Let's talk clutch hydraulics
 

Well, now that it's time for my annual clutch M-C / S-C replacement, I once again find myself pondering my situation and wondering what I will do after I've consumed the world's supply of hardware. My car is equipped with a Wilwood 260-1304 cast aluminum master and similar rig for the external slave. My clutch is a long-throw Ram with fairly stiff springs. I've been running a garden-variety DOT 3 fluid and it pretty much stays black shortly after install. It looks like ink when I drain it. I'm convinced that the color comes from the aluminum surface of the two cylinder bores. My presumption is that after the fluid becomes heavily contaminated with aluminum particles, it starts taking a toll on the rings in the slave and master. IAfter a while, I can pull either boot and find heavy deposits of the inky fluid on the outside of the pistons indicating some level of blow-by. I'm getting ready to replace both clinders and Im upgrading to Amsoil brake fluid as it contains additional lubricants like their motor oils. Perhaps the addional stiffness of the pressure plate and long travel are simply too much for the cylinders. I've heard others chime in to say that they too put hydraulic system replacement on the regular maintenance schedule. I'm probably seeking more "permanence" than is practical. I would still like to scratch one pain in the arse from my maintenance schedule.

Hey Tony,
You mention a rather stiff set up and a quick discoloring of the fluid. Your M/C is a Wilwood part, certainly a quality name. I do not see the same problem you are running into and like you wonder why this is such a problem. Have you called their tech. line to get their suggestions? Is it the higher pressure ratios of your combination?

I use Tilton M/C on the firewall with a 7 to 1 pedal ratio. On the heavier effort clutch set ups we change the the bore size of the firewall M/C to 5/8" that power the 1" bore push slave cylinder. The external slave is from Colman Racing and has external threads and nuts on the bore to allow adjustment in its mount bracket. The clutch for and length of the pivot ball are a combination that yield 3/4" movement at the pressure plate end of the fork.

I mention the spec's of the components we use so you might compare the ratios of your system. On my own car the fluid will get a little brown with time but not the INK you are getting. I am in Arizona so it is a dry heat and wonder if that is the big difference??? Do you have same problem with the brake system ? Good luck chasing the gremlin. Jeff C

Your fluid is burnt! It has nothing to do with your aluminum components, (except maybe for the excellent heat transfer properties they have). Flush, and fill, with the Wilwood High Temp fluid.

Burgs, I don't think it's heat related. I never had this problem with the old OEM clutch set up when the hydraulic line ran within a quarter inch of the header. When the new clutch was installed, I rerouted the line over the footbox and far from the exhaust system.

Just a thought to go along with the good advice of the High Temp fluid. Is the rod connecting the clutch arm to the slave in a straight line in all planes? If not, the side loading (thrust) may be causing the piston to wear in the aluminum bore puting minute aluminum particles into and discoloring the fluid. Generally speaking these cars are light enough that an extremely sprung pressure plate is not a necessity, the tire grip becomes the limiting factor, NOT the clutch slippage.

Even if you find a problem with alignment as Rick suggested, spend the the extra $12 for the high temp fluid! If you find the alignment is good, try the fluid first.

Why would all the other aluminum master, and slave cylinders, in all the other cars here, work without turning the fluid black, and yours doesn't? :confused:

rod actuator alignment
 

I concur with Rick about the alignment of the master and/or the slave relative the input/output of the work.

The more off centerline the slave or master is to the actuator/actuating rod, the more side thrust on the cylinder bore.

These cylinders are generally NOT sleeved, but a plain aluminum bore...wear to the seals and the bore will occur relatively soon if they are not mounted correctly.

I will try to post a picture of the incredible "aluminum paste muck" on the inside of a master cylinder off of a early Backdraft. We replaced this cylinder at about 10k+. Had problems for awhile, lots of bleeding out black fluid. The wear didn't happen overnight, but it was shot. (these cylinder are normally not rebuilt, just replaced) I suppose they could be sleeved, but may cost more than a new cylinder...may last longer with a steel sleeve for sure.

The master mount on some cars is WAY to far out of alignment for the pedal actuating rod and lots of input force just goes into scrubbing away the master/slave cylinder bore.

Better fluid may help if the cylinder is cooked by being close to the headers.

My ERA, with clutch/brake masters under the floor do not have discoloration of fluid at all...( I do flush the fluid every year or so).

Nothing on the ERA is in close proximity to the headers, but, lots of cars mount the clutch/brake cylinder just above the headers...most have NO heat shields or ventilation...so, the fluid cooks.

Use the grade 5 fluid and the fluid won't be a problem from boiling, but it will still turn black from aluminum filings and rubber seal degeneration.

Pete

Hydraulic Throwout Bearing
 

Tony,

I like you have replaced several S/Cs, from several different manufactures. Two of them being Wilwood. Now don't get me wrong the willwood S/C is a very good unit it just didn't work for me. Manly I think my problem was from over stroking the clutch pedal and subsequently over stroking the s/c. I say this because after the second willwood s/c that i blew out (it blew with only 40 mins of track time) I notice the shaft seal was worn on one side.

So I was frustrated and spent the next two track sessions riding shot gun in my friends vette and was jealous that he could shift when ever he wanted to. Thats when I decided to switch to a hydraulic throwout bearing (vettes have hyd. t/o bearings).

Go to :: Quarter Master :: Home and talk with their tech guys. If you are runnig a ford transmission you will have to get the input shaft bearing retainer machined to fit the t/o bearing. Not a big deal any machine shop should be able to, the guys at racing clutches will give you the dimension.
They have detailed tech support and always answer the phone very good customer service.

You will have to take some measurements but it is very straight forward. In my case with a T-5 I had to machine down the input shaft bearing retainer for the trans down to 1.370". Additionally I had to get some additional hardware to replace the anti-spin stud that came with the t/o bearing. Again for a T-5 this was a section of all threat (metric 8mm x 1.25 pitch) and two 8 x 1.25 mm jam nuts.

But the most important thing is to install a PEDAL STOP so as to not over stoke the t/o bearing. I use to have to push the pedal completely to the floor while on the track which resulted in slow shifts and ultimately leaking and blow S/Cs. Now my pedal travel is only about 6". To set the pedal stop hight first carefully bleed the t/o bearing as to not over stoke t/o bearing, if you do over stroke the bearing you will push the bearing past its seal and you will have to order a rebuild kit to replace the o-ring (which I did). After you have bleed it put the trans in gear and have a friend try to turn the drive shaft while you slowly press the pedal. When the clutch disengages and the drive shaft turns set your pedal stop for an additional 1/4" of travel.
I know it sounds like alot of work but the result is great. If you have any questions you can contact me at 757-332-4545...Happy shifting Mike

ref mac's post: ram makes a ford throwout bearing and bearing retainer that works well on the t5. got mine through jegs. fits the aluminum bellhousing. if you use qm their stuff is based on chevrolet, which will be 1.4 id for the 1.37 retainer. ford retainer is 1.4 so you need the 1.43 id bearing. the ram unit has the stud that extends through the bearing to eliminate rotation.

Guys, I really don't have any interest in converting from the external slave. At least not yet. I tend to agree with the over-stroke. My problem didn't manifest itself until after I had a Ram long-throw clutch installed. I've always had to strike a balance between complete clutch disengagement and an acceptable petal travel range. Since I have a new master and slave (and some high-end fluid from Amsoil), I will try again to reduce the travel. Maybe I can get an additional few miles before I have to replace them again. Hell, sooner or later I will need a new clutch anyway.