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F355 oil pressure sensor

Discussion in 'Technical Q&A' started by maranello71, Jan 25, 2004.

  1. maranello71

    maranello71 Formula 3

    Jan 23, 2004
    1,215
    Chicagoland
    Full Name:
    Andre
    Last year I proceeded to a full engine rebuild of my F355 - the oil pressure was low and we discovered the bearings to be fairly worn out. Plus the heads were re-done, since the valve guides were totally worn out. I wasn't happy about this - I'd expect a modern engine to last more than 35'000Kms!

    However, lately I got worried again as the oil pressure refused to go beyond 4.5 bars when hot. The mechanic checked with an external pressure gauge and stated that nothing is wrong with the engine (JUST AS WELL!!) - apparently the gauge is reading 1.5 bars too low. Als, when the engine is cold the gauge reads as much as 8-9 bars and seems to be quite erratic - surely a sign that something is wrong with the sender?

    If anyone has had experience of this problem please let me know what I have to replace: Ferrari Switzerland have told me that replacing the oil pressure sensor will cost a whopping US$ 250 - but I'm sure I can get this thing cheaper elsewhere. Does anyone out there have any suggestions, and could I replace the sensor myself or is it a complicated job?

    Thanks
    Andrea
     
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  3. yfc

    yfc Karting

    Dec 23, 2003
    212
    Geneva / Switzerland
    Full Name:
    Christophe
    Andrea,

    The hostest the engine is, the lower the oil pressure will/can be. This because the oil is getting more fluid. I therefore would not be worried by a 4 bar oil pressure when the engine is hot.

    On my first day with my F355, I also became worried when the oil pressure red light when on. It was mid of July (under very high Swiss summer temperture), with a hot engine at idle. Ouah!!! Got really upset by having a problem on my first day as you can immagine.

    My friend who was with me this day, had quite the same pressure/temp than me on his Testarossa.

    Have you checked - as per the F355 user manual - the oil pressure at 6000rpm and 100°C? Is it around 5 to 6 bars?

    Bye for now,
    Chris.

    PS : Did you register youself to the Fchat European section? There is a running list of the European Fchat members. As well as a Swiss F-car rallye.
     
  4. rexrcr

    rexrcr Formula 3

    Nov 27, 2002
    1,572
    Kalamazoo, MI
    Full Name:
    Rob Schermerhorn
    4.5 bar (67 psi) is no cause for worry with hot oil at high rpm. A slight flickering of the oil pressure warning light at idle with hot oil is not an indication of imminent failure, only an annoyance. As stated, cold oil pressure will always be higher than hot oil pressure (viscosity).

    The difinitive check is with a Bourdon-tube pressure guage connected at the same port the oil pressure transducer is located. The easiest way to manufacture an adapter is by destroying an old sender and drill/tap the correct threads for your manual gauge.

    Typical old-timers rule-of-thumb is 10 psi per 1000 rpm. I realize the WSM may state higher values. Too high oil pressure costs HP to the wheels and potential higher component wear rates.


    Best regards,

    Rob Schermerhorn
     

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