OT. Volvo F12 commercial vehicle double plate clutch

Hi

First question, why did you replace the clutch?

What is the flywheel like, any signs of wear?

And are you sure the slave cylinder/master cylinder working correctly?

Nigel

Thanks Nigel,

first Q an oddity. One day had been out pulling a trailer loaded with crane ballast. Gross weight about 120t. No sign of any problem, the old truck performed perfectly. Got home, dropped trailer and parked lorry. Next morning -- no clutch. Very odd. Immediately checked all linkages and slave/master cylinders. No leaks and all operating perfectly well within tolerances. Thus presumed the clutch had given up. It was last changed just over 4 years ago. I've had the tractor from new, nearly 1.5m kms. The 2 friction discs were well worn but not to the rivets.

Flywheel is good as is the intermediate disc. No cracks or heat crazing. Both run true and have been thoroughly checked. My feeling is that the problem lies in the intermediate disc or the 3 centralisers bolted to it, but I cannot think of a good reason for this. I don't know what the 3 centralisers do! In short, slave & master cylinders are good, flywheel & intermediate discs are good, 2x friction discs, withdrawal bearing and pressure plate are new. I think the problem must lie in the intermediate disc but I'm stumped for a cure.

Ray

friction disc in the wrong way round? (seen this done on cars a couple of times, clutch feels like it should work, but doesn't disengage)

Definitely not the case. There are 2 friction discs and they can only physically fit one way. By that I mean there is no possible way of getting the orientation of the friction discs wrong. The 'flywheel side' disc will only fit one way and will not fit the 'pressure plate' side at all. The 'pressure plate' friction disc will only fit the pressure plate side etc. Believe me, I have tried all perms. Utterly confused. Also depressed, which my clutch refuses to be! Ray.

Sorry to sound unhelpful, but if a Volvo mechanic looking at the assembly in front of him can not see the fault, I'm pretty sure that no one will be able to cure it from a written description!

Check that all the components have gone back together in the right order, and the right way round. Also check that the intermediate plate slides where it should, without sticking. Check the splines on the input shaft for damage, and that the friction plates slide smoothly on them without sticking. Do any of the parts have marks on them that show there has been contact where there shouldn't be? Check the friction plates for any warp.

I know all the above suggestions are a bit vague and generalised, but without seeing it its hard to advice better. Maybe you could post some pics somewhere?

I believe they're there to ensure that the intermediate plate is centralised between the 2 friction discs, so it can't clear one and be dragging on the other.

Can you see if the release arm is moving to its full extent, I'm assuming you've laid underneath watching whilst someone else pressed the pedal?

Steve.

Thanks SimonJ. Not unhelpful in the slightest. A written description is the best I can offer at this time. All components have been replaced in the correct order. The intermediate disc is sandwiched, and firmly bolted, between the flywheel and pressure plate with a friction disc between the flywheel and intermediate disc and another friction disc between the intermediate disc and the pressure plate. The intermediate disc does not connect to the primary input shaft other than via the friction discs. All splines on the input shaft are good and with minimal wear as the gearbox is but slightly over a year old, genuine Volvo. All bar the intermediate disc are new and genuine replacement parts. Flywheel friction discintermediatefriction discpressure plate. Primary input shaft goes through all but is attached to only the 2 friction plates and the spigot bearing. I think my description of the intermediate may be wrong. This is a machined ring contained in a cast holder and is suspended on flexible retainers. The

Hi You say no clutch in the morning? But you had clutch operation the previous night, when you parked up?

What did the clutch peddle feel like in the morning? Soft with no resistance or firm as though the slave and release arm were working?

My thoughts are, you can't have a clutch one day and not the next, without a master/slave problem. You may have operation, but if air is in the system, then you'll have the appearance of operation, but with out the reaction.. Have a good look around the clutch peddle in the cab, were the rod goes through the bulk head, make sure there's no leakage of fluid, also check the flexi pipe, on the front cab hinge, make sure it's not leaking there. And the flexi is in good condition and not swelling with the clutch depressed..

Nigel

How good a view of the clutch do you have when the gearbox is in? Is there an inspection hole of some sort, and can you see fro definite that the pressure plate is being pulled back when the pedal is pressed? (I assume that this is a pull type clutch)

Have you tried putting the old clutch back in, see what happens then?

Can you give a better description of these centraliser jobbies, what do they do and how?

Bear ( snipped-for-privacy@member.v.co.uk) gurgled happily, sounding much like they were saying :

That was my exact first thought, too - it can't be a friction plate problem. It must be an actuation problem.

Ray - So what's the difference between the symptoms now and before you started? Nothing?

Could it be a cracked clutch actuator that's just looks to be moving normally but is bending somewhere out of site?

Tim

Thanks Steve,

I imagine your explanation of the centralisers is correct. The release arm certainly appeared to move to its full extent when viewed through the inspection hole. Have now cured the problem and will post this in a separate reply to the group.

Ray.

Thanks Nigel,

Initially I was inclined to agree with you and the first things we checked were master slave cyls along with linkages and pipework. All were fine. The slave cyl was/is giving max throw . Have now cured the problem and will post this in a separate reply to the group.

Ray.

Thanks Pete,

definitely not the problem. Have now cured the problem and will post this in a separate reply to the group. Ray.

Our original thought was an actuation problem. Checked all and found to be in perfect working order. The symptoms after fitting new clutch were identical to those when the clutch failed originally. Have now cured the problem and will post this in a separate reply to the group.

Ray.

Thanks Simon,

view of the clutch with 'box fitted is poor but from what can be seen all is operating correctly. We didn't retry the old clutch because it is a real ache removing and reinstalling the 'box. The best description of the centralisers that I have seen was posted earlier in this thread by shazzbatt. Even Volvo tech. couldn't give a sensible answer to the question. Have now cured the problem and will post this in a separate reply to the group. Ray

Managed to find a new intermediate plate, refitted clutch, gearbox et al and it is now working fine. Many thanks to all have responded with such helpful and informative advice and questions.

Ray.