[Healeys] Overdrive pressure not releasing.

[simon.lachlan at alexarevel.plus.com]

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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