JD 4020 Hydraulic Noise

kaleb

New User
I bought a JD 4020 SyncroRange tractor with a loader (aux connection, not from remotes). It starts like a champ, but has no hydraulic pressure at first. When pressure does build, it starts knocking loud - as if a piston were coming on through, but it's not the motor. For the first few minutes, it has pressure, but not enough to operate the loader. I've changed fluid, filters, and checked the screen.

Anyone have any thoughts on what my problem may be?

Thanks in advance!

Kaleb
 
Couple of things could be wrong. The cheapest is that the loader valve is not a closed center one. If that is the case your dumping the oil faster than the transmission pump can pump it to the main hydraulic pump. So the first thing to do is take the return line from the loader valve off and see if you have flow without using any functions. I usually take the tractor side off and cap the fitting on the tractor. I put the hose in a five gallon bucket with a rag over the top of the bucket. (the rag is to keep from getting sprayed with oil if there is a lot of flow) When you start the tractor there should be little to no flow from the return line. IF you have a lot of flow than the valve is wrong or defective. Your system is a closed center system. Meaning the oil should be stopped at the valve so it can hold pressure and flow until you use a function.

IF the valve is working then you more than likely have a hydraulic pump issue. It can be the charge/transmission pump or the main pump. Either of them can cause your trouble.

If it is not the valve you really need to get a repair manual and some pressure gauges an check what you have going on. Truthfully unless your really mechanically inclined this is some thing you should hire out to some one with knowledge. That also does not mean your local JD dealership. Your old tractor is going to go the youngest cheapest mechanic there. He will not be trained on a JD 4020. The guy right for the repair will need some gray hair to have old enough knowledge to know what to check and repair.
 
we had a 3010 did that it turned out to be the steel disk that connected the hydraulic pump to the crankshaft. One was cracked and it knocked bad. THe only time it didn't knck was whne you used the hyd like lifting the 3 point hitch. Im not sure when deere changed from the steel disk to the other coupler but its worth a look.

gramps
 

Welcome to YT
I'll add to what JD Seller stated about possible defective FEL valve if oil exits return hose with valve levers in neutral that's if its a convertible type valve(open center-closed center or vice-versa)) via a plug that the plug could be incorrect(open center) or be CC plug with a blown internal seal.

I'll also suggest to check hyd stand-by pressure which should be 2250-2350 psi.

In reply to what Grampajohn stated check to be sure hyd pump shaft is turning constantly when engine is running.
 
If the knocking is coming from the front, check your pump coupling for worn out nylon bushings and metal on metal knocking. The no pressure could be internal leak feeding the front pump or take your foot of the clutch and see if it builds pressure quicker.
 
Does it calm down and work ok after it runs a while? If so, no hyds at startup can be caused by the check valve at the transmission pump leaking back while sitting. This drains the oil cooler which is the reserve supply for the front pump. Once started with the clutch engaged, the trans pump will pump oil to the main pump but hyds will be sluggish and noisy until the air is worked out of the pump and the inlet pressure is built up. If that is what is happening, the hyds should work properly after several minutes. There is a retrofit check valve you can add to the elbow fotting by the filter to correct this problem without removing the trans pump.
 

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Back
Top