Help With BRAKES on my 69 c20
 

Can anyone give me an idea on how to get a decent break pedal on my 69 c20.
I changed the master cylinder bench bleeding done it has drum brakes the shoes are ajusted up to drum bleeding them over and over cant seem to get good pedal. Now the master that was on truck was a double bail same size bowls with a small dimple in plunger the new one is small bowl big bowl one with hollow plunger single bail if this makes difference the pedal is just way to low to feel safe . Oh I did put all new wheel cylinders on it a few yrs back and they still seem fine. Wish I would have just rebuilt old cylinder tried to get it back but they already shipped it out.
Jeff

Re: Help With BRAKES on my 69 c20
 

Sounds like you got a MC for disc/drum brake. I would go back to the parts place and have them recheck the part number. I always try to match up the replacement part with the original as these days most counter help only knows how to look something up.

Re: Help With BRAKES on my 69 c20
 

Terry Yes this was my thought but the directions said it dident matter the new cylinder would work as did the parts store Also when I look them up at other stores they show same cylinder I bought even at Classic Parts. Im at a loss I really think this is the problem but everyone I talk to aroun here says it wont make a difference should be able to get good pedal with this one wish I could find a dealer with same style I had.
Jeff

Re: Help With BRAKES on my 69 c20
 

I rebuilt the entire system on my GMC c20 and I was able to get the correct master from rock auto. It shows both types online depending on which brand you choose.

Have you checked the wheel cylinders or removed the drums yet or are you just swapping the master and cracking the bleeders??

Are you attempting to bleed the brakes by yourself or do you have someone to hold the pedal down while you open the system??

It is also possible to flip a seal or blow out a master while bench bleeding it. Are you getting good pressure out to the rear cylinders??

Re: Help With BRAKES on my 69 c20
 

It does sound like you got the Disk/drum master, and it may work with the four wheel drum setup, but as mentioned before, have you checked the wheel cylinders? Another thing to look at (and probably replace) are the rubber lines front and back. Most people forget them, and in my experience, if they are over 8 or 9 years old, they should probably be replaced. I have had them LOOK good on the outside, bet disintegrate on the inside and act like a check valve that will allow the fluid to flow in one direction.

Re: Help With BRAKES on my 69 c20
 

OK Guys I rebuilt everything new wheel cylinders front drums rear drums cut all new lines new shoes about ten yrs ago put maybe 5,000 miles on it. Now I have checked everything it all looks good yes I did use two people to bleed brakes and I bench bleed master first. I keep going back to master cyl. my mind is telling me it should work but just cant get pedal Ive been building cars trucks since before I could drive legally and this one got me Im trying to find the type of master that was on it before problem By the way got in truck one day and pulled out of drive way no brakes master was leaking out back O-ring gone man I wish I kept it and rebuilt cause that style doesent seem to be easy to get. I was on phone with Auto Zone last nite this is where I bought it There site shows correct one but part #s match but the one they gave me doesent match pic he ordered another we will see if its a match around 10:30 today seems these rebuilding companys are building what they think should work but arent probbaly short on cores.
Jeff

Re: Help With BRAKES on my 69 c20
 

I forgot Im getting good pressure on all four.

Re: Help With BRAKES on my 69 c20
 

I have had them bad from the manufacturer. It does not happen often, but it happens.

Re: Help With BRAKES on my 69 c20
 

Jeff,
Was having a similar problem w/ my 68 C20. Went to NAPA and picked up a brand new MC, no core charge. I think it was under $80. Problem solved. You can have my old one for the cost of shipping, but I notice you are in Pennsylvania, so probably the best bet is to just buy a brand new one. The reservoirs are equal size. If I can dig up the receipt, I'll post the NAPA P/N.
68Utilty, Mark L

Re: Help With BRAKES on my 69 c20
 

Mark If you can find part # please post would be big help. Our local NAPA has the one that looks like one I bought from auto zone.
Thanks Jeff

Re: Help With BRAKES on my 69 c20
 

Jeff,
Thanks to your request, I've gone through a whole bunch of receipts that I should have filed at the time! Anyhow, found the receipt from October 7th and the MC that I got from my local NAPA (Contra Costa Auto Parts) bears a P/N of M36246. The product "Line" is NMC. It lists for $83.32 but I have an account and w/ my discount, it came to $49.99 or basically $50. So at that price, you wouldn't want to be rebuilding an old one.

One caveat; Mine is a 68 C20 w/ drums all round, the only option in that year. It was physically the same size etc. As the old one which was a replacement for the MC that came on the truck. But to my recollection they have all been the same.

BTW, it was special order which means it came from one of their warehouses, most likely Fresno. But basically I had it overnight.

86Utility, Mark L

Re: Help With BRAKES on my 69 c20
 

Mark Thank You For P/N I was at auto zone just an hour ago and got behind counter with him and showed him the one I need online the P/N I originally bought and showed him the picture so now they said it was special order and will have tomorrow afternoon Its funny cause thats the one I orderd in first place and the one they gave dident match talked to them last nite and they got me another one went in today and it was wrong again so thats when I went behind counter and showed him what I wanted now tomorrow FUNNY this will be third master cyl with same P/N The one I need is much bigger then the one you bought two bail clips one on each end although I think the one u got will work both bowls are the same size I notice when I look them up 67 68 looks like yours 69 70 looks like the one I need you would think they would be same.
Thanks Jeff

Re: Help With BRAKES on my 69 c20
 

I replaced my MC and Booster last year with a unit from Oreillys. I got the correct one 1st time. I would think it's the same part # for 69 and 70 C20's. You might try them also.

Re: Help With BRAKES on my 69 c20
 

You can clamp off your rubber brake hoses so no fluid can get past the clamps. Then try your brake pedal, if it's still low it's the master, if it feels good it's in your adjustment.

Re: Help With BRAKES on my 69 c20
 

If I'm not mistaken, the only difference is the size of the reservoir that's connected to the disc brakes. it's larger.

Sounds to me like air in the lines or a bad M/C.

This is from the MP Brakes website:

How to Properly Diagnose a Brake Problem:
If you have very poor brakes, a spongy pedal or no pedal at all you will have to do some diagnostics to determine where the problem is in your braking system. Is it in the master cylinder, the front brakes or the rear brakes? These tests assume that your system is properly installed and bled. Perform these simple tests to find where the problem is. Once you know where the problem is it will be much easier to fix.

• Disconnect the brake lines from the master cylinder while leaving it on the vehicle.
• Obtain solid tapered plugs for the master cylinder outlets with the correct thread pitch. These are available at any good automotive auto parts store. You may also use our supplied bleeder kit.
• Plug the master cylinder outlets. Step on the pedal and hold pressure for about 30 seconds. If the pedal remains firm then the master cylinder is good. If the pedal sinks to the floor then the cylinder is bad. If the master cylinder is fine, connect the line to the front brakes.
• If the pedal remains firm then the problem is not coming from the front brakes. If the pedal sinks to the floor or is excessively spongy then the problem is with the front brakes.
• Connect the rear and if the pedal goes bad then the problem is in the rear.

Re: Help With BRAKES on my 69 c20
 

Jeff,
Sounds like you are on the right track, but I thought I'd add one more thing in case someone looks at this thread in the future trying to source parts. After tdangle wrote in about replacing his MC and booster, it dawned on me that I was not clear on the fact that my brakes are not only drum, but there is no vacuum assist. So again, that is the NAPA P/N I used and appeared to be identical to the original MC that came on the PU in 1967 (68 model year). But this is correct only for the non-power brakes. I may be the only guy out there that is still driving a C20 w/o Power steering or power brakes. I intend to correct the power brake issue when I convert to Discs, but I like the uncluttered look of the engine compartment w/o the PS pump and belts etc. So I'm sticking w/ "Armstrong" steering for as long as I can handle it. Just replaced the steering box w/ a new Lares unit and it is a big improvement.

68 Utility, Mark L

Re: Help With BRAKES on my 69 c20
 

68 Utility Mark you know what I bought a used Disc Brake set up Rotors ,Calipers,Knuckles a few years ago I was going to convert mine but never did see my truck is my wheelbarrow used for coal ton a month dumping ashes I love the Old Beast but dont drive it much granny gear 4 speed 350 4bbl it also loves to drink a bit much So will sell that set up.
Thanks for your help
Jeff
Thanks to everyone who posted me ideas will update once new cylinder comes in hopefully today dident hear nothing yesterday.

Re: Help With BRAKES on my 69 c20
 

UPDATE on brake problem. Well I got the master cylinder I wanted and it works great about double the pedal I had goes to show that you need the right parts not the ones they tell you should work. I had a hard time getting it took 3 shots but my local auto zone kept working with me till they found it I took it out of box and left store wish I wrote down name its a brand new one not rebuilt a perfect match to original which is much bigger double bail much larger plunger and just a little dimple for brake rod instead of big hole. The other cylinder did stop truck but pedal was only about an 1 1/2" off floor so I guess it did work but that low pedal bugged the hell out of me.

Thanks to all you guys who chimmed in with ideas.
Jeff

Re: Help With BRAKES on my 69 c20
 

That is good to hear an update, thanks. I've been watching this thread. You may want to have a close look at your receipt or go back to AutoZone and have them look in their computer to find out what you got, and write it down or otherwise document it. As I've been going through my truck replacing various parts, I've been keeping a list of the stuff that I know some day will wear out again and I don't want to re-research it. I often replace a part, find out weeks later it isn't worth crap, and research and replace again, before finally finding the right part from the right company. So if you've got something good, make a note of it. Master cylinders don't last forever, especially if you don't drain and refill with fresh brake fluid now and then.