TR2/3/3A Clutch hydraulic problems

[Lukens]

Long story short...
On my recent 3000 mile trip, I had to bleed my clutch every 3-4 hundred miles. I would first notice a soft pedal and eventually no slave motion at all... zero clutch. The reservoir was always full.
How was air getting in the system?

I still love the car,
Russ

 

[Geo Hahn]

I have not had this problem so this is a guess -- but I would suspect a reservoir connection, either at the reservoir or at the M/C.

I say that because everything else is under a lot of pressure and would leak fluid before it would pull air. Those reservoir connections are more 'suction' than 'pressure' and the pressures involved are low.

Why isn't 'suckure' a word (opposite of 'pressure')?

 

[Marvin Gruber]

How long since you rebuilt the master? Maybe no pressure lets air in or bypasses fliud, when you pump it seal will start to seal again.

marv

 

[CJD]

I learned with mid-year Vettes that the brake calipers would suck air if the brake rotors were not true. Apparently the rapid pulsing would draw air past the seal and into the caliper, even though there was no external leakage.

So...is there a chance the clutch is adjusted wrong, so that the release bearing is riding on the fingers?

 

[TR3driver]

Did you actually get air out when you bled them?

 

[Lukens]

Did you actually get air out when you bled them?

Positively. The scenario was like this: after a few hundred miles I wouldn't get any clutch disengagement until the pedal was half way to the floor. A few pumps would bring it back but not for long. Eventually I could pump, pump, pump, and nothing. A couple of times in traffic I had to shut the motor off and start in gear... fun. One time I had the car on a lift and just by gravity feed I could see the air come out. The rest of the times I bled from above. The hot oil filter is a literal pain to work around but I was able to break the bleeder loose with a short wrench and then work the bleeder by hand while my wife worked the pedal. Not a very good way to bleed and not always 100%, but it got me going.
I put new master and slave in about 2000 miles (a year?) ago and occasionally I would feel a soft pedal but it would always go away. I'm stumped.

 

[TR3driver]

Have you checked that the clutch pedal always comes back up all the way, leaving some play in the pushrod at the MC? As noted, the entire system is normally under a slight pressure, so any leak would be fluid out rather than air in. The only way I can see for air to get sucked in is for the 'foot' valve in the MC to not open when the pedal is released. Possible causes might include the little wavy washer being missing, or the pedal pivot being sticky, or even the pushrod adjusted a bit too long (especially if you have the pedal stop on the bracket).

 

[Lukens]

Apparently I can't insert an image unless I start a new post. To see the image, go to my new post "Randall, let's try this"

Have you checked that the clutch pedal always comes back up all the way, leaving some play in the pushrod at the MC? As noted, the entire system is normally under a slight pressure, so any leak would be fluid out rather than air in. The only way I can see for air to get sucked in is for the 'foot' valve in the MC to not open when the pedal is released. Possible causes might include the little wavy washer being missing, or the pedal pivot being sticky, or even the pushrod adjusted a bit too long (especially if you have the pedal stop on the bracket).

Rhttps://i258.photobucket.com/albums/hh260/TR3driver/Manual%20pages/Fig4clutchMC300dpiannotated.jpg
Randall, help me out here. From the diagram, I just can't understand the workings of the valve seal. I understand that this diagram is for an integrated MC body, but it's virtually the same as mine with a separate reservoir. Here's what I "assume":
1) when the pedal is pushed, the seal is closed, forcing fluid to the slave.
2) when the pedal is fully depressed the valve opens. What is happening then?
3) as the pedal is released, fluid is allowed to "return" to the mc under pressure from the slave. It appears to me that if the slave were slow to return there will be a vacuum in the master. Would this not be a condition for air to enter the system?
Obviously I'm not seeing something. Educate me please.

 

[TR4nut]

Any chance a partially collapsed hose would cause this? If it collapses on return, would there be potential for air to enter the M/C?

 

[donbmw]

Is the external return spring missing at the slave cylinder. I had mine come off and it gave a soft clutch problem. Found that having the spring missing the slave piston would not retract sometimes.

don

 

[Lukens]

Nope, spring is there.

 

[CJD]

I really think you're trying to over-diagnose here.

If you are loosing fluid when this happens...your slave cylinder is bad and needs rebuilding.

If you are not loosing fluid when this happens...then the MC needs a rebuild.

Of course, the above assumes that your hose and line connections are dry. If they are wet, then that is the problem.

 

[Lukens]

Any chance a partially collapsed hose would cause this? If it collapses on return, would there be potential for air to enter the M/C?

Hmmm, I'll check that out