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456 GT clutch pedal...and more

Discussion in '456/550/575' started by JJPan, Mar 30, 2021.

  1. JJPan

    JJPan Rookie

    May 11, 2020
    5
    Full Name:
    PanPolski
    Hello everyone.
    As a welcome note, I would like to write that I have already looked through the threads regarding the clutch - e.g. this one ( https://www.ferrarichat.com/forum/threads/456-gt-how-to-bleed-clutch-master-cylinder.506517/ ), but I have not found a solution to my case.
    it is a 456GT from '94 - the vehicle started normally, gears were engaged normally - the clutch worked properly. One day I got into the car after a long stop, I wanted to start and suddenly the clutch pedal hit the floor. Lost the ability to shift gears. I checked the leaks and there were none. I bought a master clutch cylinder and replaced it - although the old one seemed good to me. Yesterday I tried to bleed the system - and what was my surprise when after unscrewing the vent at the bottom of the box (bleed) - no fluid comes out of it (even when pumping with the clutch pedal). Anyone have an idea what it might be?

    By the way, I would also like to ask about the cooling system - after starting the engine, the car tends to catch the operating temperature very quickly. Then it comes out on about 3/4 of the scale and turns on the fans. Overall the temperature is below half and the fans are running almost all the time.
    I am waiting for a timing replacement, I bought a modernized water pump, I also did a cheap test for exhaust gases in the cooling system (negative result) - any idea of this condition?
     
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  3. Robbe

    Robbe Formula Junior
    Silver Subscribed

    Aug 22, 2013
    608
    The Netherlands
    The clutch problem sounds like a problem with the slave cylinder. On a 550 it is a combined system on top of the bell housing, not sure about the 456.
    As you do not have leaks, but no pressure, it must be an internal leak. After replacing the master, this is the only part left.

    About the cooling, it is normal that the temp first rises fast, as the thermostat is only allowing the "short'route for the coolant. When it comes above a certain threshold, it opens and the long route is used. That leads to a sudden drop in temperature, rather normal.
    But the fans should not be on all the time,
    the sensor that controls it must be faulty: it does not `open ` the sensor´s internal circuit at the right lowered temp anymore, so when the temp is low enough again for the sensor to `open ` and thus no signal , it stays a closed current loop, still sending the signal that the temp is high, and make the fans work all the time.
     
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  4. JJPan

    JJPan Rookie

    May 11, 2020
    5
    Full Name:
    PanPolski
    Im not sure, in my opinion temp is too hight. Approx 100-110 C.
     
  5. Robbe

    Robbe Formula Junior
    Silver Subscribed

    Aug 22, 2013
    608
    The Netherlands
    #4 Robbe, Mar 30, 2021
    Last edited: Mar 30, 2021
    I guess I misunderstood a bit, I understood that the fans stay on too long. My mistake.

    If the temperature , minutes after starting the engine, does not drop from around middle of the meter to a little lower, chances are your thermostat is not working well.
    Test from cold:
    Try feeling the large hoses to and from the engine to the radiator.
    If they remain cold-hand warm up to the moment the fans cut in, it is not ok.
    Drain the radiator from below, and open up the thermostat housing, and test the thermostat in a pan of hot water to see if it opens or not, and closes again when the temperature is lower again. (procedure can be found all over youtube I think,)
    Don't forget to add a bit sealant to the housing when bolting it up again., the special rubber gasket often is not enough to seal completely due to corrosion over the years.

    If the fans only start working at a temp of 100-110C , then the first threshold sensor does not work. The high temperature is more or less a back-up sensor, which signals only at high temps...so at least that one works, but the first does not.
    There are 3 sensors in the cooling system, all of which are underneath the intake manifold. 2 are cheap ones , and one more expensive one is the signal for the meter in the cabin.

    So if I am not mistaken, one of the 2 cheap sensors is broken. But the complete intake needs to come off to replace it...
    But I hope I am wrong, and maybe I forgot a sensor on the radiator or somewhere, before you have to pull the manifold...
     
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