Kubota B7100 - Did I buy a big problem?

[Saskstallion]

I just picked up a 1980 B7100, and am starting to go through it.
When I bought it, it was known to have oil in the coolant (or something turning it black).
I've noticed quite a bit of smoke coming out of the valve cover vent hose when it's running (no oil coming out, and it's not moisture), and have confirmed that there is in fact slippery "black stuff" in the coolant.
I pulled to rad cap off after I started it, and it isn't bubbling (just kinda "churning").
The tractor puffs whitish smoke when turning over, but this clears up within seconds of it firing up. It is a little hard to crank over, but this may be a weak battery (I haven't checked that out yet).
What I'm wondering is... are all of these items a result of a single problem, or could I be looking at a few different issues?
Any help would be greatly appreciated.
Thanks!

 

[texasranger556]

Sounds like symptoms of a failed head gasket. You could try a leakdown test on the cooling system or a compression test to confirm. The white smoke at startup is probably coolant, if you get too much coolant in a cylinder it can hydrolock the engine and cause more damage, so be careful.

 

[Dave M7040]

You have the basics of an excellent tractor with a long history and great reputation.

Hydro transmission or manual shift. 4 WD?

Go to Kubotabooks.com and download a free workshop manual.
Index of Kubotabooks/Tractor Owners Manuals/

The cooling system is a thermosyphon one so no pump. Water circulates by gravity, hot water rises and cold water falls creating circulation within the engine and block.

The should be a whistle on the end of the rad cap vent hose which starts to whistle if the engine starts to overheat.

The fins on the rad need to be kept free of grass clippings etc.

The white smoke on startup is usually unburned fuel so glow plug operation needs checking.

If you don't know how to check the GP's don't go removing them or connecting them to a 12 volt battery..

Buy a cheap multimeter and test light for around $20

Then come back for more help understanding the GP's test procedures shown in the work shop manual.

The Orange forum has many members with B 7100's so you will get more advice from owners of your model of tractor.

OrangeTractorTalks | Kubota Tractor Tips, Classifieds, Specifications and Discussion

Before suggesting you have serious problems, some basic things need to be done such as a complete cleaning and flushing of the coolant.

Engine oil and filter need to be replaced. Transmission oil and filter.

With new fluids at the full mark, now you can watch for any changes in level of any of the engine oil, transmission oil or coolant.

I have unfortunately seen owners spend a lot of money thinking they had head gasket or cracked cylinder liners only to find out the previous owner, while not paying attention inadvertently dumped oil in the rad or coolant into the oil filler.

Dave M7040

 

[Saskstallion]

So I just did a rad pressure test, and it held pressure very well. Didn't even leak a bit.
I did a resistance check on the glow plugs, and they all showed about .9.
I dumped the coolant, and will do a flush in the morning.
I also checked the battery, and it reads below 12V. It's also only 450 CCA, so I'll buy a better one.
Any ideas on the oil in the coolant, now that the pressure test checks out okay?

 

[DwayneB]

So I just did a rad pressure test, and it held pressure very well. Didn't even leak a bit.
I did a resistance check on the glow plugs, and they all showed about .9.
I dumped the coolant, and will do a flush in the morning.
I also checked the battery, and it reads below 12V. It's also only 450 CCA, so I'll buy a better one.
Any ideas on the oil in the coolant, now that the pressure test checks out okay?

Reccon someone might of dosed it with stop leak?

 

[Dave M7040]

So I just did a rad pressure test, and it held pressure very well. Didn't even leak a bit.
I did a resistance check on the glow plugs, and they all showed about .9.
I dumped the coolant, and will do a flush in the morning.
I also checked the battery, and it reads below 12V. It's also only 450 CCA, so I'll buy a better one.
Any ideas on the oil in the coolant, now that the pressure test checks out okay?

My friend has had a B7100 since new in 1979.

He gave up on the under hood battery a long time ago and made a simple frame to hold a much larger battery in front of the tractor.

You can just see the battery box, a marine one, with Red top and white box in this photo.

He is old like me and never wants to have a non starting car so he replaces his car battery every 4 to 5 years.
The car battery has a lot of life in it and he uses it on this B7100. This rotation has been going on for decades.

He uses a heavy 3 pt snow blower and finds the extra weight out front greatly helps with his steering when the blower is raised.

Look for a rad flushing product which can remove any oil. Removing the rad might be a good idea as with the thermo syphon system, there is minimal circulation.

Flushing the removed rad with very hot water and a detergent would likely break down oil film. You could then also flush the block much more thoroughly.

A rad pressure test is only addressing one possible problem resulting in oil in the rad. The test pressures are much lower than the tractor oil pressure and even further away from the compression pressures in the cylinders. A leak down test with each cylinder might be a good idea especially if you can get an old Glow Plug which fits and which you can turn into a fitting to pressure compressed air into the cylinders,

Dave M7040

 

[rScotty]

So I just did a rad pressure test, and it held pressure very well. Didn't even leak a bit.
I did a resistance check on the glow plugs, and they all showed about .9.
I dumped the coolant, and will do a flush in the morning.
I also checked the battery, and it reads below 12V. It's also only 450 CCA, so I'll buy a better one.
Any ideas on the oil in the coolant, now that the pressure test checks out okay?

That's all good, and I hope that's the end of it and it was just a one time thing. But don't be too surprised if all it means is that the leak is very slow or only in one direction. Both aren't all that unusual when a head gasket is just beginning to leak.If it were mine, I'd do just what you are doing - and you can try one of the "miracles in a can" type of fix a this stage. There's no real downside to trying that. Some will go quite a while that way. But don't be surprised or dismayed if you eventually need to replace the head gasket. It is showing all the early signs. A head gasket job is straightforward, not expensive, and the B7100 is well worth the effort.
rScotty.

 

[Egon]

The rad pressure type test may not show up if there is a gasket or casting leak.

 

[LouNY]

If you fill the radiator full shut the fuel off and have someone else crank the tractor over several times, you can watch for bubbles in the filler neck,
other wise after you get the cooling system cleaned and flushed start the tractor and observe the filler neck if you get bubbles or and oil sheen.
Pull the head get it checked and replace the gasket.

 

[Saskstallion]

Just an update on the above... I put a new battery in, and it starts right up. No more smoking during startup, as there's barely any time spent cranking it over.
I pulled the valve cover off to have a peak under it, and there is greyish sludge present. I think this is evidence of water in the oil - am I right?
If so, it looks like I'll move on to inspecting and replacing the head gasket.
Thoughts on this?

 

[Dave M7040]

Just an update on the above... I put a new battery in, and it starts right up. No more smoking during startup, as there's barely any time spent cranking it over.
I pulled the valve cover off to have a peak under it, and there is greyish sludge present. I think this is evidence of water in the oil - am I right?
If so, it looks like I'll move on to inspecting and replacing the head gasket.
Thoughts on this?

Far more likely the tractor was used for short periods in cooler or cold weather and never got hot enough to evaporate any condensation.

Don't go crazy using strong chemicals to remove the sludge. You are far more likely to have clods come loose and plug the oil pump suction screen.

Use frequent oil changes with the proper oil and over time the sludge will diminish.

If the tractor does not have any oil pressure indicator or the existing one is not working, that is where your $ should go with a new gauge.

Leave head gasket alone for now.

Dave M7040

 

[MatHaas]

Agreed, greyish sludge under valve cover is just moisture mixed in with the oil, common from crankcase ventilation, etc.

Does the tractor run strong? Any difference when it gets up to operating temperature with a load on it?

Usually when a head gasket fails, it will be down a cylinder. The head gasket seals the head to the block, keeping the coolant in the water ports around the cylinder, and the compression in the combustion chamber. If you have coolant in the oil, the failure occurs between the water port and the cylinder, letting coolant in to the combustion chamber, which bypasses the piston rings and gets in to the bottom end and oil. When this happen, you usually see persistent white smoke. There are occasional rare cases when the head lifts just enough under load when warm, that it lets a little coolant in.

It don't think you have enough evidence yet to replace the head gasket.

Easiest way to test for sure to go buy a compression test gauge at autozone or parts store. Pull the glow plugs, disable fuel from getting to the cylinder (not sure how these older tractors are), screw the compression tester in to the glow plug hole, and crank it over ("spark" and fuel have been removed, so it won't fire). Crank it over for 5-10 seconds or until the gauge stops moving. Compare the numbers across each cylinder and what a service manual says. One will be abnormally low if it's the head gasket.

A leak down test will test a head gasket, but it's used more for testing intake and exhaust valve leakage, which i don't think is necessary in your case.

It'd be nice peace of mind that the compression is good across all cylinders before you go and do a full coolant flush/swap and it is still getting contaminated.

Best of luck.
-Haas

 

[thepumpguysc]

Just REMEMBER.. a GAS compression gauge is DIFFERENT than a diesel compr. gauge..
A gas compr. gauge only goes up to 150-200 psi or so.. a DIESEL gauge goes to 5-700 or better..
Typically a diesel will run OVER 300 psi cylinder pressure.. so a gasoline compr. gauge will NOT WORK..
& I've heard of cases where they[gas] have been used & actually blown-up.!!!!
You can RENT a DIESEL gauge from those parts stores.. getting the proper glow plug adaptor is KEY.. take a GP WITH YOU..

 

[MatHaas]

Just REMEMBER.. a GAS compression gauge is DIFFERENT than a diesel compr. gauge..
A gas compr. gauge only goes up to 150-200 psi or so.. a DIESEL gauge goes to 5-700 or better..
Typically a diesel will run OVER 300 psi cylinder pressure.. so a gasoline compr. gauge will NOT WORK..
& I've heard of cases where they[gas] have been used & actually blown-up.!!!!
You can RENT a DIESEL gauge from those parts stores.. getting the proper glow plug adaptor is KEY.. take a GP WITH YOU..

YES, Excellent point! Sorry I left that out, it has to be for a diesel, as mentioned above.