[Healeys] Overdrive pressure not releasing.
Bob Spidell
bspidell at comcast.net
Sun Apr 17 16:18:45 MDT 2022
I think that's the O-ring for the operating pistons. Mine were slightly
flat-sided at 200K+ miles.
On 4/17/2022 1:47 PM, gradea1 at charter.net wrote:
>
> Don't think that issue has been resolved. Moss sells the replacement as:
> Austin Healey 100, 100-6, 3000 Clutch, Gearbox & Drivetrain
> Overdrive BN1 <https://mossmotors.com/overdrive-bn1> 76 O-RING BN1
>
> --79
>
> 866-690 <https://mossmotors.com/o-ring-27?assoc=172485>
>
> <https://mossmotors.com/o-ring-27?assoc=172485>
>
> O-RING 89 cents each-chafe them and replace them. Hank
>
> ---------------------------------------
>
> From: "Michael Salter via Healeys"
> To: "Bob Spidell"
> Cc: "healeys at autox.team.net"
> Sent: Sunday April 17 2022 12:04:24PM
> Subject: Re: [Healeys] Overdrive pressure not releasing.
>
> Actually Bob I've never used an "O" ringed accumulator.
> I spent a little time many years back looking into using "O" rings on
> the accumulator but couldn't resolve the issue of the ring being
> chaffed when passing over the radial drillings in the accumulator body.
> Does anyone know how that has been solved?
>
> M
>
> On Sun., Apr. 17, 2022, 2:49 p.m. Bob Spidell, <bspidell at comcast.net>
> wrote:
>
> Michael,
>
> Sounds like you're implying the O-ringed accumulator is superior
> to the metal ring (OEM) type? Wish I'd known about it when I
> rebuilt my O/D (I bought the DWM 'uprated' accumulator).
>
> I'll throw out another, very unlikely, potential cause: the cone
> clutch could be stuck together. I've heard of this happening, but
> have never experienced it my self--nor has anyone I know--but it's
> theoretically possible (esp. if the clutch is excessively worn).
> Could this be the reason the manual is adamant about replacing the
> 8 strong springs, of two lengths, that oppose the operating
> pistons on overhaul, regardless if they still seem robust?
>
>
> On 4/17/2022 9:31 AM, Michael Salter via Healeys wrote:
>
> Simon,
> Based upon your synopsis I conclude that the operating valve
> is NOT opening when either the solenoid lever or the setting
> lever is being moved to the position where the operating valve
> ball would normally be lifted off its seat.
> This conclusion is based upon your discovery that the pressure
> in the accumulator, as indicated on the gauge, does not leak
> away overnight.
> There is a small clearance between the operating valve push
> rod and the overdrive housing. If the operating valve ball was
> indeed lifted off its seat all the oil in the accumulator
> would, over time, leak past the operating rod thus discharge
> the accumulator.
> This process would indeed take some time but would certainly
> completely relieve most, if not all the residual accumulator
> pressure overnight.
> If however the operating valve ball is still in contact with
> its seat (i.e. not being lifted) the oil pressure would not
> reach the small clearance between the valve push rod and the
> housing and, other than past the accumulator rings there is
> nowhere for that pressure to be relieved.
> I would presume that Overdrive Spares installed an accumulator
> with an "O" ring rather than the original cast iron rings. If
> the original type accumulator piston was still fitted, oil
> would seep past the cast iron rings to relieve the pressure,
> albeit very slowly, and again the accumulator pressure would
> be discharged overnight..
> The cam on the operating shaft, the one which lifts the
> operating valve push rod and thus the operating valve ball, is
> locked to the shaft with a small taper pin. I would guess that
> the taper pin has either fallen out or sheared.
> Bad news is that this pin cannot be accessed without removing
> and disassembling the overdrive.
>
> M
>
> On Sat, Apr 16, 2022 at 1:19 PM Simon Lachlan via Healeys
> <healeys at autox.team.net> wrote:
>
> My OD is driving me mad and I definitely need some
> inspired advice. A bit of background first. I’ll try to
> lay out all the facts in a logical sequence. (I’m
> increasingly reluctant to link ODs with logic!)
>
> 1. I’d say that the OD has done +/- 15k miles since a
> total rebuild by Overdrive Spares here in UK.
> 2. The OD had issues before Christmas (21) and was sorted
> out by OD Spares. The accumulator was uprated and
> pressure issues sorted.
> 3. OD functioned 100% on the few times I’d been able to
> take it out since then until..
> 4. One day, the OD stopped functioning.
> 5. I checked the electrics. All fine there so I delved a
> bit deeper.
> 6. It had fried its solenoid which I replaced. But…
> 7. That did not fix the problem so…
> 8. I decided that the operating valve’s adjustment might
> be off so..
> 9. I bought a dial gauge and hoped to sort it out
> precisely rather than by “feel”, which I lack in this
> area.
> 10. Prior to using the gauge I decided to see if the OD
> was functioning at all so I raised the car on stands
> and fitted my pressure gauge.
> 11. I get a reading of 500psi rising a bit when I rev the
> engine but I’d suppose that would drop when the oil
> warms up.
> 12. BUT, and this is where things go pear-shaped…moving
> the little lever on the RHS up and down does not
> engage/disengage OD. There is no change on the gauge
> to show OD engaging or disengaging.
> 13. AND, the gauge stays at 500psi even when the engine is
> off. Moving the lever 20 times has zero effect. Stayed
> at 500 overnight!
> 14. Of course, I checked for dirt in the operating valve
> area. None.
> 15. Likewise, the tiny hole in the “valve – operating”
> (the spindle thing which the ball sits on)….that’s
> clear. And surely, the pressure would diminish
> overnight if something in that area was partially
> obstructed?
> 16. When I remove the pressure valve, there’s a small
> spillage – no more than you’d expect – but repeating
> the pressure gauge process only returns the same results.
> 17. I see in the bible according to Norman Nock that
> “Holding this lever with your thumb and index finger,
> you should be able to push the lever down lightly
> about ⅜” until you feel a slight spring pressure
> resistance. The lever should go down another ¼” after
> encountering the resistance……” ie there’s about ⅝”
> movement up & down in that lever. Well, my lever does
> move and does lift the ball, but there’s not ⅝”
> movement there. Could that be the problem area???
> 18. Almost finished…keep reading!
>
> So, I’m stumped. Every time I learn something new about
> the OD, it has a new trick to baffle me.
>
> I’ve no 100% sure way of telling whether it’s gone into OD
> and stuck there or whether it’s simply not going into OD
> at all.
>
> I’ve done a lot of reading through my books and collection
> of advice from the various gurus and found reference to
> ODs being stuck but those seemed to be to do with “weak
> springs” which, particularly after a long lay-off,
> wouldn’t disengage. The cure for this being a good smack
> on the steel plate sandwiched in the OD from below. Well,
> that seems to be a stuck mechanism issue whereas I’m
> facing a hydraulic conundrum. Or am I?
>
> There is what is usually referred to as the “pressure
> relief valve” adjacent to the accumulator. The name
> suggested that pressure might be stuck in that area….but
> surely not overnight?
>
> Any ideas? I am particularly reluctant to take the gearbox
> and OD out. You’ll recall the ridiculous business of the
> defective clutch kit? Well, I forget whether we had the
> box in and out 3 times or 4. I’d hoped not to do it again
> so soon or ever for that matter.
>
> I’m hoping for a miracle of course but some sound advice
> would be a godsend…………
>
> Thanks,
>
> Simon
>
>
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