I just bought 1991 RX-7. After driving it for about 20 minutes the clutch drops to the floor and has very little pedal action. I hope this is a simple clutch master cylinder issue.
Anyone else experience this?

 

It could be, the master and slave are the easiest things to replace to find out

 

welcome to the board.

yeah, one (or both) of the cylinders are probably dead. nevertheless, have you tried just bleeding it first? could be air and in the outside chance that it is, all it would cost you is a bottle of fluid.

 

The parts are inexpensive so I will be replacing both the master cylinder and the slave. I am also going to change the spark plugs and wires.

 

Save yourself some future hassle and get a new soft line for them also

 

Will do - thanks

 

For easy reference, it is usually the slave cylinder that craps out first as it sees the highest pressure. With that said, it is good practice to replace both as the Master cylinder isn't too far from failing then too. It's a good time to add a Speedbleeder on the new slave cylinder too. Turns the 2-person frustration-fest into a one-person breeze. It's either M7x1.0 or M8x1.0, I've seen both on our SC's before

 

agreed, Akagis. up until i got my FC, i had never had to change a master before, only slaves. however, the experience (and the relatively minimal cost) got me thinking they should be just together if you can. it you saves you that extra step since you said the master may not be far behind the slave.

 

Fluid in reservoir(s) will be noticeably absent prior to the pedal going (easily) to floor. It has to leak by and out and there will be visual evidence (ie: wet around slave push-rod area. Master cyl has to be really bad in order to not work but fluid can still leak out where it is mounted.
It is also 'prudent' advice to replace the fluids (including tranny, rear AND coolant) every two years - no matter how little you drive.

 

Changed master slave and master cylinder and the problem is fixed....

 

Re: - - - Changed master slave and master cylinder and the problem is fixed....



I had same issue near end of 1000 mile trip exactly 3 years ago. It was the slave cyl. (only) but I could have prevented it - or at least made it home the last 100 miles (without improvising) by simply confirming that the fluid in M.C. reservoir was at proper level. I keep fluid so clean that I 'assumed' the level was okay by simply viewing thru the side of the plastic (reservoir).
I would at least been able to make it all the way home. Anyway, I purchased both 'cyls.' and when only the S.Cyl. showed signs of leakage - I replaced that one - - - and still have brand new M.C. Yes, I know, 99% of us would replace both at same time. But, in my case, since car has only 76,000kms., I see no point in changing perfectly working parts. Only other failures have been idler arm bushes and - - - hmm - can't think of anything else. Now, 'wear and tear' on the other hand is whole other issue.

 

The only problem that arises when you only replace ONE part is that the other will go shortly behind it.
The old part can't handle the "new" hydraulic pressure of the repaired system.So since the parts basically work together with each other and are cheap enough,they should be changed at the same time.Remember that you are dealing with parts that are at least 25 years old

..If it ain't Broke,don't fix it...

Ya,but there is another saying..Do it RIGHT the FIRST time!

 

I agree 100%. Me being one of select few who replaces fluids regularly, and master cyl. has always had fresh(er) fluid than slave cyl. (which is tucked-in behind oil filter) I saw no reason to replace the item. IF, however, it was the M.C. that failed, I likely would have also done the S.C. at same time. How many of us have had master (brake) cyls. fail, in various other vehicles, in the past? And, how many of us replace all four wheel cyls./calipers at same time as the M.C.?
Most of the internal wear of a hydraulic cyl. is due to wear and tear caused by fluid break-down and contamination - - and not due to age or neoprene fatigue.
Another problem, less common, is when the (diaphram) pressure-plate loses its' SNAP after high miles or age/heat. Then, you press on pedal and it feels 'funny' and when attempting to shift into any gear - from neutral, the disc itself is still being held by P.P. and there's no way it will shift - lest you like grinding noises. Had this happen on Tercel , Celica and Civic.