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Hi all,

I've recently tried to change the clutch on my 1982 Austin Allegro 3 1.5 HL and have run into a few problems. I followed the instructions in the Haynes for it as well as I could but after taking it apart and putting it back together 3 times now, I still cannot select gears with the engine running. I've tried bleeding the clutch several times in a few different ways. It is possible to put the car into gear and start the engine with the clutch depressed but it does appear to pull slightly which presumably shows that it is not properly disengaged. Somebody suggested using a pressure bleeder but I haven't tried that yet. I was wandering if anyone had any experience with these clutches or thoughts on the issue.
Any help greatly appreciated, thanks in advance!

Dan  

first...

how does the clutch pedal feel when you depress it...

can you feel it operating the clutch cover????

do you have a friend who can operate / depress the clutch pedal while you observe the movement of the clutch slave cylinder?

the clutch slave cylinder should move the lever probably an inch and a quarter 1 1/4" or 33MM   i don't know the exact stroke of the clutch slave cylinder on that model..

if your foot movement is not totally transfered via the hydraulic system to the clutch fork to release the clutch.  you won't have disengagement to shift gears..

its totally possible that the clutch master cylinder seals could be leaking internally..  or corrosion in the bore might limit the amount of volume displaced..   if this happens.. the slave cylinder does not move far enough to completely release the clutch .

you may also have only partial disengagement of the clutch..  so you might be able to actually start the car in gear.. and hold the brake to prevent it from rolling away.. then release the brake and the clutch and it may function what you think are normal.. but the clutch is not fully released...  so it does not remove the torque from the engine to allow you to select another gear..


can you post a picture of the slave cylinder where it is installed... to photobucket dot com.  i am not familiar with how its mounted and adjusted... i don't have a manual on this and my early 70s austin america manual is in an unlabeled box in storage.

perhaps several pictures with the clutch pedal up.. and with it depressed..  so we can see the movement..  even a movie.. the engine does not have to be running for this..

i see in the parts listing that seal kits might have a cup seal or a ring seal...  

Hi, thanks for the swift and concise reply!

I can feel resistance in the clutch pedal, it seems just as responsive as it was before I changed it so I believe that the diaphragm is operating correctly.

Here are some photos and a video of the slave cylinder in operation:
http://dl.dropbox.com/u/58655958/IMG_20120123_215726.jpg
http://dl.dropbox.com/u/58655958/IMG_20120123_215732.jpg
http://dl.dropbox.com/u/58655958/VID_20120123_215738.mp4
(if the video doesn't run on the site you can right-click and save it to your pc to view in media player)

Apologies for it being dark but its the only time I can take the photos.

As you mentioned, I can start the car in gear and there appears to be 80-90% disengagement but it does try and pull slightly and selecting gear is not possible with the engine running is not possible.

Another thing, it is possible to push the actuating arm into the slave cylinder when the clutch is released which presumably means the full travel of the cylinder isn't being used, however the clutch pedal has full resistance through the entirety of its travel so this may be a red herring.

Do any of these things shed any light?

Thanks again for the response, much appreciated!

Dan  

Quick question did you resurface flywheel???and do you know the end play of the crank?  

the video looks like it is going to release... but i really wonder..  any chance of a piece of wood.. to position under the lever between the fulcrum and the slave cylinder.. to it cannot fully retract...  and then... one time from the partial extended .. let it up and depress it again...  so it starts from say 20 percent extended.. and then  will move to 120 from normal position.. i don't want more than that.. if possible so you don't invert the diaphragm.. at that time... start the engine and see if gears can be selected.. without grinding..   without spinning the wheels... i don't want to engage the clutch.. only to verify that its full released..

i wonder..... its not like i have any around...  could you perhaps see if the bore of the clutch master is the same diameter???

if so...   can you measure the stroke of the input push rod... compare it to the stroke of the output pushrod.

the clutch master will usually have an additional 1/8 to 3/16 of an inch of stroke to allow the seals to pass the one or two tiny fill  ports in the side of the bore...

do you have any other cars with a similar engine/ trans.. where you could measure the stroke of the slave cylinder to see if it actually fully releasing..


..!!!!!~~~~~~~~~~~~~~~~

that is a good question about the thrust bearings  if the crank is moving away from the throw out bearing.. you will be able to see the crank pulley move out when the engine is idling and the clutch is repeatedly depressed and released if you can stand directly inline with the alternator and fan belts.. but looking for the relation ship of the belt through the grooves...

i have had more than one car with this problem..  not yours.. but anything is possible..

is the flywheel stepped??? where the friction surface is a different level than where the clutch cover bolts down at.

i took a 22R stepped flywheel in one day to be surfaced.. they handed me back a totally flat flywheel.. NO STEP..

they said.. well.. thats how we do them now.. you will just have to make it work..   i wanted to punch him.. i did something better.. i walked over his boss.. said we have a slight problem here..  he removed another 3/16 inch to recreate the outer step down..  they did not have a spec chart...  when that guy said.. that  to me.. i wonder if he knew how close he came to being resurfaced..


there is a compression height measurement when the cover is placed over the disc and no bolts have been installed...

so there is a gap that you have to pull down the cover with the bolts to seat it... this gap should actually be almost equal with double the measurement of the friction surface to the rivet head...  not the reversed side showing the deformed rivet shank...

this allows the cover to compress just the right amount..

the more i type... the more i am thinking that you might not have enough stroke coming from the clutch master..

so an internal leak or corrosion might be preventing the build up of pressure until the piston had lost some of the  calculated displacement volume..  

i will reread and perhaps edit or add info in the morning..  

thanks for the replies again.

I didn't re-surface the flywheel or pressure plate but I did clean them thoroughly and they aren't pitted. What did you mean by the crank end play?

I won't have a chance to try the thing with a bit of wood this evening, maybe later in the week, but I was wandering, if I did put a bit of wood in to hold the actuator pin, won't the slave cylinder only be able to push up to this point if it is pressed again? i.e. won't it just be held at the end of its travel?

I don't have any other cars to compare it with really, I probably should have measured the travel of the actuator before I took it apart but I was thinking that it may have always been like this and is only evident now that the driven plate is new and is therefore slightly thicker.

The dimensions out of the Haynes are:

Master Cylinder Diameter: 0.625 in
Slave Cylinder Diameter:  0.875 in

It doesn't have stroke dimensions in there, what would be the best way to measure?

Could you possibly explain a bit more about the compression height measurement, I didn't quite follow?

I'm also wandering about an internal leak in the master or slave cylinder but would that not mean that the clutch would gradually release itself if whilst the clutch pedal is pressed?

Thanks again,

Dan  

the idea with the wooden block is to hold the slave cylinder off slightly...   its probably not fully retracted anyway.. this is how the clutch adjustment is handled.. the diaphragm pushes the throw out bearing back up.. that pushes the slave  back just as far as needed..

this lets it start the push from 0 clearance every time..   not all the way from the back of the bore..  

cars with adjustable clutch linkage that i did not see in yours has a return spring to fully retract the slave cylinder... so you change the push rod length...

and yes.. i would like the block of wood as a trial.. between the fulcrum and the slave cylinder .. so it keeps the clutch partially disengaged.. where the next stroke of the clutch pedal will start from partially disengaged...  and move the lever even farther out.. to see it that will release the clutch disc properly..

i wish that somebody had a spring loaded rig.. to install on the end of a clutch slave cylinder hose..  with a calibrated stick to see how much displacement is actually being moved..

i have found on the 1990 jeep wranglers and similar years with aluminum clutch master cylinders..  almost identical as to what was on my former LR series 2A 109..  that the back of the piston chewed away some of the bore.. so the movement of the clutch master piston does not start displacing fluid until it's part way through the stroke..

this screws with the displacement ratio..  so there may NOT be an external leak at the clutch master.. but there is not enough displacement volume created to move the slave far enough to release the clutch fully...

you might try the wooden block to get the slave farther out.. then with your hand..  and a friend ready with the pedal.. fully retract the slave.. hold it in.. then  have your friend pump the pedal to extend the clutch,,,'

this may help in bleeding the air from the slave ..  

hope this helps.. i have about 5 other things i am thinking about right now.. so i am kinda distracted..  

Hi again,

So I tried jamming something in between the clutch push rod and the clutch cover this evening and it seemed to work the way you described. The push rod did extend further than it usually does by starting from this offset position. Here is a photo of the "hyper extended" travel:
http://dl.dropbox.com/u/58655958/IMG_20120125_192610.jpg
When you compare it with the images in the links I posted previously you can see there is quite a difference.

Unfortunately, one minor set-back is that as I've been starting and stopping the engine without running it for long periods of time, the battery is now flat and I don't have a charger. However I did put the car into gear with the engine off whilst the push rod was in its hyper extended position and tried pushing the car. It still seems to be up against the gearbox because I can't move the car. (in neutral its quite easy to push)

Would it be right to assume that given that this doesn't appear to release the clutch still, that it may be a fault within the clutch assembly or could it still be the hydraulics?

I'll try and get the battery charged somewhere and repeat the test at the weekend.

Thanks again for your time, its much appreciated.

Dan  

man.. i am feeling your pain.. i don't know how many times i had the austin america transmissions out and torn off the bottom of the engines..  i think i ran across an slightly used carb for one.. i will have to look up the part number off the tag..  thats probably simple over in the UK to get one..

is yours equipped with hydro elastic springs...  like air bags.. but filled with a fluid.. ??? front and rear hooked together..

my friend had removed all the interior seats but the drivers seat.. swore that they were like Dr Who's tartis..  bigger on the inside than on the outside..

the only other thing is to check the part numbers on the boxes.. of the new parts you installed.. compare them to the catalog..

can you measure how far the clutch  slave cylinder rod moves out from each stroke...

this will give me a rough measurement to try to reverse engineer how much the push rod for the master might need to move..

you might also want to ask the friend in the drivers seat to tell you when he starts depressing the clutch pedal.. see it the slave responds almost instantly..  

Hi again,

Sorry for the massive delay in replying but I thought I'd update in case this ever happens to anyone else. (It probably won't cause I did something pretty stupid!)

Thankfully I've now got it back together and fully working. It seems that a silly mistake the first time I tried to fit the new clutch plate caused all the problems. The crankshaft has 4 locating studs coming out of the end, one of which is slightly thicker than the others in order to locate the flywheel assembly properly. Unfortunately, I didn't notice this when I first refitted the flywheel assembly after fitting the new clutch plate. Consequently, when bolting the flywheel onto the crankshaft, the thicker of the studs was forced into the crankshaft, causing the crankshaft to develop a slight lump on one side. This caused the primary gear to seize onto the crankshaft, which meant that the engine was constantly connected to gearbox regardless of the clutch, effectively bypassing it.

Getting the primary gear off was a nightmare but with access to a gear puller tool it probably would have been easier. I then sanded the lump out of the crankshaft until the primary gear was free to rotate on it when replaced. (that might not have been the most sensible thing to do but I didn't fancy trying to remove the crankshaft to get it skimmed or whatever the correct method would have been!)


Anyway popped it all back together with a freely rotating primary gear and it all is back to normal and works like a treat!  

Just wanted to say thanks with all the diagnosis help, I'm very greatful and feel like I've learned a lot from the whole experience!

And in answer to your question yeh, it has hydragas suspension, its like driving a sofa!

Cheers  

i am so glad you were able to figure it out .. and come back and post what happened....



as for driving like a sofa...    sounds like fun..    just be sure to have brakes and take friends with you..

here is a great example of how not to drive a sofa...


http://www.youtube.com/watch?v=rzAmVCy68J8