questions:

1) What idiot said 'Audi diesel in a 50kw genset? I do believe that's a grand idea!'

2) That same idiot says 'Let's think outside the box and mount it VERTICALLY, thus screwing with 100 years of engine design based around good ol' gravity oil return to the pump'.

I'm with Curmudgeon. I can't imagine any engine's oiling system working properly oriented vertically. That's just not the way they're designed. How do you keep the oil pickup covered? You can't be using a stock oil pan that way. My bet is that the cam lost oil pressure and seized.

It does not use the stock oiling system. There is a large capacity sump mounted under the set. It also uses an accusump system. I really hate these things!! When I get a chance I will get you guys some better pictures of the whole set.

Curmudgeon wrote: I'm gonna go with 'cam seized, jumped time, cam stopped with valves open in wrong spot, piston hit valves, valves broke camshaft' for $800, Alex. But here's the really big questions: 1) What idiot said 'Audi diesel in a 50kw genset? I do believe that's a grand idea!' 2) That same idiot says 'Let's think outside the box and mount it VERTICALLY, thus screwing with 100 years of engine design based around good ol' gravity oil return to the pump'.

Actually I believe it is a 100kw set, but maybe only a 90kw set. It was holding 50kw when it failed, but in theory it was designed to take more.

Giant Purple Snorklewacker wrote: check the bearing under that cap. I bet it's welded.

This.

Cam failures were really common on Honda F-engines when the distributors would lock up. Since this thing has (should have) nothing driven off of the camshaft, I'm going to assume that the cam itself siezed.

Kenny_McCormic wrote: Valves in that engine were angled relative to the piston, in OPs case they are going straight down, on pistons that are built to handle a engine that actually runs by knocking. There is zero inclination for the valves to bend short of loading to a point of exceeding the compressive strength of steel.

The SOHC gas engines (same geometry) will bend valves if you have one with the "big" cams. The piston is dished so it gives a nice bending moment on the valve head.

Now, I don't know what the Diesel piston is shaped like, but it's gotta have some bit of dish to it since the chambers are flat.

I'm assuming this is a VW D24.

Knurled wrote:

Giant Purple Snorklewacker wrote: check the bearing under that cap. I bet it's welded.

This. Cam failures were really common on Honda F-engines when the distributors would lock up. Since this thing has (should have) nothing driven off of the camshaft, I'm going to assume that the cam itself siezed.

Actually the cam drives the injection pump (via a belt) off of the back side of the head. Strange setup for sure. I hope to have a chance to tear down the engine at some point, but I am not so sure it will happen with how busy we are with other things.

Huh, so it's not driven off of the timing belt like the various flavors of 4-cylinder? Interesting.

Isn't that 6 cyl diesel that VW/Audi shared with Volvo, that you could get a in a 240?

Yep. IIRC this was the only other application for it.

Someone posted a picture of the inside of the cabinet on Motorgeek, in the "engines found in strange places" thread. I thought it looked kinda foolish, like the rear main would leak constantly unless the bellhousing was sealed off and an oil pan was mounted to that, but I never investigated further.

Knurled wrote: Yep. IIRC this was the only other application for it. Someone posted a picture of the inside of the cabinet on Motorgeek, in the "engines found in strange places" thread. I thought it looked kinda foolish, like the rear main would leak constantly unless the bellhousing was sealed off and an oil pan was mounted to that, but I never investigated further.

Just did a search for the thread on motorgeek, and you are correct that is the same genset I was talking about. They were made by a company in San Diego,CA. The company is still in business, and we buy all sorts of genset from them to this day. Thankfully they don't make this setup anymore, or rather we don't buy them anymore.

Wow. It's not like VW just started making industrial engines. So you have an engine failure on a genset. And it has a VW diesel engine. Big deal. BTW, I am going with Curmudgeon. Cam locked and broke. But the question is WHY DID IT LOCK UP? Next someone will say it would be ridiculous to have a Chrysler Hemi power a siren. Hemi Siren (Sorry, been a little sick and feeling testy..)

noddaz wrote: Wow. It's not like VW just started making industrial engines. So you have an engine failure on a genset. And it has a VW diesel engine. Big deal. BTW, I am going with Curmudgeon. Cam locked and broke. But the question is WHY DID IT LOCK UP? Next someone will say it would be ridiculous to have a Chrysler Hemi power a siren. Hemi Siren (Sorry, been a little sick and feeling testy..)

Who was complaining about VW? I hope you weren't directing that at me. I hate the genset, but it isn't because of the engine manufacturer. It is because the whole setup sucks.

Ahhh. My apologies Mazdax605. I regret my outburst.