4230 powershift loses hydraulics

[jonesrj]

Our 4230 powershift has been having hydraulic problems. When the tractor gets hot it loses hydraulics at any engine speed lower than about 1500. Lift, SCV, steering all gone. Revving the engine restores function somewhat. Transmission pulls fine even when it is acting up, so I think the trans pump is ok.

We changed oil, filters, and cleaned screen. Nothing major found, just some fine particles in the filter. And these were pretty new filters anyway with less than 100 hrs on it since changing filters.

It has been getting gradually worse. My sister and brother-in-law had been using the tractor, then I drove it for the first time yesterday with it acting up. I drove it home and parked it because I didn't want to overheat any clutch packs. The lines were scorching hot. We use JD oil exclusively.

I'm going to check the standby pressure. What other pressures do I need to check? Reading the manual it seems like stroke control or outlet valve may be sticking or spring broke. I appreciate any help diagnosing this problem.

Rory

 

[tim s]

The trans clutch pressure should be at or near 165 psi. if the stroke valve was sticking you should have steering,,and "if" something was leaking inside to heat the oil it would make the pressure fade.. There is a possibility that the pump coupling shaft has striped out..and the possibility that the front pump has issues..just a few things to think about,,check it over and let us know what you come up with..

 

[Bob]

Any time the oil is getting HOT in these closed-center systems, likely you have a "high pressure leak to sump", apparently a MASSIVE one in this case.

With the tractor cooled down, start it and feel each hydraulic component for heating... the one that warms up first is the likely culprit, listen for flow noises/hissing, as well.

Check steering valve, brake valve, all SVC's, and rockshaft control valve, if it has a 3-pt.

 

[jonesrj]

Thank you both for the responses. I think the internal leak is probably on the right track. My dad bought this tractor about 4 or 5 years ago and we always noticed a hydraulic buzz or hum like an internal leak, but we never noticed it getting excessively hot then and couldnt tell where it was coming from. Used to, you could hear it worse when standing directly behind the tractor maybe a little toward the right side of the rockshaft housing. Most likely this leak has gotten worse.

Tim, just so I understand fully, your comment about stroke control not being the problem is if the stroke control was malfunctioning, the pump would still produce enough pressure and volume of oil to maintain steering function?

When the tractor is cold, there are no noticeable faults.

 

[fdt860]

You can put a cap on the line feeding the rockshaft and see what's happen. Unfortunately, you also loose the SCV when you do that, but this would isolate the problem prety good.

 

[fdt860]

Forgot to mention, It has to be a good hydraulic plug, you want to maintain closed center pressure, so don't put your thumb or a plastic plug unless you want to get injured.