Farm Equipment - D-19 PS sucking air, how to find leak?

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D-19 PS sucking air, how to find leak?

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Category: Allis Chalmers
Forum Name: Farm Equipment
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URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=14881
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Topic: D-19 PS sucking air, how to find leak?

Posted By: Butch(OH)
Subject: D-19 PS sucking air, how to find leak?
Date Posted: 07 Jul 2010 at 8:49pm

The power steering on our D-19 has sucked air from somewhere since we have owned it. The oil foams and froths very quickly when you start it although the pump makes no unusual noises. There are no oil leaks running or shut off. Have tried all three fluids reccomended here and no change. All the air circulating makes for very jerky steering and now and then when it is shut down it pukes a gallon of fluid out the breather, I suppose due to air in the sterring cylinder?. I rebuilt the valve and cylinder when I overhauled the engine with no net effect on the problem. Have had the entire suction line off twice since and Checked all the steel lines thoughly and installed two differant hoses. My resident expert says pump only thing left, pump is $1100.00. That's expensive guessing IMO. Never seen a pump go bad and suck air? Steering effort is light once the assist comes into effect but quick reversing of the wheel will cause a very stiff wheel for maybe a second or two, then pressure builds and effort is light. After a few minutes of running the Dextron looks like strawberry milk from air bubbles. You now know all I know, what is wrong with it?

Replies:

Posted By: Brian Jasper co. Ia
Date Posted: 07 Jul 2010 at 9:27pm

Seems like Doc Allis posted to not use Dexron for p/s oil some time back on someone else's tractor having p/s problems. If I remember correctly he said use 20 wt motor oil. How did you test the lines? Does the suction line go down far enough in the bolster? The D17 suction line has a metal tube that goes through the fitting in the casting and reaches most of the way to the bottom. If that line were shorter than it's supposed to be, I could see it cavitating. I would test the suction line with a hand held vacuum pump to ensure it has no leaks.

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"Any man who thinks he can be happy and prosperous by letting the government take care of him better take a closer look at the American Indian." Henry Ford

Posted By: Butch(OH)
Date Posted: 07 Jul 2010 at 9:34pm

Brian I have had AW32, universal tractor fluid and dextron in it and it makes no differance. I am going to remove the radiator (again) and check the depth you suggested. We tested the lines with a Mity Vac pulling all the vac it would pull.

Posted By: Brian Jasper co. Ia
Date Posted: 07 Jul 2010 at 9:46pm

If it held under the Mity Vac, I'd say the line is good. On new vehicles, a Mity Vac is what is supposed to be used to purge the air on hydraulic p/s systems. You might try filling the system full and see if you can pull a vacuum on the entire system.

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"Any man who thinks he can be happy and prosperous by letting the government take care of him better take a closer look at the American Indian." Henry Ford

Posted By: BrettPhillips
Date Posted: 07 Jul 2010 at 9:53pm

If the pump is sucking air, chances are that it is either coming through the suction line or around the shaft. I suspect that the seal is different from the one in a D14 pump, but I had no trouble sourcing one when I rebuilt my D14's pump. Cost was no worse than most other seals as I recall.

In my case, some dumb toad (guess who...) left a Caplug in the end of the suction line when he put it on the tractor and couldn't figure out why it didn't work. After about a half an hour of fussing and diagnosis, I found my booboo. Werx Gud now!

Posted By: BrettPhillips
Date Posted: 07 Jul 2010 at 9:57pm

Brian has a good point about putting a vacuum on the system. I guess the question though is where to connect? Maybe just plug off the relief and pressure ports on the pump and apply vacuum to the suction line to test the pump seals? Too many question marks in this post. Time for bed.

Posted By: JC-WI
Date Posted: 08 Jul 2010 at 2:03am

Maybe just take pump off and buy bearings and seals and rebuild it.

Cost me about $40. Don't remember but think all the stuff needed came from agco.

Posted By: gcalent
Date Posted: 08 Jul 2010 at 8:23am

If I remember right the return line also has a long tube on it, if this has been replaced and the oil does not return below the oil level it will foam and give the apperance of a air leak on the suction side. I have run into this problem on hydraulic systems before, and drove me nuts until I figured it out. Hope this helps.

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Pullin With AC

Posted By: Kevin in WA
Date Posted: 08 Jul 2010 at 9:22am

I found out on the early D17 diesels with the pump on the back of the generator, that the bypass line has to extend down into the oil in the front casting, because there was a small passage in the back of the pump went from the suction side of pump to the bypass area and if the bypass tube is not submerged it will suck air and do what you described. D19 pump may be different being it is a webster and not barnes.