Allis 7020 Hydraulics Deadheading
Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=138762
Printed Date: 17 Dec 2024 at 3:45am
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: Allis 7020 Hydraulics Deadheading
Posted By: Hurst
Subject: Allis 7020 Hydraulics Deadheading
Date Posted: 25 May 2017 at 7:45am
|
I am helping out a local friend diagnose and fix his 7020. Last year, he was round baling with the tractor and it all of a sudden bogged down and the hydraulic pump sounded like it was deadheading and not going into standby pressure mode. He drove it 5 minutes back to the shop and shut it off. He said he took off a valve on the side of the pump to see if it was stuck and that made no difference. I am wondering if he may have checked a valve on the gear pump instead of the piston pump? From my knowledge of piston pumps, I'm thinking the swash plate is stuck at full or close to full angle and not returning to its 0 degree/ 0 flow position. I see where the cam plate pivots in the pump, but the parts drawing doesn't really make clear the spool that controls the cam/swash plate pivot. I see also there are 2 pumps depending on the serial number, so if that is going to make a difference in diagnosing it, I'll get that information from him. Best, Hurst ------------- 1979 Allis Chalmers 7000 5800 Hours |
Replies:
Posted By: DrAllis
Date Posted: 25 May 2017 at 7:54am
| Should have connected a pressure gauge to verify what was actually going on BEFORE tearing it all apart. Now you have no information or data to work with on exactly what it was doing. "Sounded like it was dead heading" isn't a proper diagnosis. |
Posted By: MACK
Date Posted: 25 May 2017 at 8:00am
| Piston that controls squash plate may have come apart. Check compensated first for stuck spool then pull pump. MACK |
Posted By: Hurst
Date Posted: 25 May 2017 at 8:02am
|
Good morning Doc! It sounds as though he has it all back together again now because he said it's still behaving the same way. Where should he start taking pressure readings? He said he has a workshop manual he borrowed, but I'm not 100% sure if it's an Allis manual or I&T. Hurst ------------- 1979 Allis Chalmers 7000 5800 Hours |
Posted By: Hurst
Date Posted: 25 May 2017 at 8:07am
Mack, Is that the flow compensating spool that is circled in red at the top of the diagram? Hurst ------------- 1979 Allis Chalmers 7000 5800 Hours |
Posted By: DrAllis
Date Posted: 25 May 2017 at 8:26am
| 3000 psi gauge connected to the "tee" on the side of the PTO valve. Pressure should be 300 to 600 psi when hydraulics are at rest. If pressure is much greater, disconnect the small line at the compensator (and maybe plug the line). If pressure settles down to 300 to 600 psi, the problem is a signal from the 3pt or remote valves, not the pump itself. If pressure remains too high with signal line disconnected, check the small compensator spool to be sure it is free. If it's OK, the problem is inside the pump. Yes, the small spool is circled in red. |
Posted By: Hurst
Date Posted: 25 May 2017 at 8:31am
|
Sounds good, I'll pass the word on and let you know what he finds. Thanks for all the help! Hurst ------------- 1979 Allis Chalmers 7000 5800 Hours |
Posted By: Hurst
Date Posted: 25 May 2017 at 9:46am
|
Ok, more information. He said they did the pressure test a little while ago and it was up in the 2000+ PSI range, far from the 3-600psi it should be. They never got the tractor past idle and stopped the test prematurely because it spiked. I've never personally laid hands on a larger 7000 series hydraulic system, but he told me the spool they took out and cleaned was on top of the pump that is mounted on the side of the transmission just in front of the right-hand fuel tank. Would that be the flow compensator valve? If so, it was free he cleaned it up and put it back together. I'm going to go look at the tractor with him tomorrow since it's cold and raining here today and the tractor is outside. I feel like reading the posts about these tractors, one of the hydraulic pumps is inside the rear housing and the other is mounted on the outside? Hurst ------------- 1979 Allis Chalmers 7000 5800 Hours |
Posted By: Hurst
Date Posted: 25 May 2017 at 10:23am
|
Just looked at the parts manual more, and it looks like the piston pump bolts up to the outside of the transmission housing on the front right side belly of the housing. So it sounds like he took out the compensator valve and that was free. Looking through the diagrams, it looks like the piston pump is on the right side and the gear pump on the left (Side with the cab door)? Hurst ------------- 1979 Allis Chalmers 7000 5800 Hours |
Posted By: wheelbilly
Date Posted: 25 May 2017 at 10:38am
| actually all three pumps are stacked (georotor,gear,piston) The spool you have circled is for the stand by pressure (300-600psi) the other spool regulates demand (around 2300psi) need to check it also |
Posted By: DrAllis
Date Posted: 25 May 2017 at 1:01pm
| The large front spool isn't the problem. It's either a false signal coming from the hydraulic valve stack, a stuck or damaged low pressure compensator spool, or the broken control piston inside the pump which sees to it the swash plate (which is spring loaded) cannot be de-stroked. |
Posted By: Hurst
Date Posted: 25 May 2017 at 1:46pm
|
To rule out the false signal, is that where unhooking the sensing line comes in you were talking about earlier and starting the tractor to see if the pump is still deadheading? Hurst ------------- 1979 Allis Chalmers 7000 5800 Hours |
Posted By: DrAllis
Date Posted: 25 May 2017 at 3:11pm
|
Correct. |
Posted By: Hurst
Date Posted: 26 May 2017 at 4:58pm
|
I went over to see the tractor today and run a couple of pressure tests. When it starts up with a gauge hooked to the tee at the pto valve, it went right to 1500psi, the when revved up jumped to 2500psi. Engaging the remotes made it jump a little bit between 2400 and 2700 psi. Cut it off and plugged the sensing line at the remote valve stack (the line that goes to the compensator valve at the pump), started it up, and nothing changed. I guess now the pump needs to come off and be opened up? His son said he found metal shards in the bottom when he changed the oil. Would this be the pump throwing trash into the system and jamming up the piston that controls the swash plate? Hurst ------------- 1979 Allis Chalmers 7000 5800 Hours |
Posted By: bigal121892
Date Posted: 26 May 2017 at 6:07pm
| More than likely it's the other way around, something is failing in the tractor, and the pieces are messing up the pump. |
Posted By: Hurst
Date Posted: 26 May 2017 at 6:14pm
|
It's a power director transmission. Any ideas what would be shedding metal? Brakes? ------------- 1979 Allis Chalmers 7000 5800 Hours |
Posted By: bigal121892
Date Posted: 26 May 2017 at 8:22pm
| All three times, that we had rear end failures, the hydraulic pump failed first. |
Posted By: Hurst
Date Posted: 26 May 2017 at 8:43pm
|
Are there any usual suspects as far as rear end failures go in these tractors? Planetary gear sets? Hurst ------------- 1979 Allis Chalmers 7000 5800 Hours |
Posted By: MACK
Date Posted: 26 May 2017 at 9:56pm
| All pumps that I have seen stuck was from internal pump parts blocking squash plate. MACK |
Posted By: Hurst
Date Posted: 27 May 2017 at 8:59am
|
Ok, is there anything special I should tell him about removing the pump, or is it simply undoing lines and a few bolts? Does the transmission need to be drained if just the piston pump is coming off? It looks like parts should be readily available since Eaton still makes the pump (70422-RBK). I'll ask him about any noise in the rear end to see if anything jumps out that might point to a rat end failure dumping metal. He did say he changed both filters in the rear of the tractor and was asking if those were the only 2,which I believe is correct? ------------- 1979 Allis Chalmers 7000 5800 Hours |
Posted By: Lynn Marshall
Date Posted: 27 May 2017 at 1:14pm
| You don't need to drain the transmission. Take the left hand belly filter out and inspect it and the cavity for any filings. Usually the steering is the first to be affected by rear end filings. Leave that filter out when you remove the pump,so that the anti drain back valve keeps the oil in the rear end. It helps to have the proper fittings to cap some of the lines also. Yes,there are only the two rear end (hydraulic) filters. Two half inch capscrews hold the Piston pump to the gear pump. |
Posted By: Orange Blood
Date Posted: 27 May 2017 at 6:55pm
|
I wouldn't say it's "Common", but the swash plate spring isn't the strongest point in those pumps, I have had one fail in the no flow condition (plate perpendicular to the pump shaft) and my uncle had one in the full flow condition as the spring broke, and jammed somehow holding the plate at max angle to the pump shaft. ------------- Still in use: HD7 WC C CA WD 2-WD45 WD45LP WD45D D14 3-D17 D17LP 2-D19D D19LP 190XTD 190XTLP 720 D21 220 7020 7030 7040 7045 3-7060 Projects: 3-U UC 2-G 2-B 2-C CA 7-WC RC WDLP WF D14 D21 210 7045 N7 |
Posted By: Hurst
Date Posted: 28 May 2017 at 9:24am
|
That could make sense with what's happening. So it sounds like it needs to have the left filter pulled, then the pump pulled? Are there any good allis shops left neat central ky? ------------- 1979 Allis Chalmers 7000 5800 Hours |
Posted By: Orange Blood
Date Posted: 28 May 2017 at 11:01pm
|
That pump is so easy to rebuild, if I remember right you pulled and rebuilt your 7000 power director, you can easily handle the pump, if you want to help your buddy out. Just like anything else, keep it clean, and organized, and have a book helps. The parts were still available from AGCO as of about 5-7 years ago, hopefully still are. ------------- Still in use: HD7 WC C CA WD 2-WD45 WD45LP WD45D D14 3-D17 D17LP 2-D19D D19LP 190XTD 190XTLP 720 D21 220 7020 7030 7040 7045 3-7060 Projects: 3-U UC 2-G 2-B 2-C CA 7-WC RC WDLP WF D14 D21 210 7045 N7 |
Posted By: Lynn Marshall
Date Posted: 29 May 2017 at 7:15am
| If one of the slipper pistons is broken and jammed in there,it usually ruffs up the swash plate. Just as well look for a good used pump if that's the case. |
Posted By: MACK
Date Posted: 29 May 2017 at 9:55pm
| If you buy a used pump, take it apart and check it out. Some of the used pumps have a lot of hours on them. MACK |
Posted By: Hurst
Date Posted: 29 May 2017 at 10:09pm
It doesn't sound too bad. If he's not in a hurry and I can borrow the service manual from the other allis fanatic in our small town, I'd be glad to help him year down the pump and inspect it and go from there. Right now I have one of my fords waiting on a hydraulic pump and a lot of hay to get up in the next couple of weeks, so I hate to start on another project that might sit around taken apart. That's when you end up with extra bolts!  Hurst ------------- 1979 Allis Chalmers 7000 5800 Hours |