Diesel Engine Valve Stem Seal Replacement - PDF Manual

Due to the lower internal heat, diesel valve guide seals generally last a long time. But as these old 4 and 5 cylinder diesels age I am seeing more and more of them show up with hard and brittle seals. Bad seals will cause increased oil consumption and excess engine smoke (particularly at cold startups). It is hard to determine the life of these seals without removing a valve spring and inspecting one. I recommend replacing the seals at the same time you replace a timing chain (they seem to last and wear at similar mileage). This is also a good time to do the job as you will have to remove many of the same engine parts necessary to complete both jobs.

This job can be completed without removing the cylinder head from the engine. It can also been done without the need of compressed air (required for most gas engines). This means the injectors and the glow plugs can stay in place. Since the clearance between the valve face and the top of the piston (TDC or at Top Dead Center) is very small the springs can be removed and the seals replaced when the valve is sitting loose on the top of the piston. Extreme care must be exercised to make sure the piston is on TDC before the valve spring nuts are removed. You do not want a valve falling down into the cylinder bore.