Thread: 300tdi valve lash caps disintegrating

I am reluctant to post but noone else has mentioned it , as I have zilch experience with 300Tdi. From other posts it seems possible that if the valve timing is out one tooth that the valves can just kiss the pistons.
Maybe this could cause the lash adjusters to disintegrate.
Regard sPhilip A

Well I have replaced all rockers, rocker shaft and used gen LR lash caps(again) and after 1 week the top of the valves have a grey paste on the top of them. The caps are going again . This is the 3rd set of LR lash caps to go in such a short period of time.
So tonight I pulled No1 lash cap out and it has a concave area worn in it from the rocker pad, it appears they may not be rotating. So my only thought can be, if the top of the valve stem was shaved a bit when he seated the valves in 20thou then maybe the lash caps are catching on the valve collets. Seem like a likely scenario??? because I am lost as to why they keep wearing out like this.
I took rocker cover off when it was still warm and started it to check oil flow, and it sprayed oil all over engine bay, so I think I can safely assume that oil flow is OK.

have you got access to a good digital camera with a macro shoot capability?...

what oil are you running?

whats the shape of the top of the valve stem?

There is no oil supply problem.
Some TDI 300 motors have problems with valve stem caps and some do not.
Timing of the motor is not a cause..
The problem will occur with proper LR parts.
The above are facts that I know and I have been around in the motor trade for a while and have seen the the problem in detail.
I put it down to poor design and heat treatment.
The case hardening fatigues and then flakes off the caps that causes damage to the rocker arm too with excessive tappet clearence which further helps the problem.
The solution in my case was to replace the valve caps and to regularly keep tappets clearences to spec and listen to the motor for tappet noise occasionally when driving.
If racing, or heavy duty rockers and especially valve caps are advailible , fit them as the LR ones will not go the distance.
Note only some motors seem effected.
Keeping the tappets in spec at all times tends to reduce the pounding and any donut effects of the caps.
Unless the cap has completely disappeared and the rocker arm has been working on the valve stem for along time , the valve stem is not affected.
It is interesting to note the construction of the caps which appear to punched from plate steel which has been then hardened and the harden surface breaksaway at the punched radius first on the cap

i had a similar proplem, the top of the valve dosent wear flat, thats why they have caps, driving a around for a while with damaged caps wears the top of the valve stem, then if you get around to replacing the caps they stuff up real quick, so what I did was leave them out, have done over 200,000 with current TDI 200 head with no probs, just keep a eye on valve clearance.

Originally Posted by Blknight.aus

have you got access to a good digital camera with a macro shoot capability?...

what oil are you running?

I've been running Caltex Delo 400 for about 8 years

whats the shape of the top of the valve stem?

The top of the valve stem appears OK (But I'm no expert)as there is no pitting or marking.

Some caps look like the surface is cracking or peeling and they have a large circular flat area where the rocker pads run on them, which is much larger than the tops of the old set I had in it before this trouble started. You could be tempted to say that they are made out of a soft metal but I would've expected more from genuine caps.

I'll try to take some pics of caps and see if I can load them

After checking all the caps and replacing a few, it seemed like there was only a couple of caps that may have contacted the collets, some of the others that had also worn had plenty of clearance from collets, so my theory just got blown out of the water. Shaved down the couple that were running a little close, seemed to file pretty easily for what I would've thought would be hardened steel.

sounds like a combination failure to me...

for starters if you can file it easily, its not hardened enough.

if the internal metal is too soft under the repeated pressure of the vavle opening the inside of the cap wont support the hardening and the hardening cracks then its game on for failure.

if the rocker arm has a flat worn on it its not going to slide over the cap smoothly and will hammer at the cap as the arm slides over the cap

Thanks for help, you may have hit the nail on the head, it would appear that the LR caps may be too soft then and suspect quality, and the reason why they are failing. As I too was surprised at how easy I could file them thinking they would be hardened. Should I look around for competition caps then as CHT is installing or are there other aftermarket ones that will be better quality than genuine. Rocker arms are still good as are only 1 week old and got to them before the caps had hammered through to a dounut.