99 Forester, 134.5K miles

 

We've been suffering through a heat wave on the east coast for the past week with temperatures in the mid- to high 90s. After about 20 minutes of city driving this afternoon, my clutch pedal went soft, disengaging the clutch at the bottom 1/3 of travel and, at certain points, sticking to the floor. After the car cooled down a bit, pedal action went back to normal.

 

I didn't feel like getting stuck in bumper to bumper, mid-summer metro traffic so I rebuilt the slave cylinder with a Subaru kit. The cylinder bore surfaces looked perfect, but the old piston seal showed a bit of wear.

 

I would have thought that extremely cold conditions leading to shrinking seals would be more likely to cause this type of failure.

 

For those who experience the same problem, here are the pertinent links that have been posted on the site.

 

http://endwrench.com/images/pdfs/ClutchPedal.pdf

http://endwrench.com/images/pdfs/ClutchInfoWin04.pdf

 

There is a discrepancy between the Factory Service Manual (FSM) and the Endwrench links for the torque value on the banjo bolt --

13 +/- 2.2 ft-lbs. and 27 +/-2 ft-lbs., respectively.

 

And according to the FSM, the mounting bolts for the slave cylinder should be torqued to 27.2 +/-2.2 ft.-lbs.

I have the same issue on my '02 OB - which I'm not sure is covered by the Endwrench articles since they just mention Legacy... However, I was told to replace the slave cylinder and hose. Will be doing that shortly.

 

Out of curiosity, what is the "banjo" bolt?

Didn't know that was the technical name for it - very cool, thanks!

ANy temp change can cause an issue with a part, because metal expands with heat, and it doesnt take much of a leak to get what you saw.

nipper

Good point, Nipper -- and high heat and humidity resulting in a decrease in brake fluid viscosity and more water vapor to be absorbed only adds to the problem.

 

I was thinking of a recall on brake master cylinders, where similar hydraulic symptons would appear in extreme cold.

 

http://auto-recalls.justia.com/content/99V040000-SUBARU-FORESTER-1999.html

 

Whereas the Endwrench links suggest replacing the slave cylinder, hose, and washers, I had only the slave cylinder repair kit on hand and reused the old washers, which did the trick. Pedal feel is firmer and more consistent.

 

The repair kit comes with a new pistion & seal, piston spring, rubber boot, and bleed valve cap. After you've removed the slave cylinder, it takes only another 5 minutes to clean the cylinder & install the new parts from the kit.

How much did Subaru charge for the rebuild kit? I checked yesterday and Rock Auto had a new slave cylinder for under $25.

OEM slave cylinder is made by Nabco.

 

At 1stsubaruparts.com, the rebuild kit is 12.88 plus shipping. The cylinder doesn't really wear out, and the kit comes with all the parts that do. I ordered it along with some other parts a while back, hence had it waiting for the day to come, and sure enough, it did.

Well, the symptoms returned and were worst after the car had been parked in the hot sun and while diriving the car at slower speeds, which seems to confirm that extreme heat was the culprit. Pedal action would return to normal after I drove the car for about 5 to 10 minutes at highway speeds.

 

Bleeding the sysytem several times did not fix the issue, and as far as I could see, there was no air in the system nor were there any fluid leaks. But rather than deal with the continued agitation, I decided to renew the entire hydraulic system and replaced the clutch hose and master cylinder.

 

The old hose looked fine, and it's hard to imagine how this alone, unless ruptured, could have such drastic effects. I see in the TSB that the WRX is exempted from hose replacement, which must only mean that they come equipped with steel braided ones.

If you weren't low on fluid originally, then the MC would have been the most likely suspect. Our shop always changes the MC and slave cyl at the same time. They both seem to fail at about the same time or the other will soon thereafter. A leaking hose is very rare, never seen one go bad otherwise.

Nope, no leakage at all so I now have a spare lying around in event of an uncommon failure.

 

I looked for a rebuild kit for the Master Cylinder, but there were none to be found. When I took the old one apart, the aluminum cylinder bores were perfect. Though it's a softer metal as compared to the cast iron slave cylinder, I can't imagine the rubber seals can cause all that much cylinder wear.

 

Anybody know a supplier for just the piston seals? They seem like pretty standard parts for a 5/8" bore.

 

One nice feature on the new master cylinder was a bleeder valve on the front, which makes bleeding the system a whole lot easier.