Need advice, folks! I have a 2000 s2k with 50k kms on it. Last fall it gradually started idling rough, lost power and I got a CEL so I took it to my dealer. They found a "burnt valve" and bad valve guide. The head came off, was rebuilt and reassembled, just before the car was parked for the winter. The dealer had no explanation why this might have happened. The car has NEVER been over-revved , neither going up or coming down. This spring I brought it out, ran it for about 1500 kms and it once again started running rough at idle, and Check Engine light came on. It's in the same dealer's shop again, and this time they tell me one #2 cylinder valve has been "hammered" into the head and none of the valves are good enough to leave in the engine, so I'm waiting for a whole new set of new valves to come from Japan (none in North America apparently???). Since the first episode, the car has had a few 200-300 km road trips, and has been babied completely (I doubt if its seen 8000 rpm more than 2 or 3 times, and has never seen 9K). The shop manager feels bad and wants to work with me to cover off the cost (again) but still has absolutely no idea why this has happened again. Has anyone gone through this, or any suggestions?

 

It sounds like the cylinder head wasn't machined or reaseembled properly when it was rebuilt the 1st time.

 

That's my thought too. I wish I could have driven it more right after the first repair last fall, but it started snowing the night I got it home, and it sat for six months before I could get it on the road again. I'm going to try for repair warranty. Oh yea, when I first got it out this spring I called the dealer and told him it was still idling rough. They took a look and replaced all the plugs, and said that should have been done the first time, but wasn't, and that it should be good to go now. I wish....

 

If 1 valve seat was burned, the smart thing to do is have all of the valve seats and valves reground and lapped. Essentially rebuilding the entire cylinder head. Weather or not that was done is anyone's guess. 1500km's traveled since the head was off isn't far at all. Doesn't the shop have a basic 12K 12month parts/labor warranty? most do.

 

They probably have something like that -- we haven't started arm wrestling on the price yet ... I agree with your solution, but the head rebuilder is telling Honda that he wouldn't re-use any of the valves and that they should all be replaced, not just ground / lapped. I could look at 100 valves and not be able to confirm or argue about their condition, so I'm still back to the original problem -- Why did one valve let go and now why are all the valves toast 1500 km later?

 

I'd be guessing at what caused the 1st valve seat to burn. As with the 2nd failure.

The common causes are insufficient valve clearance, causing the valve to not fully seal. Combustion gases then burn the seat. A mechanical overrev, or anything else that would cause a valve to bend, thus not sealing against the seat. Improperly machined valve seat and valve angles.

 

I guess the first step is to find out whether all the valves were ground last fall, or just the problem valve. If all were done and now they're all beyond use, sort of sounds like the wrong angle might have been ground into all cylinders and none were seating properly for this past 1500 km, doesn't it?