This has happened to me twice now, about 3 weeks apart. After driving on the highway for more than an hour, the clutch was extremely weak/wouldn't disengage. The next day, it was fine and I have driven it nearly every day between episodes.

Has anyone ever experienced this? Any ideas how to diagnose?

Thanks!

Does your use of the phrase "extremely weak" mean that the pedal felt very soft or mushy? If so, one possibility is that, after an hour of continuous running at somewhat elevated power levels, the exhaust system heat has been sufficient to raise the temperature of the brake fluid in the slave cylinder to the point that water absorbed by the brake fluid formed vapor bubbles which were then compressed when you tried to release the clutch. When the fluid subsequently cooled, the water returned to the liquid phase and was once again "solid".
If this should be the correct scenario, a flush of the clutch and brake systems is in order; they have a common fluid reservoir.

Yep, "soft and mushy" would describe it, and your contaminated-with-water theory is something I never considered.

I understand that bleeding the clutch is supposed to be a horrible experience. I have the Haynes manual -- any tips beyond that?

I'm assuming just replace with DOT-3 or better?

Thanks in advance!

The clutch bleeding process can be a bit trying when the system has been opened, and contains air. The flushing process, however, when done with a pressure bleeder, does not introduce air.

If done without a pressure bleeder, it is best done as a two person operation; in either case, do the brakes first to assure that the reservoir has been swept of all old fluid, and be generous with the flushing of the clutch circuit, as it takes a while to sweep all of the old fluid out.

The clutch must be bled from the bottom up. The best way is to use an oil 'squirt can' The manual says to pump brake fluid up through the clutch system by attaching a hose from the brake caliper to the clutch slave, you can do that, i have many times, its a pain so when someone came up with the squirt can method, I tried it and found it works very nice. You attach the hose from your squirt can to the clutch slave, open the bleeder, pump the brake fluid up to the resivour, done, do a search, theres plenty to read, bottom line, bleeding is not a big deal. I use the clear hose from ace hardware so you can see air bubbles and remove them before hooking up to the slave.

__________________


1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

Steve, if you are going to flush the clutch line to replace the contaminated fluid. wouldn`t seem to be a good idea to flush it up into the brake reservor.

I know it does say in the FSM to bleed from the bottom up. but if you are just flushing out the old fluid, I think I would go from the top down through the slave cylinder.

Bleeding a line with air in it, I would go from the bottom up.

Here is a good video on bleeding the clutch.
BMW, VW, Porsche Clutch Bleeding - YouTube

Charlie

__________________
there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works

Good morning Charlie, Yes, for flushing just hook up the pressure bleeder and do it like brakes. Since the clutch slave is the lowest component in the clutch system all the crud collects there. I dont know what would be the best way without a pressure bleeder. Perhaps gravity? Maybe the folks that wrote the manual figured their advice about changing the brake fluid every two years would be followed and no crud would accumulate. I had a clutch slave bleed nipple that was plugged, When pressure FLUSHING I couldn't figure why I couldn't get any fluid to come out. doh. Took the pressure off and swapped the nipple from an old slave and of course that was the problem. Maybe what one should do is flush the system first then go back underneath, hook up the pump can and bleed the air out.

That video is a good one, I'll file it away to pass along.

__________________


1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

You probably know this but I gota ask..you do know the brake fluid reservoir has two chambers? the rear one is for the clutch. Its hard to see, I just move the reservoir back and forth a little and you can see the fluid move, if theres anything in there. Dot 4 is what you want to use.

__________________


1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

Yes, good morning Steve, think that was almost 2am I just got back home.

Some of the 4 & 5-spd I have pulled at PNP, when I removed the clutch line to the Slave, it looked like thick goopy black coffee coming out. you know that system wasn`t bleed in like forever.

When I did my 4-spd swap, I used the Motive to initally flush/bleed the system from the top down. the Motive pressure bleeder should push to air out, right. after all what does MB know.
well that didn`t work no matter how many time I fiddled with doing it.

Finally had to do the bottom up method.

I haven`t tried it yet, but pressure bleeding from the top down shouldn`t cause any clutch problems, ie adding air into the system.

I need to do the 240, but going to wait until I have the 300 back up and running. don`t need both cars down if I screw up. or the wife wil be....


Charlie

__________________
there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works

No, you shouldn't have a problem bleeding/flushing the system from the top down (unless your pressure bleeder runs dry) but as you learned you can't get the air out from the top down, seems like it would work and I woulda tried it if I had a pressure bleeder at the time.

__________________


1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"