Experience Dealership line mechanic on MG, Triumph, Jaguar for 15 years, Instructor in commercial mechanics school 2 yr. Product information manager for piston and valve manufacture, Instructor & hotline answer man for import car parts importer 15 yrs.
Organizations Associate member SAE
EAA member
Publications Import Car magazine
Education/Credentials ASE Master Auto with L-1 certification up to 2000
Question QUESTION: Hi Howard,
I have a 74 BGT, and have pulled the engine, put in a complete clutch kit(Victoria British).I have rebuilt the master and slave cylinders,(no apparent scarring, replaced the hose to the slave cyl. but can't quite get the clutch to disengage. I've bleed the system multiple times according to instructions you've given in other advice.(and every other recommended way, check valves...) When the clutch is pushed, the slave moves about a half inch. (no leaks ), detected, but I can't get it into gear, when I try to push it into gear there is a slight engagement(car moves forward) If I put it in gear, then start the engine, the clutch is dragging slightly, reduces idle speed by several hundred rpm,(held stationary by brake) when I release the peddle, I have a solid clutch... (can rpm sync and drive around the neighborhood with aid of what clutch peddle I have). Since the slave and master don't leak, could I be blowing fluid by internally in the master cylinder? I'm using new Prestone synthetic dot 4 fluid.
In checking old MG Manuals, I found one reference to needing to remove some clips (used to hold the clutch springs during shipping) My Haynes manual didn't indicate this, so I didn't remove anything... did I miss something?
Also before I replaced the clutch, everything worked fine except for the clutch slipping...
Hope you can help me,
Jim
ANSWER: Hi Jim,
First, how does the pedal feel. You should not have much free play, then the pedal should feel firm resistance as soon as the free-play is taken up. It is difficult to get all of the air out of a clutch system because of the large line. As you try to bleed downward an air bubble will rise in the line and bleeding keeps air in the line.
I found the best method to get the air out is to drain about half of the reservoir and take a pry bar and force the slave cylinder piston into it's bore by forcing the clutch arm with the pry bar. keep the reservoir cap loose to do this. It will fill the reservoir and exhaust any air into the reservoir. Now, push the clutch pedal down to the floor and let it up VERY SLOWLY. Then push it down again and let it up very slowly again and repeat this until you have a good feel of the clutch again. Then refill the reservoir.
I only seen a few pressure plates with clips and the ones I seen would have come out as soon as you started the engine and stepped on the clutch. This would have made a lot of noise too. I think those clips were only used on the old coil spring type pressure plates and I don't remember seeing any on the newer diaphragm type used now.
If a master cylinder is leaking around the piston it is easy to test. You just pump the pedal up and hold it down with it in gear and just sit there a minute. If the clutch starts to engage all by itself then the seals are leaking if it stays as-is even if it is dragging a little then that is not the problem.
Next question, did you have any difficulty getting the transmission to fit up to the engine when assembling? I have seen mechanics have to fight it and in the process warp the clutch disk. Did you just pull the engine or did you pull the engine and trans together as a unit and put the trans on to the engine on the floor?
Howard
---------- FOLLOW-UP ----------
QUESTION: Hi Howard
I pulled the transmission with the engine, to re-install I blocked the tranny up with 2x4's and got the shaft level as I could get it, then mated to the engine held up by the hoist. Didn't have any problem get it to slide together...
I think your right on the clips, no noise, and it's a new style clutch.
On Bleeding: I've tried the pry bar method, (found I could push it in easier with a small modified “C” clamp... tried this 4 times, each time followed by multiple slow, 30 second releases of the pedal, no luck.
Just to make sure the clutch release lever had enough travel, I hooked a small “come along” to the lever to pull/disengage the clutch… started the engine to see if the clutch was disengaged, it was and I could shift into any gear… pumped the pedal in this configuration, (slow in and out) the first cycle was very soft, the second was solid at about a half range, like the brake. This is the first time the clutch seemed to have much resistance at any point in the push in. Removed the “come along”, topped off the system, and tried the clutch again. No luck! And repeated, no luck.
I've also un-installed the slave cylinder, so it can hang straight down (air should rise out better), and used a c-clamp to keep the piston from coming too far out, and tried to bleed it, but no luck. (I may try pushing in the slave cylinder in this position next per your suggested method.
Other things I’ve tried:
Attached a tight hose to the bleed screw, then a check valve, then a length of clear tubing all the way back to clutch reservoir, (closed loop system) opened the bleed screw, then pumped the system slowly for around 5 minutes looking for air bubbles or a change in fluid level at the high point in the tube as it comes back into the reservoir, again no luck...
Attached a “veterinary” syringe filled with 120 mls of brake fluid to the bleed screw, opened the bleed screw, pushed the fluid back through and out of the reservoir… no luck
Any Ideas?
Also I have a small drip coming off the transmission drain plug couple drops a day, will a new plug help this or can I carefully us a little Teflon tape to stop the drip…
Appreciate your help… but still frustrated
Jim
Answer Jim, it sounds like you covered all the bases. In the dealerships I worked in we would get a troubled one like you have at times and I always judged them by the feel of the pedal. If it only had a small amount of free play and it got firm right away and I bled all the air out, then the only thing left was either a pressure plate that was not releasing squarely, (very rare on the diaphragm spring pressure plate)a warped disk, a disk that is sticking on the shaft or on occasion a disk with too much spring between the two linings. (also rare). Or the clutch arm is worn more on one side that the release bearing sits in. This can put a uneven pressure on the pressure plate spring plate, thus an uneven release.
Howard
