BJ8 Overdrive Accumulator Spring Tube

[AUSMHLY]

Hello,

I'm wondering why my 1964 BJ8 overdrive accumulator spring tube does not have the bleed hole.
I believe it's suppose to. (#44 in the diagram) Being I don't have the hole, how does that affect PSI?

I have about 450-470 PSI in and out of overdrive when the car is warmed up. Should be 470-490.
When OD is engaged, PSI drops 250 instantly 1 second, and returns to 450-470 in about 3 seconds. That's not what the article says should happen.

When I put it in neutral, hit the brakes, and turn off the engine, the PSI drops to 0 in about 10 seconds where I believe it should drop to about 250-300 and stay there for a several hours.

This is from the Healey technical archives, the overdrive:

Start the engine in neutral and adjust the idle to about 1500 RPM. Without feeding any gas, place the gearshift into 4th gear (OD off) while watching the gauge. The pressure should increase from 0 to 300 PSI in TWO TO THREE SECONDS. In another 10 seconds, the pressure should have gone from 300 to 470 PSI where it should remain constant. Keep the car running at 1500 RPM while watching the gauge - it should stay rock steady at 470 to 490 PSI.

Now engage OD while watching the gauge - it should drop about 100 PSI when OD kicks in, then climb back up to 470-490 in about 5 seconds. While watching the gauge, place the gearbox into neutral, hit the brakes, and turn off the engine. When the rear wheels stop turning, the pressure will drop slowly into the low 400's, then continue dropping at a rate of about l0 PSI per minute down to about 250-300 PSI where it should stay for several hours.

1) Was there a time when these didn't have the bleed hole? (#44 on the diagram)
2) Being mine does not have the hole, how is it affecting my system?
3) Would not having this hole have anything to do with not holding pressure when out of gear?
4) Why am I losing all PSI when out of gear?

 

[Bob_Spidell]

My SWAG: It's of little significance, and certainly not the cause of the symptom you describe (but, possibly, the result). The spring tube is only there to house the somewhat less beefy spring in Healeys' O/D accumulators (the reason for which was mentioned earlier). My reasoning (not documented anywhere that I know of): The O/D pump is the 'constant displacement' type, meaning it can increase pressure to the point something gives. Pressure increases until the accumulator piston is pushed back to the 'bleed' hole, which releases it (so, the accumulator is also a pressure regulator). Unless badly worn, there should be no fluid behind the accumulator piston but, in theory, if there was the hole would let it drain. My guess is Laycock decided there was no real need for the hole, and didn't bother to install it as time went by. When I rebuilt my O/D, which was still operating normally the accumulator bore was scored but the spring and tube were dry.

Did you find fluid in this tube when you (presumably) opened-up your accumulator? If so, you've found at least part of the cause of your fairly rapid bleed down; pump non-return valve, operating valve and operating pistons' O-rings could also contribute.