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Ok, your tractors engine is dying and rather than rebuild it you are
considering going with a repower. Well here is a story about doing a repower in
a first generation CASE 646 loader.
Now the cost of doing a repower is not cheap, in fact it will cost you more than
a rebuild but if your original engine is out of production like the Onan is you
will have the advantage of using a newer engine that parts are readily
available. I do love the Onan for nothing like it made today has the serious
grunt it has. But with parts availability getting fewer and farther between and
the fact that fuel costs are out of control (the Onan loves it's fuel) a repower
is a great investment. Now would I do a repower if it had a K or M series
Kohler, no not at this time. The Kohler is well supported from the factory and
the aftermarket. Even aftermarket heavy duty engine blocks are available along
with billet cranks, rods and flywheels.
Anyway, back to the cost of the repower. Typically a kit is around $1700-$1800
at this time which is about the same as a proper Onan rebuild or slightly
cheaper. Just remember with a repower you're getting a new carburetor, fuel pump
and ignition system amongst other things that are not part of a rebuild so
although the initial outlay seems a lot the trouble free aspect of new
components instead of using the old or rebuilt ones eliminate many troubles. But
the hidden costs for the repower will vary. The kits are just that, kits and not
very complete ones at that. There will be misc. pieces and parts needed that add
up quickly. You might not like certain aspects of the kit and have to redesign
and fabricate something more useful. When I bought this tractor I gave $2500.
It was complete for the most part minus the original engine. It came with a new
in box repower kit and a host of other goodies. (details on what wasn't there
will be discussed later), do not get in a hurry to dispose/sell/junk your old
engine to offset the purchase of the kit before it arrives. You'll need to take
plenty measurements, plenty of notes and plenty of pictures (key word here is
"PLENTY") I personally spent an additional $600-$700 just on the repower portion
of my tractor alone for things like bolts, mufflers, set screws, love joy, hoses,
fittings etc....
OK, If I have not scared you at this point I might do so now. This is not a bolt
in, couple of hours swap. Even if I did not have to fabricate or adapt
components
and fix other things while it was apart it is going to take a couple of days at
the minimum to do for a first timer. If you are relatively good at recognizing a
potential problem and visualizing a solution, you will do ok. If you have any
doubt, ask questions! The only stupid question is the one you didn't ask. Make
sure you have a reasonable amount of tools both inch and metric. Some areas on
the repower engine are Inch and some are metric. Don't try and screw the wrong
bolt in the wrong hole, etc. This engine, though it weighs less than the CCK Onan,
is still heavy and awkward to handle. Make sure you have some help lifting it in
and out of the tractor and make sure they are going to be available for a while.
You are probably going to have it in and out several times over the course of
the repower and it will get old. (I did this by myself about 100 times, no
joking) Lifting it over the loader super-structure is no fun and it gets heavier
as you add components.
(The next paragraph was recommended by my Girlfriend)
Now unless you are fussy about keeping your tractor squeaky clean, your going to
get really dirty and messy. Make sure you have plenty of rags, oil dry, hand
cleaner and pans handy. Also I would warn the significant other to not wash your
clothes with the rest of the laundry (It might help if you offer to take your
clothes to the laundry mat and mess up their machines and keep harmony in the
house lol)
Reference books, manuals, etc.
Lets get to work............ Ok, by now you have taken a good asesment of the condition of your tractor. You might want to fix a few sloppy things like the loader control lever (Mine was really sloppy), The travel and lift controls, the foot control, the steering and the front PTO control. During the repower is a great time to address these areas, everything is easy to get to and you even have room to get in there and improve a few things. So lets start the dismantling of the tractor.... The first things to remove would be the mower deck (if you even have one) the battery and battery tray and the lower dash panel. Next drain the hydraulic system by removing the plug on the travel valve. (%insert travel valve pic 1%) make sure you have a big enough drain pan as several gallons of oil will be coming out. Try to get as much oil out as possible by cycling the control valves and even cranking the engine over if possible. Reinstall the plug, empty your drain pan and place it back under the travel valve. remove the plug again and place the plug in a safe location where it won't get lost. There will be more oil coming out as you procede with disassembly and having the pan empty will make it easier to fish out the dropped parts later lol. Next I would remove the hood. If you decide to leave the hood on make sure you devise some way to hold it open, it makes a wonderfull remover of body parts should it decide to close unexpectedly. Next, remove the head light panel and grill from the grill shell and put them in a safe place (bag and tag the screws/bolts and the clip nuts if they are loose) Now you can remove the grill shell and side supports and the exhaust. The side supports are held on with four 3/8" cariage bolts at the upright and four 3/8' carriage bolts at the grill shell. The grill shell is held on at the bottom by 2 bolts. Once these are out of the way you can remove the radiator, oil tank and their supports. Now is a good time to take a picture or two of how the radiator, tank and mounts go together and see if your tank has been rubbing on the supports. Be gentle when removing the hoses, you do not want to damage the nipples on the tank or radiator. Better off to carefully cut them and peel the remains off than to try and twist them off the fittings. Next, go ahead and remove the fan but leave the clutch on the engine. At this time your probabally thourghly oily and dirty so clean up the area, wash your hands and grab your tape measure, a framing square, note pad and camera as it's time to take some references. Place your square on top of the frame and measure the crankshaft centerline height (%insert pics here2%). Write it down in your note pad and take a couple of pictures while your at it (this is where having a friend handy is helpfull) Next, measure the distance of the clutch from a known reference and note it. (%insert pic here3%) Go to the rear of the engine and take some reference measurements and pics of the pump placement (%insert pic here4%) Ok, break is over and it's time to get back to work. The next thing you want to do is remove the engine and pump from the tractor. Follow your service manual for removal. NOTE: If your tractor has steel lines instead of rubber attached to the pump, do not bend them! It will help to loosen the pressure line coming from the pump at the travel valve (if you do not have a rear hydraulic pto) so you can swing the line out of the way. Place the engine and pump assembly in a comfortable place and procede to remove the pump and love-joy couplings. Remove the clutch taking care to not get the spacers and spring washers out of order. The 2 screws that hold the clutch plate to the flywheel can be a real pain to remove without stripping out the heads. An impact driver with a proper fitting bit and a little valve grinding compound on the tip of the bit will usually get them out. If the heads strip anyway my favorite way is to use a nut and my mig welder to burn the nut to the remains of the screw. Beats trying to drill out the screw and the heat will help break it free. Replacement screws and conical lock washers are readilly available. At this time you can put the old Onan engine away since you won't be using anything else from it. You can take this time to clean up the tractor and around it make sure to cap/cover any open hydraulic lines. Clean up your frame and address any issues on the tractor that are easier to get to while the engine and pump are out. I have a couple of recomendations of things to do at this time. This is an excellent time to rebuild the travel, the loader valve and the center lift cylinder. After so many years of exposure to dust, dirt and use if the spool seals are not leaking now they probabally will be when your through so go ahead and do it now. If your pressure line from the pump is rubber and you don't know the age of it get a replacement. either order one from CASE or Ingersoll or take it to the hydraulic shop and have one built. While you have the travel valve apart check the pressure relief springs for correct height and evidence of coil bind and replace them if needed. (side note on the pressure relief) If you have had this tractor long enough to have had to adjust the pressure relief (%insert pic here%) you might have witnessed what I am about to tell you. Lets say you had a low pressure problem and had to adjust the relief setting. I attached a 5000 PSI gauge to the travel valve and my tractor was only getting to 850-900 PSI before hitting the relief. I adjusted the relief screw in 1/2 turn and it went to 1000 PSI. Another full turn took it to 1250 PSI. Another full turn took it to 1500+ PSI. Another full turn took it to 1800 PSI. Another full turn took it to 2300 PSI. A 1/8th turn more took it to 3500+ PSI.....oops too far or is it? (%insert pic here%) The reason for the major jump in pressure on the last 1/8th turn is the spring has worn out. Over time, use and heat a spring looses it's ability to maintain compression/tension. In other words say you took a spring that is 2 inches tall and placed it on a scale. You push down on the spring to compress it until it is 1 and 3/4" tall and the scale says 200 pounds. Now you take that spring and put it to work for a couple of years exposing it to heat and compressing/releasing it hundreds of thousands of times. You take the spring out and maybe it is only a few thousandths of an inch shorter than the original 2 inch. You place the spring on the scale and start compressing it until the scale reads 200 pounds but now your spring is 1 and 1/4 inch tall and the coils are almost touching each other. It is worn out and needs to be replaced. Now back to our pressure relief spring. Even though I might be able to get it set to the correct pressure by just tickling the adjustment at this time it will not open far enough to allow enough flow during relief. Remember, we are supposed to be doing our settings with the oil at 120+ deg F. Oil flows easier when it is hot and not so easy when it is cold. So since we were able to tickle the adjustment to 2400 PSI hot, the next morning we go out and fire up the tractor and put the travel valve under max load before we warm up the hydraulic oil. Can you guess what happens? We are well above 2400 PSI (3700 PSI was achieved in my case) because our relief cannot open far enough. The pump and drive motor survived as it was only a quick test and not at full throttle that morning.
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