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M6950 Mechanical Question Problem

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KubotaNETX
Join Date: Sep 2009
Posts: 2 Texas
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2009-09-24          165902


Howdy! I'm new to this forum, although I have owned Kubota products since 2005. Recently, I did some tractor trading and purchased a 1994 Kubota M6950 2WD Cab tractor with an 1850A Loader and 3300 hours for $17000 along with another used John Deere machine. The Kubota tractor seems to have been well maintained other than the paint has faded due to outside storage for 15 years. I have owned it for about 2 months now.

My question??
About 3 weeks ago we hooked it up to our feed grinder to grind hog feed. We hadn't used it for any heavy work since purchasing it by this point (mainly because I was in between hay cuttings), and this was going to be its first real job. It started to get hot within 8 minutes of being cranked. My wife noticed first, that a large amount of liquid was running out of the breather tube (AKA: blow-by tube)on the left side of the 4-cylinder motor. I immediately investigated, trying to figure out where it could be coming from. We determined that it had to be coolant because no volume of engine oil had been lost, and the radiator was starting to overflow due to heat along with the engine overheating. We immediately shut her down, so that the engine could cool and I could check the radiator. Once checked it was determined that about a 1/2 to 3/4 of a gallon of coolant had dissappeared. I don't think any oil was mixed in with the coolant, as besides for the missing amount it looked normal. Again, no engine oil was lost or abnormal, and no hydraulic oil either. I checked the hydraulic oil, because I'm not for sure how this model is set up, but I didn't really think hydraulic oil could get into the engine block. I decided to start with diagnosing and treating the problem, so I order the cheapest part that I thought might be the problem, a new thermostat. I removed the old one, while waiting for a new one, and turned the engine over to see if the water was flowing. It did push some coolant through, and because coolant was moving somewhere when we found the problem, I'm assuming that the water pump is working.

Is this right? One fellow told me that if the tractor had sat for a little while (It set for about two months on the dealers lot with minimal usage, before I bought it.), the thermostat may have froze up as I supposed, restricting coolant flow through the engine, while allowing pressure to build up causing coolant blow-by. What do y'all think?

In discussing this issue with some other mechanically minded folks we've come up with the following opinions, which as I've mentioned I've already started trying with the thermostat.

A) Thermostat is stuck closed allowing pressure to build creating coolant blow-by. Solution- replace thermostat.

B) Waterpump is not working. Just about ruled this one out due to the discussion of diagnostics above.

C) Head gasket or another gasket is blown or cracked head. Solution- This is hard for me to believe due to this being a solid Kubota tractor with only 3300 hours on it. Kubotas are well known for quality and longevity. However, if this is the case it will require an engine rebuild.

I'm going to install the new thermostat as soon as I get a chance and see if this fixes the problem. If not, we'll go on down the list.
Do y'all have any suggestions or advice?

If it comes to it, how hard is this engine to rebuild? What would be approximate costs?

If I did rebuild, hopefully I could get 8 to 10 more years out of this machine to justify expense, right?

I can get a complete rebuild kit for less than $400, but I don't know how hard this job would be or what it would cost for me to hire it done. Any ideas?

Hiring it done would depend on the amount of time and difficulty that it would be for me. I'm used to working on equipment, but I've never rebuilt an engine. I probably should order a service manual before starting this venture, correct?

Any and all advice would be greatly appreciated.

Thanks in advance,
Nathan




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M6950 Mechanical Question Problem

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auerbach
Join Date: Sep 2007
Posts: 2168 West of Toronto
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2009-09-24          165910


I'm sure you checked the obvious (fan, belt, air passages, coolant mixture). Get a new rad cap for the same reason you got a new stat. Then I'd run cooling system cleaner through, maybe twice. Or, given the age, you could take the rad to a shop for testing, and while it's off, power-flush the block and get a new fan belt.

Doesn't sound like a leaking HG, but if it is, you just replace it, preferably with new head bolts. Don't know what a HG or a set of bolts cost ($50/$100?). Maybe a day's work if it's your first one. Hardly a rebuild.
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M6950 Mechanical Question Problem

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kthompson
Join Date: Oct 2005
Posts: 5275 South Carolina
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2009-09-24          165913


It is hard to believe an engine could get so hot in 8 minutes.

Adding to what has been suggested two other simple items, air filter and/or radiator needs cleaning out (the fins not the inside). I have a M6800 Kubota and have seen each of those two cause mine to run hot when they really needed cleaning. The best way to me to clean the radiator is one Murf here suggested and that is a leaf blower. Taken the air filter (mine has two) and just give it a good shake, if dirty you will know it real easy.

I have been told the easiest way to test for clogged radiator is to use one of hand held remote point and check thermometer. You will be checking for cool spots in the radiator which means that area is clogged so coolant is not there.
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Art White
Join Date: Jan 2000
Posts: 6898 Waterville New York
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2009-09-25          165916



I don't feel you have enough ability to tackle an engine rebuild and if the block or head is cracked then it is not a simple rebuild and more parts would need to be changed out.
There are other things that have been suggested that would have been the first to look at before removing the thermostat housing. ....


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