Can not replacing valve stem seals create bigger problems down the road.

[super55]

My 2001 JD 4310 is starting to get pretty smokey on startup. I am 99% sure it's the valve stem seals because it's a blue smoke. It clears up after about 30 seconds when the engine starts to smooth out. I never have to add oil between the 100 hr changes so I know it's not leaking terribly. It just looks like a rebuilt engine burning off assembly lube every time at startup after a day or two of sitting. The Yanmar engine runs great with no power issues once warmed up. On really cold days you can hear a cylinder sporadically missing for about 20 seconds which I assume is the one that probably has the leaky stem seal.

My question is can a leaky valve stem seal create bigger problems if not addressed other then perhaps some carbon buildup on the valve seats?

 

[RustyA]

My money is on a lazy injector or weak glow plug causing unburnt fuel on cold start?

 

[super55]

My money is on a lazy injector or weak glow plug causing unburnt fuel on cold start?

This has an intake pre-heater so not the glow plugs but the injector idea has me thinking. I thought it might be an injector but the thing runs great once warm. Perhaps the seat is bad in the injector and could be dripping down into the cylinder once shut off. I think when I get some free time I will bench test the injectors. I might have a dribbler.

 

[Gregster613]

super55, Please do and report back the results. I, for one, would like to know how to "bench test" injectors. If you would explain what and how it's done; would be much appreciated. Thanks Greg

 

[super55]

It's going to be a little bit before I can get to it but I will post results when done. A bench injector tester can be found on amazon or ebay and are not terribly expensive. Basically all it is a reservoir for fuel, a pressure gauge and a hand pump. You hook the injector up and keep pumping up the pressure until the injector releases it's spray pattern. Give you an idea of the spray pattern and if the release pressure is in specs. This is by no means a like the fancy shop ones but it does allow you to get an idea of how the injector is performing.

Here's a vid of the tester I have.
watch

 

[Texasmark]

The check for a leaking seal is to let the tractor idle for awhile and then advance to PTO RPM in a 1-2 second sweep of the throttle. If a wad of blue smoke comes out, yes they are leaking. If black smoke comes out expect some especially on a vintage tractor....tractor engines are usually "under square" meaning they don't accelerate very fast so if you tell the governor to give it all you have, it wastes some fuel till the mechanical things get to spinning....no biggie! So on the stem leak so what????? The oil would drop off the valve assembly into the floor of the head and be returned to the crankcase without leaking.....no biggie. Personally, if the tractor ran fine otherwise I wouldn't bother with it especially if a diesel...if gas, you might run a hotter plug to burn off the oil on the tips to prevent fouling.

Not having to add oil between changes is another clue. If it were rings you would. If the smoke is black, it's unburned fuel and that could/might be an injector needing some help! But you said it's blue which is oil!

 

[super55]

Texasmark I agree. Once the tractor is warm and everything starts expanding it goes away. It's only on cold starts and much more noticeable in temps below 30. I figured if I was going to dive into it eventually I'd have the valves lapped and other things since I'd have the head off. But the tractor runs great with no issues so it seems kind of overkill to go digging that deep into the engine to address some smoke at startup.

 

[John0829]

My money is on don't worry about it, drive it like you stole it until something serious comes along. You have power, not adding oil between changes and even if you were to add a quart between changes it is still nothing to be concerned about.