L4630 low hydraulic pressure

[TheOldHokie]

Ok, shouldn’t it be 2633 at idle? Kubota gave me this.

Sorry - got the numbers confused so you are actually quite a bit low. I would still attempt adding some shims to see if it bumps the pressure up.

At this point there are two variables in the circuit - the relief valve and the pump. You said you put in a new pump so it should be capable of way more rhan 2600 PSI. That suggests the problem is in the relief valve.

Testing the pump without the relief valve in the circuit is a bit involved. Boosting the relief to see if the nymbers change is a lot simpler.

Dan

 

[ruger1980]

Ok, shouldn’t it be 2633 at idle? Kubota gave me this.

Actually the WSM does not give a spec at idle. The test is meant to be performed at max rpm see below. Like stated remove and inspect the relief poppet and seat and record the shims or lack there of. It appears it will take around 0.101 shim thickness to bring the setting to spec 2700psi. With that much shim needed, I suspect something is damaged, more likely, or you may have an air leak or restriction on the suction side.

 

[Jimmy2009]

Sorry - got the numbers confused so you are actually quite a bit low. I would still attempt adding some shims to see if it bumps the pressure up.

At this point there are two variables in the circuit - the relief valve and the pump. You said you put in a new pump so it should be capable of way more rhan 2600 PSI. That suggests the problem is in the relief valve.

Testing the pump without the relief valve in the circuit is a bit involved. Boosting the relief to see if the nymbers change is a lot simpler.

Dan

I insalled 5 .2 mm shims and brought it up to 2000 at idle and 2600 at full throttle

 

[ruger1980]

I insalled 5 .2 mm shims and brought it up to 2000 at idle and 2600 at full throttle

Interesting considering their calculations show a change of 5 0.2mm shims should make a change of 192psi. Very possible you had a slug of contamination in the relief valve.
Now add a couple more shims and you should be in the middle of spec.

The other thing I would ask, is was the plug holding the relief in tight or is it possible it had backed out a bit?

 

[North Idaho Wolfman]

Interesting considering their calculations show a change of 5 0.2mm shims should make a change of 192psi. Very possible you had a slug of contamination in the relief valve.
Now add a couple more shims and you should be in the middle of spec.

Replace the pressure relief spring!

 

[Jimmy2009]

Replace the pressure relief spring!

Already have

 

[Jimmy2009]

Interesting considering their calculations show a change of 5 0.2mm shims should make a change of 192psi. Very possible you had a slug of contamination in the relief valve.
Now add a couple more shims and you should be in the middle of spec.

The other thing I would ask, is was the plug holding the relief in tight or is it possible it had backed out a bit?

It was tight and i have replaced everything in the relief valve except for the housing

 

[TheOldHokie]

I insalled 5 .2 mm shims and brought it up to 2000 at idle and 2600 at full throttle

So clearly the pump can mske more pressure and the "problem" is in the relief valve.

Dan

 

[TheOldHokie]

Interesting considering their calculations show a change of 5 0.2mm shims should make a change of 192psi. Very possible you had a slug of contamination in the relief valve.
Now add a couple more shims and you should be in the middle of spec.

The other thing I would ask, is was the plug holding the relief in tight or is it possible it had backed out a bit?

Careful. You are off by 2X on the pressure increase. Its 38.4 PSI for every .1mm shim and he added 5 x .2mm = 384 PSI.

Dan

 

[ruger1980]

Careful. You are off by 2X on the pressure increase. Its 38.4 PSI for every .1mm shim and he added 5 x .2mm = 384 PSI.

Dan

Yes my mistake. Sorry that's what you get for working and posting at the same time...LOL.

 

[Jimmy2009]

I should replace part #10

 

[TheOldHokie]

I should replace part #10

Why? You have the pressure up to just under specification. Add another shim.

Dan

 

[Jimmy2009]

Why? You have the pressure up to just under specification. Add another shim.

Dan

Ok well thanks for your help after $3000 between 2 dealers you helped more than they did for less that $100 in parts

 

[TheOldHokie]

Ok well thanks for your help after $3000 between 2 dealers you helped more than they did for less that $100 in parts

You are more than welcome. I had a feeling you were going to be a little unhappy when the problem was actually identified. Dealers have no incentive to help and many customer service reps have minimal diagnostic skills or interest. Its easier to just sell parts.

Dan

 

[Jimmy2009]

You are more than welcome. I had a feeling you were going to be a little unhappy when the problem was actually identified. Dealers have no incentive to help and many customer service reps have minimal diagnostic skills or interest. Its easier to just sell parts.

Dan

Your right one dealer had the tech talk to me because he wasn’t sure what was wrong exactly, and I explained everything to him and he informed me they dont have hydraulic pressure gauges…..