Humber AC Clutch

Hi Chaps, we had our Humber MkIV, Vandal, at a WWII event this past weekend and during a run down a hill we suffered a complete failure of the clutch to function. It no longer makes any connection between the engine and the transmission input with only a bit of light metal clicking. The throw out arm/bell crank arm is easy to move and does not appear to have much resistance.

Who's the go to source for these at this point?

Here we are waiting for the Bluebell call to be answered.

Having worked on one of these and put a clutch in, I would say, that if you can see the arm moving with no resistance, it sounds like the arm has broken at the fork. A gearbox out job, then remove bell housing. A fibre optic viewer through the lever slot might help diagnosis.

Having worked on one of these and put a clutch in, I would say, that if you can see the arm moving with no resistance, it sounds like the arm has broken at the fork. A gearbox out job, then remove bell housing. A fibre optic viewer through the lever slot might help diagnosis.

Yeah, I have a fiber optic viewer, sadly it was at my house in Atlanta, Ga, 14 hours away by car. I don't think Jim has one at his place in PA.

I'll be back up to PA just before June to effect the engine removal as it's a multi person task. We just put it back in last fall after an engine failure and rebuild (detergent oil in an engine rebuilt but not boiled out as we had thought). I am of a mind to have a complete clutch (arm, bearing, pressure plate, fiction disk) prior to the engine removal task so as to have all parts on hand and just conduct a swap and replacement of any faulty parts.

As I understand it from the first post there is no drive to the gearbox (clutch permanently disengaged) as well as no real resistance to the actuating lever. This would suggest that the pressure plate assembly has come away from the flywheel or that the release mechanism has got wedged in the disengaged position. Both very unusual failures. Please let us know how this develops.

Good luck David

Clutch plate failure could cause the lack of drive, though that wouldn't explain the slack release fork.

I had a failure with similar symptoms (no drive, light clicking) when the hub sheared out of a clutch plate. In that case it turned out that the crank thrust bearings had failed, resulting in the crank moving as the clutch was disengaged causing an axial load on the clutch plate. The crank thrust bearing failure was not obvious, and I only realised the root cause when I came to refit the clutch and the crank slid forward as I fitted the clutch cover.

I suppose one could suggest a clutch fork or release bearing failure that might jam the clutch in the disengaged position. Is the fork end captive in the release bearing or is it free to move if the release bearing is jammed forwards?

Hopefully it's not an engine bearing issue as we JUST had the engine rebuilt. :shocked:

As to the bits inside the clutch, shearing of the connection to the center would account for it. The clutch fork lever has some resistance but not like it should if one was releasing the clutch.

Once we get it taken apart, I'll post lots of pictures.

I suggested the pressure plate assembly, not the driven plate of the clutch. It is not that uncommon for the centre to rip out of the driven plate but that would not alter the resistance to moving the actuating lever - just no drive and a bit of clicking sound.

Whatever it is you will have to take the clutch apart and then you will know.

David

Hi Ryan

First I love a mystery. Not being familiar with the Humber which design is the clutch, spring plate like Chevy or coil springs like Fords? Your mystery is a good one for all of us dealing with old vehicle to have tucked away in our heads.

I've had two sudden clutch failures in my Chevy CMPs over the years one from mouse damage, explain in a moment, the other when the dish spring plate on broke. In the case of the spring plate that was an imdiate, bang and then no connection. The mouse caused failure was a little slower but no less complete in disconnecting the engine from the transmission.

With the mouse caused failure the little critters had built a nest in the in the bellhousing. When I pushed clutch peddle in to start the engine the the nest basically exploxed and was thrown out by centrifical force to the sping assembly and wedged into the folcrum of the clutch fingers keeping them from pressing the clutch in.

Please do let us know what you find as the cause.

Cheers Phil

Update on this.

Pulling the engine/transmission and pulling the transmission off the engine back in June, we found a clutch disk that looked like this:

Clive Hughes Supplied us with the blue one in this image. The one on the upper left was a good fit but short with some concerns about throw out bearing play. As it was the one clive sent was MUCH better so we installed that one this past weekend. I've been busy with work relating to our election coverage and was just able to get up last weekend to Jim's place to work on the install.

So she's all back together....

Thats a goodlooking Humber you got there.

Good to hear the problem has been found and replacement parts sourced.

Hi Ryan, what diameter is the A/C clutch, looks pretty close to a standard Ford V8 11" Flathead clutch that Clive sent you.

Common to buy at Mac's Auto in the USA , if that was the case, Cheers Andrew.