Mondial QV: Too much oil in gearbox, too little oil in engine | FerrariChat

Mondial QV: Too much oil in gearbox, too little oil in engine

Discussion in 'Mondial' started by Andras, Aug 31, 2022.

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  1. Andras

    Andras Rookie

    Apr 21, 2022
    Full Name:
    Andras Kalmar
    Hi Mondial experts,

    I bought a decent but slightly neglected 1985 Mondial QV recently, now I'm in the process of giving it all the TLC it has missed in the last few years.
    Got new wheels and tires instead of the TRXs, changed the timing belts & tensioners, all the fluids, one wheel bearing making some nasty noises (which I initially attributed to the rock hard TRX tires), and a new fuse box.

    When I changed the fluids I observed the following:
    - there was less than 4 liters of oil coming out of the drain plug but I had to refill almost 6 liters. OK, that wasn't too worrying, the car was sitting for quite some time and the last oil change was many years ago
    - but then I wanted to change the oil in the gearbox and first opened the upper filler plug. Some 1.5 liters of oil started to spill out immediately.

    - have you ever experienced something like that? I wouldn't know how to overfill the gearbox by that much.
    - There are the separate drain and filler plugs on the clutch housing, where only a small amount of oil (100 grams according to the manual) is required. Are the gearbox and the clutch housing connected? Can you overfill the gearbox by overfilling the clutch housing?
    - since there was oil missing from the engine and but approximately the same amount of extra oil was in the gearbox I'm wondering if there is any link between the two where oil could move from one to the other. The oil in the gearbox was looking and smelling like gearbox oil, no indication of motor oil being in there.

    Do you have any idea what my problem could be and how serious it is?
    The car is driving nicely, no issues with the engine or the gearbox at all.

    Thank you very much for your help
    Andras from Vienna/Austria
  2. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    #2 Steve Magnusson, Aug 31, 2022
    Last edited: Aug 31, 2022
    It's a common problem caused by a leaking shift shaft seal between the engine oil sump and the gearbox main reservoir. A search on "shift shaft seal" should get you many prior threads.

    If the engine oil was "clean" you might not notice it being in the gearbox oil; however, if the engine oil was black/dirty, then it should've been noticeable in the gearbox oil, too.

    Yes, but the clutch housing reservoir is located "above" the gearbox main reservoir (so the clutch housing reservoir can't be overfilled as the excess "waterfalls" down into the gearbox main reservoir).

    Yes, if the gearbox main reservoir fill plug is reinstalled and then a large amount of gear oil is continued to be added at the clutch housing; however, your report of the engine oil being low by a similar amount seems an additional clue. (We have had reports of this overfilling being done on TR where the TR OM has a misprint of adding "17 pints" to the clutch housing reservoir, rather than the correct value of "0.17 pints", but not on Mondial/308/328.)
  3. Andras

    Andras Rookie

    Apr 21, 2022
    Full Name:
    Andras Kalmar
    Hi Steve, thank you very much for the quick reply.
    My apologies for not having found the shift shaft seal threads.
    I have no clue how long it took for the 1.5 liters to bypass that seal but I assume its better to replace the seals immediately.
    Thanks again for your help

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