Yanmar 336D Engine rebuild??

murnere · Apr 20, 2020

I have a Yanmar 336D that my father bought new in 1983ish. When he downsized, I took possession and have loved it. It recently began overheating really badly to the point that it would die. If it cooled down it would fire up again until it got hot. I changed the thermostat, but the problem continued.
I took it to a local farmer/auto mechanic/wrecker operator and he checked it over. He believes it needs a rebuild or a new engine. He thinks parts for a Yanmar will be very expensive and he believes a new engine is the better bet. He would even go so far to say that I should look for a new tractor.
I don't think I'm ready for that since this is the first problem I've had with this tractor and it only has 800 hours.
My questions are:
1. Are parts (or even a new engine) going to be more expensive than other utility tractor brands?
2. I would get my parts at Hoye Tractor (I have before), but do Yanmar rebuilds require special tools?
3. Is it better to do a rebuild or to replace an engine with 800 hours?
Thanks for any help and I apologize in advance for my ignorance. I have basic auto mechanic skills so this will be a big jump for me.
Ed

PILOON · Apr 20, 2020

Have U checked the compression?-- that tells a lot.
How much oil does it burn? blue smoke?

Overheating---remove the thermostat and see if it continues.
Is the radiator clogged? fins blocked?** do a radiator flushing perhaps.*
Even a dirty air cleaner can contribute to heating problems.

All to say that at 800 hours, unless totally abused, any problems should be far short of overhaul.

*auto parts will have a flushing solution for cheap. Good start.
** Blow with compressed air to clear fins.

As to the big question, rebuild as the hours are low (unless knocking badly) but with those low hours probably a ring/valve job would make it like new again.

HoyeTractor · Apr 20, 2020

Does the tractor start easily when it cools back down? Do you have a temperature gauge on the tractor or was the temp light coming on? I'm just wondering how hot it was actually getting (and why). Usually when I have seen engines get so hot they stopped running they didn't run well (or at all) after they cooled back down.

murnere · Apr 20, 2020

I have not checked the compression and there was no smoke at all. It literally would be running fine and would just bog down as if I were pulling a plow that hit a hardpan. Even if I was just driving with no implement at all.
I have blown out the radiator and I did a flush last year when I replaced the thermostat.
I do like the starting cheap method.
Thanks

murnere · Apr 20, 2020

HoyeTractor, Yes it does start easily after it cools down. I have a temperature light on the tractor, but not a guage. The light does come on right before dying. When I remove the dipstick for the oil pan, it has smoke, or steam, coming from it. It has oil in it...the smoke made me think it was empty of oil at first, but it was fine. When it starts back up, I can run it for 5-10 minutes before it bogs down again and dies.
Thanks for your answer and I hope to talk with the guy who said it would be too expensive and have him check out your site. I was looking at rebuild parts and I'm hoping he can get some from you all.

HoyeTractor · Apr 20, 2020

I'm hoping you might not need any parts. This might still be something simple/cheap/free to fix.

The cause of the temp light coming on before it dies needs to be found & fixed but bogging down after 5-10 minutes and then restarting after sitting for a while is frequently a fuel problem. Very often a fuel tank vent problem or fuel tank clog. I would start by being sure you have a steady stream of fuel going directly into the injection pump. Remove the hose going into the injection pump and see if you can fill a quart bottle with a steady stream, for example. Is there any extra smoke from the exhaust before it dies?