Anything else to do when changing a head gasket?

[Lobanz]

I'm not saying keep them out of the rain; but if it's 100 degrees and the grass is four feet tall maybe better planning would be better for both tractor life and owner wallet.

Now, I DO keep them out of the rain. They live in a little tractor house all to themselves. Mr Kubota and Mrs "One-eyed-Susan" Yanmar (she has a headlight missing). In their house they have food (a 55 gal drum of diesel) and a toilet (another drum for waste oil from oil changes). A happy elderly Asian couple. May they live happily ever after -- if they survive their open heart surgeries...

 

[rsallen]

Very odd about the Yanmar. No thermostat. Wonder how they keep the temp up when air temps drop, they must have a restriction someplace within the coolant system. Short sighted if you ask me and I'd be tempted to redesign it if it were mine.
Anyhow, sounds like overheating is endemic to that model Kubota. I did a quickie web search, top of the list I guess was bearings of the mowing deck!!??? An answer I found I thought worth considering if everything else is correct was injection timing. The writer felt the factory was retarding the timing for one reason or another but stated that after he'd advance the timing there was none zero problems there after. He didn't say how far or give any specs, but talking to a Kubota mechanic may yield some answer.

 

[Lobanz]

Very odd about the Yanmar. No thermostat. Wonder how they keep the temp up when air temps drop, they must have a restriction someplace within the coolant system. Short sighted if you ask me and I'd be tempted to redesign it if it were mine.

Don't know why. It what it is. From what I read the older Yanmar engines were very good. I'm glad I have a water pump though.

Anyhow, sounds like overheating is endemic to that model Kubota. I did a quickie web search, top of the list I guess was bearings of the mowing deck!!???

Yep. I completely restored by mowing deck. I have a thread on it with pics and stuff HERE.

An answer I found I thought worth considering if everything else is correct was injection timing. The writer felt the factory was retarding the timing for one reason or another but stated that after he'd advance the timing there was none zero problems there after. He didn't say how far or give any specs, but talking to a Kubota mechanic may yield some answer.

Well, that's cool. Do you have a link to that? Would like to read up on it some. Thanks for looking.

 

[Coyote machine]

I'm sure many/most of you guys are much more experienced with this engine stuff than I and may even be professional mechanics. I appreciate everyone's feedback. But I don't think that I "thrash" my equipment or abuse it. Bush hogging high grass on a hot day is what the tractor was designed to do. Not abuse. We do mow some high grass with the mower from time to time, but if it's too high, we use the bushhog on the tractor. I don't take off boiling hot radiator caps and I wouldn't run an engine designed with a thermostat without one. I don't turn wrenches for a living, but I'm not an idiot either.

For the record, no one here is suggesting you're an idiot, or anything close to one. My reference to thrashing your machine is wrong and could have been better stated as work them hard as done previously. Sorry for the misleading statement.
I think we're all here to help figure out what your particular dilemma is in having three machines suffering 'heat stroke' type symptoms.
Rebuilding any engine without a clear link to what cause/effect are is difficult at best. If there were a cracked head, blown out gasket or similar it might lead to clearer causes, but so far nothing jumps out, at least not to me.
Any further progress on the rebuild?

 

[Lobanz]

Any further progress on the rebuild?

Just checked with machine shop. Kubota head showed some stress cracks, but they didn't leak. He said that this is pretty normal. Guides were fine. Seals were fine. Did valve job because 2 valves needed it. They have started on the Yanmar head -- cleaned and ready for pressure check.

I have all the Kubota parts cleaned and new parts on order. Need to clean Yanmar parts and new Yanmar parts should be in transit.

 

[rsallen]

A cast iron head that shows cracks!!!!!!!??????? And it's okay????

What does everyone else think of that?

On to the timing thing, note I'm not advocating this only that it's something I ran across and maybe worth considering. And I wouldn't do it to one of my machines without first doing a lot more research. But here is the thread; Kubota g5200 overheating - Yesterday's Tractors

 

[Lobanz]

An answer I found I thought worth considering if everything else is correct was injection timing. The writer felt the factory was retarding the timing for one reason or another but stated that after he'd advance the timing there was none zero problems there after. He didn't say how far or give any specs, but talking to a Kubota mechanic may yield some answer.

OK I think I found that HERE. He said:

"My B2150 did the same thing when new. After replacing the rad, fan, etc. I decided the problem was somewhere else. I found it. Injection timing!! Advanced the timing and it starts and runs better along with cooler running. If you don't know how ,get a good book or have a diesel shop do it for you. I think they run them like that for emissions or warrantee reasons."​

I checked the service manual and it lists the following as reason why the engine may overheat:

• Engine oil insufficient
• Fan belt or alternator belt broken or tensioned improperly
• Insufficient cooling water
• Radiator net and radiator fin clogged with dust
• Inside of radiator corroded
• Cooling water flow route corroded
• Defective radiator cap
• Defective water hose
• Defective thermostat
• Defective water pump
• Defective mechanical seal
• Overload running
• Defective head gasket
• Incorrect injection timing
• Unsuitable fuel used

NOW, on page 1-87 of the Service Manual, it talks about adjusting the injection timing. I don't know if this has anything to do with it because I don't understand what the flywheel and shims have to do with injection timing, BUT, see the three outputs from the injection pump? These were quite LOOSE when I was disassembling the tractor -- like at least 1/2 a turn loose. Given that they are mounted on the shimmed up part, I wonder if this could be it?

 

[Lobanz]

A cast iron head that shows cracks!!!!!!!??????? And it's okay????

What does everyone else think of that?

He said that it didn't leak in the pressure test. He said that it's pretty normal. Guess he sees it a lot.

 

[rsallen]

Only if they were leaking fuel.

 

[rsallen]

He said that it didn't leak in the pressure test. He said that it's pretty normal. Guess he sees it a lot.

Cast iron does not stress well.