still have blowby

tractorexc · Mar 28, 2001

I posted before and all asked questions about the blowby in my 1520 ford then my computer gave me fits so now i can try again when i bought the tractor in dec. the tractor was great ran well and did not smoke out the breather at all not even a wisper. the small dealer i bought it from changed the oil and filters in the entire tractor the filters used were new holland brand oil and air.the oil he used was deisel 10w30 after about 15 hrs at the most of using the tractor for plowing snow and cleaning ditches one day from out of the blue( no pun intended) i was useing the tractor and smelled hot oil.when i looked at the tractor it was smoking out the breather not just a little you can see it puffing from a good ways at the time it was cold out and the tractor ran fine.With no overheating the temp was normal cab heater was working fine not excessive heat and no noticeable loss of power.just smoke out the breather at idle when reved up it was a little worse not much.2 or 3 days later the tractor lost power big time and wouldnt idle and hard to start called dealer he came and got the tractor and found the injector pump and injectors needed cleaned and serviced he sent them out to be done and when he had them out he took a compression test all 3 cyls have 425lbs and whenthe pump and injectors came back he put them on and now the power is back to normal and the smoke is still there when the engine is at normal temp. tell me if im wrong but with good comp. and no smoke or oil out the stack running fine how could i need rings? it just dont make sense also after the smoke started i changed the oil back to deisel 15w40. the tractor was not run hard mostly at 1500 to 2000 rpms and the tractor only idles to warm the eng at most 10mins when cold about900 rpms any help you can give i thank you for. ijust dont want to spend alot of money i dont need to after just spending a lot to buy the machine. I looked inside the air intake hose from the air cleaner to the engine and all was dry and clean.
THANK YOU ALL

jinman · Mar 29, 2001

When I first read your message, I immediately thought about contaminated fuel. After re-reading it several times, I am beginning to change my hunch. You said the tractor does not smoke out the exhaust (stack) but rather from the breather (intake). If the compression is good, it makes me think of a high pressure diesel fuel leak (fuel under pressure will atomize and look like smoke). Is it possible that the smell is/was diesel instead of oil? I suppose you could have an oil leak which is smoking from the hot engine and the cooling fan is causing smoke/fumes to look like they are coming from the breather. After all, you did say that the breather lines were clean.

Frankly, you have described a very baffling situation. If you look for high pressure leaks, be sure to use a piece of cardboard and run it along your lines to see if fuel appears on it. Don't get your hand close to the lines. High pressure leaks can penetrate your skin.

Maybe someone else has a better idea, and I'm sure you will hear from the experts on this board. There is a lot of knowledge here. Good Luck.

JimI

bekxsteins · Mar 29, 2001

hi first how many hours on engine second, i question the compression test remove the fuel injection pump electric wire so tractor wont start, (left side of engine just to the rear of injection pump) crank the engine over for 10 seconds, take note to engine cranking speed is it constant or up and down, third , hook wire back up start tractor while watching breather tube labor the engine by stalling the trans. see if the smoke increases then replay back

tractorexc · Mar 29, 2001

the tractor has 814hrs on it had 795hrs on it when i got it.the smoke comes out where the breather tube is conected to the valve cover also out where you fill it with oil it is coming from inside the engine and is a hot oil smell not fuel smell the compression was taken with the injectors out andturned over with a deisel comp gauge. ill try your method and let you know thanks again

SteveV · Mar 29, 2001

My two cents worth would be a bad valve or guide. These won't show in a compression test since the valves are closed when the gauge is getting its reading. A quick check would be to pull the valve cover and run the engine and watch the valve springs and push rod galleys for leaking vapors. SteveV

Keoke · Mar 30, 2001

Your best bet is to run a "cyl leak down test". This is done by applying shop air to the cyl at TDC on compression with a "leak down tester " as used by auto mechanics. This gauge/regulator will tell where and if the compression pressure is leaking. You can use the fittings on the diesel compression gauge to plumb this auto tester from from shop air to cyl. This gauge is far more accurate then a compression gauge for checking all cyl leakage. A compression gauge has a one-way check valve in it and only traps the air pressure spike at the top of the compression stoke. It does not measure how well the cyl seals beyond the spike capture, consequently, it will not pick up minor pressure leaks.
As a quickie, you can also plumb shop air into each cyl at exact TDC compression and listen at vent tube for the air leak to get a rough idea of how well each cyl is holding pressure. This is not as good as the leak detector mentioned above but is better then a compression gauge. Note, when doing this test it is best to use an air regulator to hold test air pressure constant. Also, if cyl is not on exact TDC (rod straight up valves closed) the engine will do a half a turn when shop air is applied, so be careful.

good luck,
george

Anonymous Poster · Mar 30, 2001

Steve,

You are absolutely right. It has to be a problem of valve guide seals. When I finally got my brain working, I came to the same conclusion, but you had already properly diagnosed the problem. Also, I'v noticed that if it is the intake valve seals, the engine normally smokes because that port is under vacuum when the valve is open and oil is drawn down into the cylinder. If it is exhaust valve seals, the blowby will increase if you use something metal to restrict the exhaust since the port is under pressure when it is open. This can help identify the problem without having to do any disassembly.

Just an additional thought. Hope this helps.

Jim Inman

skent · Mar 30, 2001

This may be way off, but check for a partially clogged muffler (high back pressure)
Let us know how its going. . . . . .

SteveV · Mar 30, 2001

Rereading the start of the thread, there's a couple of indications of what may have happened. First the tractor was probably stored outside at the dealer before its sale. The question here is: how long? A new owner wouldn't be using the tractor to its limits right away. Second clue is the use of the word stack. Moisture. My bet is that we were having fun with a hung up exhaust valve that eventually loosened, either damaging the guide or maybe even unseating it from the head. SteveV

Keoke · Mar 30, 2001

Hey guy's here is my two cents on the blowbye problem.
In regard to valve seals, diesel engines have almost no cyl vacuum as compared to gas engines. This is because there is no throttle butterfly or carb on a diesel, so almost all the air that wants to get in, get's in. Thus little or no vacuum above piston is generated. Futhermore, any oil entering the cyl from either the intake or exhaust valve guide would end up in the combustion chamber. This oil would burn at cyl firing giving a blue-white smoke out of the exhaust pipe.
From what I know, crankcase pressure (blowbye) comes from only one place, and that is combustion gases slipping by the piston or rings on the power stroke.

take care,
george