Lmackattack Posted March 1 Share Posted March 1 My 77 mack with 283 tipturbine has about 25psi warm idle and 42psi at warm high idle. Cold start is 60psi I feel the oil pressure is low for this engine. It's been like this for 10 years and want to try and correct it. I did an oil sample and results were normal for a hobby truck That idles more than ddriven.i thought I was going to see high copper values but they are normal. I will be replacing the plungers and springs in both the oil pump and filter pedistal. Is there a procedure to adjust the oil pump relief spring. Or is it just bolt in and go? Thank you Quote Link to comment https://www.bigmacktrucks.com/topic/73924-oil-sample-results-low-oil-pressure/ Share on other sites More sharing options...
Popular Post Joey Mack Posted March 1 Popular Post Share Posted March 1 that seems good for an older engine. heck 17+(low idle) on some E-7's that are at work all the time was common.. I say... leave it alone.. I also look forward to other opinions, and I may learn something .. jojo 2 2 Quote Link to comment https://www.bigmacktrucks.com/topic/73924-oil-sample-results-low-oil-pressure/#findComment-547494 Share on other sites More sharing options...
Lmackattack Posted March 2 Author Share Posted March 2 2 hours ago, Joey Mack said: that seems good for an older engine. heck 17+(low idle) on some E-7's that are at work all the time was common.. I say... leave it alone.. I also look forward to other opinions, and I may learn something .. jojo It's not horrible for a hobby truck but I'm use to seeing the 2v and 4v engines jump to 60psi right off idle. This engine oil psi is barely increasing off idle and It takes all of 2100 to reach 41 psi. I was surprised to see my copper readings so low. I was ready to roll in a new set but now I'm wondering if thats the issue Quote Link to comment https://www.bigmacktrucks.com/topic/73924-oil-sample-results-low-oil-pressure/#findComment-547500 Share on other sites More sharing options...
Joey Mack Posted March 2 Share Posted March 2 is the oil sendor line to the gauge clogged? may need to un do it and pull the throttle stop and crank the engine while the gauge line is in a catch can.. Quote Link to comment https://www.bigmacktrucks.com/topic/73924-oil-sample-results-low-oil-pressure/#findComment-547501 Share on other sites More sharing options...
Lmackattack Posted March 2 Author Share Posted March 2 46 minutes ago, Joey Mack said: is the oil sendor line to the gauge clogged? may need to un do it and pull the throttle stop and crank the engine while the gauge line is in a catch can.. That's a good suggestion. I'd suspect it's not because it reads 60 psi at cold start but it's worth looking into. Quote Link to comment https://www.bigmacktrucks.com/topic/73924-oil-sample-results-low-oil-pressure/#findComment-547502 Share on other sites More sharing options...
Joey Mack Posted March 2 Share Posted March 2 ok,, good call.. just hoping its a minor issue,, 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73924-oil-sample-results-low-oil-pressure/#findComment-547503 Share on other sites More sharing options...
Popular Post MACKS Posted March 2 Popular Post Share Posted March 2 We used to run straight 40 in our older engines for better oil pressure.. 3 Quote Link to comment https://www.bigmacktrucks.com/topic/73924-oil-sample-results-low-oil-pressure/#findComment-547509 Share on other sites More sharing options...
Popular Post mrgumby Posted March 2 Popular Post Share Posted March 2 Have you checked it with another gauge ? That happened to me. It was a bad gauge giving a false reading. Just a thought 2 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73924-oil-sample-results-low-oil-pressure/#findComment-547522 Share on other sites More sharing options...
mechohaulic Posted March 2 Share Posted March 2 7 hours ago, MACKS said: We used to run straight 40 in our older engines for better oil pressure.. back in the good simpler days it was 30 or 40 weight and 10 was considered hyd oil. now engines run 0=20 !! how can this be I ask. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73924-oil-sample-results-low-oil-pressure/#findComment-547525 Share on other sites More sharing options...
mechohaulic Posted March 2 Share Posted March 2 1 hour ago, mrgumby said: Have you checked it with another gauge ? That happened to me. It was a bad gauge giving a false reading. Just a thought my thoughts also;; if possible tap into another live port with a gauge you know is accurate while leaving old gauge in dash for comparing notes. to go and parts change another gauge only to see same results $$$. it is possible to show start up at 60 = 1-- oil cold // 2 -- no restrictions in line or gauge // 3-- if gauge totally faulty it would not bottom out to 0 after shut down 4-- gauge or line hopefully. Quote Link to comment https://www.bigmacktrucks.com/topic/73924-oil-sample-results-low-oil-pressure/#findComment-547526 Share on other sites More sharing options...
mechohaulic Posted March 2 Share Posted March 2 what are the readings AFTER an oil /filter (s) change . been this way for ten years ; had to have a number of oil changes in that time frame. also did you change oil brands or type to see if a difference happens ?? been this way for ten yrs also brings question ;; how long did you have this unit prior to the ten yrs??did you see a difference 10 yrs ago or was just the way it was ?? Quote Link to comment https://www.bigmacktrucks.com/topic/73924-oil-sample-results-low-oil-pressure/#findComment-547527 Share on other sites More sharing options...
Popular Post Joey Mack Posted March 3 Popular Post Share Posted March 3 I was just in my shop.. I cut some of my oil filters to check the health of the oil, and I thought I would post this. I bought this cutter on Amazon for around $35.00.. May I suggest getting one.. 2 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73924-oil-sample-results-low-oil-pressure/#findComment-547554 Share on other sites More sharing options...
mrsmackpaul Posted March 3 Share Posted March 3 So what was your findings Joey? Paul Quote Link to comment https://www.bigmacktrucks.com/topic/73924-oil-sample-results-low-oil-pressure/#findComment-547560 Share on other sites More sharing options...
Joey Mack Posted March 3 Share Posted March 3 All good in my wifes truck, clean as a whistle. My old Heavy Chevy has some sludge but no debris or silver dust.. 2 Quote Link to comment https://www.bigmacktrucks.com/topic/73924-oil-sample-results-low-oil-pressure/#findComment-547562 Share on other sites More sharing options...
Joey Mack Posted March 3 Share Posted March 3 back when i was new at this, Earl Harnden, (my old timer) taught me to cut filters open.. I have been doing it ever since.. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73924-oil-sample-results-low-oil-pressure/#findComment-547567 Share on other sites More sharing options...
Lmackattack Posted March 4 Author Share Posted March 4 When I bought the truck 15 years ago. It was running about 50psi at 2100rpm. It might hold that psi with clean fresh oil but not older oil with some fuel delution in it. I swapped in a new dash gauge 5 years ago and it read the same. The truck has really only had 3 oil changes since I have owned it and every time it had fresh oil it was a few psi higher. I have mobil 1 synthetic waiting to go back in now. I dropped the oil pan and pulled the presser relief today. Spring measured 3.46" . Plunger had a little wear on it but nothing I could feel with a fingernail. The picture makes it look worse than it is. Regardless I ordered a new spring and plunger. I did find a metal chunk in the pan stuck to the pick up tube. The tube did not have a screen on it like i thought it would have. It just was some grooves cut into the pipe. I forgot to grab a pic of the tube but will tomorrow. I may pull the pump to see if any metal went thry it. If anything to inspect the pump gears. 1 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73924-oil-sample-results-low-oil-pressure/#findComment-547572 Share on other sites More sharing options...
Freightrain Posted March 4 Share Posted March 4 That glob looks like a chunk of weld? Strange. My 237 pegs my 80# gauge at start up. Runs 60# mostly I remember. Maybe 40 hot idle. Like on my hot rods, we shim the pump relief a touch to get more pressure. Throw a 1/8" washer in there to see if it helps? Way back I'd buy the 100# spring for my motors. I had to buy 200# gauge as it would got 150+# cold start!! That is when we just shimmed stock spring to get 100#. 1 1 Quote Larry 1959 B61 Liv'n Large...................... Charter member of the "MACK PACK" Link to comment https://www.bigmacktrucks.com/topic/73924-oil-sample-results-low-oil-pressure/#findComment-547577 Share on other sites More sharing options...
Lmackattack Posted March 4 Author Share Posted March 4 12 minutes ago, Freightrain said: That glob looks like a chunk of weld? Strange. My 237 pegs my 80# gauge at start up. Runs 60# mostly I remember. Maybe 40 hot idle. Like on my hot rods, we shim the pump relief a touch to get more pressure. Throw a 1/8" washer in there to see if it helps? Way back I'd buy the 100# spring for my motors. I had to buy 200# gauge as it would got 150+# cold start!! That is when we just shimmed stock spring to get 100#. That's what 2 people have said now that it looks like welding slag. I think it looks like block casting that may have flacked off. I definitely will be putting in a new spring and a shim washer to see if it helps pressure come up. Your right about most of these endt675/676 motors coming right up to 80psi on start up. This is lucky to see 60. I 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73924-oil-sample-results-low-oil-pressure/#findComment-547578 Share on other sites More sharing options...
Freightrain Posted March 4 Share Posted March 4 Ya, definitely molten metal. Could have been from the original pour? Porous spot in the sand? I think R model has higher reading oil pressure then a B? It's okay after a few minutes of running but if you drive it while it's cold it will just peg it. Quote Larry 1959 B61 Liv'n Large...................... Charter member of the "MACK PACK" Link to comment https://www.bigmacktrucks.com/topic/73924-oil-sample-results-low-oil-pressure/#findComment-547597 Share on other sites More sharing options...
mechohaulic Posted March 5 Share Posted March 5 11 hours ago, Lmackattack said: That's what 2 people have said now that it looks like welding slag. I think it looks like block casting that may have flacked off. I definitely will be putting in a new spring and a shim washer to see if it helps pressure come up. Your right about most of these endt675/676 motors coming right up to 80psi on start up. This is lucky to see 60. I based on older engines , my thoughts were engine casting; but what does an old man know. question for me is the piece seems to be bent in half == why ?? have seen endt/675 and older peg 80 psi at start up . have to consider those days oil was oil ;; not synthetic 0=20 or what ever . fragment casting pieces were NOT uncommon then. just removed them and go on our way. Quote Link to comment https://www.bigmacktrucks.com/topic/73924-oil-sample-results-low-oil-pressure/#findComment-547601 Share on other sites More sharing options...
Lmackattack Posted March 7 Author Share Posted March 7 So I dove in a little further. I removed the upper and lower plungers from the filter pedestal. The blackend plunger with wear was from the top of pedestal and was kinda stuck in there. I could push it in all the way in but about half way out it was binding. I had to use needle nose pliers to pull it out. The lower plunger is from the bottom of pedestal and came out with my finger. The 3rd pic shows both side by side. Both have the same 21A stamp on them so I assume are the same plunger but obviously one has the chrome worn off it. The plunger spring also had some caked on crap that was not metal but was hard like plastic. Not sure what it was but it was stuck in the spring. I hope to have replacement plungers/springs next week 2 Quote Link to comment https://www.bigmacktrucks.com/topic/73924-oil-sample-results-low-oil-pressure/#findComment-547774 Share on other sites More sharing options...
Lmackattack Posted March 13 Author Share Posted March 13 Pulled 2 rod caps down today. The bearings were spotless. If im reading the bearing numbers right they are noted as a P1 / standard size. I plastigauge them both. Got .003 clearance. Is that within spec? I shimmed the oil pump with new plunger and spring. Installed new plunger and spring in the upper and lower parts of the fuel pedestal. Put the pan back on and filled with oil. I Still have what I consider lower than usual oil pressure. Hot idle pressure is slightly better. Previous was 25psi now its 30psi. However i still have to spin it to 1600Rpm just to see 40psi. And at 2100rpm it is at 50psi. the oil pressure spec per my mack manual says 40-95 psi at governed 2100rpm every maxidyne I drove the oil pressure jumped to 50 right off idle and by 1200 it was pedded at 60-70psi all the way to 2100. This needle barely moves untill over 1200rpm then it slowly increases with rpm until high idle. Still scratching my head at this Quote Link to comment https://www.bigmacktrucks.com/topic/73924-oil-sample-results-low-oil-pressure/#findComment-548053 Share on other sites More sharing options...
terry Posted March 13 Share Posted March 13 Sounds like nothing to worry about to me! Terry 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73924-oil-sample-results-low-oil-pressure/#findComment-548059 Share on other sites More sharing options...
Joey Mack Posted March 13 Share Posted March 13 looks like you pulled rod caps.. good deal, however, Main #2 + #5 feed the top end. Did you pull those? Quote Link to comment https://www.bigmacktrucks.com/topic/73924-oil-sample-results-low-oil-pressure/#findComment-548061 Share on other sites More sharing options...
Lmackattack Posted March 14 Author Share Posted March 14 On 3/13/2024 at 6:08 PM, Joey Mack said: looks like you pulled rod caps.. good deal, however, Main #2 + #5 feed the top end. Did you pull those? I did not. I was hoping the bad plunger I found was the issue. Talking with others it seams .003 is the upper limit for good rod clearance. General consensus is I should just roll in a standard set of rods and mains next to see if it cures my concern. If that don't fix it it's probably worn auxiliary shaft or cam bearings. I may pull the valve covers just to see how oil flow up there is. Quote Link to comment https://www.bigmacktrucks.com/topic/73924-oil-sample-results-low-oil-pressure/#findComment-548104 Share on other sites More sharing options...
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