7040 oil pressure issue
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=148293
Printed Date: 31 Oct 2025 at 2:21am
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: 7040 oil pressure issue
Posted By: ezlle71
Subject: 7040 oil pressure issue
Date Posted: 08 Mar 2018 at 12:54pm
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Pop has a 1977 7040 powershift, right at 5000 hours. Was field cultivating and oil pressure lite came on. Immediately throttled down and idled to end of field. It never knocked. Parked it at that farm, him and hired man put a mechanical gauge on it and had 15 psi at idle, throttled up dropped to 5 psi. Fast Forward 3 years. we hauled it home couple weekends ago after we finished my 190xt project. Fresh batteries and a sniff of ether she fired right up to load it. So far him and hired man have checked the pressure relief valve and spring by the oil cooler, the variable oil pressure valve wherever that is, pulled the pan and main cap and rod cap. Bearings look Surprisingly good for 5000 hours. very clean inside, no sludge. Springs for the pressure valves both measure correct length but haven't checked spring pressure. Oil pump moves oil in bucket of oil but haven't figured out how to bench test it for pressure. Any and all ideas would be appreciated. where and what to check. Also its of course a maroon belly and 3500 engine serial # 3D 46253 Thanks guys
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190XT, 185, D15 SII, 7040 is living again, 7010 retired for parts.
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Replies:
Posted By: DrAllis
Date Posted: 08 Mar 2018 at 4:12pm
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Sudden oil pressure drop makes me think a blown gasket between the oil pump body halves, or a loose suction tube or discharge tube nut or gasket. I had one 7045 that after 6000 hrs had the oil pump gear work almost off of the shaft causing the red lite to come on.
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Posted By: MACK
Date Posted: 08 Mar 2018 at 10:07pm
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I would make sure pump gear or drive gear has not slipped on shaft. MACK
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Posted By: ezlle71
Date Posted: 08 Mar 2018 at 11:23pm
Thanks for the ideas. I made it to the farm and inspected the parts myself. The gear is welded to the pump shaft so no slippage there. I checked the gaskets on the suction and pressure side of the pump and they seem to have pieces missing and I checked the parts that mount to it and the missing gasket pieces aren’t there. I think we are gonna replace both pressure relief springs and all new gaskets on all that stuff, Oil cooler included since it’s off anyway. We gonna try this first and see where it lands us in oil pressure.
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190XT, 185, D15 SII, 7040 is living again, 7010 retired for parts.
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Posted By: LeonR2013
Date Posted: 08 Mar 2018 at 11:45pm
Posted By: tbran
Date Posted: 09 Mar 2018 at 9:39pm
we have had this issue 3 times. Each time either the gear that mates to the crank was spinning on the pump shaft or the gear was spinning on the shaft inside the pump. About the only explanation of decreasing oil pressure when the engine is revved up since you have no blown gaskets...
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When told "it's not the money,it's the principle", remember, it's always the money..
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Posted By: ezlle71
Date Posted: 09 Mar 2018 at 10:02pm
TBran, sorry I wasn’t clear in my post, I think the gaskets are blown out in the suction side and pressure side of the pump. The gear on the pump is welded to the shaft. But I haven’t checked the gear in the pump it’s self. What did you do to remedy that problem? The gear in the pump slipping on shaft. Thanks for the idea to look at.
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190XT, 185, D15 SII, 7040 is living again, 7010 retired for parts.
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Posted By: ezlle71
Date Posted: 18 Mar 2018 at 10:56am
We split the oil pump, replaced the gasket there and the suction and pressure side. Resealed the oil cooler and new springs in the oil bypass valves. Fired it up and have 25psi at an idle and 55 full throttle, even after warm up. My dad is pretty darn happy! The 7040 will live again.
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190XT, 185, D15 SII, 7040 is living again, 7010 retired for parts.
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Posted By: Ron(AB)
Date Posted: 18 Mar 2018 at 10:45pm
Good save! I would be very happy too!
So, it was the broken gasket(s) on the oil pump that caused the problem?
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Posted By: ezlle71
Date Posted: 18 Mar 2018 at 10:53pm
Yea I think it was the gaskets on the suction side and pressure side. Yea we were pretty excited Friday nite lol
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190XT, 185, D15 SII, 7040 is living again, 7010 retired for parts.
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Posted By: Tbone95
Date Posted: 19 Mar 2018 at 9:19am
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That there's some great news!
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Posted By: Reindeer
Date Posted: 19 Mar 2018 at 9:54am
Always a relief to find simple fairly inexpensive solutions to what could be pretty ugly! Sweet!
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Posted By: ezlle71
Date Posted: 19 Mar 2018 at 1:19pm
Yea, i think 225$ in parts. it could have been alot worse. glad it was relatively straightforward and simple repair. This tractor has 3 jobs, pull the plow, the offset disk and the tandem disk. We will be happy to have it back. Sorting out some wiring issues, the rat had a hayday under the cab with the wiring.
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190XT, 185, D15 SII, 7040 is living again, 7010 retired for parts.
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