Rear Main Seal - YANMAR 155D

[BPoy]

Does anyone know the easiest way to replace the rear main seal on a Yanmar 155D? I have a hydraulic blade on the front and a 5 foot woods brush hog on the back so if I have to separate the tractor it’s going to be very difficult so I’m looking to see if there’s any other alternative? Has anybody ever used one of those oil sealer additives or is that a bad idea?

 

[winston-HT]

Are you confident it is motor oil leaking? If it is leaking badly I would doubt any sealer additive is going to do it. A split is the only way to replace that seal.

 

[BPoy]

It’s black and coming out between the block and the bell housing for the fly-wheel so I assumed it was oil. Definitely not antifreeze and it’s not clear so I didn’t think it was tranny fluid.

If I have to split open the tractor, would you replace anything else in there if it was you, like the clutch even if it’s not slipping? I think this is a 1980 tractor with probably 2000 to 2500 hours on it.

 

[winston-HT]

I will be slow to advise on that. I think a clutch kit is available for around $180. At that price I would sure consider changing it. From your other thread we know you have low compression and starting difficulty. That indicates engine wear. I would sure examine the rear main bearing based on your stating the oil leak is pretty severe. A loose bearing is one cause of oil seals going bad. You might consider checking your oil pressure. Should be between 21 and 35psi. One indicator of worn bearings is Low oil pressure.

 

[Harry in Ky]

Another very simple test is crankshaft endplay. An engine with high hours can be tired in many ways, but consider taking a couple of pry bars and working the crankshaft pulley back and forth to see if there might be any noticeable movement there. In theory the endplay should be nearly non existent checked in this manner, but if you detect any movement at all with just a gentle pry, that's too much and could be a factor in rear seal performance.

 

[bmaverick]

Does anyone know the easiest way to replace the rear main seal on a Yanmar 155D? I have a hydraulic blade on the front and a 5 foot woods brush hog on the back so if I have to separate the tractor it’s going to be very difficult so I’m looking to see if there’s any other alternative? Has anybody ever used one of those oil sealer additives or is that a bad idea?

Removing the rear Woods mower it simple enough off the 3-point. Common task for most of us with multiple rear attachments.

See my reply in the other thread about the vent tube being clogged. IF clogged, then the engine pressure would find the weakest area to leak.

Like @winston-HT said, lower end could be the crank bearings with too much play, but it's not conclusive for compression loses. Piston rings would be the main culprit.

The YM155 has the 2TR13A engine. The good news is, this engine has sleeves. Running the engine hard very often at the top end of rpms would cause wear on the inside walls of the cylinder sleeves. This too can cause a lose of compression. The sleeves begin to take an egg shape pattern, meaning tight tolerance normally at the top and wider at the bottom. I try and not push my machine to the rpm edge to keep engine overhauls to a minimum. So if a PTO mower says 540rpms max, and my field grasses are thinly, I would run about 400 to 480 on the PTO, this helps with longer engine life and less frictional wear.

We have all the repair and parts manuals for this model on the YTOG for free for the YM155 with the 2TR13A engine. The repair manual helps with the compression leak-down test. Then you can determine the next steps.

 

[BPoy]

Thanks guys for all the information and advice. It looks like from what you’re saying, I’m going to have to do a complete engine overhaul with bearings, rings, clutch and anything else I find.
2 things to clear up though —I still don’t think I got a accurate compression test by going through the existing fuel injector with the top inner parts still in the injector. And about the brush hog —it was just that the brush hog is up against the back of my garage and I don’t have enough room to split open the tractor there so I’ll have to take it off and drag the tractor where I have enough room to work on it.
(Also sorry for the delayed reply— I take care of my 94-year-old mother, work full-time, and I only get out to my house on the weekend if that to work on the tractor problem. I appreciate all the help.)

 

[winston-HT]

I would think injector removal would be necessary to get a good compression check. Those injectors are set to pop off at a certain pressure. If you have had them apart you may have screwed that up. Sounds like you are a busy fellow.

 

[bmaverick]

Thanks guys for all the information and advice. It looks like from what you’re saying, I’m going to have to do a complete engine overhaul with bearings, rings, clutch and anything else I find.
2 things to clear up though —I still don’t think I got a accurate compression test by going through the existing fuel injector with the top inner parts still in the injector. And about the brush hog —it was just that the brush hog is up against the back of my garage and I don’t have enough room to split open the tractor there so I’ll have to take it off and drag the tractor where I have enough room to work on it.
(Also sorry for the delayed reply— I take care of my 94-year-old mother, work full-time, and I only get out to my house on the weekend if that to work on the tractor problem. I appreciate all the help.)

As @winston-HT mentioned about removing the injectors to get a good compression test. See this posting on the injector removal tool.

John Deere 750 Yanmar 3 cylinder motor fuel injector stuck

www.tractorforum.com

 

[BPoy]

Thanks, but I can get the injectors out. It’s an adapter for doing a compression test to fit in the same size hole as the injectors is what I can’t find online. Hoye doesn’t have one that fits.

 

[bmaverick]

Thanks, but I can get the injectors out. It’s an adapter for doing a compression test to fit in the same size hole as the injectors is what I can’t find online. Hoye doesn’t have one that fits.

Did you check Harbor Freight? I'm not sure if the hole is metric sized too.

 

[winston-HT]

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