Help please: Master cylinder problem

[Kentguy13]

I am having an issue with half of the master cylinder not working. I hooked up the front brakes to the two ports on one half, they seem to work fine. The single live axel caliper is hooked to the single port on the other half, it is not working.

To trouble shoot: I switched one of the front brakes and the rear brake. Rear and one front brake is now working, front on single port is not. I feel I’ve narrowed it down to the single port of the master cylinder.

Any suggestions or secret tips to prime or fix the master cylinder? It’s brand new, never installed or used.

 

[Karttekk]

Have you talked to the vendor of the master cylinder or wasn't it purchased through a vendor? Normally to bench bleed a master cylinder you need to fill the master reservoirs, hook clear brake lines to each outlet port and place the other ends in a container of brake fluid. Push the master cylinder plunger in several times until all fluid is coming out of the bleed lines with no air bubbles. Close the outlet ports off then mount the master on the vehicle. You may or may not need to do additional bleeding once installed. Use the same procedure.

 

[Kentguy13]

Thanks Karttekk. I'll see what I can do. I bought this set up off ebay, it was shipped from Australia. I wouldn't know who to contact even if there was a vendor. It was supposedly pre-primed and a sealed system, but the lines didn't work for my custom application so I had to modify. I think in the process air got introduced. Thanks for the input.

ryan

 

[gegcorp2012]

I tried a similar type of MC, but I think mine had more ports than what I see in your pics. I used the two bottom ports and had to close off one on the end.

Is the side with the pressure switch the side with the dead port ?

Did you check the pressure switch to see if that piston is building pressure ?

The threads for the pressure switch were different than the brake line threads on the one I tried (not interchangable).

I switched to another MC because the volume of the pistons was too small for my liking.

BTW, nice work on your dual piston to pedal pusher.

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[Kentguy13]

Is the side with the pressure switch the side with the dead port ?

Did you check the pressure switch to see if that piston is building pressure ?

Good idea! I didn't even think of that. My neighbor was a mechanic back in his younger years, so next week he's going to help me with this thing. We'll keep that pressure switch idea in mind.

This unit has two ports on the one side, a single port on the other side. It is the single side that isn't working. If I have to buy a new MC, I may look for a bigger one as well. This is a pretty heavy duty kart.

 

[Kentguy13]

Well no luck today. I primed the MC, bled the lines, and for a few minutes had some friction. I never had complete lock up, I could always move the wheel by hand.

I changed ports, still no luck. I'm not sure what the problem is with this MC, but its coming off and I'm heading to Summit Racing tomorrow to pick up a Wilwood Aluminum Master Cylinder.

 

[Felineman]

Sounds like you may have rolled the seals, you MUST bench bleed..... IE gravity bleed the cylinder before you apply pressure to the system or you chance ruining the seals, you can maybe save them by taking it apart and reseating the seals, don't forget to bencg bleed it after replacing seals.

 

[Kentguy13]

Took the master cylinder off the kart, broke it apart, and to our untrained eye, couldn’t see any visual defects. We bench bled it at one point, but I can’t remember if it was the very beginning or after I noticed it wasn’t working.

Anyways.....

Decided to buy a car unit from Summit Racing. I didn’t go with the Wilwood one, it only had one port. I found a $25 one with two ports, but man is this thing massive. After bench bleeding the new unit and hooking up a caliper, it worked brilliantly. I’m excited to get this put together. It’s going to be interesting craming this thing behind the pedal.

 

[Kentguy13]

I’m making progress again. I hope tomorrow to have working brakes.

 

[landuse]

Looking good there Kentucky!

 

[Kentguy13]

Just like everything on this Kart... I’m learning as I go. So, the brakes are hooked up and bled. Incredibly stiff pedal, to the point I can barely push it.

Did I overcompensate and get too big a master cylinder? Is the volume on this giant thing too much for the little calipers?

What if I extended the pedal higher to get more leverage?

still need help

 

[Karttekk]

You'll need some free play in the pedal. Loosen the rod a bit to give the pedal & piston some breathing room.

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[Kentguy13]

You'll need some free play in the pedal. Loosen the rod a bit to give the pedal & piston some breathing room.

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I know it looks pretty tight, but the push rod lets the piston fully depress.

My theory is.... the volume of fluid this car master cylinder is designed to push is too much for these small go kart calipers.
The calipers are “working”, but I’m not getting the tire to completely lock up, even by hand turning it.

The current MC pedal travel is maybe an inch before it becomes to difficult to push further

 

[Karttekk]

Have someone push the brake pedal while you go around and crack each caliper bleeder one at a time to see if you're getting fluid to all 4 wheels. You might have a seized caliper piston. Not much to these systems as far as I know, there are only so many things to check. The brake pedal needs to move a little before the rod contacts/moves the master plunger.

I know it looks pretty tight, but the push rod lets the piston fully depress.

"Looking" pretty tight doesn't really mean anything. Loosen the rod adjustment nut until the pedal moves slightly before the plunger begins to move. We're not checking to see if the piston fully depresses, we're looking to see if the pedal fully retracts. Other than that, I have no more suggestions. Put the kart on a trailer & take it to a motorcycle shop, they might be able to figure it out. Do you want to spend hours trying to fix the brakes or spend hours riding the kart?

 

[Kentguy13]

Well problem solved! Turns out.... it was never the master cylinder. The calipers were upside down. Only took 3 different master cylinders before my neighbor noticed the bleeders on the bottom. Exchanged the left and right and they worked like a charm. Chalk that one up to another learning moment.

 

[landuse]

Well problem solved! Turns out.... it was never the master cylinder. The calipers were upside down. Only took 3 different master cylinders before my neighbor noticed the bleeders on the bottom. Exchanged the left and right and they worked like a charm. Chalk that one up to another learning moment.

I'm glad you got it sorted out!