Nicholas Fluhart

May 19, 2013

Project Loadstar: Brakes Part 2

Filed under: Project: Loadstar,Trucks & Equipment — Nicholas Fluhart @ 11:19 pm

Time for some power brakes! In this sixth installment of the Loadstar Project I’ll be addressing the power brake booster, sometimes referred to as a “hydrovac”. Into the shop it goes…
Dump Truck In Shop 1
Dump Truck In Shop 2
Now this has been one of the more “pain in the neck” repairs I’ve done to this truck. First off, I knew the main diaphragm in the brake booster was bad. I had a similar booster from my F-700 with a stuck piston but a good diaphragm. I was desperately hoping all I needed for mine was the diaphragm because parts for these, specifically an overhaul kit, are expensive and hard to find. If I could switch out the diaphragm with the F-700 unit, it would be an easy fix. These boosters are not even made anymore, and although a remanufactured booster can be had for around $250.00, I really hadn’t budgeted that in to this project.

So once I had it in the shop I rolled under the truck to begin. The lines and fittings looked rusty and hard to remove, so at first I thought I would try to repair the booster with it mounted on the truck. I removed the main diaphragm cover to reveal, as anticipated, a broken diaphragm. What I did not anticipate was that half of the chamber would be full of old brake fluid which splashed everywhere and was the actual cause of the deteriorated diaphragm. Now, bare in mind this is supposed to be a dry chamber, so the fact that it is full of brake fluid reveals a more sinister problem than a broken diaphragm. It means the piston rod seal is leaking fluid from the cylinder into the diaphragm chamber. This explains why the previous owners told me they were having to add fluid, thinking it was a leaky wheel cylinder.

Time to find an overhaul kit. I searched high and low and found nothing. Finally, I happened across a brake parts remanufacturer’s website called They had a series of kits in their online catalog, so I just needed to figure out which type of booster I had and locate the correct part number. Like all boosters are supposed to have, there was an aluminum tag on the unit with a series of numbers. These numbers identify the brand and model of booster. I made note of my numbers and searched the website for the rebuild kit for my unit. Unfortunately, my number didn’t pull up anything. However, as a last resort, I called the phone number on the website and they actually have a parts counter for customer support. Surprisingly, the guy I spoke with knew exactly what I had and exactly the correct kit I needed, which they had in stock by the way, and he shipped it out that same day. If I remember correctly, I think the cost was about $85.00. I couldn’t be happier.

So trying to do this with the unit still on the truck, I now have to remove the steel brake line and the end of the cylinder which is a large nut as seen below, so I can slide the piston and rod out in order to replace the leaking seal:

Cylinder End

Chamber Side
Removing Piston
I went ahead and removed the smaller diaphragm on the bottom along with the springs and other components as everything would have to be cleaned thoroughly and seals replaced.

Small Diaphragm Chamber
Now I have to remove the main shaft seal and “retainer” for lack of a better word. This is where the problems begin. The seal and retainer are pressed in. Once the piston was out, I removed the appropriate snap rings and tried to use a punch to drive out the retainer. Fail. I hit it with everything I had and it didn’t budge a bit. It was at this time that I determined I would have to remove the entire unit from the truck so I could put it in my hydraulic press. Below you’ll see a photo of the chamber side. In the very center is the part that I have to press out from behind once the snap ring is removed.

Chamber Side
To fit the part in my press, I remove the chamber housing and put the cylinder in the press as shown below:

Cylinder In Press
I didn’t have much problems pressing out the retainer and spacer, but the parts being plastic were slightly damaged. Unfortunately, the kit did not come with replacements so I’d have to repair these and reuse them.

Seal Retainer & Spacer
So now that I had the entire unit disassembled, it was time to clean. No easy task. As seen below, the parts were heavily rusted. I could only hope the cylinder would take a rebuild, otherwise I just wasted $85 on the kit.

Booster Parts
I washed everything in my parts washer and air dried it before bead blasting in my blasting cabinet. I laid out all the parts and the rebuild kit along with the instructions.

Booster Rebuild Kit
Cleaned Parts
I polished the piston and rod with a wire wheel so the seals would travel smoothly. Then I installed the piston cup seal. I also honed out the inside of the cylinder with a brake cylinder hone.


I pressed the seal retainer with the new rod seal and o-ring into the cylinder. Then the entire unit is reassembled the same way it came apart. Now it’s ready to go back on the truck.

Brake Booster
Once back on the truck, I manually bleed the system. When adequately bled, the moment of truth arrives. It’s easy to tell if the diaphragm portion works. I start the truck and if the engine dies when I push the brake pedal, the diaphragm is bad. If it stays running and I hear a vacuum sound, it’s good. As for the cylinder portion, I would have to drive the truck to test it.

The verdict: I start the truck and push the pedal. The engine stays running and I hear the booster working. So far so good. I drive the truck out of the shop and hit the brakes hard. The wheels easily lock up. Success! I drive it around the yard and test it thoroughly. I then re-check my brake fluid level. Looks good. The only unusual thing about it is that the brakes are a little slow to release. Other than that, everything works. I now have power brakes on my Loadstar!

April 21, 2013

Project Loadstar: Brakes Part 1

Filed under: Project: Loadstar,Trucks & Equipment — Nicholas Fluhart @ 7:59 pm

In the second installment of the Loadstar project, I will be addressing the brakes. To make it possible to at least operate the truck around the yard, and certainly anywhere else, I figured the first mechanical repair attempt should be the brakes. It appeared that all the rear brake lines were replaced recently before the truck was taken out of service, however the front lines appeared to be original and in poor condition. I inspected the master cylinder. The fluid was low and the piston was stuck at the bottom of the bore. I knew I would probably need a new or remanufactured master cylinder if I couldn’t get the piston unstuck in order to rebuild it, but why was the fluid level low? The previous owners told me the brakes worked when they parked the truck, but they were having to add fluid regularly due to what they said was a leaking wheel cylinder. I began looking for leaks. I check the inside of the wheels/brake drums for leaky wheel cylinders. No sign of a wheel cylinder leak now or ever. Also, the brake shoes looked really good. I checked the firewall around the master cylinder location, and again, no sign of a leak. Oh well, it will all come out in the wash when I repair the master cylinder.

Turns out the master cylinder was beyond repair. I ordered a remanufactured unit with a 1-year warranty and front brake lines from Bumper to Bumper/Crow-Burlingame. You see the brake master cylinder in the photo below; it is the one on the left and the clutch master cylinder is on the right.

Master Cylinder

The front rubber brake lines were still available, but I couldn’t find the intermediate lines around the vacuum booster which is located under the driver floor on this truck, so I used steel lines there. Below you see one of the new rubber lines connecting from the frame to the wheel cylinder.

Rubber Brake Line

Results: Well there is good news and bad news. The good news is the brakes bled out and the master cylinder works fine. The bad news is that the vacuum booster is not working and I have no power brakes. At least I can move the truck around the yard and stop, although stopping requires me to fully stand on the brake pedal. This most assuredly would be difficult if the truck was loaded. Looks like I’ll be addressing the booster later on, but first I definitely need to power wash the frame and chassis; it has years of caked on mud from the oil field.

Until the next installment…

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