B7100 White Smoke

[TxRzrBk]

I have posted a few times on this tractor that I recently aquired. B7100, D750 motor, hours unknown (there isn't a meter or a place for one). Tractor was originally sold in 1979 according to Kubota so it has seen some significant use and the maintenance history is unknown. When I got it the former owner was having fits getting it started. I fixed several electrical issues which I believe were preventing the glow plugs from fully heating and also make the engine crank slowly. I have also fixed a leaking center injector and adjusted the valve clearance to factory spec.

I have got it to where it starts just fine, idles very smooth (even with throttle at lowest setting) and seems to make decent power although I have not put any significant load on it yet.

The bad part - I am getting a steady light stream of white smoke from the valve cover vent tube (blow by) and getting a decent amount of white smoke from the exhaust at wide open throttle. I dont have a compression tester that will handle this engine but plan on a compression test at some point. I am thinking it probably has worn rings but wonder if there is anything else I can check that would be causing the problems I described.

 

[North Idaho Wolfman]

Yes smoke out of the valve cover is a bad thing, worn rings and valve stems or guides can both cause that problem, being that it's also smoking out of the exhaust at high RPM's would point more to the valve stems or guides.
Pull the valve cover and start it up if it's smoking and puffing out the valve stems then that's it, if it's smoking out of the bottom of the oil return holes then it's rings.

 

[Apogee]

You're going to have to run it for a while to figure this one out.

First, make sure you the fuel tank has been cleaned out, you have fresh fuel in it and the fuel filter has been changed and the system bled.

Next, I'd run the snot out of it because if it's sat for any length of time, it could be that the rings need to seat back in. Diesels like to work! If it's been idled most of it's life, you might be dealing with something as simple as it just needing to be worked hard.

The white smoke *could* be from a blown head gasket. These engines will overheat if the radiator becomes clogged with weeds and such, so you *might* be dealing with that. You will need to run it to figure out if it's drinking water or not.

Otherwise, you could also be dealing with a leaking injector. That too could cause white smoke but it wouldn't affect the blow-by issue. If the engine has lots of hours on it, you might consider just pulling all of the injectors and having them rebuilt. At the very least take them to an injector shop and have them checked for spray pattern and pop pressure. They need to be right or it will either smoke or not make all of the power it should.

Finally, Harbor Freight sells a cheap diesel compression test set. You might consider picking one up. It comes with an adapter that will fit the Kubota glow plug openings.

Congrats on the new toy and nice job thus far!

Good luck and keep us posted!

Happy Holidays,

Steve

 

[MagKarl]

Can you tell what the smoke smells like? Fuel, oil, or coolant?

 

[TxRzrBk]

I know blow by isn't good but is it bad enough that I shouldn't plan on getting any more hours out of this motor? A friend of mine has an old 70's Deere diesel that gets about 100 hours of use per year, it has been smoking like that for 10+ years and still gets the job done.

Really good point, I need to get some fresh fuel in it before I get too much further. What is the typical cost of injector testing and calibration?

Great tip on Harbor Freight, they have 20% coupons available until the 23rd making the cost of the kit less than $30 which is unbeatable. Based on past experience I doubt any Harbor Freight tool is going to provide a great deal of precision but it will probably get in the ballpark. Has anyone used this particular kit on a D750? The clearance around the glow plugs is pretty tight, particularly on the middle one. Finally, is there anything special to be aware of on the compression test or is it as simple as squirting a little oil in and turning it over for a few seconds?

 

[North Idaho Wolfman]

The blow-by tells me it's probably not injector, water, or oil getting into the cylinder, but just warn rings or valve guides.
Doing a compression test will confirm it's bad rings or bad valve guides, Pulling the valve cover will tell you if it's rings or valve guides.
The white smoke your seeing is poorly burnt diesel fuel, it poorly burnt because it's lacking the compression to fully heat the piston and firing ability.

Yes you can run it forever with blow-by it's just that your losing a lot of power and if it gets worse it will be really hard to start.

 

[TxRzrBk]

I am looking around for a shop to check my injectors. Not sure if this is normal but it wants almost zero throttle applied at startup, thinking this could be from a leaking injector. Going to see if I can run to Harbor Freight today and grab the compression tester, I will update with test results.

 

[TxRzrBk]

I got the harbor freight kit but I cant seem to make it work via the glow plug inlets (too long). The injector adapter looks like it could work but the tester manual does not show compatibility with Kubota. Can someone help me out here with the harbor freight compression tester on a D750?

 

[hodge]

I don't have experience with the compression tester, but I do know that the Harbor Freight tester has been covered here before- someone with experience will chime in sooner or later.

 

[TxRzrBk]

Since I am not getting any replies I will provide a little more context. There is a Kubota glow plug adapter in the Harbor Freight compression testing kit. The problem I am having on the B7100/D750 is that the intake manifold is in the way of being able to hook the hose on the adapter once it is threaded into the head. I had not seen any mention of removing the intake manifold for a compression test so I am assuming I must be missing something.

 

[Tx Jim]

Removing intake man should be fine for completing compression test. Where are you located in TX?

 

[TxRzrBk]

Removing intake man should be fine for completing compression test.

Right, I know it could be done but I don't have a replacement gasket and I had not heard this was necessary, trying to make this as easy as possible.

Where are you located in TX?

North of the DFW area

 

[lsmurphy]

Do you own a camera?

That would help.........a lot.

 

[TxRzrBk]

Here you go

 

[lsmurphy]

Yeah, I see where that would be a problem.

Gasket material is about $5 or so.......make your own.

 

[olthumpa]

Gasket material is about $5 or so.......make your own.

Always keep some gasket material on hand never know when you will need it. Also keep some RTV Silicone Gasket.

 

[TxRzrBk]

I started this thread a while back but had not gotten around to getting a compression test done...until today. To my surprise the compression numbers look fine, all three cylinders had minimum readings of 350 and maximum of 400 on several tests. I am still getting excessive blow by from the valve cover vent.

I would think this pretty well narrows it down to the valves. If so I am assuming I would need to pull the head and do a valve job and replace the valve guide seals?

One other theory I had, not sure how likely this is. I noticed after I purchased the tractor that the oil was overfilled. One of the first things I did was change the oil and get the level correct, this didn't seem to affect the blow by in any significant way, might have decreased it some but didn't eliminate it. I checked my oil after running it for a few hours and it was again slightly above the mark. Could it be possible that I have a leaking injector that is watering down the oil?

Any other theories before I go to the trouble of pulling the head?

 

[Apogee]

I deleted my previous response because I'm still thinking on this one...

I'm guessing the blow-by issue is rings. You can likely run this tractor as it is for a very long time if it starts easily and the blow-by isn't bad enough to puke oil along with the air when its running.

Wolfman and I both gave you good advice at the beginning. He is 100% on target regarding pulling the valve cover and starting it up to see what you find. Yeah, it'll spew some oil while running, but you'll immediately be able to see if the problem is valve guides or rings. That will get you to the bottom of the blow-by issue without spending any money.

Valve guide seals won't make any difference on the blow-by issue. The issue is worn guides if that's the problem. The seals *could* affect the smoke issue if the guides are worn and the seals are shot so it's sucking oil on the intake stroke, but not the blow-by issue.

Regarding the oil being overfilled, if the oil level is increasing then the shaft seal on the injection pump needs to be replaced. What happens is the pump leaks fuel into the crankcase and you see it as the oil level increasing. You will need to run it a bit to figure out if it's really increasing. Also, if the oil is significantly thinner than it's supposed to be, that *could* help explain the smoke as it could more easily get past the rings and seals.

I still stand by also getting the injectors checked/rebuilt if it's got a lot of hours on it.

Finally, have you run it for any length of time to know for sure if it's using any coolant or not? I'm sure Wolfman is right in that the smoke is unburnt diesel, but if its white smoke not blue, it could be water being burnt.

Hope this helps!

Steve

 

[North Idaho Wolfman]

Leaking injector pump or lift pump would be possible to leak diesel into the oil to thin it and yes cause problems.
Set the oil level and run it, if it's rising then you have a problem.

 

[TxRzrBk]

Thanks, I'll try to dig up some info on the injector pump seals, if you have anything send it my way.

I am a little confused on the rings though. If the rings were excessivly worn to the point that it was causing the blow by wouldn't that show up in my compression test?

I just changed the coolant and it was full and free of oil when drained.
Aside from the blow by and dripping oil from the vent tube, after getting the glow plugs working properly I have it to where it starts easy and runs fine.