Couple of B7100 operation questions

[Elsie71]

I have a B7100HST I bought new in 1981. It always overheated when mowing, but I also had a PTO Trac-Vac that used a 8 hp. motor if you didn't get the PTO model. Probably too much of a load, but we used it for years. We now have it on a JD X495 that has a little more power and handles it better. After cracking the head twice and having it welded once and replaced once, I finally learned that the only way to really solve the problem was to take the radiator completely off and wash it out with a pressure washer at least once a year. You can not get all the gunk out of it while it is on the tractor. We mowed about three acres with this until three years ago, and still mow about half the area with it. It has been a very good strong tractor, now with 3,500 hours and still going strong. I did replace the old MR6000 mower with a newer RC60-B made for a B2400 a few years ago and added power steering, but it has never been overhauled. It does emit oil vapor out of the breather pipe from the valve cover, but it doesn't seem to affect it any.

P.S. Kubota reps I have talked to over the years pretty much refused to admit that there was a problem with the 7100 overheating, but everyone I know that had one had the same problem. I nearly always just add water and then drain it and put anti-freeze back in for winter.

 

[B2400]

My 1994 7100 started running hot about a year after I purchased it used from another party. I found the fan belt wasn't in too good of shape, so when I replaced it I pulled the radiator off. I always cleaned the radiator and chaff screen when finished mowing and thought it was in good shape until I removed radiator. As others have said the core (outside) was filled with dirt and grass and after carefully cleaning, never had trouble again( 4+ years later). It looked good until you tried to see thru the cooling fins and then the problem was easy to see.

 

[chrisjbell]

My B7300 has always tended to run hot. Lack of a water pump is what I blame...

 

[Tig]

B2400 brings up a good point about the fan belt which leads me to another question. Is the fan shroud intact and properly installed? Problems with the shroud (poor fit, cracked, broken, missing) will guaranty poor cooling.

 

[bobm39]

Thanks for all the comments. Wish I had asked some of these questions earlier rather than just put up with the problem.

Up to now I have been using compressed air to clean out grass, dirt, etc form the radiator. I do this at the start or end of mowing. If mowing for a few hours and the grass is real dry and dusty I will usually stop and do it again. When it is hot out and I see boil over after mowing for a couple of hours I stop, blow out the grass & dust, cool down and check coolant level.

I generally run in 4 wheel drive and full throttle. I see from a couple of posts I may be at too much throttle.

When blowing out the dust & grass I have never taken the radiator completly out and cleaned it that way. That I will do.

As mentioned in my first post on this thread, I am looking at trading this tractor for a newer one due to a few issues, one is the overheating. Appreciate the advise as I really don't want to be to quick to part with cash.

 

[Danno1]

.

Some of the guys on the motorcycle board are swearing by a product called Water Wetter. It is supposed to lower the surface tension of the coolant thereby enabling better heat transfer from the block to the coolant and then coolant to radiator. They've used it in bikes and trucks w good results.

.

 

[Egon]

I may be at too much throttle.

Keep running at full throttle but back off on the hydro petal.

 

[charlz]

Or maybe you need to put a water pump on there Check out this thread:

http://www.tractorbynet.com/forums/kubota-owning-operating/106321-b7100-mystery-pump.html


Do HST's work the engine more? I have an old b7100 gear and it gets hot while bush hoggin but has never spit out any coolant. I just spent all day yesterday moving dirt where it pretty much spent the whole time at full throttle and didn't overheat. I run Prestone 50/50 premix in the radiator.

Charles

 

[bobm39]

Well yesturday I took the front end of the B7100 and removed the radiator. When I held it up to the light I was very surprised at the amount of blockage that I had. About 1/3 of the cores were blocked with dirt, grass etc. As long as the radiator was off I took it to a radiator shop for them to give it a go over. I will also be replacing the hoses and fan belt, keep old parts for spares. Another thing I found was a massive buildup of dirt under the lower pully/front PTO. Cleaned all of that up and now waiting to pick-up the radiator and put it back together.

Hopefully this will take care of my overheating. I will also be doing this once a year in the future.

 

[Mike058]

I'm sure you've hit the nail on the head here. I suspect you won't have to add so much water to the radiator after it gets all cleaned out. Wouldn't hurt to have the radiator cap checked too. Low cost, low effort thing to do. I have a pickup that's always used a lot of coolant. I marked a milk container in two spots, one mark is where the jug holds twice a much as the lower mark. I started by filling it with water to the lower mark. I added coolant to the truck as needed. When I ran out of water, I added straight antifreeze to the higher mark. I added that to the truck as needed. I figure, over time, I have close to a 66/33 mix in there. Of course, I could just have added the water to the lower mark and topped it off with antifreeze, but I just like doing it this way.

Well yesturday I took the front end of the B7100 and removed the radiator. When I held it up to the light I was very surprised at the amount of blockage that I had. About 1/3 of the cores were blocked with dirt, grass etc. As long as the radiator was off I took it to a radiator shop for them to give it a go over. I will also be replacing the hoses and fan belt, keep old parts for spares. Another thing I found was a massive buildup of dirt under the lower pully/front PTO. Cleaned all of that up and now waiting to pick-up the radiator and put it back together.

Hopefully this will take care of my overheating. I will also be doing this once a year in the future.