TheSamba.com :: View topic - 1.9 TDI ALH piston to valve clearance after skimming head

Fri Sep 23, 2011 11:48 am

Story: Leaking oil cooler causes coolant loss, car overheats on ascent. Oil cooler fixed but engine is still loosing coolant. Wet around overflow valve constantly and black spots in the reservoir. Head is dismantled, new gasket is ordered. Old head gasket looked terrible, the sealing coating when stuck and torn everywhere.

Now: New gasket is the thickest, 1.71 mm, three holes. I thought the original gasket was one hole (misread it for being one of three holes elongated meaning thinnest). So from what I remember now, the original gasket is two holes. There were some other holes on the right also spaced from the left group of holes, but from what I have understood, the first holes after the last elongated hole on the left is the number of holes that describes the gasket thickness. Alright, I will measure piston protrusion. But it's probably between 1 and 1.1 mm. My gasket can do 1.2 mm and head is skimmed 0.15mm (6 thous). This is combination with the thickest gasket will be enough for piston protrusion of 1.05 mm.

Skimming head when there is no combustion chamber will very little affect the compression ratio, so the only thing to worry about really is valve to piston clearance. I can still see a little step down from head surface to the valve seat, like before the skimming. When the valves are seated they protrude a little above the head surface.

So to sum up, being unlucky the combination of head gasket thickness and skimming of the head, I can be left with 0.05 mm (2 thous) to little clearance according to safe spec set by VW when combining head gasket and piston protrusion, not much but still out of spec. One fix would be to take some material off the piston pockets of the pistons.

Any thoughts?

Sun Sep 25, 2011 8:03 pm

I love my '03 TDI, but this question would be better answered on a tdi forum. Good luck with your project.

Sun Sep 25, 2011 8:34 pm

clearancing valve pockets incorrectly can cause hot spots and alter compression ratio...Id upgrade the valve springs to help eliminate valve float and run it.

Mon Sep 26, 2011 9:14 am

johnnypan wrote: Id upgrade the valve springs to help eliminate valve float and run it.
valve float at 4500 rpm? lol i don't think so. this is a tdi. there is no need to ever rev it past 3500. and redline comes at around 4500. there is nothing to "upgrade" in the valve spring department.

did you use the correct multi-stage torquing procedure for the cylinder head? and torque them in the correct order? tdi's have 17.5:1 compression ratio and turbo boost spikes to 12 psi. gotta make sure that head is on there correctly. also tdi head bolts are one-time-use stretch bolts. they are not reusable....