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Power brake assist.....

Nosferatu49534

Nosferatu49534

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Ok, so I'm not sure if this would be the right place for this question and if it's not could one of the mods move it for me? Well I replaced my power brake assist in my 97' 2500 silverado 6.5l. It was leaking out the weep hole pretty bad. According to my code in the glove box it say the truck should have the jd7 booster. So that's what I ordered and installed. That being said the number that was stamped into the booster that was on the truck was 962 D 5, and the one that came in the box from orielys had 962 D 7 stamped on it. Could the wrong one have been installed by a PO? My question/ problem is now that I switched boosters it feels like the brake assist portion of the booster isn't working very well. I have to really step on the brake pedal to stop. I bled the system according to the instructions that came with the box. Any ideas, thoughts as to what could be going on?
 
Describe how you bled it? How much power steering fluid did you flush out? Degrease and clean the entire area under and around the booster. Spray some brake cleaner in the weep hole and clean up so you can see if the new one leaks fluid?

Is it making any squish noises while braking? How does the pedal travel feel? Is it lower or same? Is it spongy or firm? Did you take off master cylinder or just push it out of the way? How many miles on master cylinder, brake fluid, and brakes?

Its normal to feel some loss of power steering and brake assist when lugging the engine and turning while braking going slow with a full turn. See if you experience that and how much stronger assist feels when it returns for comparison. It should be pretty obvious.

Does the pedal feel recover any with pumps? Is it worse at speed and a hard stop or anything else?
 
You should have the front tires off the ground and slowly turn the wheel from stop to stop several times and keep a check on fluid level.... it sounds like some air is still in the system, give it a few days and if no change may be a bad unit...
 
I bled it by having the truck off the ground as per instructions and turning the wheel back and forth slowly. And then unloading the accumulator by pumping the brakes 4-5 times. There are no leaks from the new booster. I did not take the master cyclinder off just moved it. There was no lose of power at the pedal when turning it the engine lugging with the old unit. I have no idea of the mileage on the master or fluid. It makes no difference when I try to stop quick or any speed. I need to put way more foot into the pedal for it to hold the truck from moving.
 
After turning lock to lock did you have the low pressure booster return line off (put another line on routed to a bucket) and pump the brake pedal to flush out some power steering fluid and air?

Crank up then shut down engine and slowly depress brake pedal 3 times. Crank up shut down and recheck fluid level. Then crank up and push the brake pedal a few times with engine running to purge the fluid/air. Watch the PS fluid level so it doesn't get too low and entrap more air. It won't pour out return line while running but it will surge and puke some power steering fluid each time you let off the brake pedal after applying the brake.

IMO its a good practice to flush out all the old fluid with the old unit so new fluid goes in with new unit and flush the new unit a little too. Some advise to put a filter inline once you change the powersteering/hydro boost
 
I did not have the line off I will try that either later today or tomorrow. I wondered if it was necessary or not. It's definitely not gonna hurt to flush the system. :) hope it's not a dumb question, still learning, the smaller of the two thread in lines is the low pressure?
 
iirc its the one with short piece of rubber hose and hose clamp. The high pressure lines at the booster are metal lines with ferule type nuts not one of those.

Should be a couple of threads/posts and a how to article on it on the forum somewhere if you search flushing hydroboost or power steering etc for some videos etc.
 
I understand that depressing the brake unloads the accumulator, but does the accumulator fill with the power steering fluid?
 
The D5 was for the lower GVWR any leak through the weep/vent are due to the main power piston seal failure usually due to sand etc in the fluid the main hydro-boost power piston could be damaged too.

If you can't get the replacement booster to work then suspect it was not rebuilt properly 'common', I've taken to rebuilding my hydro boost because of all the so-called commercial rebuilt units being no damn good.
 
Gotcha. Makes me curious as to why the D5 would've been on the truck when the glove box code was for the 7. Either way it's got a 7 in there now and hopefully if I can get that thing bled out I'll be a happy camper.
 
Yeah ps fluid fills accumulator some. Don't know but probably has air bladder and or spring for energy storage. But air needs to be out of fluid side. The accumulator just helps hold system pressure evenly and provide some power if engine dies while driving and u need brakes.
 
schiker said:
Yeah ps fluid fills accumulator some. Don't know but probably has air bladder and or spring for energy storage. But air needs to be out of fluid side. The accumulator just helps hold system pressure evenly and provide some power if engine dies while driving and u need brakes.
Click to expand...
Nitrogen for later units springs in some older units.
 
So I've bled the system with the return line off for about half an hr got some air out. Pedal definitely feels better, but the truck still won't stop as quick as it did with the old booster. Any ideas on that?
 
Also schiker you suggested an online filter would that go in the return line? And where/ what kind would be best to get one?
 
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