DS BVH gremlins
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Thread: DS BVH gremlins

  1. #1
    skp
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    Default DS BVH gremlins

    Greetings,

    We have just overhauled a BVH box, and all went well for a few days.. Then it started not going into some gears... and now not any, but stuck in 2nd.
    I strongly suspect air in the lines, but how do you bleed this out? We are trying the obvious messy opening of the hydraulic 5 line union at the gearbox end, and hope this will suffice..

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    Does anyone have any guidance on this??

    Stuart

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    Fellow Frogger! mberry's Avatar
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    At a guess I would expect the air in the system is collecting in the CR and that is likely restricting the clutch movement, I would be running bleed hoses from CR and CRC back to the tank as per the manual. Then keep doing it, assuming the front wheels are off the ground. Doing everything to promote moving fluid around the system, steering lock to lock, suspension, would try the manual clutch control lever also. Then doing the brakes. It makes sense that given the work completed bleeding the entire system may take longer than you might expect for the changing of the CR for example.With limited bleed options, brakes front and rear and the CRC and the CR, I'm not sure of any other bleeding options available, so you may just have to be extra vigilant. I hope this serves as encouragement to persist, for me, bleeding has always proven fruitful for some very odd BVH behaviour in the past.

  3. #3
    BVH Roger Wilkinson's Avatar
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    I can think of a couple of ways to bleed BVH. One is to keep running it through all the gears by selecting them all in turn while the engine is running. The other is to bleed the centrifugal regulator (assuming your system has one) while each of the gears is selected.

    Roger

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    There are a couple of things that might cause your problem, air in the lines is a good place to start. Not sure how familiar you are with the system so going to start with the basics. On the centrifugal regulator (CR) there are 2 bleed screws. The one closest to the pulley bleeds the CR and the rear one bleeds the front brakes via the right hand brake calliper. Fit a piece of clear hose to the bleed screws and run them back to the tank. If The brakes haven't been bled for a while it would be worth collecting and assessing the condition of the fluid that comes out of the brakes, If it's not bright green, toss it. With the car running open the front one slowly as there is always pressure behind it. Open the rear one with your foot on the brake pedal. Keep an eye on the level in the take so the pump doesn't start sucking up air.

    There is another bleed screw on the fast idle device bolted to the carby. Fit a clear piece of tubing to the bleed screw and open it while depressing the brake pedal. This should bleed the front left calliper as well. On an EFI car this unit is located on the side of the engine block buried underneath the auxiliary air valve and is barely visible under all the air pipes.

    You have two options for bleeding the gear selector. Jack up the front end and remove the wheels. The first is to cycle through all the gears a good few times. The other is to loosen the flare nuts at the gearbox cover, not the 5 pipe union, and cycle the gears.

    Now with all that said, air in the lines won't cause the car to remain stuck in a gear. In order for that to happen, LHM must be prevented from returning from the slave pistons to the tank or the slave pistons are jamming in their cylinders. It is possible for a small piece of rubber to break off the rubber seals and block the pipework and slide valves. Undo the return lines from the top of the tank and the rubber hose from the gear selector to check for fluid flow.

  5. #5
    skp
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    Quite familiar with the BVH system... Tho' some things still mystify me..
    The standard bleed procedures I am familiar with. Even with this, the gearbox actuators are still a dead end, and the fluid just oscillates along the length of the line to the selector 'brain'. I have bled them ( and pre-filled them on replacing the internal o-rings and re-setting the actuation distances..) I feel that the great pressure of the hydraulic system would result in any trapped air being dissolved into the fluid. Bleeding this AT the actuators seems sensible. Still no resolution.
    After thinking it through, I have come to the conclusion that the problem lies not with the hydraulics, but with the mechanical aspects of the gearbox - specifically the lock out bar. This seems to have stopped operation, and so prohibits the selector shafts from moving.

    Pity, as the bloody thing is stuck in 3rd! Made moving it to the hoist an interesting challenge....

    Fortunately, the clutch lock-out valve is working well, so having the motor running ( after starting the car with the wheels off), powers up the clutch piston - so despite being "in gear", the clutch is still disengaged. Just to be sure, I un-coupled the lock-out link to the 1st. / 2nd shaft, so that it remain in neutral, and so powers the clutch cylinder. What fun!!

    I have a sneeking suspicion that the Lock-out bar has jammed... it would explain why it all operated wonderfully for a few days, then started to 'loose' a gear here and there.... then mistake 1st for reverse... and so on, until NOTHING works!

    The gearbox was rebuilt by a professional workshop ( out of my competence / experience!), and the synchro's were replaced.
    I had the fun of figuring out quite how the gearbox cover selector actuators should be set, but it is quite simple - even if the workshop manuals make it almost incomprehensible.... I am happy with these set-ups, and am sure that they are operating correctly.

    We took the lid off the box, and find that we cannot move ANY of the selector shafts. Surely this must indicate that the lock-out bar is not moving as it should...? Perhaps it's spring has broken.. ?? Unfortunately, this looks like a total engine gearbox removal to get AT the lock-out shaft... Bugga!!!
    More tomorrow....

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    skp
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    Speaking of which..... Anyone interested in a better guide on how to re-set the selector rod actuator pistons than is provided in the manuals..?? I took a number of photos along the way to enlightenment !!

    skp
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    Tadpole
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    When you remove the lid you have to move the reverse selector rod a tad forward to to get neutral ,check then if you can manually select the gears ?

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    Quote Originally Posted by skp View Post
    Speaking of which..... Anyone interested in a better guide on how to re-set the selector rod actuator pistons than is provided in the manuals..?? I took a number of photos along the way to enlightenment !!

    skp

    Yes. I have a leaky BVH cover that I need to reseal and would welcome some insight.
    Cheers,
    John T.

    54 11BL; 61DS19 LHM (son's); 71DS21 BVH; 73SM 3.0; 73SM 2.7EFI; 73SM 3.0 (other son's); 74 Maserati Merak

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    skp
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    Ahh! John, I was hoping that you would join in this conversation..
    As you will have read, I think the problem is more mechanical than hydraulic. Getting another, professional gearbox opinion today, so we will see where that leads me.

    Yes, I will write up the actuator reset procedure into something resembling understanding. The manuals tell you WHAT to do... sort of, but not WHY. If you don't know why you are doing something, then you don't know if you are doing something wrong.
    I'll get an article together in a day or so.

    Also been having some fun with an SM dizzy that has had incorrect advance weight springs fitted - much too loose! About 3mm of free play before the low tension spring acted. Getting it sorted back to the correct advance curve.

    Stuart

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    skp
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    Yes, understood about the reverse gear placement. What was puzzling is that the car drove perfectly for 3 days - then gradually deteriorated.
    More information tonight, I hope.

    S


    Quote Originally Posted by myourd View Post
    When you remove the lid you have to move the reverse selector rod a tad forward to to get neutral ,check then if you can manually select the gears ?

  11. #11
    skp
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    Bugga. Problem has been identified, and it is indeed mechanical. The 3rd. / 4th cluster has 'overshot' and the keys inside have come out of place, locking it in place. Have to pull the bloody thing out and apart.
    How to prevent this? Appears that although we set the actuators as per the manual, I will have to mal-adjust the throw of the .. 4th. gear(?) actuator to LIMIT the throw of the 3rd gear actuator piston. Not happy about this, but there appears to be no other way of doing this.

    skp

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    Don't forget that I have a 'spare' BVH gearbox, slightly cooked, sitting attached to "Vicky" in my hay shed! ;-)
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    Quote Originally Posted by skp View Post
    Speaking of which..... Anyone interested in a better guide on how to re-set the selector rod actuator pistons than is provided in the manuals..?? I took a number of photos along the way to enlightenment !!

    skp

    ME! ME! ME PLEASE! I've always found the instructions for those little pistons on the gearbox couplings a complete mystery!
    1968 DS21bvh Pallas in Gris Palladium

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    Too many posts! JohnW's Avatar
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    Quote Originally Posted by skp View Post
    Bugga. Problem has been identified, and it is indeed mechanical. The 3rd. / 4th cluster has 'overshot' and the keys inside have come out of place, locking it in place. Have to pull the bloody thing out and apart.
    How to prevent this? Appears that although we set the actuators as per the manual, I will have to mal-adjust the throw of the .. 4th. gear(?) actuator to LIMIT the throw of the 3rd gear actuator piston. Not happy about this, but there appears to be no other way of doing this. skp
    Bugger indeed. Good luck with it.
    JohnW

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