barnaclebill Posted April 7, 2004 Report Share Posted April 7, 2004 Having just got the engine running sweetly on Malcolm`s superb PI system, I took my rebuilt CP for a quick spin. Once everything has warmed up, the clutch drags like mad, causing difficulty in engaging any forward gear and a disconcerting crunch when engaging reverse. Bleeding the clutch has not sorted the problem and pumping the clutch pedal like mad before a clutch movement proves it`s not air in the system. Everything else seems to be moving [ie not seized] altho` there is quite a lot of lost motion in the link between clutch pedal lever and the master cylinder. As the subject of a 3 year total rebuild, everything is re-conditioned or new. Anyone with any ideas?? Quote Link to post Share on other sites
Richard Crawley Posted April 7, 2004 Report Share Posted April 7, 2004 If drag only occurs when the engine is warm, I would suspect that friction plate clearance is probably only marginal when cold & thermal expansion just takes it “over the top”. The whole clutch actuating mechanism is “marginal” at the best of times & to get it all working properly, you have to ensure that literally everything is A1; slave cylinder OK, new yolk & correctly seated pin, no wear in the cross shaft bearings, no wear on the clevis pin hole/pin/slave cylinder actuator, good quality release bearing, within tolerance crankshaft end float, a correctly aligned gearbox &, above all, “a decent clutch” - lots of **** about + posts on this. No consolation I know but I paid particular attention to all of this lot & my clutch is a sweet as a nut! Quote Link to post Share on other sites
marvmul Posted April 8, 2004 Report Share Posted April 8, 2004 Once at the International Week-end, a member of the belgian TR Register had the same problem. The lost motion in the link between clutch pedal lever and master cylinder (forked rod) was cured by filling up the hole in the lever. The hole was worn to an oblong shape : a 1/4" piece of the shaft of a small bolt was put in this hole together with the clevis pin : this was enough to be able to select gears again. But this can't be the only fault. Sometimes it's difficult to force the air out of the slave cylinder : is the bleeding nipple on the upper side? Is the spring in the slave cylinder present : this can easily be lost and then the piston can return too far, loosing contact with the slave cylinder rod. It's helpful to notice when the cross shaft starts moving when someone else is slowly depressing the clutch pedal, to make a distinction : if the end of the lever of the cross shaft is moving less than 10mm or so, the problem is almost sure before the cross shaft (mostly hydraulic). Quote Link to post Share on other sites
Andy Moltu Posted April 8, 2004 Report Share Posted April 8, 2004 As you've bled the clutch it sounds like the cross-shaft pin has broken. Quote Link to post Share on other sites
barnaclebill Posted April 8, 2004 Author Report Share Posted April 8, 2004 Thanks for the replies so far chaps! Thare was a lot of wear in the pedal lever hole [as mentioned, it was elongated] and the clevis pin was oval. New drilling and shouldered bolt has solved that, nice tight fit now, but it didn`t totally solve the problem. The actuating lever arm on the bellhousing has 3 holes.......strictly speaking the manual says to put the arm of the slave cylinder in the middle hole [which it was]. Having moved it to the INNER hole, the slave cylinder seems to give the lever a bit more throw, plus the return springs have less lever arm to push against. It`s 200% better now, and driveable. I suspect the root of the problem may be the thickness of the clutch plate [i remember reading that on a past post]. I strip it down when I get round to it!! Perhaps slipping the clutch may wear it down a bit, but as a driver it goes against the grain! Car past it`s MOT today following the 3 yr re-build..and it sound the DBs with the pheonix exhaust [thanks Andy and Dan!!] and drives beautifully! Quote Link to post Share on other sites
Guest ron Posted April 8, 2004 Report Share Posted April 8, 2004 If you run with the slave pushrod in the inner hole it seems to accerate the wear in the crank thrust bearing, a more 'professional' but expensive solution is to fit a 3/4" master cylinder if you have a .7" one. Ron Quote Link to post Share on other sites
marvmul Posted April 8, 2004 Report Share Posted April 8, 2004 Isn't the force on the crank thrust bearing not the same whatever hole the slave cylinder rod is in? It's true that with the inner hole, you have to push harder on the clutch pedal, but the leverage on the cross shaft is shorter. I think the force on the thrust bearings must always be the same as the force needed to flex the springs in the clutch cover. To save the crank thrust bearings, it's important not to depress the clutch pedal when starting the engine. Quote Link to post Share on other sites
Richard Crawley Posted April 8, 2004 Report Share Posted April 8, 2004 Isn't the force on the crank thrust bearing not the same whatever hole the slave cylinder rod is in? Yes, so it will not make any difference to the forces seen by the crank thrust bearing or clutch release bearing. But the force required on the slave cylinder push rod will be greater; the lever is shorter so the mechanical advantage is less - the clutch will be harder to operate + higher forces on the clevis pin/actuator will make it & the crank pin hole wear more rapidly. Quote Link to post Share on other sites
MARK Posted April 9, 2004 Report Share Posted April 9, 2004 I had similar problem on my 73 TR6. On checking the clevis pin joint between the clutch pedal and the master cylinder I found the cevis pin very worn and the hole in the clutch pedal arm was very elongated. This was cured by removing the clutch pedal, welding up the hole and re - drillig it to the correct size for the clevis pin. I found a small amount of play at that joint translated ito a suprisingly large amount of movement in the clutch pedal. ps dont remove clutch pedal on the hottest day of the year like I did unless you like working upside down in a sauna ! MARK Quote Link to post Share on other sites
Richard Crawley Posted April 9, 2004 Report Share Posted April 9, 2004 On checking the clevis pin joint between the clutch pedal and the master cylinder I found the cevis pin very worn and the hole in the clutch pedal arm was very elongated. Good point Mark, I had forgotten the "other end" of things in my previous post! Quote Link to post Share on other sites
barnaclebill Posted April 10, 2004 Author Report Share Posted April 10, 2004 Apparently similar problems are experienced with the 2.5PI saloon.........a fix from that club seems to be to replace the TR6/2.5PI saloon master cylinder with one from a Triumph 2000 saloon [vitesse/GT6 etc]. The 2000 one has a slightly longer throw, so allieviating the dragging problems. Parts available [cheaply, from Rimmers]. Anyone done that on a 6?? As for the previous, the sorted problem on the elongated hole, and the inner hole on the lever, all works. I rest my case, your honour. Quote Link to post Share on other sites
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