PeachParts Mercedes-Benz Forum - View Single Post - Delivery valve internal leak as a cause of nailing? Yes? No? Maybe???

Diseasel300 · #1 05-18-2017, 06:52 PM

So polishing the faces of the DV's works.

I took the 2 DVs from Cyls 4 and 6 that were causing such loud nailing and gave them a polishing session. Cleaned well and swapped them into 1 and 2. I had no nailing before the swap and have no nailing after the swap. I'm currently running straight pump #2 without any additives, so any nailing would be very obvious.

I'll keep driving it and give a status report after a few days worth of driving and some cold starts. Seems promising though and could explain quite a lot of nailing issues that seem so hard to resolve.

It is important to note that the DVs I used were the last thing replaced to eliminate irritating nailing. Injectors were tested, DV seals were redone 3x, ran diesel purge, adjusted timing, added 2-stroke oil to the fuel, tried cetane booster. Nothing worked. As the engine warmed up, it would start to nail and just get louder until the engine reached temperature at which point it was ridiculous. Swapping in different DV's killed the problem in both cylinders. Now those DV's that I pulled got polished and reinstalled in different cylinders that were NOT nailing and continue to NOT nail afterwards. Far from scientific, but certainly seems to suggest that polishing/lapping the sealing faces helps.