[Mgs] Clutch pedal sticking down

[Barney Gaylord]

The pedal itself should never remain down.  It shoud have a tension 
spring near the pivot point above your toes that will lift the pedal 
to top position, even if something else sticks.

The clutch pressure plate has very strong springs, enough to put 1200 
pounds squeeze on the clutch friction disc, 400 pound load on the 
clutch release bearing, 220 pounds on the slave cylinder pushrod, 280 
psi hydraulic pressure, 120 pounds force on the master cylinder 
pushrod, and about 35 pounds on the clutch pedal pad.  If anything in 
that mechanisn sticks in the actuated position, it is indeed a very 
serious problem.

If you can reproduce the condition when the pedal sticks down you 
will have an easier time diagnosing the problem.  If opening the 
bleed nipple releases pressure so the slave piston and release lever 
will return, then you may have an internally collapsed flex hose in 
need of replacement.  See here:
      http://mgaguru.com/mgtech/hydraulics/ht104.htm
The hose is fairly cheap and easy enough to replace.

If relieving the pressure does not return the slave piston and 
release lever, then the slave piston may be stuck in the bore.  Five 
years ago there was a case of an aluminum piston in a slave cylinder 
with very odd excessive wear.  The piston should be steel, not 
aluminum.  See here:
      http://mgaguru.com/mgtech/faulty/ft032.htm
If you suspect a slave cylinder problem, it bears disassembly for 
inspection.  A simple honing operation and a repacking kit can be 
easy and cheaper than a new slave cylinder assembly.

If the slave cylinder and hose appear to be in good condition, then 
by process of elimination you have a sticky pistion in the master 
cylinder.  Same applies here, disassemble for inspection first.  If 
the bore looks good, then honing and a repacking kit may be cheap 
fix.  If the bore is scratched or pitted beyond being able to hone it 
clean, then having it bored out and sleeved may be cheaper than a new 
master cylinder (or maybe not).

Barney Gaylord
1958 MGA with an atttiude
http://MGAguru.com


At 12:17 PM 6/26/2011 -0400, Bob Donahue wrote:
>I forgot to mention that it's a '71 MGB.
>....


>----- Original Message ----- From: "Barney Gaylord" <barneymg at mgaguru.com>
>....
>>What kind of car?


>>At 09:08 AM 6/26/2011 -0400, Bob Donahue wrote:
>>>Just got back from a long club drive. Along the route my clutch 
>>>pedal stuckdown (disengaged, engine revving freely) several times. 
>>>It felt like it was catching on something, although there is 
>>>nothing in the footwell for it to catch on. It's acting normal 
>>>again, but I'm afraid it might happen again. Any ideas on what 
>>>could cause this???????
>>>....
>>>Cars:       52 MGTD - #17639
>>>                71 MGB - #GHN5UB254361
>>>....