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Oil pressure relief valve cap - leaking

Discussion in '308/328' started by Peter, Apr 24, 2011.

  1. Peter

    Peter F1 Veteran
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    Dec 21, 2000
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    #1 Peter, Apr 24, 2011
    Last edited by a moderator: Sep 7, 2017
    This is one of the few items I have never touched on this engine, and probably has never been touched by anyone else prior to my ownership and has been dry up until this point. As I'm in the midst of doing my annual oil change, I've been poking around underneath and there was a sizable drop of oil clinging to the bottom of this cap (I wiped it up before I took the photo).

    Can I remove this cap in situ? I know there's a spring and piston behind it, but is that spring exerting a tremendous amount of force (in other words, is it going to poke my eye out when I remove the cap)?
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  3. fastradio

    fastradio F1 Rookie
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    Sure can, just be aware of the spacer shim which is typically "stuck" inside of the cap. The spring tension is minimal in that you'll have no safety issues removing the cap.
     
  4. Peter

    Peter F1 Veteran
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    Thanks!
     
  5. pad

    pad Formula 3

    Sep 30, 2004
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    I had a B^#$# of a time removing that cap even with an air gun. I ended up soaking it with penetrating oil for a few day before it would move. Hopefully, you'll have an easier time.
     
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  6. spgribben007

    spgribben007 Karting

    Nov 11, 2010
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    Can you post pics of this cap removal? I have to do my first oil change and would enjoy not to have any surprises.
     
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  8. WaltP

    WaltP Formula 3

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    I think it would be a mistake to remove "this" cap for an oil change.
     
  9. smg2

    smg2 F1 World Champ
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    spring loaded bypass valve, there's a spec for the free length on them. the shim is 2mm thick and the 2v spring is 76mm long free length and the Qv is 74mm, I don't recall the tension force to length off the top of my head though.

    check to make sure it's within spec and moves freely, you can also move the piston internally to see if it holds a seal. you'll get a bit of oil dribbling out when removed so have a rag handy.

    the only adjust-ability would be via shims, and that's not something I'd recommend for the avg DIY as this controls the oil pressure in system and you don't want to blow seals or wipe bearings with the wrong pressure.

    If you're concerned about the pressure it's a good idea to check it with a mechanical gauge.
     
  10. Robz328

    Robz328 F1 Veteran
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    I wouldn't remove until I verified the leak was coming from the cap. The oil could be from elsewhere.
     
  11. Peter

    Peter F1 Veteran
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    Dec 21, 2000
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    Sure.

    I'm not doing it just for the oil change. Like I said, I've had no reason to remove this before, only now because it's leaking.

    DEFINITELY leaking. Everywhere else was bone-dry

    Thanks for the hints/tips.
     
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  13. Peter

    Peter F1 Veteran
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    #10 Peter, May 1, 2011
    Last edited by a moderator: Sep 7, 2017
    Okay, I tackled this on Saturday morning. It couldn't have been any easier. It was seriously tight - couldn't budge it with a 24" breaker bar - so I used my 1/2" electric impact wrench. The hex size was 32mm (although an 1 1/4" socket fit perfectly). It didn't take much using the impact. I allowed it to rattle it a bit and then it free-spun quite quickly. I stopped it about three threads short of it coming off. I spun it off by hand and there was only a slight pressure behind it. As my car has been sitting a while, the oil had drained out so I didn't spill a drop.

    Now the problem. It seems to be that the sealing face (either the cap or the casting) is not perfectly perpendicular to the threads. You can see the wear pattern and the staining on the copper gasket of the uneven contact. My next step is to confirm using blue layout dye to see where the unevenness is. I'm not sure at this point how I'm going to remedy this, but I can say one thing, I ain't hauling out the engine for this! I'd rather just use either teflon tape or Hylomar on the threads as a bandaid, or try to make a facing/lapping tool (like lapping in valves into their seats) at the most... This car has to be done by the end of May (or preferably sooner) as I have a club event I'm organising, so I can't get too involved in this repair.

    The piston moved very easily, although you can see some polishing on the piston. Also on the spring where it sits in the piston. The shims don't appear to be accurately made - certainly not like a valve shim but stamped out like a washer. The free length of the spring is 73.86mm.
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  14. magaoidh

    magaoidh Karting

    May 12, 2009
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    Check the thread is not crossed and fit a new copper washer,its not rocket science!
     
  15. WaltP

    WaltP Formula 3

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    Steve, My my post was directed to Steve, sorry I wasn't clear on that.

     
  16. Rod

    Rod Formula Junior

    Jan 18, 2004
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    Agreed. I recently uprated the spring with the later item as mine my oil pressure reading was starting to drop... The later spring sorted the problem. As for the seal, mine was the same, a new copper washer will do the trick...


     
  17. 85QVEuro

    85QVEuro Rookie

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    I have an 85 308 QV Euro Mondial. My front cover is apart now to change the cam drive pulley bearings and I also removed the plug, piston and spring for the oil pressure. However, I did not find a shim in there and I don't believe this car was taken apart before. TAV 16 of the spare parts catalog shows the shim as item #30 or part # 106238.

    Two questions: 1) is it possible this car came with no shim? 2) why does the poster above (Peter) show two shims in his photos? Thanks for the help
     
  18. Rifledriver

    Rifledriver Two Time F1 World Champ

    Apr 29, 2004
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    I have no idea why he has 2. It is supposed to have one. You should too. In 1986 Ferrari made a change to increase oil pressure in the 3.2 motor and it was too high. Cars were blowing oil hoses off and blowing up oil coolers. They did a recall and in addition to installing better hoses were were told to remove the shim. All 3 liter engines should have a shim and all 3.2 engines should not.
     
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  19. 85QVEuro

    85QVEuro Rookie

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    Rifledriver - Really appreciate the quick response. I'll get a shim (will look first in the bolt/cap)
     
  20. Rifledriver

    Rifledriver Two Time F1 World Champ

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    Make sure because they stick in the cap due to the oil.
     
  21. waymar

    waymar Formula 3

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    I have yet to succeed in removing the cap. Afraid it will break something off. Guess I will have to soak it......
     
  22. Rifledriver

    Rifledriver Two Time F1 World Champ

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    I use a 1/2 inch air gun to remove. I really doubt soaking will do anything. Rust isn't holding it on.
     
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  23. 85QVEuro

    85QVEuro Rookie

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    Thanks Rifledriver - you are spot on here - the oil stuck the shim to the cap
     
  24. Rifledriver

    Rifledriver Two Time F1 World Champ

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    Good. Glad someone said something that reminded me of that.
     
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