Brake Booster


The workhorse

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Post Thu Jun 16, 2016 8:31 pm

Brake Booster

Hello all. I purchase a '74 Loadstar 1600 w/ a 345 last week. It is in need of a brake booster. The seller provided one that he has purchased but didn't have time to put on. What degree of difficulty is this job? I have never put a brake booster on a car, let alone a medium duty dump truck. Any feedback will be greatly appreciated.

Thanks.

Golden Jubilee
Golden Jubilee

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Location: Lyman, IA

Post Fri Jun 17, 2016 8:32 am

Re: Brake Booster

I believe the Loadstar should have a frame mounted booster or hydrovac. Very easy to replace, just unbolt the old and disconnect the hyd lines and vacuum lines and re connect in reverse order. Bleed the hydrovac 1st then the furthest wheel cyl and work your way back toward the closest wheel cyl.
Hydrovac's rarely fail, what are the symptoms of it needing replacement?

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Post Fri Jun 17, 2016 3:54 pm

Re: Brake Booster

Hello and thanks for the response. Yes, the booster is located behind the driver's door step. The problem that I have is that I have to pump the breaks before the brakes will engage. After I pump the brakes a couple of times, the brakes do their job. I have not taken any troubleshooting steps at this point. The previous owner stated that the booster needed replacement (and provided a used working booster) and that's what I was basing the need to replace it on. Can you provide any troubleshooting steps to take before I swap the booster out?

Thanks again.

Golden Jubilee
Golden Jubilee

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Location: Canada's left Coast

Post Fri Jun 17, 2016 4:01 pm

Re: Brake Booster

Google is your best friend. I Googled troubleshooting a hydrovac and got lots of options, including a YouTube video.
I would rather have tools I do not need than to need tools I do not have
Thinking risks being controversial and possibly being offensive

Golden Jubilee
Golden Jubilee

Posts: 5170

Joined: Thu Nov 29, 2012 9:28 pm

Location: Lyman, IA

Post Fri Jun 17, 2016 4:13 pm

Re: Brake Booster

Pumping to get brakes is NOT the sign of a bad booster. It is indicative of needing too much fluid to move the brakes against the drums.
Reasons for this can be many. 1st and easiest to check is air in the system. Bleed the brakes.
Medium and heavy truck brakes are different than automotive brakes. On truck (foundation brakes) the bottom of the shoe is mounted to the backing plate and piviots on a pin. In many cases there are two or more adjustments for the shoes. The correct procedure must be used. On many the lower pivot must be adjusted 1st, then the scroll adjuster is adjusted for wear.
Also drums that are worn out can lead to excessive travel in the pedal.
Signs of a bad booster are leaks (both internal and external) and no boost (takes a lot of force on the pedal to apply the brakes) and vacuum leaks ( a constant hissing or engine runs rough esp at idle) Vacuum leaks can be tested for by removing plugging the (vacuum) line to the booster and seeing if the engine runs smoother.
Once the pedal travel is correct, the booster can be checked for proper operation, but from your description, the booster is likely to be ok. Hang on the spare, but fix the brakes 1st. A Booster doesn't increase travel, it reduces the force required to apply the brakes, so if there is too much travel it is not the booster.
If you are not sure how to work on heavy hyd brakes, find someone who is. Brakes are one of those things that shouldn't be "learn s you go" esp with the weight of a truck.

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Post Fri Jun 17, 2016 6:10 pm

Re: Brake Booster

Thanks for the info. I will check brakes and booster prior to pulling the booster. I have not taken a look at either the brakes or the booster. I just picked up the vehicle this past Monday. Are the bleeder valves on the brakes similar to a car and pick up? Or, is there something different that I should anticipate?

Thanks again for all the information. I like to have some idea before I jump in.

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Posts: 11

Joined: Tue Jun 14, 2016 9:19 pm

Post Sun Jul 24, 2016 8:21 am

Re: Brake Booster

I cranked my truck up yesterday and drove around the farm a little. Noticed that I didn't have any brakes. Checked the master cylinder and discover that there was little if not any fluid inside. I check each tire to see if there were any signs of obvious leaks at the wheel, but I didn't see any. I didn't notice the master cylinder or booster showing any wetness. I need to add more brake fluid. What type of brake fluid is best suitable for this braking system? And, any suggestions on troubleshooting?

Thanks.

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Post Sat Jul 30, 2016 11:43 pm

Re: Brake Booster

Standard Dot 3 if I am not mistaken.

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