[Healeys] Overdrive pressure or clutch slip Step 2!

Thu Apr 25 16:26:38 MDT 2024

Simon, re: the throttle switch, just short it out by putting a wire across the two terminals.  Mine was shorted out when I bought my BT7 because the PO did not like it.  I re-connected (or dis-connected the short to be accurate) and came to the same conclusion.  Mine is now permanently shorted out of the circuit by choice – personal preference.

Mirek

From: Healeys <healeys-bounces at autox.team.net> On Behalf Of Simon Lachlan via Healeys
Sent: Thursday, April 25, 2024 4:17 PM
To: 'Bob Spidell' <bspidell at comcast.net>; healeys at autox.team.net
Subject: Re: [Healeys] Overdrive pressure or clutch slip Step 2!

I’ve not looked at that yet. Not ruling it out but I’ve a feeling that, even if it had “gone intermittent”, the OD would jump in & out quite abruptly rather than slip/fade which I’m currently experiencing. But I’ll certainly have a look. The relay is one that I’ve rebuilt…..gutted the old stuff out and swapped in a little modern relay. I’d expect that to be fairly reliable, likewise to (probably?!) fail 100% or work 100%.

Next on the list seems to me to be the Throttle Switch which, I suspect, could just about give one a slipping effect.

OD clutch? Never done that. Never been there. I’ve pretty well drawn the line at accumulators/pressure issues. Always with help and advice from “The List” . 

Could my problem be OD clutch slip? 

How do I diagnose that and how do I get myself in a position where I know it’s the OD clutch and I know that it’s sensible to take the box out and drive it up to ODSpares one (very) early morning?

Simon

From: Healeys <healeys-bounces at autox.team.net <mailto:healeys-bounces at autox.team.net> > On Behalf Of Bob Spidell
Sent: Thursday, April 25, 2024 6:00 PM
To: healeys at autox.team.net <mailto:healeys at autox.team.net> 
Subject: Re: [Healeys] Overdrive pressure or clutch slip Step 2!

Simon,

What have you done to rule out the O/D relay (the one on the scuttle). I've had them go intermittent.

Bob

On 4/25/2024 9:29 AM, Simon Lachlan via Healeys wrote:

So, here is Michael’s “Step 1” completed. (See his email, below).

1.	Removed the operating valve and, just for luck, disconnected the two wires into 3rd/4th switch. Took the car for a spin. Up/down longish/steepish hills, 10 miles on motorway. Various rpm…..no slippage at all.
2.	Had a puncture…..nail in tyre. Rear RHS. Flat as a pancake at once. Nearly onto rim. Nail! I imagine the inner tube is shredded and the tyre may be a write-off. (Usually are!). Anyhow, I bore you with this as I’m convinced that I’d never have got the wheel off without the little scissors jack which I carry to get the car up the first few inches until the Healey jack comes into play. Just a suggestion…….
3.	Got home and jacked car up to test pressure. Steady at 520psi which, I recall, is plenty. Stayed at 520 across rev range. Dropped very slowly once engine was off and dropped to zero as I engaged/disengaged OD a few times. Which is normal I think?
4.	Solenoid makes a robust “click” when it should and engages the OD when activated.

So what’s a sensible “Step 2”??

I have been urged to check the setting of the Throttle Switch (TS). Assuming that the slippage returns (and why wouldn’t it?), I’ll short the TS out to see if that fixes it. If it does, I’ll check the adjustment.

Suggestions would be more than welcome……I do dread having to take that box out again. I’ve got a very adequate ramp and a very strong volunteer(?) but, regardless of all that, it’s still quite a task. And, like a few of us, I’m not as young as I once was. I’ve always enjoyed the lines from the manual which I reproduce, below. “Gently ease”!?! 

Thanks, Simon

From: Michael Salter  <mailto:michaelsalter at gmail.com> <michaelsalter at gmail.com> 
Sent: Monday, April 22, 2024 3:21 PM
To: Simon Lachlan  <mailto:simon.lachlan at alexarevel.plus.com> <simon.lachlan at alexarevel.plus.com>
Cc: Healeys  <mailto:healeys at autox.team.net> <healeys at autox.team.net>
Subject: Re: [Healeys] Overdrive pressure or clutch slip

Correct diagnosis is 1/2 the repair!!

First you need to confirm whether the clutch (on the flywheel) or the overdrive is causing the slippage. 

To do this you ABSOLUTELY MUST disable the overdrive as a badly misadjuster overdrive operating valve can produce similar symptoms. 

To do this I would remove the overdrive operating valve completely. (There are other ways but this is absolutely definitive).

Now drive the car up a long hill where you are amle to use full throttle at around 3000 RPM (maximum torque) for a few seconds. If it is the clutch (on the flywheel) that is causing the slippage these operating conditions. Test this a few times to be sure.

If there is no slippage we have confirmed that the overdrive clutch is at fault.

Step 1 completed. Please report results. MS.

On Mon., Apr. 22, 2024, 8:08 a.m. Simon Lachlan via Healeys, <healeys at autox.team.net <mailto:healeys at autox.team.net> > wrote:

You may recall the very extended overdrive and clutch saga last year. Long story short(ish)…

OD was slipping in and out depending on oil temperature.

Correctly diagnosed pressure. Checked with gauge.

Attempted rebuild…going only so far as accumulator and related seals.

Stymied as could not get pump out. Turned out to have been “fixed” at some stage with some form of “chemical metal” which was coming loose/apart.

Took it up to OD Spares who fixed it..new housing etcetc

Why not a new clutch I thought? Sensible while you’re in the area looking at a 30+ yr old item.

New clutch…no good. Noisy, wouldn’t engage/disengage/play at all.

Gearbox out again.

Refit clutch. Presumed I’d made some beginner’s mistake.

Refit gearbox…no good. Same

Can’t recall whether I tried again. Lost count and enthusiasm by now.

Turned out that the new clutch kit was defective. (Thanks Mirek) (Genuine B&B from AHSpares).

New one did work.

Saga over until yesterday.

Same sort of symptoms…..

All’s well for first 10 or so miles. Then the dreaded slippage(?) starts. But it’s not quite the same. Reminds me more of a slipping clutch. (But NO smell)

Symptoms continue if it’s in or out of OD.

Symptoms reduce at speed.

Yes, plenty of oil. Over the full mark. Looks very clean. Pretty sure it’s 40wt non-detergent topped up with 30wt non-detergent. (Or vice-versa). Am confident in state of the filter, magnets etc.

No, I have not pressure tested it yet and yes, I dread restarting the whole bloody process all over again. I’m not sure I can face taking the box out again once, let alone multiple times.

What I want and experience tells me I’m unlikely to get is a miracle cure!

One initial question…..do OD relays either work or not work? ie, can the relay hover between on and off which might lead to the OD coming in and out? I think that could happen if the switch is off but the unit still hasn’t got the message to disengage from the bulkhead switch.

And a supplementary….how do I bench test the relay?

Simon

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