1086 Acceptable Engine blow by

Bemhoff · Feb 28, 2009

Can any one tell me at what amount of blow is acceptable before it is time to do a rebuild. Ours is hard to start, and has some white smoke once started till it warms up. We did a blow by test on it and at operating temp. it has 2.9 inches water, and at full throttle it has 6.0 inches or water column. Thanks

Allan in NE · Feb 28, 2009

They are supposed to have blowby; it's how they are built and they will have blowby when they are brand spankin' new.

It's the "hard to start" thing that would tell ya when it's time for an engine, as that is the "compression judge".

Allan

Bemhoff · Feb 28, 2009

Alan, thanks for the reply. I agree they will have blow by when new. What i am lookiing for I guess is the amount of blowby when new. As the compression decreases the blowby will increase and you can measure that which is what I did. This should tell you how much compression is being lost past the rings. This is how semi truck engines are gauged as for when they are at the rebuild point. It may be that the AG industry never got this technical or detailed.
Thanks again, Bemhoff

Allan in NE · Feb 28, 2009

Whatever,

But still think yer walking clear around the barn just to get to the other side of the stanchion.

Allan

Bemhoff · Feb 28, 2009

Yep, you are probably correct and it may be a meaningless walk. But if i have this data I can prove my point with out having to spend the money on a rebuild and hope that it fixes the problem. I don't have years of experience like a lot of you guys out there that can walk up and stick their hand under the breather tube and judge if there is excessive blowby or not. Never done that. I just thought i would ask to see if anyone knew then it would be a no brainer. Thanks again. Bemhoff

Anonymous-0 · Feb 28, 2009

IH has specs for blowby. I think it is 4.5 inches of water on these engines when equipped with the pressure balanced piston, wide gap second ring, of course with the correct orfice on measuring tool. I would say that 6 inches is high regardless of which ring or breather system you have. Blowby is of course only one of the reasons to consider overhaul, hard starting, oil consumption etc being others. That being said, the wide gap second ring did a good job of drying up the oil consumption on these engines but it did lead to some other unintended problem. When moving the crankcase breather to the valve cover some of the oil mist that was carried out over the camshaft was lost and there fore more cam failures started to show up so they had to come up with solutions for that, and the top ring life is greatly reduced so another problem to overcome.

Steven f/AZ · Feb 28, 2009

When idling if you can hook a hose to the breather and blow leaves like a shop vac - that's too much blowby...

If idling for 5 minutes and it leaves an oil ring on the ground 10 inches around - that's too much blowby...

Our 1256 would leave an oil spot about the size of a silver dollar in 10 minutes of idling. Started OK, but not great. Still running for the next guy.

Neighbor had a 3688 would leave an oil slick in about 5 minutes, but started just fine so he kept running it.

Hard starting can be caused by a few things:
1. low compression
2. bad injectors
3. low injection pressure (bad pump)
4. incorrect timing of the injector pump
5. poor quality fuel
6. low temps

I can't say I've ever seen our 1086 blow white smoke at start up... Depending on how long and hard you run it before shutting it down, the white smoke could be condensation (water) in the cylinders just burning off. Or it could be a slight coolant leak.

Personally, for determining an overhaul, I would not use blowby. Low oil pressure, high oil consumption, and low compression would be reasons to overhaul. Compression check isn't all that difficult.

Bemhoff · Feb 28, 2009

Pete 23 Thanks for the reply. It is hard to start, doesn't use oil or any water. When we did the test it was with a tool that is used to test Semi truck engines, I was wondering about the orfice size, that will make a big differance. That would probably need to be determined by the size of engine and I don't know what the tool was designed for. It was my friend and I did the test and he rebuilds engines for a local truck shop and said that is the most air i ever seen commong out of the test tool. It has about a 1/2" orfice in it. The number 1 & 4 cylinder exhaust do not heat up as fast as the other 4. It takes them about 2 minutes to get up to 200F and the others are at that in a 15 seconds. We put rebuilt injectors in it about 40 hours ago. Made no differance. It is a 79 and it looks like the original injector pump. Thanks again.

Anonymous-0 · Feb 28, 2009

Just looked up the specs, the orfice size is .406 for that series of engines and .277 on the german diesels. It does show 5.5 inches of water as max. I have checked many over the years and they do vary quite a bit even on engines that are performing well but it is still a very good indicator of wear. The DT 414 started using the pressure balanced pistons and larger breather at engine sn 118713. A lot of engines overhauled over the years have that piston and ring installed, not every one installed the breather kit however. If they didn't there was a lot of oil carry over out of side mounted breather. Food for thought.

Bemhoff · Feb 28, 2009

Pete, thanks for the info. Sorry for the delayed reply. I was at work all day and was popping in and out of the office to check my post. The local IH dealer suggested about the pump. That would be easier done than a engine kit. I can check the orfice size on the blowby tester next week. It builds about 60 psi oil pressure when it is first started, and after working it for a while it drops to 15 at idle. The way I have been starting it when it's real cold out is with ether but I moved the line from the intake to the air cleaner canister, it doesn't seem near as hard on it but you go through a little more ether. Thanks again for your time and efforts. Bemhoff

Owen Aaland · Feb 28, 2009

The either injection system is designed to be used only while the engine is already cranking over. If you have good cranking speed and then give it a shot of either it should fire up without a lot of knocking.

When cranking, before it starts, are you getting smoke out of the exhaust? When you replaced the fuel injectors you most likely increased the opening pressures. If the pump is getting weak you may not be getting enough pressure to open the nozzles at cranking speed. This is not an unusual problem after servicing the injectors.

Bemhoff · Feb 28, 2009

Owen, thanks for the reply. You bring up a good point! We just got this tractor about 3 years ago and really don't recall it being as hard to start then as it is now. We put rebuilt injectors in it about a year after we got it. That may or may not be the answer but it sure is a possibility. That is what I love about this discussion forum, you get everyone looking at the problem from many different angles.
Thanks again, Bemhoff

Bemhoff · Feb 28, 2009

Owen, thanks for the reply. You bring up a good point! We just got this tractor about 3 years ago and really don't recall it being as hard to start then as it is now. We put rebuilt injectors in it about a year after we got it. That may or may not be the answer but it sure is a possibility. That is what I love about this discussion forum, you get everyone looking at the problem from many different angles.
Thanks again, Bemhoff

Bemhoff · Feb 28, 2009

Owen, thanks for the reply. You bring up a good point! We just got this tractor about 3 years ago and really don't recall it being as hard to start then as it is now. We put rebuilt injectors in it about a year after we got it. That may or may not be the answer but it sure is a possibility. That is what I love about this discussion forum, you get everyone looking at the problem from many different angles.
Thanks again, Bemhoff

Anonymous-0 · Mar 1, 2009

HI, got to throw some more in here. There is a common saying among mechanics about a diesel hard start. If it won't start cold it is compression or cranking speed, hard starting when hot, injection pump. I have repaired that 100 series ambac pump when it was so worn out it wouldn't idle below 1000 rpm hot, but it still started cold . Just like oil pressure when cold or hot.Lot harder for cold fuel to leak past plunger than hot fuel. That being said, there are exceptions to everything of course.

Bemhoff · Mar 1, 2009

Thanks Pete, that being said it is sounds like it is time to rebuild it. Hard to start when cold, starts just fine when hot. Will idle at 750 all day when hot and never miss a beat. Thanks again, Bemhoff

1086 Acceptable Engine blow by

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