Brand new to Yanmar and this board. I've owned two 8n's and an old D-6 from the Alcan Highway, but still "new" to this 40 year old technology. This question may be a little pre-mature as I am waiting on my manuals and haven't any resources other than online to troubleshoot the problem myself. Hoping someone has simple answer, or can point me in detail where to look. Bought this 187D that has obviously been neglected. The dealer told me the brakes were dragging, hence the reason it just didn't seem to want to "go" when under power. They also said someone had added gear oil to tranny, which made it sluggish. The yard was flat where I test drove and it did okay, but definitely not as fast or as quick to respond as it should. I confirmed brakes were stuck before I bought and was hoping this was the problem. Simple fix, I thought. Once I trailered it home, I removed brakes completely from both side, and sure enough, rusted solid. Test drove with brakes out hoping that was it. It wasn't. I actually had my doubts as soon as I unloaded it as my property is sloped and the thing rolled freely down the hill until I dropped the bucket. That was my first clue it wasn't the brakes holding it up. So now, my question is, what is it? It doesn't seem like the clutch. I have had slipping clutches before, and they usually seem to just slip the more you use, or the more power you apply. This feels as if the thing slowly builds up the more power you apply and the longer you wait and then limited power finally gets to the wheels, but still isn't right. Will barely climb the slightest slope. On flat ground isn't too bad. Best in 2nd gear, mid-range. Engine starts and runs great. What it reminds me of is an old Ford I had with a leaky automatic tranny that when it got a little low on fluid, the car just didn't want to go until the fluid pressure built up from the little fluid it had. Add fluid and, bam, back in business. I have no idea how the "power shifter" on the 187 works. Is it a fluid type auto tranny? I'm actually a lot confused on the two "trannys" to begin with. The basic one on the floor is pretty straightforward, but the "on the fly" power shift on the steering column, I don't get. I mean, I get what it does, I just don't understand how it does it. Is it an electronic shift like a split axle, or an entirely separate transmission? Can't wait to get my manuals, but any insight before then??
Just won't go
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careyo63
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Gear oil may be the reason or who knows what was added. But my guess Is the pickup screen dirty. Clean Tans. Hyd. is most likely needed. You Can easily clean and replace it. Your Man. will go over it.
HYDRAULIC SCREEN: Yanmar Tractor Parts
HYDRAULIC SCREEN: Yanmar Tractor Parts
clemsonfor
Super Member
Like cary said clean the screen/filter. I bet it's plugged solid and gear oil is like 3x to thick. It runs on tractor transmission fluid, 303 spec, or you can use automatic trans fluid
normde2001
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Does the PTO work as it should under a load? (eliminates clutch slippage). If changing trans oil and cleaning screen do not fix it's probably a bad power shift relief valve spring, accessable externally in transmission.
California
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The shifter on the right side is three ranges. Like a Jeep that you shift to low range for heavy going, to give an example. Think of the three as Road Gear, Second Range where you will do most heavy pulling, and Low Range for creeping with a rototiller.
Then (logically) behind that range transmission is a second transmission, the Powershift. It is near identical to an automotive 3-speed automatic transmission - clutch packs engaged hydraulically, planetary gears, etc. But one big difference: There's no torque converter.
Move the dashboard shifter. After a moment hydraulic pressure builds and engages a clutch pack, and off you go with a direct mechanical connection from the engine to the rear axle. The internal hydraulic clutches soften shifting, but if you come to a stop still in gear you will stall the engine. You can shift without clutching but most of us soften the shock on the transmission by using the clutch pedal in the normal manner.
Another characteristic of Powershift is you can let the clutch out in Neutral and get a heavy rotary mower or rototiller spinning without moving the tractor then shift into gear to start moving.
Thanx for the quick replies and suggestions. Not sure about the PTO under a load yet as I don't have anything to run on it. I'll flush the tranny and clean the screen and give an update in a few days. Thanx again
Sorry for delay in updating, had some things - family - come up. Did the flush of tranny fluid, cleaned the screen (wasn't really that bad, a little slimy, but not clogged), changed the spin on hydraulic filter as well. I was actually disappointed when I saw the screen as I was hoping it was clogged solid and that would be the problem. When I saw it, I knew it wasn't. I even fixed my brakes which were frozen/rusted solid.
Verdict: much better than it was, but still not right. It definitely is sluggish in the power getting to the wheels. Doesn't matter if in 4wd or 2wd, forward or reverse, although I usually leave it in 4wd. I give it throttle and it just sort of sits there for 3-4 seconds, I can feel the power building (not the engine...it runs strong), then finally it begins to go, and then really go. Sort of makes it difficult to fine tune positioning a load of dirt with the scrapper. I have noticed if I am backing up a slight grade, it can take 4-5 seconds or longer to finally get going, and then if I make a gentle turn as I'm backing - which puts an additional load on - it slows slightly and has to build again. All I can figure is, it's got to be something to do with the clutch packs. It isn't the dry clutch slipping, I'm pretty sure. Engine would over speed and giving throttle would make it slip worse. This is the opposite of that. It's usable as is, and I plan to keep using it until this winter when I guess I'll have to open it up and see what is going on. Any one ever experience this and it not be the tranny screen?
Verdict: much better than it was, but still not right. It definitely is sluggish in the power getting to the wheels. Doesn't matter if in 4wd or 2wd, forward or reverse, although I usually leave it in 4wd. I give it throttle and it just sort of sits there for 3-4 seconds, I can feel the power building (not the engine...it runs strong), then finally it begins to go, and then really go. Sort of makes it difficult to fine tune positioning a load of dirt with the scrapper. I have noticed if I am backing up a slight grade, it can take 4-5 seconds or longer to finally get going, and then if I make a gentle turn as I'm backing - which puts an additional load on - it slows slightly and has to build again. All I can figure is, it's got to be something to do with the clutch packs. It isn't the dry clutch slipping, I'm pretty sure. Engine would over speed and giving throttle would make it slip worse. This is the opposite of that. It's usable as is, and I plan to keep using it until this winter when I guess I'll have to open it up and see what is going on. Any one ever experience this and it not be the tranny screen?
California
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Has an amateur been into that transmission before?
There's a feature in the Powershift that provides some braking when the tractor is stopped in neutral. I think this is so the tractor won't roll away with the dash shifter in neutral. Those clutch packs always have some drag and the brake counteracts this. It may select two gears at once or something to provide the braking. The braking was barely noticeable on the YM186D I sold, more noticeable on my present one.
It is most apparent when the engine is cold and the PS is in high range. Letting out the clutch cold loads down the engine noticeably more than just moving the tractor would cause. (This may also be why the manual calls for a five minute warmup).
If this braking feature were out of adjustment, it could cause what you describe.
There's a feature in the Powershift that provides some braking when the tractor is stopped in neutral. I think this is so the tractor won't roll away with the dash shifter in neutral. Those clutch packs always have some drag and the brake counteracts this. It may select two gears at once or something to provide the braking. The braking was barely noticeable on the YM186D I sold, more noticeable on my present one.
It is most apparent when the engine is cold and the PS is in high range. Letting out the clutch cold loads down the engine noticeably more than just moving the tractor would cause. (This may also be why the manual calls for a five minute warmup).
If this braking feature were out of adjustment, it could cause what you describe.
I don't really know the history of the tractor, but did call the owner just before I bought it. He definitely seemed unsure of himself and hesitated when I asked if he had ever added STP or equivalent to the tranny. Made me suspect he had, which I suppose could casue clutch pack problems, but I would suspect symptoms more along the lines of a slipping dry clutch if that was the problem.
I will look into the braking feature you are referring to. This problem doesn't go away when tranny is warm, and I really only use mid or low range, and usually low on power shifter. I probably only have 5 hours on the machine, so still figuring it out, but runs unlike any tractor I have owned or operated before.
normde2001
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See post #4.
Missed the second half of your original reply somehow. I will look into that. No way to test the pto under load yet as have no attachments other than a scrapper.
normde2001
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Can't tell you exactly where it is located, but every Yanmar powershift has it. Usually a plug with large screwdriver slot holding it in. You may need a parts manual unless someone has more info.
rScotty
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First of all, welcome to the forum. The YM187D is an excellent example of a vintage Yanmar.
I'll post some literature for you at the end of this message. Good on you for ordering the manuals. Yanmar printed several versions of workshop manuals. There is a bound version that is sort of a synopsis, and then the large OEM shop manual that is the heavy red plastic ring binder type. I see there is one of those on ebay right now for the YM336D. That's the one to get. Yes, they are expensive....but are argueably the best shop manuals ever printed. Very high quality paper and pictures. Lots of multicolored artist's exploded diagrams and technical discussion of how things work. Very impressive manuals. I used to collect shop manuals and those OEM Yanmars are among the best - right along with the JD technical manuals. Big heavy clunky manuals, but nice.
Regarding the brakes, they were deliberately made to be sealed against water. Yanmar advertised that this was because the tractors were developed in Japan for use half-submerged in rice paddys. Frankly I doubt that because if true the sealing would have been better. Anyway, for the USA use, those sealed brakes were horrid on every model. They always rusted. You will be better off to fix the brakes and then modify the brake covers so that they have lots of ventilation and drainage in the brake covers. Drill half a dozen quarter inch holes for drainage in the bottom of the cover and fabricate a rain shield, Thenput some air intakes in the top of the cover. For air intakes I use soft copper tubing. That way I can tap the cover neatly and then orient the air intake down so it does'nt collect rain water. To repair: Turn out the brake drums on a lathe - there's plenty of meat there which is good because of the way those drums rust pit. Next badly pitted ones that I do I'm going to look into industrial hard plating for the drums. Then have the shoes re-coated with friction material to match the new drum radius. Just about any set of soft brake springs will work if the pivot and pivot bushings aren't worn.
Put JD 303 trans-hydraulic fluid or equivalent in the tranny. Get ALL the heavy gear oil out. System will not work with that oil. This may require several flushings. Flush with your favorite oil/diesel mix or cheap trans-hydraulic fluid from some wholesale tractor shop. That will work fine.
The power shift has it's own internal hydraulic pump for both clutch pack pressure and forced lube pressure. They are 2 different internal circuits. The whole tranny is very, very clever. No, I've never had one apart...wish I had, though. They are nifty and I'd like to see one up close. Problem is that they are nearly bulletproof. You rarely ever hear of a power shift having a problem other than dirty filters. Although yours may require a disassembly and internal cleaning. But check the pressures first. The shop manual will give you complete instructions for testing the pressures of each circuit. In the manual, transmission mechanicals are in section 50, testing procedures in section 250.
Test the power shift pump pressure (1/8" NPT in top or side of regulator case, front plug is control pressure 200 psi, rear is lube oil pressure 6 psi).
From what I've heard over the years, if pressure is low or takes more than a half a second to build then it's either worn pump, restriction in the galley, clogged filter, or stuck relief valves.
Good luck....get all the manuals you can. That's a machine worth the hassle. BTW, there was an optional power steering cylinder available at one time.
rScotty
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normde2001
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Aaron posted a pic in the Hoye forum on 7/10 from the service manual. Apparemtly totally different.
Thank's for the very thorough and thoughtful reply. I appreciate the time you took to help me figure this out. As it is right now, the machine is working, just not correctly. Unfortunately I am in the middle of a project with it and have decided to continue using it as is, since I really don't know what all I am going to find once I start crawling thru the thing. I'm afraid if I open it up, that will be it for a while and I still need it, even if its just for 15 minutes a day.
It really is sort of weird, one day it almost seemed normal after I had used it for about an hour, then yesterday right back to looong hesitation before it finally starts to go. It definitely is some sort of build up of fluid pressure not happening, or being by-passed thru a valve. I probably will at least open the cover tho the relief valve and see if there is anything obvious.
I'll report back what I find but it may be a while before I really look into it. Again, thanx to everyone for pointing me in the right direction.
Forgot to mention rScotty...thank's for the very cool original brochure pictures. Sure wish mine still looked like that!
clemsonfor
Super Member
aren't there springs or something in these valves that can cause issues. I was thinking we saw one here a few years back that needed a spring or a check valve replaced. I don't remember the issues it had but I do not think they matched this tractor, but If I recall there were several of those "valves or springs" in the tractor that could cause issues with the PS
Yeah, the springs and/or the relief valves have been suggested before (post 4), I just have been hesitant to open anything up to start snooping around as I am using the machine in a project right now and hate to ground it if I run into trouble or parts I can't find. It does work, even as is, just at about 20% of what it should be doing. Don't think it is doing any more damage running it easy as apparently the previous owner used it this way for several years. Not sure exactly what I will be looking for when I open the relief valves, but hoping it is something obvious, like broken springs or full of crud. The 187D seems a bit more than just unscrewing an inspection plug to access, and it shows a number of o-rings and such I'm sure I'll have to replace even if all I do is inspect. I also think I'll do another flush of the entire tranny in case some gear oil remains in some of the nooks and crannys. Done it twice already and gets a bit spendy, but it definitely seems better than the first day I ran it.
I'll post an update if I get too impatient and start taking things apart.
clemsonfor
Super Member
im thinking its maybe like ball bearings and springs....I probably am making that up though! ha! I think previously there were springs that were broken and maybe hard to locate? Just a note I learned from Aaron at Hoye. Yanmar uses Japanese spec orings for many things, your metric or SAE wont qite be the right size. They may but also maybe not seal right. I suggest looking at the orings you need for the job and or calling Aaron or emailing him a question and asking what orings you would need for the job your doing and then buying 2 of each of them to have on hand before you start.
