[Mgs] Clutch pedal sticking down

Charley & Peggy Robinson ccrobins at ktc.com
Mon Jun 27 09:47:03 MDT 2011


I had much the samel problem in my MGB.  The clutch pedal returned but 
the clutch did not engage.  This happened in a restaurant parking lot 
after parking the car, thank goodness.  When we returned to the car the 
clutch was engaged.  However, one push on the pedal caused the clutch to 
disengage and it stayed that way.  So I called my towing insurer and had 
the car flat-bedded to the house.  After troubleshooting it turned out 
that the flexible hose to the slave cylinder had failed internally, 
preventing the slave piston from returning to "at rest"  immediately.  
The blockage wasn't complete apparently; as the pressure in the slave 
cylinder would bleed off over time.  A new flex hose and a thorough 
flush-and-bleed solved the problem.  The easy way to isolate the problem 
to the hose is to disengage the clutch and immediately go under the car 
and open the slave cylinder's bleed port.  If  the slave piston returns 
to "at rest" immediately then you know the pressure in the slave 
cylinder didn't drop when the pedal was released.  Then you push and 
release the pedal again and open the fitting at the clutch master 
cylinder and observe the slave piston for motion.  I'll leave deductions 
to the reader as an exercise in troubleshooting logic. :-)     Actually, 
this is a common problem in "wet" clutch actuation systems in older 
cars.  I ran into it several times when I used to buy, repair and resell 
older cars.

CR  '69 MGB

On 6/27/2011 3:19 AM, Paul Hunt wrote:
> I can't see it being anything in the bellhousing or the hydraulic 
> hose.  The master cylinder and the pedal have return springs, and 
> normally these would be enough to pull the pedal back even if there is 
> no return hydraulic pressure.  The master seals are designed to pull 
> fluid past them on the return stroke when there is no return pressure 
> for any reason.  I had a release bearing break some years ago, so no 
> return pressure, the pedal worked normally (albeit very light) and 
> just a couple of pumps were enough to push the slave piston out of the 
> end of the cylinder.
>
> I'd be looking at the pedal pivot, linkage, and master push-rod and 
> piston.
>
> PaulH.


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