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oil pressure low

Discussion in '1982-Present GM Diesel' started by jp0863, Nov 22, 2005.

  1. jp0863

    jp0863 1/2 ton status Premium Member

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    what is normal oil pressure in an 85' 6.2 diesel? mine is military and the pressure drops way low when it's warm at idle. i know some of the ford 6.9's run at a low 3-5 psi at idle and thats normal for them according to a local shop. pressure is fine at startup and it has a new oil pump. does anyone make a high pressure pump?
     
  2. DieselDan

    DieselDan 1/2 ton status

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    I'm reachin' here but this is a 6.2 block, right? The reason I ask is I know 6.5 turbo blocks have piston oil squirters. The oil pressure drops real low on idle. I've NEVER heard of a CUCV getting a 6.5 swapped in, but I've been surprised before. How many miles are on the truck? (not really a good indicator on a ex-military vehicle) Maybe your bearings are just worn (clearances are too big).

    Oh ya, the block should be marked on the front of the engine, just below the passenger's side head (behind/bleow the altenator).
     
  3. kennyw

    kennyw N9PHW Premium Member

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    You may also have a problem with the guage or sending unit itself... if you have not already done so I would add a mechanical oil pressure guage temporarily under the hood to double check it.
     
  4. jp0863

    jp0863 1/2 ton status Premium Member

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    it's a 6.2 and has about 78 or 79,000 miles on it. i have tried a mechanical gauge and now have an autometer gauge and both read low. i'm throwin around the idea of tossin in a big block anyhow, but kinda like the diesel for mileage and being able to take any angle offroad.
     
  5. DieselDan

    DieselDan 1/2 ton status

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    Well I'll probably be spanked for suggesting it: but you could drop the pan and slap some new bearings in. It's not really the right way, but if your compression is still good I'd hate to have to rebuild the engine so early.

    Check Northern Auto Parts for some the better prices on rebuild parts. :wink1:
     
  6. imiceman44

    imiceman44 1 ton status

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    I have done that before, it works if the engine was in good shpe but the bearings where bad.
    :D
     
  7. jp0863

    jp0863 1/2 ton status Premium Member

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    i'll have to look at that. i like the diesel, even if it's gutless. and it gets better mileage than my 04 powerstroke. thanks for the info.
     
  8. diesel4me

    diesel4me 1 ton status Premium Member

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    get the crutches..

    Maybe since you live in CA,you could use thicker oil,or add some Lucas motor treatment to boost the pressure up..I run 15W-40 in my 6.2,but if I lived in a warmer climate I'd use SAE 30 all the time--you might be able to use SAE 40 out there....if you only have a true 78K on the motor,I'd think the bearings shouldn't be worn that quickly ,unless it had infrequent oil changes..it could be just the oil pump relief valve spring is letting pressure bleed off too early,or worn gears in the pump..or the oil is breaking down..

    Sometimes oil will break down and lose viscosity when it gets hot..I had one customer call fuming about his corvette's oil pressure dropping to 15 psi at idle after it warmed up,after he changed the oil with "Amalie" brand 20W-50 oil
    I sold him!..he showed me the gauge in the parking lot when he came back to the store,and complained to my boss,said "that Amalie oil is crap--it wrecked my motor!"-my boss told him Kendall made Amalie,and its as good or better than many other major brands--

    -the customer bought 5 qts of the usual Valvoline 20W-50 he usually used and a new filter,and changed it right in the parking lot!..my boss said he'd GIVE him the oil and filter if the oil pressure went back to normal when hot (he figured the bearings or oil pump were on their way out)..but after a 20 mile drive with the customer,it still had 35 psi at idle!..

    He also put a "Wix" filter on with the Valvoline ,instead of a "Fram" (we only had the 1 Fram in stock I'd sold him earlier,so I had to sell him a Wix instead!)...my boss had me hand his money back--but he said it was probably the Fram filter bypassing that caused the pressure loss..who knows?? :dunno: :screwy: All I know is his Corvette never went below 35 psi after that,and he drove it at least a few years after that!..swore he'd never use Amalie oil again,or Fram filters,after I showed him a cutaway display comparing it to the Wix!..might be something to think about..

    I remember when Quaker State put SAE 40 oil in 10W-40 bottles up here about 15 years ago,and many motors suffered cold start damage that DID start--many others would not turn over at 0 degrees!..We never really know WHAT viscosity is REALLY in those bottles--might be mis-labelled!..

    "Cheap" oil seems to lose pressure more than high quality name brand oils at operating temparature..I noticed a difference in a 350 I had when using Wal-Mart "Tech 2000" brand VS Castrol GTX 20W-50--about 10-15 psi difference at idle after a long highway drive!...anyway,I hope your bearings are not the problem... :crazy:
     
  9. DieselDan

    DieselDan 1/2 ton status

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    OK I'll bite: what the hell is a bearing roll? Can I have some butter on that and another cup of coffee? :haha:
     
  10. mudnmyvayne

    mudnmyvayne 1/2 ton status

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    :doah:

    Man,that one took me by suprise. Fill us in plz :D
     
  11. jp0863

    jp0863 1/2 ton status Premium Member

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    i'll try a better oil and filter next time...... i did use cheap oil last time cuz they were out of delo 400. and come to think of it, i have a fram filter on it right now. i'll let everyone know what happens. delo and wix this next time. thanks!
     
  12. BiggBlazer

    BiggBlazer Registered Member

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    My 86 cucv1009 had 54k when I bought it and when hot, really hot the oil
    pressure drops to 12psi at idle, and 37psi at 2000rpm. In summer I use 15w40
    and winter I use semi-syn. 0w40.
     
  13. jp0863

    jp0863 1/2 ton status Premium Member

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    well so far i have spoken with 3 different mechanics about the issue. all of them highly recommended diesel mechanics (one is a diesel mechanic instructor) all have said the same thing...."oil pressure as low as 5 psi at idle when warm is no problem and is inherent with the 6.2 chevy and 6.9 ford diesel" and all said "i wouldnt worry about it". spoke to all at different shops at different times and they were pretty cool to deal with. anyway, i will still try the different oil, got some delo 400 the other day.
     
  14. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    My oil pressure is about 27 at idle and operating temp, 45 psi on the freeway. Cold it hits 55-65 depending on ambient temps...

    My 6.2 has 230,000 miles on it.

    Rene
     
  15. DieselDan

    DieselDan 1/2 ton status

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    Not to sound pessamistic, but every HMMWV I've ever seen has never dropped oil pressure that much. We have 19 variants in our company, plus I've been driving them since '89. That being said almost all were 6.2's. Although we did have six Conact Maintenance trucks with (normally aspirated) 6.5's, but they're pretty new still.

    Now most big diesels run full-floating rods with oil passages through the rods and/or piston oil sprayers. This really drops oil pressure at low RPMS. 6.2s don't have all that. You could check with GM to see if there are any TSB about low pressure at idle.

    If were mine, I wouldn't worry that much about it either. :D
     
  16. painterbccc

    painterbccc Registered Member

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    Heard it was take take main cap off others loose stick it on crank with stp and turn crank over by hand and roll bearing into place. That might not be it. Never seen it done or tried it.
     
  17. joez

    joez 1/2 ton status

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    That sounds very low. My 6.2 has over 235K on it and doesnt get that low. At cold startup and driving it makes 50-60psi, when hot it drops to 20-25 idle and then runs ~40 above about 1200rpm. 15w40 Rotella and a 2 quart wix filter, I run that combo year round in both diesels.
     
  18. jp0863

    jp0863 1/2 ton status Premium Member

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    ok, recently changed oil. using chevron delo 400 and a wix filter from nape. oil pressure is around 20 at idle after it's warm. 45-50 when it's cold. also i switched the power wire on my oil pressure gauge to another location. seems the old location was powering intermittintly causing the false reading....
     
  19. DieselDan

    DieselDan 1/2 ton status

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    SWEET. Glad you found the problem(s). Bet you can sleep better :D
     

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