John Deere 4020 - Steering Motor Pinion Seal

[Glen D Anderson]

Good morning,

Our '72 4020 leaks significantly from the steering motor pinion seal during cold weather operation. The colder the weather, the worse the leak. For reference, last week when operating at - 20 F, the leak was a steady stream. Once the tractor and/or ambient temp. warms up the leak stops or slows to an imperceptible amount. This is spite of the motor being completely resealed several years ago.

To test: I removed the motor case drain line and operated the steering and found no discernible flow coming from the motor.

I installed a pressure guage on the hydraulic cooler where the steering motor case drain line connects to check for back pressure. At med. idle the back pressure was 10 PSI and rose to 16 PSI at high idle.

This testing was done at + 32F so one might assume that back pressure readings would be significantly higher at - 20F???

I'm planning on checking the cooler return plumbing for restrictions but was curious if anyone has run into this before & if there is any valving or components in the cooler return circuit that could cause the back pressure?

Thanks in advance!

Glen

 

[Glen D Anderson]

Good morning,

Our '72 4020 leaks significantly from the steering motor pinion seal during cold weather operation. The colder the weather, the worse the leak. For reference, last week when operating at - 20 F, the leak was a steady stream. Once the tractor and/or ambient temp. warms up the leak stops or slows to an imperceptible amount. This is spite of the motor being completely resealed several years ago.

To test: I removed the motor case drain line and operated the steering and found no discernible flow coming from the motor.

I installed a pressure guage on the hydraulic cooler where the steering motor case drain line connects to check for back pressure. At med. idle the back pressure was 10 PSI and rose to 16 PSI at high idle.

This testing was done at + 32F so one might assume that back pressure readings would be significantly higher at - 20F???

I'm planning on checking the cooler return plumbing for restrictions but was curious if anyone has run into this before & if there is any valving or components in the cooler return circuit that could cause the back pressure?

Thanks in advance!

Glen

Forgot to mention that this tractor is a synchro range....

 

[tim s]

My thoughts are to re-seal the steer motor,,it's hard to say if it has ever been re-built..and I want to also add that if the 4 bolts holding the steer arm or narrow front are changed out it is very important not to use any bolt more than 2 1/8" long the will tighten into the seal..

 

[Glen D Anderson]

My thoughts are to re-seal the steer motor,,it's hard to say if it has ever been re-built..and I want to also add that if the 4 bolts holding the steer arm or narrow front are changed out it is very important not to use any bolt more than 2 1/8" long the will tighten into the seal..

Tim,

It was completely resealed a few years ago using OEM parts. The bolts are the factory / correct length & are not rubbing on the seal.

Given the style of seal that is used on the pinion is not a spring loaded design with a pronounced lip it seems that it would do a poor job of holding back any significant pressure which makes me wonder about whether the amount of back pressure I am seeing on the cooler return line is normal. Never having tested that before I don't know what's normal?

 

[tim s]

I'm with you there,,it's pretty much an open shot to the transmission case. And maybe the oil your using is a bit heaver,, Cold weather is a game changer,, here in central Ohio we don't get much single diget cold

 

[Glen D Anderson]

I'm with you there,,it's pretty much an open shot to the transmission case. And maybe the oil your using is a bit heaver,, Cold weather is a game changer,, here in central Ohio we don't get much single diget cold

We're running the same oil in our tractors for as long as I can remember & it's never caused leakage like this before even in temperatures that have been colder. There's no doubt that running a synthetic or "winter rated" oil would be ideal but I feel that if you use discretion at initial start up, running the engine at low speed with an SCV loop engaged allowing the oil to circulate and warm up before revving the engine you can get by.

I guess I'll check the cooler return plumbing for restrictions.......

 

[tim s]

It's a straight shot from the cooler,, the cooler it's self may need a good flushing,,you may try removing it and back flushing it with some solvent..

 

[Glen D Anderson]

It's a straight shot from the cooler,, the cooler it's self may need a good flushing,,you may try removing it and back flushing it with some solvent..

Well, I got chance to look further into this...

There is no obstruction in the return pipe going to the transmission or in the tee coming out of the cooler. The connection on the cooler for steering motor drain line is located at the outlet portion of the cooler so any restriction that might be present shouldn't affect the backpressure the steering motor is seeing. That said I had the hyd. cooler and tank off a few years ago to replace the lower hoses and I cleaned the cooler at that time with solvent and then the pressure washer.

I also removed the steering motor pinion seal to inspect and found that the seal was still in good shape. There were no tears or damage to the lip and it still had tension when placed on top of the pinion seal surface.

Not sure what's going on here but I'm tempted to rig up a dedicated drain line to the trans. sump to use during cold weather to see if that alleviates the problem.....

 

[tomstractorsandtoys]

Well, I got chance to look further into this...

There is no obstruction in the return pipe going to the transmission or in the tee coming out of the cooler. The connection on the cooler for steering motor drain line is located at the outlet portion of the cooler so any restriction that might be present shouldn't affect the backpressure the steering motor is seeing. That said I had the hyd. cooler and tank off a few years ago to replace the lower hoses and I cleaned the cooler at that time with solvent and then the pressure washer.

I also removed the steering motor pinion seal to inspect and found that the seal was still in good shape. There were no tears or damage to the lip and it still had tension when placed on top of the pinion seal surface.

Not sure what's going on here but I'm tempted to rig up a dedicated drain line to the trans. sump to use during cold weather to see if that alleviates the problem.....

Your tractor already has a plastic return line from the hyd. pump. I wonder if you could tee into that and use it for your return line as well? Tom

 

[Glen D Anderson]

Your tractor already has a plastic return line from the hyd. pump. I wonder if you could tee into that and use it for your return line as well? Tom

That's exactly what I wanted to do Tom. Just install a branch "tee" fitting into the pump to connect the motor drain line to. However this is another case of Deere using oddball fitting & line sizes. The threads in the pump are 3/16 ORB and the plastic line is 5/16 JIC neither of which are sizes carried by any of my local suppliers. Looking online 3/16 ORB & JIC fittings are few and far between with 5/16 having only slightly more selection but I might be able to cobble something together...

If they just could've used 1/4 or 3/8 it'd be no problem at all but where's the fun in that? LOL

 

[tim s]

That's exactly what I wanted to do Tom. Just install a branch "tee" fitting into the pump to connect the motor drain line to. However this is another case of Deere using oddball fitting & line sizes. The threads in the pump are 3/16 ORB and the plastic line is 5/16 JIC neither of which are sizes carried by any of my local suppliers. Looking online 3/16 ORB & JIC fittings are few and far between with 5/16 having only slightly more selection but I might be able to cobble something together...

If they just could've used 1/4 or 3/8 it'd be no problem at all but where's the fun in that? LOL

4430's already do this,, you can get the tee fitting from that parts page.

 

[Glen D Anderson]

Thanks Tim!

Just looked at the parts diag. That is exactly what I had in mind!

 

[Albert Hargreaves]

Glen, I just registered to this forum to visit with you about this problem. I have over 30 years experience with JD. I have never seen this problem before, but I have a customers tractor that is doing the EXACT same thing. It's a 4020 under the 200,000 serial number. The steering motor seal has been replaced by me twice and another mechanic once. The seal leaks when it's really cold, but doesn't leak when warm. I've thought about installing a T in the pump like the newer tractors use, but I would also like to figure out what is causing the problem. I'm working on figuring out this problem. I will let you know of anything I find on it and would be curious to hear if you find out anything.

 

[Glen D Anderson]

Hi Albert,

I don't have any hard evidence to report back with as I still haven't put this tractor back into service but there is something that I've noticed that may be worthy of mention.

While the tractor was apart I removed the steering motor pinion to replace the seal as a preventative measure. As previously mentioned, the motor had received a complete re-seal only a few years so the "old" seal was found to be in good condition, it was supple and still had noticeable interference on the shaft. It didn't seem likely to me that the new seal I installed was much of an improvement.

That said, after I got the motor reassembled, something caught my eye. I noticed a small amount of "end play" in the pinion shaft. While I never got technical and measured things up properly to confirm my suspicion, I think that if the snap ring or the groove in the shaft is worn enough(or even if the bearing has enough play), the pinion may be allowed to drop out of the case enough to cause a loss of seal tension. This is just a guess though, not a statement of fact.

I did end up replumbing the motor drain circuit using the "tee" fitting from the 4430 application that Tim S recommended. However I did not feel comfortable plumbing the motor only to the pump drain as it is my belief that the motor relies on the backpressure(& oil) from the cooler circuit for lubrication. So I installed a three way valve that can be switched to allow the steering motor to drain into either the cooler circuit(as per factory) OR into the "tee" on the hyd. pump case drain. The thought being that the alternate drain circuit will only be used during cold weather operation.

Hope this helps,


Glen

 

[Albert Hargreaves]

Glen,
I was just doing some research on this problem. I found that the system has an oil cooler bypass valve in front of the radiator on synchro range tractors.
"The oil cooler bypass valve (Fig. 230- 10-12)is located between the top and bottom tanks of the oil cooler and serves two functions: it protects the cooler from excessive pressure buildup during cold weather starting, and allows oil to dump from the cooler to the main pump when the "closed center" system ls depleted of oil, such as during single-acting cylinder operation."
I would bet that this is the problem on both of our tractors. I'm guessing that the valve isn't opening and during cold weather operation, there is too much pressure and it is backing up into the steering motor. I also believe that since the steering pinion seal doesn't have a spring loaded lip, the seal won't need replacement after the problem is fixed.

Albert