Hi Guys. I'm new to threads but have been an avid reader. I have a 743B that has a massive leak. I think it is similar to a previous thread by Alan Bechard - 743 Hydro Leak massive cannot locate in 2010. I am interested in what the solution was to that problen as it sounds just like mine. The hydraulic oil was coming out bigtime somewhere behind the fan. The section under the seat seems not to have any obvious leak. Will I need to pull the motor to sort this out? Thanks, Rod
Help Support SkidSteer Forum:
How massive of a leak are you talking?
Its possible its the rear seal on the pump or even a hydrostatic drive hose. They have metal parts that run behind the pump and can possibly rust or wear.
Pulling the motor is very simple, a lot easier than you may think. 4 engine mounts, a few hoses and wires. Lift it up and pull it out. There are 2 lifitng points on the head.
Its possible its the rear seal on the pump or even a hydrostatic drive hose. They have metal parts that run behind the pump and can possibly rust or wear.
Pulling the motor is very simple, a lot easier than you may think. 4 engine mounts, a few hoses and wires. Lift it up and pull it out. There are 2 lifitng points on the head.
Hi Tazza, Thanks for the reply. The leak emptied the reservoir in a matter of a minute or 2. I noticed it because the oil was being sprayed onto the exhaust from the fan housing.I had the cover plates off because there was a small initial leak & I thought it might have been the oil cooler. I have the machine on stands & am on my own with a reasonable mechanical knowledge. Do I lift the engine or slide it back onto a table levelled at the frame height. Cheers, Rod
Hi Tazza, Unfortunately it's not the oil cooler, the leak is from lower down. Is it best to slide the engine back onto a stand to get behind & find the source of the leak. The manual is a bit light on detail on this bit. Thanks again, Rod
As mentioned, removing the engine is pretty easy, re-installing is a little harder as you need to line up the coupling to the pump. I can remove/replace an engine in about 3 hours, that included working on the U-joints. Make sure you check them and grease them before putting it back in.
Hopefully its something simple.
You do have tube lines that run near the base of the blower housing for the lift and aux hydraulics. I wonder if one has rusted through?
I'm sure with the engine out, you will have a bar better idea of what's what, also makes cleaning easier.
if it is not the pump seal then I would bet that one of the steel tubes that crossover under right at the end of the chain case has a big hole rusted in it , you would have to pull the engine to replace the tube , if you can determine which tube it is then you can disconnect the tube on both ends and route a hydraulic hose in it's place , the ends of the tube may have to be cut off to give clearance for the hose if it can't be bent out of the way --------- you really need to figure out whats leaking before pulling the motor cause if it ain't obvious where the leak is then you are really going to be scratching your head --a way to determine whats leaking is to take your best guest and start disconnecting hoses and blow air thru them ----------------
Hi Gents, I pulled the motor today. I found the cause of the leak which I thought was a bit strange. The diecast aluminium cap that covers the spool valve on the lift cylinder section of the hydraulic control valve has broken away at the base. I probaby should have seen this earlier but there was a fair bit of muck in the area & I throught the leak was more from behind the motor. My issue is the spool valve is exposed & there is a thin spring sticking out the side of it. The manual has helped me sort out what part of the valve it is & I think the spring is a detent spring but there is no more detail. Has anyone seen such a problem & is there any detailed repair data on the control valve that provides more info than the manual. I'd appreciate any help. Thanks , Rod
Hi Gents, I foound the leak & think this might be a strange one. The diecast aluminium cap the covers the spool on the lift cylinder section of the hydraulic control valve has broken away from the base. I pulled the motor before I knew what the problem was & found the broken cap sitting behind the fan cowl. There is also a thin spring poking out the side of the spool which I think (from the manual) is the detent spring but should there also be a ball? Has anyone heard of this fault before, I don't know what could cause it. Also is there a more detailed repair manual on the control valve as the manual is a bit light on detail. I'd appreciate any help. Thanks, Rod
lfutrell
Well-known member
- Joined
- May 29, 2011
- Messages
- 144
It won't be a big job now that you have the motor out you can get in there to it, I did mine with the motor still installed, remove the linkage and cap from the front of the spool and the spool will come out from the rear, get a new spool kit to go in this as there is no better time to rebuild it and it don't cost very much. You can get the detent kit as well and it will have all of the springs and balls that you will need. They changed the (cover) you talked about failing to a stamped steel and it comes with different length screws you will need to use them, this (cover) is part of the detent assy, but I don't think it comes with the kit. with your knowledge it should be a piece of cake
Without, a seriel #. I'm going to assume it's a gresen V20 valve. IF you're "wide open " to the back of the valve, and want to keep this machine for awhile. Reseal/work the valve. Good valve, in it's time. Nastey to work on with no access. There R rebuild kits for the lift/ float section.Price out #6659344.
Hopefully the rear of the spool is not damaged causing the leak. With the spool out, replace the quad rings front and back. It would't hurt to replace both tilt and lift spool seals.
The spring you mentioned sounds like the detent spring. There are balls at either end that lock it into the housing to hold it in place. The service manual will show this.
Hi Guys,
Thanks again for your thoughts. It has helped with the confidence.
I have picked up the hydraulic manual 9096838 for the machine (Serial number >15000) & pg 6 fig 2 of the manual is suggesting the valve is a Melroe B6757.
I've attached a photo of the (uncleaned) valve. Any thoughts if it is the Gresen or Melroe valve.
Also, any suggestions for a reasonably priced source of parts within Australia.
Sadly, the dealer is your only option over here.
If you are not worried about the detentto allow the bucket to float, you just need the alloy end cap and not the spring/balls and cover that the balls engage into to lock it in place.
Before you start, drain all the oil you can, its all going to drain out.
That valve used quad rings to seal the spool. Remove the linkages at the front where the rubber boots are, remove the allen bolts front and back. Remove the rubber boot at the front, grab the spring end of the spool and slide it out the back. DO NOT BEND the spool, it should slide straight out. If there are any tube lines in the way, bend them out of the way.
With the spool out, use an O ring pick and pick the quad rings out, they are only a few mm in from the ends. Get new ones from your locak seal shop. The dealer will sell you a kit, but it will cover multiple machines. The quad rings you want are about 50c each. I'd suggest you replace them all (except the rear aux hydraulics). So that is 3 sections. Lube the spools up before installing them back into the valve body.
That is a very brief guide of what to do, hopefully it will give you enough detail to get it done.
7LBSSMALLIE
Well-known member
- Joined
- Feb 2, 2012
- Messages
- 1,294
dealer should stock indivuals as well abot ten bucks do not forget the plastic plug and littlte bitty oring under allen head screw in lift spool or may be sad, to get the plug out heat a small screwdriver push into plastic plug remove and cool should screw out now, the tiny o ring i use a #2 aberdeen bronze hook straightened, before going after o ring put something thru hole in spool so dont you push it in farther.
Hello, think mine has some of the same problem, could some of you say which item numbers(see links) I should replace when I open it up? http://bildr.no/view/dHR2ZTls http://bildr.no/view/R3VpaXRs http://bildr.no/view/ejdIQnlv
http://bildr.no/view/R3VpaXRs
http://bildr.no/view/ejdIQnlv
