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740 hydraulic clutch system problem

gear whine

gear whine

advocate of k-jet
Joined
Dec 17, 2006
Location
18452, NEPA
91 740 B230FT m46 w/ hydraulic clutch


ok lets be frank here


driving to work everything fine, all of a sudden, no clutch.

a day later or so at work i pumped the pedal and saw fluid leaking out past the little U-seal in the slave cylinder.

i figured, oh cool its just that. ill pop that out and throw another one in.

ordered one from fcp got it the next day(today) and proceded to put it in after work. got it in and started to bleed the system. built up a bit if pressure but ONLY at the very end of the pedal travel. built it up a bit more and it got stiff for a couple presses and then it went away WITHOUT touching the bleeder screw.

i figured, ok, there is still air in the system we need to bleed it more. pumped it up, cracked the bleeder, pumped it up again a fluid SHOT out of the same U-seal out of the BRAND NEW one i just put in.

BTW the fluid level in the master cylinder resov. was checked and full the whole time.

ANY IDEAS?

clutch master cylinder?

this system seems pretty basic i dont know how it blew the seal out of the new slave cylinder

please help, urgent...need to get car drivable again asap, its my daily

volvo techs?

thanks ANYONE for help.
 
I had the same problem before, second seal leaked too. The problem ended up being my clutch fork was broken allowing the slave cylinder to extend farther than it is supposed to. I replaced the the fork and the slave seal and its been fine since.
 
damit i really didnt want to hear that but ill keep that in mind, thanks

im pretty sure its not broken, bent? maybe?
 
Worn pivot pin?

Worn hole where the piston meets the fork? I have seen some forks so blown out the pin is about to push thru the fork.
 
so i talked to one of the techs they have at fcp and he said i need to hand bleed the slave cylinder instead of bleeding it with the pedal. he said i over pressurized the seal and thats the way i blew it.

matt, or rob is this the way you've bled clutches b4?

all i know is to bleed them like brakes
 
You may have to bench bleed the master cylinder for the clutch. But the slave cylinder should never need that. Hydraulic pressure from the master cylinder will fill up the slave cylinder just fine. Either the release arm is bent, pivot pin worn or the arm came off it. Sometimes the rod from the slave cylinder has just worn the area where the rod pushes on the release arm. Welding it up or using some kind of cup washer on there could make up the difference from the wear due to all the years of use. That could be why the arm overextends but the release arm itself seems to be OK.
 
I have a 940 .pivot pin has worn through, can the pivot arm be removed without removing gear box
 
I replaced the clutch fork (pivot arm) on my 740 without pulling the tranny, I did however have to loosen the bellhousing bolts to slide the tranny back a 1/4 inch to get clearance to do so. It was a total pain in the ass mostly getting the spring clip thing back on the fork thru the little access hole on the bottom of the bellhousing. But still better than removing the tranny all the way.
 
stefanapolis said:
I replaced the clutch fork (pivot arm) on my 740 without pulling the tranny, I did however have to loosen the bellhousing bolts to slide the tranny back a 1/4 inch to get clearance to do so. It was a total pain in the ass mostly getting the spring clip thing back on the fork thru the little access hole on the bottom of the bellhousing. But still better than removing the tranny all the way.
Click to expand...

thanks mate, could not find a pic of the fork ,but thought that it could be removed that way .
 
samsonv8 said:
thanks mate, could not find a pic of the fork ,but thought that it could be removed that way .
Click to expand...

no probs with the spring clip. removed the pivot ball and cliped it in then put the fork back. with tje ball ,just room to tighten it up ,
 
well it turns out the clutch fork was broken and that obviously caused 3 slave cylinders blow past the seal. the broken fork made it too hard for the slave cylinder to move it causing an overpressure with in turn caused the slave u-seal to malfunction.

the best part is that the old slave cylinder is still good.

oh well $70 from volvo aint too bad. i thought about coming on here and looking for a used one but i say **** it just get a new one asshole.

anything to look out for when changing the fork?
i presume you have to drop the trans to change the fork?
anything i should change while im under there?
 
well i didnt have to drop the trans
just take the pivot pin off, remove and install new one, pretty easy actually.
bleeding it was very easy as well.

i still think i need to think about replacing my u-joints. vibrations accelerating 1st and 2nd
 
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