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Feelin' the Pressure of Low Oil Pressure!

Discussion in 'Technical Q&A' started by Dano's-Dino, Jul 6, 2005.

  1. Dano's-Dino

    Dano's-Dino Rookie

    Jul 6, 2005
    18
    Mountain Home, AR
    Full Name:
    Danny Ohler
    I've been racking my brain (which don't take much). Hope you guys can help. Recently bought a 78 308 GTS. When I first start the car, the oil pressure is just below 85. As I drive awhile, it drops down to around 42 when rev-ed, and at idle it drops to virtually 0, no alarm though. It makes me scared to drive very far, and don't know where to start. Checking the oil cold looks to be at the max. I'd really appreciate one of you "Ferrari veterans" giving me some advice to get me back on the road.

    Thanks,
     
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  3. Mike328

    Mike328 F1 Rookie
    Rossa Subscribed

    Oct 19, 2002
    2,655
    Boulder, CO
    Full Name:
    Mike
    What brand and grade/weight of oil are you using?

    A number of us guys are running an oil which gets low-ish on the oil pressure on hotter days.
     
  4. spang308

    spang308 Formula Junior

    Jul 17, 2004
    887
    York, PA
    Is this a new problem or has the car always run pressures this low?
    What oil are you using?
    How many miles on the car?
    Has anything recently been done that would impact oil pressure?

    308's have a pressure adjustment at the oil pump, but I would not monkey with it unless there is no internal engine factors appearent. If all is well inside the lump, you can screw in the pump adjustment to increase pressure or in some cases shim the pressure relief spring.

    DO NOT do this to cover up something sinister like worn main or rod bearings. You will certainly pay dearly if you do.

    Good luck and welcome aboard,

    John
     
  5. Frank R. Masiarz

    Nov 10, 2003
    126
    Full Name:
    Frank R. Masiarz
    Hi...........

    Zero oil pressure is very bad news !!!

    Could be a bad pressure relief valve or simply a bad gauge. Have the pressure checked by a mechanic ASAP.

    Good luck !!

    Frank......23005
    www.masiarz.net/bb_resource
     
  6. Dano's-Dino

    Dano's-Dino Rookie

    Jul 6, 2005
    18
    Mountain Home, AR
    Full Name:
    Danny Ohler
    I've only had the car a few days and thus don't know several of the specifics. I believe it has 20W-50W Synthetic oil. The car has 47,000 miles, but had the major service two years ago.
     
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  8. spang308

    spang308 Formula Junior

    Jul 17, 2004
    887
    York, PA
    20W50 should rule out light oil. Frank above is correct in stating it could very well be the guage or sending unit. They are know to be, uhh, well, crap..

    Check the pressure with a mechanical guage and compare to what your guage is reading. At least then you could rule out the guage or sender.

    John
     
  9. Steve King

    Steve King F1 Rookie

    Feb 15, 2001
    4,366
    NY
    Could be the oil pressure sending unit. Need to get a oil pressure gage on the block to check to see if it is the engine or sensor.
     
  10. pete04222

    pete04222 Formula Junior

    Nov 1, 2003
    613
    Maine, USA
    Full Name:
    Peter Cyr
    Since you just got the car I guess you are not absolutely sure what it has for oil or when it was last changed. I'd start there first.

    And it should actually be overfull when cold. The filter drains down. You want to warm the car up, shut it off and check it within a few minutes. It holds 9 quarts.
     
  11. f355spider

    f355spider F1 World Champ
    Rossa Subscribed Owner

    May 29, 2001
    17,176
    USA
    Full Name:
    Hugh G. Rection
    Good point, read the manual on how to check the oil. For a 78, you need to warm it up good, shut down, and wait a couple minutes....I believe the manual states to check after 15 minutes for the most accurate reading. Do not read when cold...it will (should) read over max.
     
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  13. Iain

    Iain F1 Rookie

    Jan 21, 2005
    3,217
    UK
    Well, the cold pressure is good & you wouldn't want it much higher - but that may be a product of the oil you are using which would be quite thick when cold I think.

    The warm pressure is maybe a bit low & I'd be more concerned about the 42 rather than the zero. Lots of 'em register pretty close to zero at warm idle.

    As has been suggested, maybe start by replacing the sender and checking all the connections to the guage.

    I
     
  14. Dano's-Dino

    Dano's-Dino Rookie

    Jul 6, 2005
    18
    Mountain Home, AR
    Full Name:
    Danny Ohler
    Hey guys,

    Thanks for all the great advice, that'll give me some things to get started on. I appreciate your help.

    Dano
     
  15. DN35

    DN35 Formula Junior
    BANNED

    Nov 22, 2003
    599
    Illinois
    Full Name:
    D. Norton
    I have a '78 and mine reads very low when hot as well.
     
  16. pma1010

    pma1010 F1 Rookie

    Jul 21, 2002
    2,559
    Chicago
    Full Name:
    Philip
    As has been said, the senders are guilty of poor signals as they "wear". Mechanical gauge or replace or both.
    Philip
     
  17. Wasco

    Wasco Formula Junior

    Dec 9, 2003
    486
    Salem
    Full Name:
    Randy
    I have had simular prob. remember a rule of thumb I learned here. 10 lbs for every 1k revs. I was on the borderline until I ran Valvoline Racing 60 weight. I don't think anyone else here will approve but my pressure is fine now. Watch your temp, oil temp that is. when mine gets around 210 is when I have problems. Usually going from intown to freeway even on a hot day will lower my oil temp 40 degrees and increase oil pressure by 10 lbs.

    Another note is that the gauge is 20+ years old what can we expect!

    I spent 53 bucks on an oil sender with no noticable difference after. However it is a very small investment to eliminate possibilities. I find that if I wait over ten minutes to check oil on a hot day it has already emptied the extra oil from cooler and filter and reads over full. I just change regularly and use 8.5 quarts then add the other pint in a couple hundred miles.
     
  18. delaney

    delaney Formula Junior
    Silver Subscribed

    Nov 8, 2003
    665
    St Petersburg, FL
    Full Name:
    PETER DELANEY
    a) Change the oil and filter if you don't know when it was last done, and see if that fixes the problem.

    b) By a mechanical gauge out of AutoZone or whatever for $15 and stick it on. The hardest part of this bit is finding a crossover that will take the male part of the mechanical gauge and allow you to screw that into the female bit on the engine.

    I did this on my 355 and found the gauge in the car to be low by ~ 25 psi. My problem was a bad earth .. easily cured.

    Regards,


    Pete
     
  19. Ken

    Ken F1 World Champ

    Oct 19, 2001
    16,078
    Arlington Heights IL
    Full Name:
    Kenneth
    My Lotus is similar. 80 lbs when revved cold (I use 20W50 as well) and when warm at revs goes to about 45, but maybe 15 at idle. Maybe less! This is normal. If your gauge drops to zero at idle, I'd not panic and suspect the gauge, but get it checked with an external pressure gauge. It will not cost much to do this and you'll either save your engine, or sleep a lot better at night.

    Ken
     
  20. Jdubbya

    Jdubbya Two Time F1 World Champ
    Silver Subscribed

    Dec 28, 2003
    24,059
    PNW
    Full Name:
    John
    As usual the advice here is right on. I can tell you that it actually sounds pretty normal. My car does the same thing, high when cold and will drop very low when idling warm. You said the light doesn't come on though when it drops low, correct? The light does come on when the ignition is on but the cars not running correct?

    I also agree that it sounds like you are a little low on volume. It should read above full when stone cold. The best advice is to change it, be sure the correct amount is added and then (this is only my opinion, not per the manual!!) note where the level is when cold and full. It is easier (again only my opinion!!) to check the oil this way. My start up ritual is to check the oil before starting, add any if neccessary, THEN start the car.

    The only way to do it properly per the manual is to check it after you park it.
     
  21. Dano's-Dino

    Dano's-Dino Rookie

    Jul 6, 2005
    18
    Mountain Home, AR
    Full Name:
    Danny Ohler

    Once again thanks for all the great advice...I feel better already. The light does come on with the ignition switch before starting, and sometimes there is a buzzer. I will plan to change the oil and if the problem persists, get a gauge on the block this weekend and see what I find. Does anyone know of anything outlining exactly how/where to connect an external gauge, maybe with a picture? Probably not that lucky. If all looks well, I will replace the sender, then gauge as a last resort. I'll report back the results.

    Cruise on.......

    Dano
     
  22. Mr Iceman

    Mr Iceman Karting

    Mar 3, 2004
    101
    Canterbury, England
    Full Name:
    Scott
    I totally understand how anxious low oil pressure can make you feel, and I'm not suggesting that the figures you report are not worth investigating and possibly may need some rectifying, but its worth noting that oil pressure is not what lubricates and cools the engine, its oil flow. and as the oil warms up and becomes thinner you require less pressure to get adequate flow. Its worth bearing this in mind and noting at what oil temperatures the various pressures are associated with. you may have a problem with cooling, does your car have the adjustable flap for the oil cooler?

    AEHaas is acknoledged as the expert on oil on this forum and has a very good in depth explanation on this website : http://63.240.161.99/motoroil/ its definately worth reading and can help destroy some of the myths that suround oil.

    Cheers for now
    Scotty
     
  23. MJT328GTS

    MJT328GTS Formula Junior

    Mar 30, 2005
    356
    St. Louis
    Full Name:
    MJT
    Great post Mr. Iceman! Thanks for the link.

    I had a similar concern about my '88 328 and reading this post and previous ones about this subject really helped me understand what is normal for pressure readings.

    I've only had my car for a few weeks (just about to change my oil for the first time) and I recently took notice how my oil pressure drops to slightly below 42 lbs during idling. Once I rev it up and get it in gear it goes back to 85 lbs, but I had the same questions as Dano about it being too low.

    The prevous owner used 50 weight oil but I'm going to use Mobil 1 10W-40 and see how that works out.
     

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