Update 3. Chevy C60 brake problems

[wremele]

After having blocked off the MC 1st, then the booster, results were instant hard pedal from both units. Hooked up the total system and power bled from the MC, twice. 1st stroke of the pedal has the pedal going nearly to the floor regardless if the engine is running or not. Bled the system 3 times with the engine running. Lengthened the MC pushrod by 1/4 of an inch with no change in operation. With the top off the MC pedal depression produces a large fountain. When the pedal is released a very small fountain is observed. When moving the truck 1st application of the brakes does produce a braking action, although a weak one with the pedal near the floor. 2nd pedal stroke produces excellent stopping. Seems like there is still an air/bleed problem that needs to be resolved. Any input would be gratefully received!

 

[JDIH]

Drum brakes out of adjustment?

 

[big jt]

Typical old truck hydraulic brakes. I have a 77 IH that does pretty much the same thing. Has a small leak somewhere in
the system (pretty sure it's a wheel cylinder). I only use the truck for harvest but do need something when getting it out
and back in the shed when moving other equipment.

MC might be dry after sitting for winter or a couple months in summer. All I do is fill it up anytime I move it and just
figure on using the parking brake for moving it that time. So far it has gravity bled and when it comes time to go to work
I have brakes for harvest.

Don't know what your endgame is with the truck but unless you are gonna be in tight quarters with people don't worry about
it, You will drive yourself batty trying to keep those brakes working 100%. If you intend to use it as a long distance
driver or daily rip out the whole system and put in dual brakes, and do the whole thing from master to all the wheels and
replace all the lines. If it's for seasonal use just live with it and make sure your parking brake is up to snuff.

JM2CW
this is just my opinion and of course not a official recommendation.

jt

 

[Eagle Beagle]

I second your opinion.

Beagle

 

[Fritz Maurer]

The squirting you are observing in the master
cylinder is normal operation. If you have good
brakes on the second hit, you are correct, still have
small air pocket (Assuming the brakes are in
adjustment). If you have a camel-back in the line
anywhere in the system this is where the air is. With
1/4 inch line it is hard to push air downhill. The key
here is velocity. You need to have the bleeders
clean and lubed so you can open them wide and
close them quickly with your fingers.

 

[Steve@Advance]

This may sound extreme, but if you have a loader. pick up the back of the truck
as high as you dare, then bleed the back, do the same for the front.

Possibly the air is floating back between bleed strokes. Tipping it may let it
float toward the cylinder bleeder so it will come out.

 

[Steve in VA]

Consider that the flex brake lines may be
expanding under pressure. You may need to
replace the flex portion of the lines. A
quick test would be to clamp off and
retest.

 

[rustred]

i say its still air in the system. as i said before keep a very close eye on the fluid level when bleeding . once it gets to half way in m/c
fill it. and are you doing this with two people or a bleeder? not telling you what do do but once you open the bleeder with the other person
stepping on the brake make sure you close the bleeder before they release the brake. i call the UP - DOWN thing when i am under the vehicle.

 

[redtom]

Boy, with second pump hard pedal, I sure have to think its adjustment of the shoes. Anytime I've had residual air in the system, the second pump hard pedal would be spongy.

 

[sotxbill]

Use a piece of clear tubing on the bleeder that goes down into a jar with around 2 inches of brake fluid in it. That way I dont need to close the bleeder valve, and while the driver pumps, I keep watching till the bubble stop coming out in the jar... then close the bleeder without letting any air back in... This jar can also be used empty.... to first allow the dirty fluid to come out.... and then emptied when the newer clean fluid starts coming out. This works well on troublesome systems.. One can also put a finger tip over the tubing to act as a oneway valve when the lines are empty or turn the bleeder shut.... so the driver can let up on the pedal.

 

[Fritz Maurer]

That is a good idea, I think that would do it.

 

[T.R.K.]

You did adjust the rear brake shoes, didn't you?

It sure sounds like your first pump pushes them out against the drums and then the second pump applies them.

 

[MARK ROBKE]

I agree. Mark.

 

[used red MN]

He already he a round of suggestions down the lines
mentioned here. I would suggest now that you have
driven it some give it another round of brake
adjustment. Crank them out tight the back off until
they turn hard a half turn and then free up. Are you
sure all the brake shoe links for the cylinders that push
the shoes out are all seated correctly this will be
difficult to verify. Another question I thought of but did
not ask it about the replacement hose you have on
there coming off the hydravac. Is that for certain an
acceptable type of hose for brake fluid? I am also
wondering does it loop up above the point where it
connects to the fitting in the frame? It looks like it may
have a larger ID which may not let air move through
with the fluid to bleed out. You may have to
temporarily tie it down so it only slopes up to the frame
to help bleed air out that may be trapped in the hose.
Previous post

 

[PA Case Man]

Hello, I didn't read all the previous posts. But after reading this post, I would make sure the master cylinder bore is capable of
pushing enough fluid for all the wheel cylinders. Unless you know the full history of the truck, someone over the years might have put
the wrong master cylinder on the truck and you might be chasing your tail!!! Just a thought, I hope this helps.
Steve

 

[Dune Country]

Air in the line= soft pedal

some of those older trucks had a primary and secondary adjuster for the shoes.

 

[Determined]

With the symptoms you describe the first thing I would be checking is the brake shoe adjustment.

I believe you stated you had done this but as someone already pointed out it was quite common on those trucks to have a separate adjuster for each rear shoe(2 per wheel)

Cranking on only one of the adjusters until the wheel wont turn then backing it off is not going to set both shoes in proper adjustment.

Sounds like you have already eliminated a lot of things by plugging them off so keep going a little further and you will find the problem.

If you were to say block off the flex hose at the rear before it splits off to each side and you then had a rock hard pedal you would know the problem was downstream from there.

You also mentioned earlier that you changed some lines as required when you replaced the wheel cylinders.

On the rears you need to have;
- the main supply line going to the lower fitting of the lower wheel cylinder
- the next line goes from the upper fitting of the lower wheel cylinder to the lower fitting of the upper wheel cylinder.
-finally the bleeder needs to be in the highest hole on the upper wheel cylinder.

 

[Papaw8]

I would say for sure shoe adjustment.tighten until wheel is locked then back off a few clicks. Make sure to do both adjusters per wheel.

 

[used red MN]

He said in his very first post that he has replaced 6
wheel cylinders and he had all the wheel end brakes
down to the backing plates and disassembled the
adjusters and cleaned and lubed them. So hopefully he
knows at least for the rear he has 2 adjusters at each
wheel. Hopefully he would know both need adjusted. I
know on some trucks it was nearly impossible to adjust
them without the proper brake adjustment tool. See
photos.