Where to start on this brake issue that I have?!

[WrenchingtheWretched]

Not really sure where to start, and rather than flying blind I thought I’d come here again, previously on my 1982 F350 1 Ton 2wd with 400 4spd I spoke of removing the braking valve, I took a lot of members advice and left it. I haven’t done anything to the system at all. I’ve had brake issues since I bought it. The “BRAKES” light is on. I’ve tried resetting the valve to no avail. I have “tested” the brakes in my field with leaves on the ground so it would slide and all the wheels are in fact braking……but with that said the pedal almost bottoms out before it stops. If I pump them up only the right rear engages if I slam on them all 4 work but the pedal fades. No visible leaks. There is a relatively new master cylinder on the truck. I didn’t install it so I can’t vouch for the bench bleed. I just don’t want to start cracking bleeders when it could be more simple than chasing the entire system. I’m new to fords but not wrenching, I know these trucks have all kinds of little “Easter eggs” that may not be obvious to someone uneducated like myself.

[Gary Lewis]

If there are no leaks and the pedal fades then you must either have a leaking master cylinder, meaning fluid is leaking past the piston, or have air in the system.

Your statement of "If I pump them up only the right rear engages if I slam on them all 4 work but the pedal fades" is telling.  That really sounds like air in the system.

So I would bleed the system, starting in the right rear, then left rear, then right front, then left front.  It won't cost much, if anything, and I think that's where the problem is.

[WrenchingtheWretched]

Sounds like a plan, should I do anything special with the valve other than buying the bleeding tool? I plan to buy a vacuum bleeder or pressure bleeder to help speed this process along.

[Gary Lewis]

Check out this post.

[FuzzFace2]

WrenchingtheWretched wrote

Sounds like a plan, should I do anything special with the valve other than buying the bleeding tool? I plan to buy a vacuum bleeder or pressure bleeder to help speed this process along.

For get the vacuum bleeder go straight to the pressure bleeder.
I never got a vacuum bleeder to work right.
Dave ----

[Gary Lewis]

I haven't gotten a vacuum bleeder to work very well either.  The bleeder screws always leak at the threads.  But pulling them out and coating the threads with PTFE thread sealer worked fine that one time.

I really like my later model master cylinder that has a single cap.  And I've made a cap with an air connector, so I just put about 3 psi on it and open the bleeders and let the fluid come out.  Easy peasy.

[WrenchingtheWretched]

Will do gotta make time to get it done with short days here in NC now time is of the essence😂

[WrenchingtheWretched]

What’s the part number for the newer master cylinder? And will it work on my 1ton? Didn’t know if anything was different.

[Gary Lewis]

That's a good question.  We have a thread called Master Cylinder Upgrade Part Numbers.  But I think it only deals with F150 or Bronco brakes.

For your one ton you'll be looking for one with a bigger bore.  In Big Blue's parts list document I have this note: "1 5/16” bore, probably ACDELCO 18M886 from a ’99 F450 Superduty."  But for your truck you will probably want to get one for another F350.  Here's a search from Rock Auto's catalog for a 1990 F350, and you'll see several there.  But make sure you get one with a reservoir - and the residual pressure valve, which you'll need as it adapts the threads to match your brake lines.  But I didn't check to see that any of those come with the residual pressure valve, so you'll have to check that out.  

Speaking of the brake lines, the newer masters have the front and rear ports switched so you have to bend your lines a bit, but it is easy.

[WrenchingtheWretched]

Okay I’ll give it all a look do I need to do anything special with the multifunction valve?

[WrenchingtheWretched]

So taking your advice I tried searching for the newer master cylinder weeding through RockAuto I found that the “original” MC for my F350 has a 1.063in bore. The 1990 newer style has a 1.125in bore. I did find a newer style with the 1 5/16in bore in a 1994 F350 7.5l. I may just stick with the old school bail style since it’s kind of all over the place with sizing.

[Gary Lewis]

You don't need to do anything to the multifunction valve.  I'm still running mine.

And, by the way, the issue about the speed control that is mentioned in the RA catalog isn't an issue on a Bullnose.  Our speed controls don't use the switch, so there's no need for it but it doesn't hurt to have it.

[Gary Lewis]

Jim/ArdWrknTrk just informed me that Uhaul Truck Parts has one of the master cylinders you are looking for, and it is only $52.18 + $4.95 shipping.  Plus they have 99.99% positive feedback on over 25K sales says a lot.

He's working and can't post right now but wanted you to have a chance to get that one.

[WrenchingtheWretched]

Thanks! I too have been very busy with work! So I still haven’t cracked into the brake issue but I will return with what I find!

[WrenchingtheWretched]

Indeed air in the lines! I appreciate all the insight. I apologize for not suspecting that first!

[Gary Lewis]

So you have it fixed?