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HD5 with 2-71 Oil Pressure Problem

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ALW_HD5 View Drop Down
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    Posted: 28 Apr 2020 at 5:11pm
Need a little help. My HD5 with a Detroit 2-71 is losing oil pressure when it warms up.  I  put fresh oil and filter when I got the machine last year. I have not had the chance to run it much. Maybe 10 hours. When I checked the oil it was totally black however I pulled the filter and the oil is clean as brand new. I'm thinking I have a flow problem and maybe the cooler is plugged? Looks like it sits behind the water pump? Any suggestions on what I should be looking at would be appreciated. Thanks

Edited by ALW_HD5 - 28 Apr 2020 at 5:12pm
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Coke-in-MN View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Coke-in-MN Quote  Post ReplyReply Direct Link To This Post Posted: 28 Apr 2020 at 5:41pm
2-71 don't have great oil pressure to start with but the main source of low pressure is rod and main bearing leakage . 
 The oil system is a bypass system with just a small amount of oil diverted to filter , evidently your orifice in that line is plugged - it should be about 1/8" hole in fitting and line to filter . Cam bearing wear also leads to low pressure . 
 When I bought my machine owner told me they had put bearings in it but thin oil for winter use was why pressure was low , changing oil didn't bring pressure up nor did replacing the oil pump with a new one . Later I developed a oil leak at rear main and found they put rod bearings in but not mains and crank was worn enough at center main it moved enough to take out rear seal , Had crank turned , new rod and mains and replace thrust shields , new rear seal of modern type , replace flywheel bearing with sealed bearing and remove wick in end of crank for old bearing oiler , 
 Pressure came up but still seems lower than I would like to see - Only have 25 years of running since so it might be OK . 
 I did put a oil pressure switch into system so I can tell when running at a angle or up or down hill if oil pump is starving - big red light on dash comes on so you can correct situation before damage 

Faith isn't a jump in the dark. It is a walk in the light. Faith is not guessing; it is knowing something.
"Challenges are what make life interesting; overcoming them is what makes life meaningful."
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DMiller Quote  Post ReplyReply Direct Link To This Post Posted: 29 Apr 2020 at 6:22am
Have to laugh a little, old history. Fleet of City Sanitation trucks, had 6L71 Detroit Diesels and Murphy Switch auto shut down systems. Were Fine brand new but then as aged a little(Less than a year) the old Driptroits began losing oil pressure as is customary down to where would barely flicker the gauge needle at idle and Murphy being Murphy would DIE. We added hand throttles to all of them to keep the engine rpm up when sitting still so would not auto shut down. Normal was 4-5psi on a Shop gauge at idle and quite fine except could only dial the murphy sets down to somewhere near 6psi, 25-30 at Hi Idle and good for DD Specs. Detroit Believed in Volume oil lubrication not extreme pressure,
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ray54 Quote  Post ReplyReply Direct Link To This Post Posted: 29 Apr 2020 at 12:15pm
All the diesels of that vintage seem to make the oil black in just a little run time. And DD even faster.

Another DD 2 stroke weakness is the little fuel lines on top of the head. The flare on the line will crack and leak diluting the oil with diesel.


A engine machinist I am friends with always tells  me the racing guys don't want more than 7 psi for oil pressure as they don't want power wasted on the oil pump. He maintains as long as it get pumped all over your good.

But trucker out here would run 40 wt oil rather than 30 year round to get a little more psi out of 2 strokes DD.   
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Coke-in-MN View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Coke-in-MN Quote  Post ReplyReply Direct Link To This Post Posted: 29 Apr 2020 at 3:50pm
Fuel lines to injectors Detroit says to replace each time they are removed - but big problem is overtightening them when service is done . I had one crack and dilute oil , then when getting a replacement for that one found previous owner has reflared other lines himself and so I replaced all 4 of them when I changed the injectors , kept a couple old lines - just in case but never needed them so far . 
 HV7 injectors have worked well and last time i worked on engine i just had them tested and were fine . 
 Still have a core 2-71 out back i got with one salvage machine i bought - never figured what was wrong with it - former owner said lost oil pressure and he just found another engine from generator and put into machine . I rebuilt that machine and sold it several years back - another HD5G  
Faith isn't a jump in the dark. It is a walk in the light. Faith is not guessing; it is knowing something.
"Challenges are what make life interesting; overcoming them is what makes life meaningful."
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ALW_HD5 Quote  Post ReplyReply Direct Link To This Post Posted: 30 Apr 2020 at 12:06pm
Thanks for all the info. I did a complete oil change and ran it for a bit. When I checked the fresh oil it looked like it had metal in it. Looks like time for a rebuild.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tad Wicks Quote  Post ReplyReply Direct Link To This Post Posted: 03 May 2020 at 11:39am
Detroits don't have great oil pressure at an idle, one thing you can do, I used the oil pump for the hydraulic fan that came with the engine. It came from a COE and the fan was driven on the end of the crank with a hydraulic coupler, and taller oil pump, my 11 runs 25 psi at idle and then 60 at 1600
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ALW_HD5 Quote  Post ReplyReply Direct Link To This Post Posted: 23 Jul 2020 at 1:41pm
I finally got a chance to dig into the old 2-71. It looks like the former owner did some interesting repairs. This guy was very fond of orange silicone. I pulled the water pump and oil cooler housing and found gobs of of the stuff clogging almost every oil passage in the top end. He also did some kind of bypass on the oiling system for the top end. Any idea why he would have done this? Seems like this would limit the amount of lubrication getting to the top end?
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Post Options Post Options   Thanks (1) Thanks(1)   Quote DMiller Quote  Post ReplyReply Direct Link To This Post Posted: 23 Jul 2020 at 2:27pm
Basically not knowing he screwed up with all the Silicone and tried a bypass retrofit to fix what he could not mentally support.  Blue Glue is NOT our friend in most conditions and is not used in liberal slatherings.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DMiller Quote  Post ReplyReply Direct Link To This Post Posted: 24 Jul 2020 at 9:30am
Sheet gasket material even old paper grocery bags were good for replacement hand cut gaskets in a pinch with a LIGHT coat of HiTack or Indian head style sealers.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ian Beale Quote  Post ReplyReply Direct Link To This Post Posted: 24 Jul 2020 at 6:04pm
Re gasket material.

A bloke here bought a HD 16 and knew it had a leak from the sump.  When he removed the guard the "leak" was a hole in the sump from where it had been run without the guard.  The "fix" was a piece of plate Tek-screwed on.

The gasket was cut from a beer carton.


Edited by Ian Beale - 24 Jul 2020 at 6:05pm
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Post Options Post Options   Thanks (1) Thanks(1)   Quote dieselbob Quote  Post ReplyReply Direct Link To This Post Posted: 18 Aug 2022 at 9:28pm
I've solved a problem with low oil pressure on a 2-71 I rebuilt!  I had tried just about everything, pump clearance, reduced main and rod bearing clearance, shimmed pump regulator - nothing worked!  At best 25 psi fully warm with SAE 40 oil.  Then recently I got looking at the cam bearings that had been replaced when I had the block tanked at a NAPA machine shop.  To my shock, the bearing that had come out were marked 0.030 inch undersized!  I had unknowingly put in standard bearings with an undersized cam and balance shaft.  So, instead of having about 0.004 inch clearance for the 5 cam and balance shaft bearings, each had about 0.034 inch clearance.  When I looked at a Detroit Diesel parts book, I found they sold bearings and that were 3 sizes: Standard, 0.015 and 0.030, with the  undersizes apparently for reground cams!  I had another set of parts in my shop and found another one that used 0.015 bearings.  I have heard of cams that had profiles reground, but in all my years working on engines had never run across undersized cam bearings.  After over 2 years, I pulled the engine and installed a set of 0.030 undersized bearings from Detroit Diesel and I now have excellent pressure.  Full story of myFaramall 400  repower with the 2-71 is on my website;  https://dieselbobllc.com/farmall-400-2-71-repower-project/, I'll eventually add more detail and part number there.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote LouSWPA Quote  Post ReplyReply Direct Link To This Post Posted: 19 Aug 2022 at 1:16am
Originally posted by DMiller DMiller wrote:

Sheet gasket material even old paper grocery bags were good for replacement hand cut gaskets in a pinch with a LIGHT coat of HiTack or Indian head style sealers.  
Thats what my dad used, dog food bags and Indian Head shellac
I am still confident of this;
I will see the goodness of the Lord in the land of the living.
Wait for the Lord;
be strong and take heart and wait for the Lord. Ps 27
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Post Options Post Options   Thanks (0) Thanks(0)   Quote doctorcorey Quote  Post ReplyReply Direct Link To This Post Posted: 09 Sep 2022 at 10:35pm
I read this whole thread, and I am jealous that you can still buy parts for these machines, but I have to wait 6 months to buy a new Smileclutch disc for my HD6G. Anyways, glad you solved your problem, and once again, never throw the old parts away..........

Semper Fi USMC    1958 HD6G, 1959 MF 203 loader, 1960 Case 420B Backhoe, MF 65 Tractor/Loader Diesel
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Coke-in-MN Quote  Post ReplyReply Direct Link To This Post Posted: 12 Sep 2022 at 11:00am
Detroit had enough of a market for all there engines that parts were out on the market for years , nice thinng is 2-71 pistons are the same as 6-71 pistons . Sleves interchange also - 
Faith isn't a jump in the dark. It is a walk in the light. Faith is not guessing; it is knowing something.
"Challenges are what make life interesting; overcoming them is what makes life meaningful."
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Post Options Post Options   Thanks (0) Thanks(0)   Quote doctorcorey Quote  Post ReplyReply Direct Link To This Post Posted: 12 Sep 2022 at 11:56am
Originally posted by Coke-in-MN Coke-in-MN wrote:

Detroit had enough of a market for all there engines that parts were out on the market for years , nice thinng is 2-71 pistons are the same as 6-71 pistons . Sleves interchange also - 
  Same with the AD4 Perkins in my MF65. Bought brand new crank, rods, gaskets, etc. 
Semper Fi USMC    1958 HD6G, 1959 MF 203 loader, 1960 Case 420B Backhoe, MF 65 Tractor/Loader Diesel
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