Truck brakes

If your brake hoses have been on the truck along time, you might consider changeing the brake hoses. My dad and I found, on his Hudson truck, the brake hoses were expanding under pressure. This gave the same sensation of air in the system. They were only 14 years old at the time. Or, the inside of your hoses could have deteriorated so much that they will not allow all the brake fluid to return to the master cylinder.



Another thing that came to mind was that you mentioned the rear end came out of a Nova. Brake drums on most Novas are 9 1/2 inches in diameter except station wagons which had 11 inch drums. There is a great deal of difference of braking leverage power between 9 1/2 and 11 inch drums. My 47 Hudson PU has 11 inch drums, therefore I'm quessing your truck originally came with 11 inch drums too.



Is your pedal up where it should be or is it stopping closer to the floor?



Just some thoughts I hope may be of help.



Lee

I agree with Lee and 'Ol Racer. If you can pump the pedal and get brakes you may need to adjust the shoes.... Also your problems maybe up front since most of the brakeing action is on the front wheels..or should be... Make sure all your brakes are adjusted to a slight drag and are centered in the drum. A visual check of the shoes to see if they are making full contact with the drum might tell you if there is a centering problem due to bent ,wrong, or worn parts. The return springs will cause the wheel cylinder pistons to retract and displace a lot of fluid ,unlike disc calipers that don't have springs and need very little movement to make contact. If it takes more than one push of the pedal, there is too much travel required to make solid contact with the drums.

Since the pedal goes to the floor after you hold steady pressure you need to replace or rebuild the master cyl. The reason it is going to the floor is the brake fluid is by passing the piston seal as pressure is applied. Probably best to rebuild the master if rebuildable. I have had problems with master cly's leaking because they set on the shelf so long the seals stuck to the cly balls, and tore when the piston was pushed in.



I hate to say this but just because someone says it worked doesn't necessarily mean it worked properly even it it was used to pull a race car. If it had trailer brake system the trailer may have been doing most of the brakeing.



I think the master cly and brake hoses will solve most of your problems. However, I would suggest doing a complete rebuild of the brake system to bring everything back into specifications and follow the manuals brake adjustment proceedures.



Don't try to peace meal this problem. That is alot of frustration and time consuming. You get the pressure back in the master cyl and the new found pressure maybe start the cylinders to begin leaking. Do it all at once. Make it right and it will stop like it should.



Lee

Adding some additional information.



If you have a copy of the July/Ausust 2006 WTN look up" Walt's Garage Hudson's Brakes". This is some important information on the proper shoes to anchor pin fit. The arc of Hudson brake shoes, that fit against the anchor pin, is different than modern brake shoes that are the same size. The modern shoe will fit but will not center in the drum, even if the brakes are adusted according to the manual. Also, he shows how to make the modern shoes work. If the anchor pin to shoe fit, and the anchor pin to shoe adjustment, is not correct there is no way you will get good braking.



Walt also talks about how to adjust the anchor pin while adjusting the brake shoes, so that the brake shoe will be centered in the brake drum.



Another tip I have found to solve many brake adjustment problems, is to back off the parking brake adjustment before beginning the brake adjustment. When the brakes are adjusted properly then adjust the parking brake. I have found that many people will adjust the parking brake, because the parking brake handle moves more than it should, when in fact it is the brake shoes that need adjusting. Once the brake shoes and hand brake are adjusted properly, there should be no need to make another parking brake adjustment until the next brake job. If someone feels the need to adjust the hand brake adjust the brake shoes first.



Also, check the backing plates. I have come across many cars where the

brake shoes have worn groves in the backing plates. If deep groves exist they must be welded up and ground smooth again, for the brake shoes to move smoothly.



If any brake lines show signs of rust replace them.



What are the rear brake drum diameters?



I'll repeat again that I believe your main problem is the master cyl. but I would also change the brake hoses,



I hope you do not mind my rambling. Just trying to help. Lee

I can but add my two-cents worth, and re-iterate that it is absolutely essential to have the correct clearance, at both ends of the shoes. You may have a drag, but it could be either at the heel or toe of the shoe. Go back to those essential adjustments, and follow the book procedure. And a tip for anyone assembling brakes after a rebuild, fill the wheel cylinders before you fit them, saves a lot of pumping. Just loosen off the bleeder valve, and fill the cylinder and bolt it in place. Then when it comes to bleeding there is a minimal amount of air in the cylinder, (just a few bubbles) that you have to pump out.

FYI

Here is another Tip if all the advice provided earlier fails consider installing a 2lb Residual Valve in the Line. I have one in my Drum Brake Terraplane primarily to prevent fluid drainback.



You can read the Theory yourself in www.ecihotrodbrakes.com then click Brake Facts... If everything mechanical checks out and you have to pump the pedal to get better brakes may be the way to go for $10 investment.....