Piston damage from valve contact....thoughts please

[jtanguay]

you could probably get away with using those pins...  i would much rather just go with the TDI sprocket upgrade if i were you.  it's probably going to be about as much trouble as re-welding the crank nose & filing it down.

[vwt4]

you could probably get away with using those pins...  i would much rather just go with the TDI sprocket upgrade if i were you.  it's probably going to be about as much trouble as re-welding the crank nose & filing it down.

Can you elaborate jt?

What pins?? do you mean that pin 'fix' where the sprocket is drilled and the crank nose is too?

The problem with doing the TDi sprocket upgrade is that it means engine out. This is a problem because the t4 is currently located in a tricky place to get an engine crane in and its outdoors and its cooooold....so I dont fancy removing it if I can avoid it!

Welding the crank nose can be done in situ, and if I do it right first time, it shouldnt take too long...

At the end of the day, my belief is that the locating groove is to locate the pulley only, not retain it? (the bolt should do that)


The fact that the right hand side of the groove is ok, should mean in theory that timing the engine up and torquing the bolt (clockwise) should be ok as the pulley should stay in situ..

I might be being hopeful there though

[VW_Commuter]

I just did the dowel pin repair on the end of my 1.6L TD crankshaft and it went really well.  I had a couple of friends make the drill guide/jig for me.











While the drilling of the crankshaft took a bit of time and effort, the results were great.  When the crankshaft timing gear is on the end of the crankshaft with the dowel pins inserted there is absolutely no play.  I used 3/16 inch hardened steel dowel pins that were 1.5 inches long, drilled the holes in the crankshaft as deep as I could, and ended up shortening the pins by about .15 inches.

I can't claim originality on the idea or design, that was from GoKraut and here is the thread that explains how he repaired his crankshaft.  GoKraut sent me the CAD file that he developed for the repair and if you want it just let me know.

I still haven't torqued the timing gear on yet since I just got my engine gasket kit and will be replacing the crankshaft and intermediate shaft seals before the final torquing of the crankshaft bolt.

[jtanguay]

i suppose the pins would be a good idea if only you had that special tool vw_commuter has (maybe he will be nice enough to 'rent' it out?  :lol:)

i know there are people out there who machine the crank in place, and others weld it up and machine that... but what kind of setup are we talking about to machine the end of the crank for the TDI sprocket?  definitely don't want to start going at it with a grinder, but is there any simple solutions?  maybe bolt on a plate to the crankshaft with just enough off of one end to simulate the flat end of the normal TDI crank nose, and then remove that material using a grinder or other tool?

i think you might be able to get 3-4 tries at it before the nose is completely ruined... if that helps any  :lol:

[vwt4]

Because the rotation of the crank is clockwise and driven by the pistons, which in turn drive the sprocket, which in turn drives the injection pump and cam, all of the rotational force acting on the sprocket is working to rotate the sprocket counter-clockwise, toward the direction that the crank nose is damaged, and loosen the bolt.  Couple that with the fact that the force is not constant but rather pulsed, the whole system is set up to loosen the crank bolt if there is play in the keyway.  

Yes, the pinning mod would be where various holes are drilled through the sprocket and crank nose in order to prevent any motion.  Like the welding option, that could also potentially be done in situ.

Andrew

Good point re the forces on the sprocket... makes sense as to why the keyway is damaged on that side as well  :?

I like the look of that pinning mod, especially with the new pictures added..but Ive just spent a lot of $$$ on a welder so Im going to weld it no matter how hard


VW Commuter - thanks for the pics etc. I dont have any facilities really to meka that adaptor tool though

jtanguay - I think the TDi sprocket would not be as simple as it seems because the machining would have to be done in the perfect place to keep the crank sprocket in the correct position relative to the other sprockets.

I think the only way to do it properly would be with engine out of the car, and a proper jig setup.

[vwt4]

jtanguay - I think the TDi sprocket would not be as simple as it seems because the machining would have to be done in the perfect place to keep the crank sprocket in the correct position relative to the other sprockets.

Actually, the timing of both the pump and cam are infinitely adjustable and so the orientation of the crank sprocket on the crank is not important.

I fully understand wanting to go ahead and use the new tool.

Andrew

Good point again  

Well, ive managed to weld a nut on and get the stuck bucket out.
Will post a picture up later of what I found, but basically the valve had punched a 10mm dent into the bottom of the bucket, impaled it if you like!!
So I had to get that off as well once the bucket was out (no wonder it was stuck in there!)

I had to use quite a lot more power than I expected to penetrate the lifter, this is only a 150 amp welder but should definately work on the crank, I hope, but I dont currently have any suitable bar stock to test on, so I am starting to like the pinning mod more and more!!

Posibly even in conjunction with the welding.



VW COMMUTER

If you would be good enough to send me the cad drawing for the adapter piece I would be very grateful.
My email addy is

[email protected]

Thanks[/quote]

[VW_Commuter]

Nice link Andrew.  If I would have been able to snag drawings of the jig to machine that flat onto the crankshaft I think I might have gone that direction.  My plans are to find a nice hydraulic lifter 1.6L TD engine and rebuild it for replacing my current mechanical lifter motor.

[vwt4]

Check out this thread;

http://www.vwdiesel.net/phpBB/viewtopic.php?t=2719

That is where I snagged the crank sprocket pic.  If building the jig for the pinning, it might be a similar range of difficulty to build the jig that Andy2 shows and do the TDI sprocket.  I lean toward using the TDI sprocket because of future crank sprocket replacements.  If VW is not super consistent on the placement of the pulley bolt holes, then if the sprocket ever needs to be replaced it will be very difficult to line up the pin holes.

Andrew

Thanks, thats a really informative link.
The TDi sprocket mod they have done, is a bit beyond the equipment and time I have to be honest.
Im not sure I would be happy tackling it, whereas the pinning I have all the tools for (apart from the jig)

Also, Im planning a 1z TDi swap early to mid 2009 so this doesnt have to last 100k miles... (would be nice if it did though!)


VW_Commuter

Many thanks for the DXF file  :wink:  Much appreciated.

Here are the pics of what I found when I got the stuck bucket out....







Spot the damage!!!
ive included a good lifter on the left of the pictures. The valve was more bent than this (it still is to the eye) but I had to hammer it out of teh guide as it was stuck so tight.

Im guessing replacing valve guides needs an engine machine shop to do it?
Not sure if its worth reusing this head (the cam lobes have a few minor scratches) and also several of the lifters have some minor scuffing on the surface.

Ive found a supplier for recon head using pattern casting, unlimited mileage guarantee for 12 months....$500 approx. They are a well known trusted supplier of recon VAG derv engines so I trust them. Just not sure if its a good swap. although Ive heard it is.


I may have to take the recon head route for speed as I need the engine back but I would still get mine repaired, I think.
how much are 4 new lifters? valve guides? 2 valves (may buy 4 to be safe), and a new cam or polishing of the lobes if they think its salvageable... ( I havent taken pics as its hard to get them in the light! but there is only one that concerns me a little ,but its still only maybe .2 mm deep at a wild guess  

[jtanguay]

if you're looking for some cheap lifters, prothe has some at his site www.dieselvw.com although nobody's commented on the quality... but if you're looking for a 1Z conversion anyways, then you might as well cheap out a bit.  i would  :wink:

[vwt4]

if you're looking for some cheap lifters, prothe has some at his site www.dieselvw.com although nobody's commented on the quality... but if you're looking for a 1Z conversion anyways, then you might as well cheap out a bit.  i would  :wink:

Thanks

that site looks like the worst laid out gold mine of parts that I could ever need!
edit// found them, I enlarged the text!

Doesnt list any for the ABL engine though...

[vwt4]

ok guys.

Another question.! I was deburring the top of the damaged piston today with a flat file as advised.

it worked a treat and the burr is now gone, however I noticed that there was more play than I expected from the piston in the bore....

I remember the last petrol engine I built there was virtually zero lateral movement (side to side or front to back).

i checked the other pistons that hadnt been hit and they were all about the same. maybe .5 mm + of movement in the bore, when I pushed them from side to side...(noticeable put it that way!)

Does anyone know what the tolerance should be??

I was expecting some wear but just dont know what is 'ok' and what isnt.

I dont want to buy a new cylinder head and fit it to find Im down on compression or have piston slap!! (not noticeable before)

Is this usual on a diesel engine?

[vwt4]

0.08 mm is the wear limit for the piston to bore clearance.  That, however, will be measured at the skirt.  The piston crown is more narrow and so will move more.  I've never seen, gotten or even wanted the spec for the crown to cylinder spec.

Andrew

Thanks Andrew

To put it another way    
Can anyone else move their piston from side to side slightly by pushing the piston crown....when the piston is at TDC of course.

As you say Libbybapa, I have never noticed or looked for such a thing in the past and it was only because I was filing the piston crown quite speedily at one point that I noticed the movement in the bore.

I'm unsure of how to proceed in the light of this...

Three choices:

1/ Leave it be, stop fussing and buy and fit the new cylinder head and other bits.

2/ Take the engine out and do a full stripdown (bad option)

3/ Buy a 'new' fully reconditioned engine from a known good supplier for a lot of $$$
(pretty bad option)

[vwt4]

Do you have a mic set?  If so, you could measure the bore.  Without a mic set, once the carbon is removed from the top of the cylinder (scotchbrite works wonders) then there should be virtually no ridge.  The new piston to cyl clearance should be .001", the wear limit is .003".  Considering that some of that clearance will be piston wear, then you're really wanting a ridge of less than .001" in order to be within the wear limit.  

Andrew

Thanks for the suggestion Andrew. I have digital bore gauge and a full set of Micrometers and verniers. I just didnt have the tehnical info on what the ABL bore should be from the factory (or the blueprint spec) so I would have been stabbing in the dark a little!

Does anyone know the stock ABL piston size please? (also, does anyone sell oversize ones OTC? out of interest)

I will do as you suggest.....

measure the bore in two places height wise and at all 4 compass points at those two heights to come up with an average reading...
and then measure the 'ridge' and see if the bore is in spec.

I did check the condition of the bore quite carefully and the ridge is very very small and almost non existant which is a plus point I suppose. Nowhere near big enough to catch a finger nail on or be called a 'lip', fingers crossed it will be in spec.... but Im still not sure if that will give me the all clear  !!!

I suppose it will be a good indicator as bores and pistons I would expect to wear together at a similar rate..

[vwt4]

If you're planning on a swap anyway in the not-too-distant future and the bore came in within spec or even slightly out of spec, I'd button it up and run it.

Andrew

Cheers  
Will post back as soon as I've done the measurements with an update on if all is good...or bad!!

[vwt4]

ok, well the good news is all seems to be ok!

I used a bore gauge on the bore and they are all very similar in size. The ridge is pretty much in spec, ive checked clearance with the piston when its deep in the bore and it seems fine and solid.

It must just (hopefully) be when the crown is at the very top position in the bore that a lttle movement can be elicited from the piston top.

Got a new cylinder head coming early next week....so we shall see.

Will post an update shortly