Destroy all lifters

[belchfire]

The bypass hose blew on my 1.6 TD and I fried the head into oblivion.
Bought a new one and used my old valves (ground and checked for concentricity), and cam. I installed new hydraulic lifters as the old ones clattered a bit. Timed everything and fired it up. Ran kind of funky due to air & veg oil but then cleared up. All of a sudden an unhappy sound appeared and I shut it down. Inspection revealed that 7 out of 8 lifters had shattered. I could not get the cam gear off so I had to cut the belt cover plate and pull it out. It seems that the gear had slipped on the taper and threw out the timing causing the pistons to smack the valves and break the lifters. I removed the broken ones and was able to salvage the bores with a bearing scraper. I used a puller to remove the pulley and it came off with a bang. It appears that they had friction welded themselves together. I reassembled everything and timed the cam. I then disassembled it removing the cam through the slot I cut. I carefully removed the bolt and installed a dutch key between the shaft and gear. Everything is back together and seems to be working. I've got smoke issues so I think that's IP timing.
 So here's the deal. Has anyone had this problem? I do not like the idea of a gear being held in position merely by a taper especially when there's a key slot in the shaft. Is the timing that critical that it has to be within a half of a degree? Seems that every other engine runs perfectly fine being within a degree or two. Yes, I did tighten the bolt to 33 ft/lb and I have done cam timing on race engines. It seems that the valves are ok, I hope.

[arb]

My experience has been that when you install a new belt, you are looking at up to half a tooth - that's more than a degree.

Here's the rhetorical question back - The crank cog is the only one with a fixed location. The IP and cam cogs were designed to be adjustable. So, if you wanted to fix the cam, where would you fix it? Also, have you tried to slip a new belt on with the cog not loose and the cam locked into position ? It puts quite a bit of stress on things.

On the other hand, I had a 1.6 blow a cheap Miejer's oil filter and the idiot light was out.... it stopped running, but when I put a new filter on and new oil, it ran for another 50K miles ! Sorry about you luck.

[burn_your_money]

So did you pull the head a second time and make sure the valves weren't bent?

Did you clean the taper on the cam and gear? I usually overtighten that bolt on purpose, 33 sems to low

[saurkraut]

I never have had a problem with the taper holding the cam gear.  Never.

There is a little punch hole in the back cover.  Your supposed to put a small drift through the hole and smack it sharply with a hammer.  On the older ones with out the back cover, its a good wack with a copper mallet, and off it comes.  Maybe the uneven sudden pressure distorts the whole pully enough to make it release.  But I've never had a problem getting a pulley off that way.

Make sure the taper in the pully and on the cam are squeky clean and torq it tight.

If you haven't pulled the head after the lifters were broken, you have to pull the head to see how many valves bent.


How do you fry the head by blowing the bypass hose?

What is a Dutch key?

[Dakotakid]

I believe that running with a key on the cam will earn you the ability to buy much more replacement parts than just the valves, guides, and stem seals.

The interference fit has provided literally millions of miles of travel in many of these engines. I'm thinkng there was some other problem which contributed to the demise.

[Vincent Waldon]

My opinion would be that the IP and the cam sprocket have to be very closely aligned... to within one tooth... when the belt is at the exact right tension.  In order for this to happen something else has to be slightly movable.... namely the cam sprocket.

At least for me, I find that I can't get the timing belt aligned to the right teeth *and* the right tension without the cam sprocket being free to rotate.

[belchfire]

Let me try to work through your replies one at a time. First, when the bypass hose blew, the coolant went bye bye and it turned into a very inefficient air cooled motor. I was doing 80 at the time. Second, a dutch key is created by drilling and tapping a hole where 1/2 is in the shaft and 1/2 is in the gear. A set screw is inserted and viola, a key.
  It  fired up after installing the old lifters and polishing a few dings on the cam. I fought with the timing for an hour and got it dead nuts.
I took it on the road and the cloud of smoke is still there. I think that my injectors have died. I did a compression test with a home made tester and it said 175-200 psi. I' not sure that my gauge is good. anyway, I pulled the head. There are no marks on any piston!! I will pull the valves and check them but they look good.
  I know that VW has logged millions of miles with a tapered fit but the tell tale gall on the gear leads me to believe that there was slippage. 33 ft/lb was straight from the book. Might have gotten some grease from the seal on it.
  As for the timing, if the crank and IP are locked, then slack will be taken up by cam gear rotation (no locking bar). the groove looks reasonably horizontal so it's not off that much. 1 tooth is about 13 deg and that can throw things off quite a bit but I don't think that this slight of adjustment isn't that critical. If so, I can remove the key and go back to the taper. Maybe lock tite.

[saurkraut]

OK, I was thinking the bypass hose was the hose that went from the god auwful blow off valve to intake.  'I blew a coolant hose' would have been clearer.  Which one is the 'bypass hose'?

I'm with libbybapa,  33 ftlbs is not enough, and probably twice that is ok.  I'm predisposed to reach for a torque wrench. But on the cam pully, I'm more concerned with the sprocket not moving while its being tightened so I focus more on the wrenches.  I'm also a two feeler gauges under the cam lock proponent.

I snug the cam bolt with the cam lock plate and feeler gauges in, then pull them out and go for the big reef.  I use a sprocket holder and short breaker bar and reef on it till I'm fairly tensed up.  (I'm probably over 66 ftlbs.)  Twice around with the crank, then back in with the cam lock and feeler gauges again.  If its right, cool.  If it off, off comes the cam sprocket and start over.

[arb]

Even at 66 ft lb I doun't think I'd be happy if there was grease between the cog and the cam tapper.

[saurkraut]

Squeeky clean, bone dry, with brake clean, both the taper on the cam, and the inside of the pully

[burnt_servo]

more than likely the cam slipped on the sprocket when the lifters self destructed .

i've never seen a stock engine with a tapered cam / sprocket slip if it was put together right ......  ( dodge uses a similar setup on many of it's engines . )

that said i wipe everything down with laquer thinner , then  i use a few drops of red locktite on the taper , and bolt holding the sprocket ......

the problem with a dutch key is , what if it doesn't line up the next time the engine is taken apart  / worked on ... this  is very possible  , and more than likely the reason vw didn't use a keyway on the cam on most of it's diesel engines .

[burn_your_money]

I wouldn`t use locktite on the taper. Just metal on metal.

It`s all every big drill press uses, and they have a hell of a lot more torque than what is being transfered to the cam pulley

[Duster 5.9]

I wouldn`t use locktite on the taper. Just metal on metal.

It`s all every big drill press uses, and they have a hell of a lot more torque than what is being transfered to the cam pulley

i agree

[Vanagoner]

This country was built on Bridgeports with the Morse taper.  I trust a clean tapered fitting any day.

[Mark(The Miser)UK]

Never had a sprocket slip either. Always dry surfaces. Sometimes use scouring powder to clean. I can tell if things are right by a gentle nipping up of the bolt and checking to see how well the sprocket begins to adhere. I have a beautiful Snapon torque wrench, but admittedly I've never used it on those bolts. I probably get it somewhere close to the book spec.
What is the strength of a bolt that allows twice spec to be applied?
[Andrew restate that hammer tap procedure. It just struck me that if the bolt is tapped then theory makes me wonder that if the bolt was a tight fit then it is moving the cam away from sprocket...Nah I'll leave that thought in, but the ability to tighten  bolts with fingers straight away disproves my idea.]  
It IMO will never slip unless it comes across a problem. Ie cam seized due to oil starvation. or crank pulley slippage. Maybe if the cam wedges due to lifter-valve- piston marrage then belt would snap first? Very hard to say. I think unless bolt undoes itself; catastrophic slippage is always a secondary event.
 What is the best kind of failure to have??
 Ie whose engine rises out of the ashes?
I guess one that only kills one piston's worth of machinery...
At #1 TDC only one valve open, and only partly. would a clash push cam round slightly and then back with the other pistons and so on until engine quickly stoppped?