Intermittant Clutch Pressure

[WTS]

Just wondering if anyone has encountered the following problem in the past.

Details 1988 Vette

Standard Transmission 4 + 3
The clutch master cylinder was replaced with an aftermarket unit.
The line from the clutch master cylinder to the slave cylinder also replaced.

System was bled in accordance with maintenance manual.

Symptoms

Initial clutch pedal pressure observed as normal allowing full clutch disengagement.

Upon a subsequent engagement of the clutch, the pedal travel before pressure was encountered was approximately half way to the floor. As you can imagine the clutch in this case did not fully disengage.

The next clutch pedal action revealed full clutch pressure with little or no free play. Complete clutch disengagement achieved.

At first I thought that there was still some air in the system but after several attempts at bleeding the system the same results occur. Clutch pedal pressure is intermittent.

On occasion I am able to shift through all four gears without incident.

I am now thinking that the after market Clutch Master Cylinder has an internal problem with a seal possibly rolling internally.

WTS

 

[Schrade]

Your description seems to allow for nothing else but air still in the pipes. And if it's air, the reservoir fluid could be replacing the DIS-placed air. No fluid on the floor? And no fluid inside the firewall inside where the pedals mount?

 

[vigman]

This is assuming 2 things

1) The after market slave is of good quality....
2) That ALL the air is out of the slave...

( roll movie )

I remember back when... I was working on an 86 ( similar to yours ) .. and had a similar issue...
Long movie short...
The master was the original ( 100K plus ) it had really REALLY dark fluid ( read coffee color ) ...
and since we were MUCH younger ( read no cash ) didn't have money for good parts.

So the following were our issues...

1) When the slave is mounted the bleeder valve is NOT the hi point... the other side was... ergo we couldn't get all the air out on the initial bleed.
We solved that by removing the slave and tilting it... and behold more air.... firm pedal.

2) We bled till ALL THE FLUID was exchanged... which flushed all the junk into the slave..

1 week later same issue.. plus all the " dirt " that was sealing the scratches in the master was no longer there..it started leaking...
the slave bore now was scored.. and the rubber seal was damaged.

exchanged the salve
got new master
repeat process
and all was good till he sold it 30K later....

Mike

2)

 

[WTS]

Hi Mike

Thanks for the reply !

I still find it strange that one moment the pedal is hard and the next time it goes half way to the floor.
I would think that if there was air still in the system it would react with a soft pedal all the time.

I will try bleeding it once again with the slave tilted at a 45 degree angle, bleeder at the highest point.

Regards

WTS

1) The after market slave is of good quality....
2) That ALL the air is out of the slave...

( roll movie )

I remember back when... I was working on an 86 ( similar to yours ) .. and had a similar issue...
Long movie short...
The master was the original ( 100K plus ) it had really REALLY dark fluid ( read coffee color ) ...
and since we were MUCH younger ( read no cash ) didn't have money for good parts.

So the following were our issues...

1) When the slave is mounted the bleeder valve is NOT the hi point... the other side was... ergo we couldn't get all the air out on the initial bleed.
We solved that by removing the slave and tilting it... and behold more air.... firm pedal.

2) We bled till ALL THE FLUID was exchanged... which flushed all the junk into the slave..

1 week later same issue.. plus all the " dirt " that was sealing the scratches in the master was no longer there..it started leaking...
the slave bore now was scored.. and the rubber seal was damaged.

exchanged the salve
got new master
repeat process
and all was good till he sold it 30K later....

Mike

2)

 

[vigman]

Describe the problem....

So before you did all this... what was going on?
What color was the clutch fluid when you started the repair?
Who's slave did you go with?

Mike

 

[WTS]

Your description seems to allow for nothing else but air still in the pipes. And if it's air, the reservoir fluid could be replacing the DIS-placed air. No fluid on the floor? And no fluid inside the firewall inside where the pedals mount?

Thanks for the response !

There are no leaks of fluid anywhere.

I will attempt once agin to purge what remaing air there may exist in the system.

Regards

WTS