MGB & GT Forum

I just finished replacing my clutch master in my ‘73 GT w/ a new AP branded unit (Moss #180-695). I finally took the time to fill/bleed it this afternoon. The master cylinder was the only thing I changed. No changes to the clutch itself.
Everything went fine and it engages fine, but is quite heavy compared to the way I recall it feeling before and compared to my roadster.
Any thoughts.



Edited 1 time(s). Last edit at 2024-04-27 04:30 PM by PaulP.

Update - For the sake of trying something, I disconnected the clevis pin at the slave cylinder and gave the pedal a push. As expected it moved pretty effortlessly. I can't figure out why replacing the MC would change the amount of effort required to push in the clutch.

I compared with my roadster again, and it's definitely easier to push in the clutch pedal on the roadster.



Edited 1 time(s). Last edit at 2024-04-28 09:05 PM by PaulP.

What is the inside diameter of the cylinder?

I just pealed back the boot to measure: std 0.75 dia.

Why did you change the MC?
How old is the flexible hose to the slave? It may be breaking down internally and blocking fluid flow.

---

The important thing is not to get ahead, but to get along.

Odd, I too would check the hose or replace with a Goodridge type hose.

My B&B HD clutch from BPNW about 8 years ago has a very fine feel.

Lynn - It started with this: https://www.mgexp.com/forum/mgb-and-gt-forum.1/clutch-master-new-or-resleeve.4770185/#msg-4770185

The hose was replaced 2-3 years ago. When checking the bore dia, I did notice a bit of rust around the lip between the circlip and the end of the bore. Hate to take the new unit apart, but may do that next.

Do both of your cars have the pedal return springs?

Those are pretty lightweight springs, but yes both cars have them.

Really appreciate all the suggestions.

Sounds like either the hose is deteriorating (rubber these days. Don't get me started) or the slave actually is bad inside. Maybe you shook some crud loose doing the fill and bleed.

New parts don't mean GOOD parts.

---

Wayne Sanders
Rose Lodge, OR
(TD 4288)

"I don't care to belong to any club that accepts people like me"-joined Willamette Valley Club in 2011

79/65 MGB - Carmine- V-6 - T-5

This car is now very nearly completely done. Sure to find something else, but not now.........And 12 years later, I'm starting to fix things that were new when we built the car. It's pretty well de-bugged!

All, A bad slave would not make the pedal hard, it would make it soft. And a bad hose would transfer less fluid so the clutch might not disengage fully. A hard pedal is either a sticky piston in the master or the slave or a linkage issue o a pressure plate issue. Since the OP did not replace the pressure plate or the disc, one must assume those are not the issue. I would diagnose by disconnecting the slave from the clutch fork and see if the pedal is still hard. If so, it's an internal hydraulic problem. If the pedal feel improves, I'd start worrying about the linkage but the only change made was replacement of the master cylinder so that's the most obvious culprit. Basil 707.762.0974 basiladams@yahoo.ciom

---

Basil C. Adams
1956 MGA Coupe (Show Car)
1957 MGA Roadster (Driver)
1958 MGA Coupe (Racecar)
1959 MGA Coupe (unrestored)
1960 MGA Coupe (unrestored)
1960 MGA Roadster (Driver)
MKIII Elva Courier (E1056)
1967 427 Cobra
1972 Alfa Romeo Montreal
A coupla late MGBs
1960 Austin Healy BN7
More Cars than Brains

Well, I’m stumped! I drained the system and took the new MC apart and as expected it looks perfect. I tried to poke my simple borescope camera into the bell housing and just saw a bunch of black.
Everything on the hydraulic side is new within the last couple years (used a rebuild kit in the slave). Everything inside the bellhousing is unknown



Edited 1 time(s). Last edit at 2024-05-09 09:23 AM by PaulP.

Basil, if you disconnect the slave from the clutch fork then press the clutch pedal, won’t the pin push out of the slave?

---

1978 MGB
When diagnosing issues related to running and stalling, always check to see if you have gas in the tank first.

Bob - I did try this, but only pushed the pedal once and had a zip tie around the slave ‘just in case. As mentioned in one of the previous post, the pedal pushed down easily.

One other thought: the fulcrum pin (bold) and the spacers are tricky to get setup exactly right. Verify the pedal moves freely when disconnected from the MC. If the spacers are not just right the pedal will be sloppy or bind under load.