The mystery of the failing tram seal

[marrt]

Good evening everyone.....

Over the years, there's been at least three different types of pumps, three different engines, and I think four different engine/pump arrangements. In addition, some used a lovejoy connector and some used a splined connector. It "sounds" like the seal is on the side facing the engine, correct? To my recollection, I haven't seen a seal in this location (I've had three different 425's) as no oil in normally present. If you have a Bondioli and Pavesi pump, I can probably give you a contact at the company where you can ask a question. Of course, we'll need to figure out your exact pump model (Power Trac usually won't tell you).

Regarding the issue of replacing hoses and getting the air out, I welded up a simple connector that allowed me to spin the pump in the tub. The engine was out of course but everything was connected in the wheel circuit (you don't need to worry about air in the other circuits). Using a heavy duty variable speed drill, I was able to slowly spin the pump until all the air was out. I had the tractor on blocks of course. And you have to use something to hold the purge hose in the tank and wedge the tram pedal down (purge the circuit first until you see no air then wedge the tram pedal). Once you've put everything back together, with the tractor still on blocks, crank the engine and tram forward and reverse for 3 or more minutes while at low idle. If you want to be really cautious, let the tractor sit for 30 minutes and repeat. At that point you should be good.

 

[BobRip]

I think you should talk to Power Trac and see if you can leave it with them until they figure it out. If I were them I would like to inspect every piece of the hydraulic system. Take everything apart and figure it out. They need to know what caused this.

 

[BobRip]

I would think Power Trac would want to know what is causing this problem. Talk to them and make it seem to them that understanding this problem will help them deal with it if someone else has the problem. They should take the hydraulics apart and inspect everything. Perhaps they would do it at their own expense. I would if I were the manufacturer.

 

[Wyenot]

Hi guys, I got the PT towed to a place I can work on it. I disconnected the 2 bolts that mount the tram to the bell housing and supported the pumps with some straps and my engine crane. Pulled the coupler off. Not sure if it is a coupe or a lovejoy. It has two metal pieces that come together with rubber piece in between. The metal part on the pump shaft slides off easily to reveal the seal around the shaft. The couple part will not go back onto the shaft enough to hit the seal. I have included some pictures of the damaged seal. I labeled a set as inside facing and outside facing. The others should be self identified after looking at the labeled ones.

 

[MossRoad]

Hope you don't mind, I put spaces between the photos.

 

[ponytug]

Yes, what you are describing is a Lovejoy coupler.

Yes, that is a catastrophic seal failure. It looks to me more like a bad seal rather than something caused by alignment, because there are chunks torn off rather than abrasion of the rubber. Is the rubber noticeably hard to the touch, i.e. overheated or “aged”. I wonder if you want to try to replace it locally to get a different manufacturer or lot of the seals.

I have only seen seals in this condition on 50+ year old equipment, and even then only a few times.

All the best,

Peter

 

[MossRoad]

Well...

Since it's happened multiple times in short hours, whatever is doing it is consistent.

So what are some things that are consistent?

- The seal?
- The way it's assembled?
- The fluid?
- Contaminants in the fluid?
- The bleeding process after reassembly?


Why do new seals blow?
- Are they damaged before installation?
- Are they damaged during installation?
- Are they damaged during assembly of the halves?
- Is something able to get in there to gouge it out?

Since you show your picture that says the damage is on the outside of the seal, not the inside of the seal...
- Would that suggest the problem is not debris in the fluid?
- Would it suggest an air buildup in the pump blowing the seal out?
- Would it suggest debris on the outside gouging the seal?

I'd guess, at this point, that if the seal is blowing out, air is building up in the pump and pushing the air out the seal, blowing it out. If it was debris on the outside that was large enough to gouge out the seal, I'd think you'd see damage on the metal around the seal as well. I didn't see any scratching on those areas.

If air in the pump is the culprit, it's either not getting bled properly after the surgery, or something is introducing air into the system during operation. This is called aeration and/or cavitation.

So think back... when moving the machine, do you ever hear noise that sounds like gravel in the system. It's pretty evident to the ear. Sounds like gravel rolling around inside.

Is your hydraulic fluid foamy during operation? Open the reservoir lid while the machine is running. It should not be foamy.

You may have an air leak in a hose or fitting or at the filter.

Anyhow, lots of causes and effects on air in the system, if that is the problem at all. I'm just grasping and most obvious to me straws.

Here's some links to so reading. The 2nd one also has a video. The guy moves around too much, but if you close your eyes and listen to him, it's good info.

7 Common Failures of Hydraulic Seals | Machine Design

https://gpmhydraulic.com/is-my-pump-cavitating-or-aerating/

 

[PowerTracManiac]

I am no hydraulics expert but I thought I read somewhere that it is possible to have the fluid tested for debris/contamination? I don't know how expensive that is but it would seem to be easy to take a fluid sample and then send it off to a lab for analysis. That way 1 potential issue could be assessed and taken out of the possibilities if the fluid turns up OK.
Sorry for your troubles. Ease of repair is the one concern I have with PT equipment in general.

 

[ptsg]

It almost looks that it's building case pressure and blowing the seal.

Does the case drain line have a free flow path to the tank? Nothing blocking?

Also, that looks like just a regular seal that seals a shaft on something that doesn't have pressure.

Pumps and motors uses a better seal with much harder rubber that can handle higher pressures.

 

[flyerdan]

It would appear that the seal resides in a removable housing; pull the snapring from the pump, remove the seal and housing, remove the snapring on the back of the housing and remove the seal. From the looks, I would strongly suggest that the splines in the shaft might be nicking the seal upon installation, as it appears that the step isn't chamfered as one would expect on a shaft of this type. Without seeing the shaft sans seal, it's only a guess on my part.
If you can post any number that might be on the seal, I can look it up in my big book of seal cross reference and hopefully find a bunch of alternative numbers to look for in case PT has a bad supply.