Help with my JD755 crawler loader

[xXThunderGodXx]

we have a jd755 crawler loader that wont crank. we were running it one day and the next day it wouldn't crank. the starter engaged and bumped the motor a tiny bit (just enough to make the fan jump) so we yanked the starter and had it rebuilt. got it back in and same story. So we dropped it for a while and asked around and a fellow we know said it may be the hydrostatic system may be causing the motor to be stuck. the only reason im buying this is one-I'm trying to be optimistic and two- if the motor was seized i wouldn't think it would even budge let alone make the fan belts move. and it doesnt help that im not too familiar with hydrostatic drive systems. i spent most of yesterday crawling all over and under the machine poking and prodding and found a rod sticking out from between the splitter box and the bellhousing and i am assuming this is disengaging the splitter from the flywheel but couldn't get it to budge. we acquired this machine for a fairly low price because the fellow who owned it before bought it for a single job and had no other use for it. I am not even sure what year it is and have the serial number 2592521. Aside from the tracks getting close to the point of just scrapping them the only problems we could find were just a multitude of small leaks in the hydro systems (both drive and boom) the motor is pretty tight with only minor leaks and some minor leaking on two of the injector lines at the pump. we were gonna fix all these problems once we figured out what the problem is with trying to get it started. it was used in our quarry for clearing castoff and rubble for maybe 20 hours making sure all fluid levels were maintained throughout. we wanted to see if the thing had the guts for the job before we put the work into buttoning up the system.
what im really getting at is, is there someway to disengage the drive system aside from unbolting the two prop shafts from the splitter box so we can see if it is a motor or drive problem im not afraid of rebuilding the motor if it is the problem but i find the possibility of having to work on the hydro-drive daunting especially if it requires work to either of the drive units.ANY info would be helpful, Thanks.

 

[Groo]

got a big enough something to pull start it?

does sound like its stuck "in gear"

 

[xXThunderGodXx]

i wouldnt think that would work with a hydrostatic drive system would it?

 

[Bob Rooks]

Those are also the symptoms of a dead battery - and a generator or alternator that is not charging...

 

[beenthere]

Yup. Sounds like a dead battery or bad cable connections to me.
Hope you have covered that first (before ripping off the starter).

Do you have a tech manual?

 

[xXThunderGodXx]

nope and nope, been through all that. new batts new 0ga. lines clean grounds full amperage at the starter. we had disengaged the clutch and tried and no go. figured out that either the motor is seized or its water/fuel in one of the cylinders. gonna yank the injectors and try and bump her over if no go gonna drop the pan and have a look.

 

[Bob Rooks]

Did you check for a dead-headed hydraulic pump? But it sounds like you're on the right track...

 

[tlbuser]

try the guys at jdcrawlers.com for some suggestions. Pretty helpful bunch.

 

[beenthere]

There are two threads going with this problem.

http://www.tractorbynet.com/forums/showthread.php?p=2033252#post2033252

 

[Eagleview]

Sounds more like water has seeped into a cylinder and created a hydraulic lock . The fan may have moved a little as the water was compressed . Do not force it until you find out if it is this as the conrod will be bent .

First thing to do is to pull out the injectors or glow plugs if it has them and see if it will wind over . Stand well clear as water will jet at huge pressure .

On Edit , if it is water , you must find out if it is rain water that may have got in via an uncapped exhaust or if it is coolant before you pull the head off .

 

[jenkinsph]

thundergod,
On this post as well as your post in the JD forum you need to determine the cranking voltage at the starter terminal while cranking. This is an important step I wouldn't overlook. I wouldn't assume anything.

Other than the cranking voltage I see that the same possibilities are being drawn, hydrolock with water from rain or coolant and the suggestion to pull the injectors.

O guage wire is not very big either for this purpose 3/0 would be more appropriate.

 

[xXThunderGodXx]

the are about as big around as my pinkie, and its cranking at 24 volts at almost full amperage (combined on both batts about 1800) if i have time today i will be yanking the injectors and giving that a shot. worse case scenario my father is going to call in a guy who is quite familiar. im mostly doing this to see if i can troubleshoot it. trial and error. nothing destructive. what I really want is the Cat 953 we had about a month back. That was leased by one of the companies we have in there cutting stone. was a sweet piece but a bit rich for my budget. I was flipping huge slabs out of the ground with that beast while we rebuilt the road.

 

[Eagleview]

Did you get a chance to pull the injectors/glow plugs and wind it over ?

 

[xXThunderGodXx]

no not yet:mur: been busy with maintenance on equipment that actually runs at the moment. I may have time at some point today. got my extra large can of bee spray. (bee allergies) they seem to like the boom pockets right next to the engine compartment. one question, if I have to rebuild this pig how epic is the job? I'm positive that rebuilding it is well worth it. or unless I can find a running engine for a good price. I am just having a hard time forcing myself to think of having to rebuild the motor because before we had problems with it we didnt have a chance to give it a full shakedown and there may be worse problems lurking besides this. worse case scenario it gets parted out if there are worse problems (i.e hydro drive).

 

[Eagleview]

It will be no more difficult than any large engine , as long as you can get the sump off .

The things you may find if it has in fact got water in a cylinder and the water did not get in the exhaust are :- leaking pre combustion chamber seals , leaking injector tubes , leaking head gasket , leaking cylinder liner "O" rings , holes in cylinder liners caused by electrolysis , cracked head etc .

That is why it is imperative to eliminate the possibility that rain water may have entered via the exhaust . If you cannot , it can be a very difficult task to find the problem once pulled down as you disturb gaskets and other things which makes visual inspection difficult . You then need to strip the engine completely and do crack testing etc to find the point of the water ingress .

First , check to see if the exhaust is capped with a tin etc for future reference , check the oil for water . Pull the injectors/glow plugs and see if it will wind over . If it does and water is evident , did it get in the exhaust or is the radiator level low and that's more likely the source ? Once the water is out , squirt some WD40 down the holes and reinstall the injectors . Fill the radiator to the top and start the machine , watch for bubbles that keep appearing in the header tank , this will give you an idea as to whether it has a blown head gasket/cracked head etc . If it has got bubbles that do keep appearing you have then got to remove the head . (That is if you don't want to try some chemiweld etc to get a bit more life out of it ) . If the head is not cracked and the gaskets and "O" rings are OK , the liners are the next to come out .

 

[xXThunderGodXx]

Didn't have time yesterday. jumped a track on our old cat and spent a couple hours getting that back on, and you know it never happens someplace easy. but i wouldn't be surprised if it did indeed come from the exhaust. no muffler straight stack with a 45 on the end and me bitching about no one capping the stack almost every day.