Intermittent (but becoming more frequent) clutch problem ....

[michaelpbreen]

Hello,

Apologies if you are seeing this post twice, as I posted in the incorrect forum.

Appreciate any advice for a very inexperienced, wannabe DIY mechanic with a '68 SRl311. Recently started to experience issues with engaging the clutch. Here are some of the symptoms:

- After driving for a while and coming to a stop, unable to put the car in any gear. I have not pushed so far to determine if there is gear grinding. I am able to resolve this apparently by pumping the clutch vigorously, although I have not been able to determine if this is definitely the reason the problem stops.
- When I have experienced this problem, if I turn off the car and try and start up again with the pedal depressed and the car in first gear, first gear is engaged and the car will lurch forward if I continue to start.
- When I am not having this issue, all gears seem to work as they should.
- I did notice once or twice some stronger resistance in pressing the pedal.
- After experiencing this issue I did have a real mechanic change the transmission fluid and check things out, but he was unable to identify any issue and of course, the problem did not occur while he was testing the car.

Hoping this may be a hydraulic issue with the clutch master or slave and not something more serious in the transmission.

Any ideas?

Thanks,

Mike

[datsun65]

Sounds like a classic Clutch hydraulic issue. Recommend you swap outthe Clutch master, slave and hose.

I several vendors have a kits available. Sin City Datsun has a kit for $130 for all three pieces.

http://sincitydatsuns.com/store/c3/Brak ... Parts.html

[unklpat]

Mike, did you flush the clutch system? The brake fluid used in the clutch will lose it's properties when hot, if old and moisture contaminated. Chech the color of the fluid in the resevoir, should be clearish, not brown/green/black. Easy DIY process, cheap try before replacing parts. Pat

[C.Costine]

As Dan and Pat have said it is almost certainly the hydraulics. The standard brake fluid used in the system tends to absorb water. The brakes tend to drive the moisture off with use but not so much the clutch. Silicone based fluid doesn't absorb the moisture or harm paint, but the swap over requires complete flushing as in bleeding until the fluid comes completely clear. It is well worth the time to eliminate bad fluid before swapping out.

[michaelpbreen]

Thanks Pat and Dan. Given the relatively inexpensive cost of a master and slave cylinders, I purchased those at Autozone:
Beck Arnley master (PART NUMBER: 072-6521) and Duralast slave (PART NUMBER: 10030) for a total of $42.00. Found these on the parts interchange section of the wiki on 311s.org. Should have both tomorrow, so I can give that a try.

I did just have the "manual transmission fluid exchange" service, but I do not believe they did a complete flush of the system (as opposed to a draining of the old fluid). Inspection of the fluid in the master shows it full to the brim and "clearish" in color.

Any more advice is appreciated and thanks for your help and quick response. I'll let you know how it goes.

Thanks,

Mike

[michaelpbreen]

So I started this thread by describing myself as a "very inexperienced, wannabe DIY mechanic", well here is the proof:

I never actually had the clutch system (master/slave) flushed or even had the fluid replaced. I was confusing the fluid exchange for the transmission itself. What a dope.

Anyway, I will flush/replace the fluid in the clutch system, bleed to be sure there is no air, and then test. If that does not resolve the problem I will move on to replacing the master and slave.

This sound like a good plan?

Thanks,

Mike

[Solex68]

My 2 cents. When bleeding the clutch, depress the pedal slowly when pumping out the air.

[bossbob]

Or leave both ends open and let gravity do the work...........

[fj20spl311]

Sometimes you need to pump the system slowly to get the fluid flowing with the slave cylinder bleed valve open. It just need to be open a half a turn or so. Keep an eye on the fluid level in the master cylinder.

[mraitch]

thought the clutch system was just 'gravity fed'. no need to 'bleed' like brakes.

[C.Costine]

There is no need to"flush" a manual transmission. Allow plenty of drain time if you want to get it really cleaned out of old fluid.

[michaelpbreen]

Thank you everyone!

[unklpat]

I usually put a piece of tubing from bleed valve into a jar, open valve, pump clutch till dry, wipe out resevoir with lint free cloth, fill resevoir, pump a few times until fluid runs clear, then let drip for a bit,close bleed valve. I pump the fluid thru, to purge the lines, not to release air.The resevoir will have a coating of gunk in it, so you want that out also. Oreilly's has cheap synthetic DOT4, works well. Pat

[FergO2k]

One word of advice.
Lucas Synthetic Brake Fluid, Compatible with Dot 3 and Dot 4.

Tried it, and that "compatible" statement is a lie. It caused me fits (exactly the condition you are experiencing) when hot, heat soaking.

Only started to go away when I started flushing it, and even though clutch system holds little, it took 2-3 flushes to improve the condition.
Let's not start the discussion of Dot 5, because this is not DOT5 brake fluid.
IMHO, this stuff is crap, maybe only good for paint remover. (though I have yet to test that)

[C.Costine]

When I converted over to the silicone there was no inter-mixing. I had the few lines that I did not replace and reservoirs open to drain for days if not weeks. As I bled the brakes and clutch I could see just a little yellow fluid flowing under the purple silicone fluid through the clear vinyl tube. I kept bleeding for awhile after there was no more yellow. Again, they did not mix.