Is it ok to grind 1.6td valves for a valve job? or do they need to be replaced because of a coating on them?
Coating? - word is that VW TD valves are sodium filled, like those in the high revving evo engines and mercedes multivalve heads.
just go ahead and do a lap job on it, and you are good to go for grinding, just make sure 101% that your valve stem height comes out at exact spec without much shrouding on the face side - it matters like night and day for these engines.
The Bentley says: seats and exhaust valves are lap only... not to be ground.
So I hand-lap them all. So far, so good.
I read somewhere that sodium filled exhaust valves have the possiblility of exploding when ground. I dont beleive everything I read but I think something along those lines is why Bently says lap only.
My machine shop recommends replacing them with stainless.
the sodium is in the valve stem, just dont go ahead n cut it in two,
Most of the time a lap job is only that is needed if you get OEM spec valves, and yes stainless are a good idea too.