Farmall 400 Hydraulic problem

Farmguy400

New User
Hello, I'm in need of some help with a Farmall 400 I just recently purchased. The hydraulics didn't work at all when I brought it home. So I put another pump on it. It pumps great for the first 2 minutes when operating my dumptrailer. Then the pump,lines and hydraulic tower get hot and hydraulics are weak and slow. Fluid is full and screen is clean. Anywhere I should start next?? I know it's going to get messy but I just want to get it fixed. Any input would appreciated !! thanks!!
 
Bolted to the side of your control valves, under the hood, is a
pressure relief valve. Carefully unbolt the top of it (4 bolts...under
spring pressure). There is a small plug with an orifice and a screen,
remove it with a large flathead screwdriver. Make sure it is clean,
and the screen is not damaged or collapsed into itself. If it is, it
will cause the system to labor non-stop and things get very hot, very
quick! That little screen plug is pricey!
 
(quoted from post at 04:23:29 07/26/15) Bolted to the side of your control valves, under the hood, is a
pressure relief valve. Carefully unbolt the top of it (4 bolts...under
spring pressure). There is a small plug with an orifice and a screen,
remove it with a large flathead screwdriver. Make sure it is clean,
and the screen is not damaged or collapsed into itself. If it is, it
will cause the system to labor non-stop and things get very hot, very
quick! That little screen plug is pricey!

Thanks for the reply!! I took it apart like you said.(it was a pain) took screen out and it had some dirt in it but very little. The screen was in perfect shape too. I changed the hydraulic fluid while I was at it. Now I can't get the pump to prime. These hydraulic systems on Farmalls are my weakness. Any advice will be a big help. Thanks !!
 
On the top of the reservoir there is a long pipe nipple with a
breather cap on top of it. Unscrew the breather cap and push a rubber
tipped air nozzle on top of the nipple. As you start the tractor, give
the reservoir a shot of compressed air, that should get the pump
primed for you...always worked for me on my 300 and 400 anyway. How
did the screen inside the reservoir look when you changed the fluid?

One other thing to check that has given my problems in the past, on
top of the hydraulic valves, there are wrench flats so you can change
the valves from single to double acting. There are roll pins that act
as travel stops and point to either an S or a D depending on how you
have your valve set. Those roll pins can bend so a valve may be set
somewhere in between S and D even though it looks OK. Would be worth
checking into that as well and making sure they are properly set. Can
have the tractor running while you are turning them to see if the pump
starts or stops laboring to find the correct positioning. Do one at a
time.
 

Will do. Screen wasn't too bad had a small hole in it. So I took res. cap off and put air in it. (Sort of like when I'm priming diesel pumps) and I got a fluid bath !!! Hahahah the gasket at the top of the hydraulic tower and steering shaft hold down casting is blown. So now when I apply air it comes out there. Could that be causing a suction leak on the pump side and making everything hot and lose pressure??
 
Probably not. The small device you checked in the valve is a pilot control. It unloads the system back to the reservoir when there is no demand. If it moves to the demand position when there is no demand it will make noise and the excess pressure will heat the oil. Be careful to check the single or double acting control knobs on all valves for the hitch, or remotes. They have a roll pin that is cptive under a tin strip and the roll pin points to either S for single acting, or D for double acting cylinders/motors. the roll pins must be in one of those two positions. sometimes the tin retainers are missing, sometimes bent, and moving the pin direction past the A or D, or inbetween either xuses the loading as well. Jim
 
(quoted from post at 09:26:03 07/26/15) I would not think that would be causing your problem.

Thanks for all the advice and expertise. After a long hot morning I replaced every seal in each valve and metal to metal mating surface. The o-ring on the suction side of the of the pump where it mates to the hydraulic tower was half gone. After that every O-ring was dryed,cracked and fell apart when I touched it. It seems to work fine now. So mayb I will never know what was the problem was but as long as it's fixed and dosnt leak I'm happy. Thanks again guys. It's awesome to have a forum and knowledgeable people on here !!!
 

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