Two seperate questions

Is that output pressure being read directly at pump output or hooked up to the steering unit? Use a gauge with a dump valve going back to the tank to ck only the pump. What is the rpm rating of the pump. The second question,, Can you see the area of the leak through the fill pipe? If so use sloshing compound that is used for motorcycle tanks. If not, one time I fixed a tank by creating a vacuum and sucking an anaerobic sealer up into the hole. Of coarse the tank has to be cleaned first. I cleaned my 12 tank, first by flushing with hot water, then with thinner/acetone.

The gauge is on the pump side of the relief valve about 3' of hose off the pump nothing between the pump and the gauge. (I have a second gauge on the downstream side of the relief valve also, that one doesn't even budge.) The pump is rated at 2000 rpm, 3600 rpm max. rated at 7.81 gpm and 14.06 gpm max. I can see oil cycling back into the reservoir.

The leak is on the opposite end from the fill, I cannot see it at all from inside. Did you do all this with the tank still under the seat? Or did you remove the tank and work on it free from the grader?

Hi, Jumbo.
Could it be that your pressure relief valve is faulty and allowing bypass all the time?

I have used a product called 'Knead-it' with good results on leaks in diesel fuel tanks. Itza 2-part epoxy style compound with the 2 parts in different colours in the one stick - if you can access the leak, clean off all around it, break of a piece of Knead-it that you think will be big enough to cover the leak, knead it until it is uniform in colour all the way through and press over the hole inna sorta rivet-head shape - sets in about an hour but best left overnight. A dry surface is recommended.

BTW, I have both arc and oxy welded diesel fuel tanks on quite a few occasions - not recommended and maybe one day, one of them will 'bite' me. I also once oxy welded a car gasoline tank by running the car exhaust into it via a length of bicycle tube for about 10 minutes prior to welding and during the welding process - again, NOT recommended but,
when you're stuck out beyond Thebackabuggery, you do what you gotta do to get home.

Just my 0.02.

[quote="Deas Plant."]Hi, Jumbo.
Could it be that your pressure relief valve is faulty and allowing bypass all the time?

I have used a product called 'Knead-it' with good results on leaks in diesel fuel tanks. Itza 2-part epoxy style compound with the 2 parts in different colours in the one stick - if you can access the leak, clean off all around it, break of a piece of Knead-it that you think will be big enough to cover the leak, knead it until it is uniform in colour all the way through and press over the hole inna sorta rivet-head shape. A dry surface is recommended.

Just my 0.02.[/quote]

I think the relieve valve is OK, prior to this go around, I had screwed the relief valve down tight cutting off the bypass to see if I could get pressure to the torque generator. I had stalled the pump enough to burn the belt on the drive. That is when I installed the two gauges to see just what I was doing if anything….

I like the idea of Knead-it I just have to find it here in the States.

Just looking at some numbers...
Power control drive shaft runs at engine rpm = 1,800 full load engine rpm
Pulley ratio 4" drive, 2" driven = 2:1 = 3,600 rpm = maximum pump flow rating of 14 gpm
Suction hose not to exceed 4 ft/sec requires 1.0" ID
Return hose not to exceed 10 ft/sec requires 3/4" ID
Supply hose not to exceed 15 ft/sec requires 1/2" ID

Why are you running 14 gpm capacity?
The #12 Grader hydraulic steering utilizes 7.5 gpm @ 1000 psi @ 1800 rpm.

A sketch of your configuration would help.

I would re-check your rotation on the pump as a first point? the simple test is with a flow meter with a load tap. tctractors

Only way you build up pressure is for the torque generator unit to block the flow through it to return and direct it to twist the shaft. Then the ultimate pressure depends on how hard it is to turn the shaft.

If you can block the flow out of the pump and build up pressure, the pump must be good. Either a plumbing problem or a defective torque generator valve/motor unit.

Are you turning the wheel when you check pressure. If the steering valve is in neutral (not trying to turn) the only pressure on the pump is what it takes to push the oil thru a open circuit. Much like a heating or cooling system in a building. When you engage the valve by turning the steering wheel the hyd pressure should go up the amount of pressure it takes to turn or bypass, whichever is lower.