1980 F350 4X4 C6 Project

[FuzzFace2]

Gary Lewis wrote

My experience is that the bleeder valves leak at the thread and introduce air into the stream, creating bubbles.  You might try packing a heavy grease around the base of the bleeder valve to seal it.

X2
Dave ----

[Atlas75]

I tried adjusting the wrench about every I could to get rid of the bubbles.  I will try the grease and see what that does.

If that works and there are no more bubbles but the pedal is still soft, are we looking at master cylinder?

[Gary Lewis]

I doubt the master would make the pedal soft, unless it is leaking by pretty badly internally.  If so, it would be time to replace it.

Instead, I'm thinking you'll need to bleed the system more.  And drive it and then bleed it.  Sometimes there are air bubbles lodged in the system that don't want to come loose w/o bouncing.

[ArdWrknTrk]

If it's only one wheel cylinder I would definitely try grease around the threads.

I never have much luck using my Silverline, as far as bubbles go.
But it is handy to pull fluid through.
You can also use them in reverse. But you really need to keep an eye on the reservoir so it doesn't overflow.

[Gary Lewis]

There's the beauty of the later master cylinder with the plastic reservoir.  Holds much more and shares it between front and rear.  Plus, it is easy to put 3 - 5 psi on it and pressure-bleed the system.  

[FuzzFace2]

Gary Lewis wrote

There's the beauty of the later master cylinder with the plastic reservoir.  Holds much more and shares it between front and rear.  Plus, it is easy to put 3 - 5 psi on it and pressure-bleed the system.

They do sell a plate / cap for the older masters so you can pressure bleed the system.
BTW that was the only way I could get a pedal.
Dave ----

[Gary Lewis]

If I remember correctly the price of that plate to pressure bleed was more than a new later model master.  And then you still have the individual reservoirs for front vs rear, which makes it easier to run out while you are pressure bleeding.

Granted you have to go to the salvage and get an extra cap and gasket for the later master in order to make an adapter to pressure bleed it, but that's peanuts.

[Atlas75]

Tried the grease around the threads trick tonight.  Not quite sure what happened but I had a hard time getting fluid to flow.  Once I finally did I still couldn't get rid of the bubbles and the fluid was dark the whole time.  The other 3 flowed pretty easy and the fluid cleared up relatively quickly.  Any other tips?  I'm wondering if I should try disconnecting the line from the cylinder and pull a vacuum on the line to see what happens.  Thoughts?

[Gary Lewis]

I wouldn't pull the line.  Instead I'd pull the bleeder screw and put PTFE paste on its threads and put it back on.  That will seal the threads.

[Atlas75]

Thanks Gary!  I’ll try that as soon as it decides to stop raining for 30 min or so!

[Atlas75]

As far as tires are concerned…according to the door sticker my truck originally had 9.5 x 16.5 tires.  It currently has 12 x 16.5 tires.  Is there a converter anywhere that will show an equivalent size in modern nomenclature for a 16 inch wheel?

[ArdWrknTrk]

There's no number before the 12?
Usually it would be something like 33x12 R16.5

12" is 300mm wide (more or less) but you need OD or rolling circumference in addition to width and rim size.

[Atlas75]

These are the only size marks on the tire.

[ArdWrknTrk]

I imagine you can measure diameter yourself if you're only looking for a tire that won't effect your speedometer.
I don't recall any '83 or later trucks having 16 1/2" rims, as the world was moving away from that size.

Later trucks came with skinny (pizza cutter) 235/85 R-16 E rated tires.
A 300mm width is going to be wanting a wider rim than stock.

Any tire website should have a spreadsheet that shows circumference or reveloutions per mile.

[oldmansimek]

12-16.5 is just shy of 33" (32.8" I think) hate to say this but do yourself a favor and get rid of the 16.5 wheels, almost no one makes tires for them. A 33x12.50R16 or 17 will be roughly the same size, you should be able to find some cheap steel wheels or used aluminum.

[ArdWrknTrk]

So a 285/75 R16 would be the closest if I did my math right?

285x.75=213.75x2=427.5
16x25.4=406.4
406.4+427.5=833.9/25.4=32.8  ?    

[oldmansimek]

12x16.5 is 32.8"x 12.5" so a 33x12.5r16 would be an exact match.  285/75r16 is same height but I think only 11" wide.

[ArdWrknTrk]

285 is very close to 11 1/4", but we all know that tread or carcass width is affected by rim width, inflation pressure and more.

I am not well versed in off-road tires or even imperial sized tires.
So I appreciate your comments.  

[bp17oang]

I am fighting some brake bleeding on my truck currently too, so I feel your pain.

Sometimes letting them gravity bleed helps, at least in my experience. You can do this while you work on something else in the shop while not getting your temper too flared up... unless of course you let the master cylinder run dry which is why I stay in the shop while I let them bleed.  If you're like me and you go do something somewhere else you will surely come back frantically to a dry master.

And as Gary mentioned sometimes you gotta just drive it around, and bleed, and drive around, and bleed...

[oldmansimek]

those 12-16.5 are real old like probably early 80's, I think they still use those sizes on skidsteers.
As for your brakes make sure your not having a problem with the proportioning valve I have had a few of these cause problems with bleeding especially on trucks that sat for long periods.  Another trick on bleeding the brakes that I have found works is pump up the pedal and then have someone open the bleeder while you are not holding pressure and then stab the pedal to the floor.  If you are not getting good flow try to bleed a front brake then go back to the rear sometimes this will reset the proportioning valve.