oil pressure
Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Construction and other equipment
Forum Description: everything else with orange (or yellow) paint
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=196640
Printed Date: 08 May 2024 at 10:09pm
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: oil pressure
Posted By: lost in h3
Subject: oil pressure
Date Posted: 12 Aug 2023 at 7:24pm
| Suddenly lost oil pressure on my allis h3. New rebuild only started about 6 times. Up till now had good 30 plus psi. I read on internet they lose prime, Is that common? I always think the worst but they said to just reprime pump? |
Replies:
Posted By: doctorcorey
Date Posted: 13 Aug 2023 at 6:43pm
|
Hope you solved this problem. If it lost oil pressure while it was running, it wasn't because of losing prime. ------------- Semper Fi USMC 1958 HD6G, 1959 MF 203 loader, 1960 Case 420B Backhoe, MF 65 Tractor/Loader Diesel |
Posted By: lost in h3
Date Posted: 14 Aug 2023 at 10:10am
| It did not lose pressure while running. Lost pressure between startups. |
Posted By: DrAllis
Date Posted: 14 Aug 2023 at 9:49pm
| Did you "rebuild" the oil pump ??? Every time you overhaul one of these engines, the vanes and springs should be replaced. Also, the physical condition of the pump rotor and housing needs to be inspected for wear. I have never had one of those pumps lose prime if they are in good condition. Never remove the suction tube from the bottom end when working on the engine. If you do, there could be an air leak where it threads back into place. Must loctite those threads !! |
Posted By: lost in h3
Date Posted: 14 Aug 2023 at 10:55pm
| Live and learn. No I did not rebuild oil pump. Looked good to me. At seventy six years old and lots of cars, trucks, tractors and dozers I've seen pumps slowly lose pressure but never lose prime just sitting there. I guess I'll just do like I did as a kid. Before I use it just Prime the Pump. |
Posted By: DrAllis
Date Posted: 15 Aug 2023 at 8:50am
| Probably all the other engines you've worked on didn't have the oil pump 12 inches above the oil level either !! |
Posted By: Les Kerf
Date Posted: 16 Aug 2023 at 6:21pm
Indeed! When I overhauled my first Model C some 35+ years ago I was perplexed by its rather bizarre oil system; this was before the days of internet and I was unable to source new parts so I just cleaned it up and it ran fine, never gave any trouble. My 1941 John Deere Model A, on the other hand, has its oil pump submerged at the bottom of the sump where it is impossible to lose prime so long as there is oil; I have had water condensation settle down there and freeze, causing the oil pump drive to strip out  I am most circumspect about draining any condensation out of it after that little learning episode. |
DrAllis wrote:Posted By: doctorcorey
Date Posted: 16 Aug 2023 at 9:02pm
|
Did the pump eventually "reprime"? ------------- Semper Fi USMC 1958 HD6G, 1959 MF 203 loader, 1960 Case 420B Backhoe, MF 65 Tractor/Loader Diesel |
Posted By: lost in h3
Date Posted: 17 Aug 2023 at 12:35pm
| I got the pump reprimed by taking oil line lose from filter (supply side) and slowly filling line with oil till full. Since then it has lost prime again. Always when I shut it off never when running. I guess I'll drain oil and check the sump and pick up tube again but I went over it real good before? |
Posted By: Les Kerf
Date Posted: 17 Aug 2023 at 8:02pm
Yikes! I would install an oil accumulator to pre-charge the system before I would split my tractor just to access the oil pump... Yup that's a poor bandaid approach and doesn't address the root cause, but I am fundamentally lazy  |
Posted By: Codger
Date Posted: 17 Aug 2023 at 9:21pm
|
These pumps don't make any vacuum for pulling the oil from the sump after a drain interval? Sounds like the pump body and gears are worn severely to me. There should be a specification in the manual for this. Clearance from gear tip to housing, gear backlash, scoring of parts, etc. all should be checked at rebuild or refurbish time. I'd wager these are way past tolerance limit if losing prime. Some pumps utilize a ball check and spring also. I don't know this application at all but something was missed at rebuild I'm thinking. Not being critical at all but this needs checked really well. ------------- A career built on repairing and improving engineering design deficiencies, shortcomings, and failures over 50 years now. |
Posted By: Les Kerf
Date Posted: 18 Aug 2023 at 5:47am
I think the H3 uses a vane-type pump similar to the Model C pump which is a weird contraption driven directly off the end of the camshaft which is hollow and acts as the initial oil gallery; as Dr. Allis noted above, it is way high above the oil sump. They do seem to work ok when everything is in good condition. You do get to split the tractor and remove the flywheel to gain access; my Model C is about the easiest tractor on the planet to split but it is still an aggravation, the H3 crawler is certainly more difficult. |
Posted By: Codger
Date Posted: 18 Aug 2023 at 6:10am
|
Thanks Les; I would not have suspected a vane type pump for engine oil at all. I've never been into, or worked on one of these myself. Vane pumps inherently draw more vacuum during rotation than gear type pumps so there is a definite problem rearing it's ugly head here. Wonder if it has anything to do with the filter not being original? Seems a bypass type is used rather than full flow from an earlier post?
------------- A career built on repairing and improving engineering design deficiencies, shortcomings, and failures over 50 years now. |
Posted By: DrAllis
Date Posted: 18 Aug 2023 at 8:23am
| If it is a G-149 or G-160 from a D-15/H-3 chassis, it is a FULL-FLOW system. The G-138 and old G-149's used in D-10-12-14 tractors were bypass oil filter. Oil pumps were very similar but were different because of the two different oiling systems. |