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Master cylinder sanity check.

gt1guy

gt1guy

Apparently a racist
Joined
May 19, 2020
Member Number
241
Messages
3,137
Loc
New Iberia, La.
Front port is front brakes correct?

IMG20240903154825.jpg


Bought it a while back and can't find the receipt, so no clue what it's originally from. Pretty sure it's a Ford of some sort.
Was the only thing I found with the brake lines coming out on the inboard side and the bore that I needed.
Front port is 9/16 and rear is 7/16, which leads me to believe front is in fact front brakes.
 
irate4x4.com

Master Cylinder & Combination Valve

I am mashing parts into my 97 Dodge Ram 2500 at hydroboost and master cylinder as there aren’t any OE replacement available to just bolt in & send it. I am looking into to put PV2 (disc/drum) combination valve (also known as proportioning valve) in my truck, along with RWAL deletion. I am...
irate4x4.com irate4x4.com
 
TrailTamer said:
irate4x4.com

Master Cylinder & Combination Valve

I am mashing parts into my 97 Dodge Ram 2500 at hydroboost and master cylinder as there aren’t any OE replacement available to just bolt in & send it. I am looking into to put PV2 (disc/drum) combination valve (also known as proportioning valve) in my truck, along with RWAL deletion. I am...
irate4x4.com irate4x4.com
Click to expand...

So rear port is for the front brakes.

Sirching the Internet it seems every single person on earth is confused about it.

Fuck:flipoff2:
 
Looks like the rear port of the MC has a check valve on it. Usually goes to the rear brakes to keep the pedal up/fluid in.
 
TrailTamer said:
Best off to identify what you have or buy another!

Or just try and see
Click to expand...

Found another pile of receipts, but no joy. Only thing I know for sure is that I got it from Rock Auto and I'm 99.9% sure it was for a Ford.

If it comes to it, "try and see" will be the plan.


arse_sidewards said:
That looks like a 99-04 Master cylinder. I'm pretty sure rear is rear brakes.
Click to expand...

Now were getting somewhere.

Gumbybronco said:
If it is a 99-04, then it would be metric. At least both of mine are.
Click to expand...

Not metric. I screwed in the AN adapters that were 9/16 and 7/16 and they fit perfect and went all the way in.

arse_sidewards said:
I'm pretty sure that's true, in which case I'm incorrect. I missed the stuff about the threads.
Click to expand...

Shit

Grendel said:
Looks like the rear port of the MC has a check valve on it. Usually goes to the rear brakes to keep the pedal up/fluid in.
Click to expand...

I'll pull it off today and have a look at it.


I do remember that it was somewhat of a unicorn in my searching, in that it has the ports on the inboard side. That was the sole reason I was looking for a different master. I needed the brake lines to leave the master on the engine side of it. Tire comes really close when stuffed.
Also for some reason, a van application is stuck in my head.
 
On a hindsight I seriously think your master cylinder’s front ports are for front, and rear port is for rear.

This probably matter even less if whatever it’s going in has disc/disc. Disc/drum has different reservoir sizes, the larger reservoir is for disc (front)

And if you read carefully, I said front ports, with the S. Looking like your master cylinder has 2 front ports, likely for front brakes.

My $0.02
 
TrailTamer said:
On a hindsight I seriously think your master cylinder’s front ports are for front, and rear port is for rear.

This probably matter even less if whatever it’s going in has disc/disc. Disc/drum has different reservoir sizes, the larger reservoir is for disc (front)

And if you read carefully, I said front ports, with the S. Looking like your master cylinder has 2 front ports, likely for front brakes.

My $0.02
Click to expand...

Yes there are two ports on the front. 9/16 and the other is 3/8. It's the same type flair as the 9/16.


On the rear port, what Grendel was talking about isn't a check valve. It's straight through.

What screws into the master is o-ring port, with the other end being the 7/16 flair. It just seems to be an adapter.

IMG20240904121758.jpg


IMG20240904121825.jpg



Straight through, nothing inside.


IMG20240904121807.jpg
 
gt1guy said:
Only thing I know for sure is that I got it from Rock Auto and I'm 99.9% sure it was for a Ford.
Click to expand...
If Rock Auto keeps track of your purchases, there's the real possibility you could learn exactly what it is from them.
 
RockCockSuck sends you an automated email with a parts list so if you search your email for something related like Master Cylinder it will come up. That's how I keep track of what I bought in the past.

So many years ago all MCs were plumbed the same. Seems like with the advent of disc/disc where the piston bores are the same that rule is no longer relevant.

I just had the same issue when installing a bigger MC on my 1 ton S10. All of the 2000s vintage GM trucks switch port location. They are also a straight shot with no valving because the ABS takes care of everything else.

Regardless once you find out what you have I'd check the specs of a available on the RockCockSuck page. I'd also look up the factory manual to see if they have a diagram just to be 100% sure.

Like I said it was very confusing trying to figure it out as there is no hard rule anymore.

Also I fucking hate Rockauto, they can rot in hell in case you haven't figured that out :lmao:
 
Grendel said:
Looks like the rear port of the MC has a check valve on it. Usually goes to the rear brakes to keep the pedal up/fluid in.
Click to expand...
Disc/drum 90s Fords use a check valve like that. It looks like a little brass hexagon adapter fitting from the outside.

I don't understand why something for a disc-disc application would have that though.

Edit: Never mind that last sentence since it's just an adapter without a valve
 
gt1guy said:
Yes there are two ports on the front. 9/16 and the other is 3/8. It's the same type flair as the 9/16.
Click to expand...
Are you 100% sure. There's a metric size (one of the normal sizes for 3/16 line) that a male freedom sized fitting will screw nicely into but not seal. Maybe 10mm and 7/16 or maybe 10 and 3/8 or something like that
 
TrailTamer said:
I looked on RockAuto.

1994 Ford F-SuperDuty seems most likely a match....
Click to expand...

TrailTamer said:
Click to expand...

You are the MAN!!!!:beer:

That's not exactly what I ordered, I'm sure it's the same part though.
But it got me to look around for a phone number to try and call. Instead, I found what Skinny was talking about.....................put in your email and they send a list of your orders.

Fuck me running. I got that stupid feeling going right now.:homer:

So this is what I ordered on 5/12/20

Capture.JPG






Still doesn't say which port is the front brakes and which is the rear brakes. Says primary and secondary. Primary being the rear port. I don't know what they mean by that.
 
Funny thing me finding this thread. I just posted in the Ford section my confusion with an Expedition MC. Argh guess it’s time to crack open the lines and flip flop them.
TrailTamer said:
And if you read carefully, I said front ports, with the S. Looking like your master cylinder has 2 front ports, likely for front brakes.
Click to expand...
The other front port is for a pressure switch.

SuperDuty MC ⬇️
IMG_9759.png
 
WiscoF100 said:
Funny thing me finding this thread. I just posted in the Ford section my confusion with an Expedition MC. Argh guess it’s time to crack open the lines and flip flop them.

The other front port is for a pressure switch.

SuperDuty MC ⬇️
IMG_9759.png
Click to expand...

Which line did you have going to which end?

Have you driven it?
 
The picture above is from my KOH rig, I had it plumbed rear port front brakes. Dayton calipers front, notorious Chevy disc swap rear. I never had any problems but that’s how I assumed it was supposed to go:homer::homer::homer: I picked the MC directly off the donor in the JY but with modern spaghetti plumbing I didn’t verify before leaving. No goofy check valve just straight up 7/16 x 24 (rear port) and 9/16 x 18 (front port) OEM Superduty seen below
IMG_9760.jpeg


Now I’ve got an Exped MC in a different old truck and I’ve got a big problem. Plumbed rear port front brakes and they’re holding pressure.:mad3: My adapter is operational not straight through like yours. Picture below is incorrectly plumbed :homer:

IMG_9756.jpeg
 
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This has my attention. :laughing:

Screenshot 2024-09-04 at 7.28.24 PM.png


Edit: Based on my 10min of research I'm concluding that it's an E-350 cab and chassis but with the F-superduty rear disc setup (8-lug). All I'm finding are mini-buses and ambulances so that kinda makes sense. Front parts are all the same "3/4 to 1.5 ton" Ford 2wd spindle setup you find on everything they've made going back into the 1960s.
 
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Ok, so the thread WiscoF100 started had a great post in it.

Here's the picture. Look at the green and blue lines.

brake-png.904872


That's going to show you which port puts out more volume. So even if you had a master cylinder where both ports were exactly the same, you know which one should go to the front.
 
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