View original topic: Problem with new EMPI master cylinder
livingskies Thu Jan 14, 2021 8:14 pm

The 1964 bus has all new brakes, from one end to the other, just installed this week. I have done lots of brake systems on all kinds of vehicles, including three complete brake system replacements on VWs recently.

The new master cylinder is an EMPI single circuit unit. It appears that there is a problem with the master cylinder and I either have to replace it with the old unit or find a more reliable unit.

It took unusually long to bleed the brakes - as if the master cylinder was not pushing much fluid. At one point before fluid reached the wheels, the push rod in the master cylinder jammed and the pedal would not go more than half way to the floor. A short while later, the pedal again moved through the full range of motion and we could resume the bleeding process.

When fluid finally reached all four wheels and all the air was out of the system, the pedal went about half way to the floor and felt good. Pumping raised the pedal even higher. Then, the pedal suddenly went completely to the floor - no brakes. A few strokes later, and the brakes felt normal again. This happened a few more times in the following minutes. I bled the brakes again a few times, but no more air came out, only brake fluid.

The answer seems obvious: this master cylinder is faulty and unsafe to use. My guess is that the rubber seal on the plunger is catching on something internally and folding back enough to allow brake fluid to pass and the pedal to go to the floor.

Am I missing something? Has anyone else experienced something like this?
If this is a faulty part, as it appears to be, I'm hoping that the supplier will stand behind their product.

Thompson2 Thu Jan 14, 2021 8:35 pm

Sounds like a DOA part... certainly wouldnít be the first time thatís happened (I know Iíve had my fair share). Iíd pursue replacement.

esde Thu Jan 14, 2021 10:37 pm

Every mistake passes inspection.

halfassleatherworks Fri Jan 15, 2021 9:55 am

replace it. any time a piston jams in a cylinder there is a problem. probability rolled a lip on the rubber piston.

aa390392 Fri Jan 15, 2021 10:09 am

I wouldnt bet my safety on EMPI.

velvetgreen Fri Jan 15, 2021 11:12 am

I too would take a pass on pretty much anything made by EMPI- old brakes don't stop the greatest to begin with so if it were me I would spend the money and buy a good quality MC

buseric Sat Jan 16, 2021 7:18 am

You live in Canada. Buy a chinese 67 only dual circuit from concept one vw parts in Calgary. I have run 2 of them on my buses, one for 8 years now. Get the extra short brake line and brass Tee needed for 67s. Have better safer brakes for negligible cost. Its a super easy conversion, you essentially splitting the front to left and right with the Tee.[/code]

Bruce Amacker Sat Jan 16, 2021 10:17 am

Plug the MC outlet and see what your pedal does- it should be rock-hard and not even move. The best way to plug the outlet is to make a plug by brazing a flare nut closed but you could do it the hillbilly way and use a vise-grip to pinch a line shut right at the nut. If your pedal is soft like this, try finger-bleeding the outlet at the MC by holding your finger over the outlet while stroking the pedal a couple of times. This is all easily done by yourself from underneath by pulling down on the brake arm.

Good Luck!

livingskies Sat Jan 16, 2021 10:34 am

I just reinstalled the old MC, with a new fluid reservoir. Appears to work perfectly. I had considered going with the dual circuit system, but haven't done so yet. I can see the advantages of that, for sure.

The only complete brake failure I ever had in a vehicle happened when a pin came out of the brake linkage on an old Corvette - the restorer (not me) had forgotten to install a cotter pin retainer. A dual circuit would not have helped there. Fortunately, the e brake worked and catastrophe was narrowly avoided. I had to choose between hitting the back of a Hummer or people on the side of the road. I chose the Hummer, but the e brake stopped the car first.

Busted-bolt Sat Jan 16, 2021 11:12 am

esde wrote: Empi
Every mistake passes inspection. Hey have you heard of those high performance Porsche style swivel rocker adjusters? I just bought some. They had a revolutionary new design that incorporates two flat surfaces inside the swivel assembly that bind together at midpoint of rocker travel to totally waste any valve guide they are used in conjunction with.True Empi quality.... And no those adjusters are not even good enough for my scrap pile.Sorry about getting off topic but I'm pretty that the brake parts are not much better.

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