Newer Style Master Cylinder Swap

[Machspeed]

I'm seriously considering a newer style master cylinder swap on my truck. I know Cory and Gary have made this swap, both addressing it in slightly different ways using different year OEM style master cylinders.

That said, I'm trying to figure out what year OEM style Master cylinder would be best for my truck giving me full capability and utilizing my OEM Booster and proportioning valve. I want for my brake light to work and I'm not exactly sure how that's all wired in! I've not looked yet but I know there is no wiring going to my OEM master, while wiring does go to the upgraded master. Suspect electrical signals sent via the proportioning valve in my trucks current OEM state??? I understand I will have to reverse lines and I'm fine with that. In fact, I will likely make new lines with copper nickel brake lines....easy to bend and flare.

I'd appreciate advise on this and any other input I may be overlooking.

Thanks!!!

[Gary Lewis]

The proportioning valve grounds a wire to light the BRAKES light on the dash when the balance between the front and rear is upset, like if you blow a hose on one side or the other. So if you go with a later master and retain the proportioning valve you won't need to change any wiring.

And if you make your own lines you won't need the residual pressure valve that adapts the existing front line to fit the master. But, it won't hurt to have that valve and then you wouldn't have to make lines, find the right fittings, etc. Or, you could do like I did and use 1990ish lines. Those trucks still had the proportioning valve but went to the later master, so screw right in to the proportioning valve you have an a later master.

But some of the later master cylinders have a port in them for a switch. You don't need that port nor switch, but if you get a master with one then I'll send you one of these brass plugs. I bought 10 and there are now 9 in there after I used one on BB's master cylinder. Would love to farm them out.

 

[Rembrant]

And if you make your own lines you won't need the residual pressure valve that adapts the existing front line to fit the master. But, it won't hurt to have that valve and then you wouldn't have to make lines, find the right fittings, etc.

Gary,

Do you have the residual pressure valve installed? I didn't think it was possible to go without it?

 

[85lebaront2]

The proportioning valve grounds a wire to light the BRAKES light on the dash when the balance between the front and rear is upset, like if you blow a hose on one side or the other. So if you go with a later master and retain the proportioning valve you won't need to change any wiring.

And if you make your own lines you won't need the residual pressure valve that adapts the existing front line to fit the master. But, it won't hurt to have that valve and then you wouldn't have to make lines, find the right fittings, etc. Or, you could do like I did and use 1990ish lines. Those trucks still had the proportioning valve but went to the later master, so screw right in to the proportioning valve you have an a later master.

But some of the later master cylinders have a port in them for a switch. You don't need that port nor switch, but if you get a master with one then I'll send you one of these brass plugs. I bought 10 and there are now 9 in there after I used one on BB's master cylinder. Would love to farm them out.

If you order the MC for without cruise or the pre-1993 cylinder there is no extra port. I used one for with cruise as I needed the extra port for my trailer drake controller.

[Machspeed]

And if you make your own lines you won't need the residual pressure valve that adapts the existing front line to fit the master. But, it won't hurt to have that valve and then you wouldn't have to make lines, find the right fittings, etc.

Gary,

Do you have the residual pressure valve installed? I didn't think it was possible to go without it?

I noted that in your thread Corey and I'm glad you brought that back up. I await Gary's response on this.

Bill thank you! I was perusing through Rock Auto looking at MC's and wondering why cruise made a difference.

So gentlemen, if I order an 87 MC spec'd for like truck to my 86 (351, 4x4, etc) , I should have no issues?

[Gary Lewis]

And if you make your own lines you won't need the residual pressure valve that adapts the existing front line to fit the master. But, it won't hurt to have that valve and then you wouldn't have to make lines, find the right fittings, etc.

Gary,

Do you have the residual pressure valve installed? I didn't think it was possible to go without it?

No, Cory, I don't have the residual pressure valve. That is Huck's 1990 lines, which screwed into the '95 master cylinder on the top end and the Bullnose proportioning valve on the bottom end. No need for a residual pressure valve to adapt the fitting sizes.

[Rembrant]

No, Cory, I don't have the residual pressure valve. That is Huck's 1990 lines, which screwed into the '95 master cylinder on the top end and the Bullnose proportioning valve on the bottom end. No need for a residual pressure valve to adapt the fitting sizes.

Gary,

That master has the residual pressure valve, circled in yellow. Is that not what that valve is? That is what I have been calling it. There is no way to connect a brake line without it.

[Gary Lewis]

Gary,

That master has the residual pressure valve, circled in yellow. Is that not what that valve is? That is what I have been calling it. There is no way to connect a brake line without it.

Well, I'll be a .....

How did I miss that? I was thinking that valve was in the front. Boy, I'm embarrassed!!!

Cory, thanks for correcting me. Good catch.

[Rembrant]

Well, I'll be a .....

How did I miss that? I was thinking that valve was in the front. Boy, I'm embarrassed!!!

Cory, thanks for correcting me. Good catch.

Ha, it's nothing. The reason I'm such a stickler about that residual pressure valve is that it was a bit of an issue for me initially. I kept reading that in swapping the later master cylinder on, nothing else was required (as in, no extra parts). That IS true if you go to the junkyard and grab a master cylinder from a later truck. However, if you do like I did an buy a later master cylinder, that residual pressure valve is not included with it. All you get is a new o-ring to swap the old one over to the new master.

The good news is that the residual pressure valves are easy to find at the junkyard, and easy to remove. All you need is something to cut the brake line with, and an adjustable wrench to remove the residual pressure valve (if you are not taking the whole master complete, like some do).

Here is what it looks like all alone:

In any case, back to John's questions:

I bought a new master cylinder for a 1991 F150. As a general rule of thumb, when buying "upgrade" parts for the later trucks, I typically try to stick within the Bricknose 1987-1991 years as there were some changes in 1992 that may or may not be compatible. 1991 is my go-to year.

The later master cylnder bolts directly to the Bullnose booster, no problem. I did have to adjust the booster pushrod slightly, but that's it.

The lines are reversed front to rear as noted previously.

The wiring. I was gutting my entire brake system at the time, so my old prop valve was removed and discarded. This is why I connected the old wiring to the new master cylinder.

Technically you could wire them both in if you wanted to (I think). That way you get the brake warning light to also illuminate if your brake fluid gets low.

[Machspeed]

Well, I'll be a .....

How did I miss that? I was thinking that valve was in the front. Boy, I'm embarrassed!!!

Cory, thanks for correcting me. Good catch.

Ha, it's nothing. The reason I'm such a stickler about that residual pressure valve is that it was a bit of an issue for me initially. I kept reading that in swapping the later master cylinder on, nothing else was required (as in, no extra parts). That IS true if you go to the junkyard and grab a master cylinder from a later truck. However, if you do like I did an buy a later master cylinder, that residual pressure valve is not included with it. All you get is a new o-ring to swap the old one over to the new master.

The good news is that the residual pressure valves are easy to find at the junkyard, and easy to remove. All you need is something to cut the brake line with, and an adjustable wrench to remove the residual pressure valve (if you are not taking the whole master complete, like some do).

Here is what it looks like all alone:

In any case, back to John's questions:

I bought a new master cylinder for a 1991 F150. As a general rule of thumb, when buying "upgrade" parts for the later trucks, I typically try to stick within the Bricknose 1987-1991 years as there were some changes in 1992 that may or may not be compatible. 1991 is my go-to year.

The later master cylnder bolts directly to the Bullnose booster, no problem. I did have to adjust the booster pushrod slightly, but that's it.

The lines are reversed front to rear as noted previously.

The wiring. I was gutting my entire brake system at the time, so my old prop valve was removed and discarded. This is why I connected the old wiring to the new master cylinder.

Technically you could wire them both in if you wanted to (I think). That way you get the brake warning light to also illuminate if your brake fluid gets low.

Corey, that's great information, thank you! Need just a little more though, at least for me, I'm slow!

It seems I read somewhere that the use of the residual pressure valve is no more than an adapter. The post I read stated that and, in fact, the guy took the guts' out of it to utilize it merely as an adapter. I believe I read that here: https://www.ford-trucks.com/forums/1493345-swap-to-newer-style-mc-2.html

Thoughts on this? If it's not merely an adapter for our purposes, why is it needed in the conversion when the OEM unit (cast unit) does not utilize one?