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Hi All, In my GMC truck 1500 Sierra, it makes an abnormal noise under the brake pedal area while pressing it. The sound comes directly from interior and its like a whistle sound and called sometime a hissing noise. The brake system functions properly and without any defects except the mentioned noise. Is it possible from the brake booster? or could be from other sources? Appreciate sharing your experience feedback in this problem. Regards, Abdulla brake gmc.xspf
Just had this happen. Going under 15mph, applying the brake causes the pedal to become stiff and lock up and not work. This has caused me to almost hit someone twice. Sounds to me like brake booster. Anyone else having/had this problem???
Duel booster break system trouble shooting
Wade R posted a question in Ask the GM TechnicianHello who's ever eyes land upon this. I seem to be having trouble finding anyone who might have knowledge pertaining to the dual booster break system that is on my 1981 gmc B6000. This isn't the hydro-max nor the hy-power this is the dual power booster system that has a vacuum booster attached to the firewall followed by what I have found to be called the power head which is essentially a hydro booster but unlike the hydro booster it cannot be taken apart to replace the seals and O-rings.That is then attached to the MC. Any litterateur or knowledge one might have would be greatly appreciated!!! As of now I have found one picture of my exact system and it is a drawing from a catalog. Yet to find any literature anywhere
Brake upgrade ponderings
Trevor Lucas posted a topic in Gen III and IV Small Block & DrivetrainI own a 04 chevy silverado 1500. The brakes are spongy ( I've bleed them throughly, new everything except booster and master). My work trucks brakes are great 06 Sierra 2500 hd dual piston calipers all the way around same pads as the ones in my chevy. The question is can I upgrade to a dual piston the rear? They currently have the wimpy single piston. If an upgrade is possible do I need to upgrade the Master cylinder to accommodate the extra volume? If so can I just order the 2500 hd master cylinder?
Silverado/Sierra Vacuum Pump Replacement - How toFor the last 5,000 miles or so, I have noticed a (louder than normal) ticking noise coming from my engine bay. Recently. while navigating a parking garage at the airport, I lost all brake boost vacuum and almost hit a column. I did some research and found all of the info online relating to the NHTSA investigation etc. I went to my local dealership. They wanted $900 to replace the vacuum pump. It broke out as $615 in labor and $285 in parts. After looking around online, I couldn’t find a detailed write-up or video on this repair. I put together a write-up for anyone else who might want to save a few hundred bucks Be easy on me, I do a little light mechanical work but and have never done a write-up. I’m sure I screwed some things up… Supplies I Used: · Flathead Screwdriver · Plastic Pry Tool · Small Hook Pick · 3/8-in Ratchet · 3/8-in Torque Wrench · 3/8-in Drive 3-in Extension · 3/8-in Drive 6-in Extension · 1/2-in Drive 24-in Breaker Bar · 1/2-in Drive 5-in Extension · 10mm Socket (3/8-in drive) · 11mm Socket (3/8-in drive) · 15mm Socket (3/8-in drive) · 24mm Socket (1/2-in drive) · 7 Quart Drain Pan · OEM Stretch Belt Installation/Removal Tool (AutoZone Loaner P/N 27272) · Red Paint Pen · Small Bungee Cord · Medium Strength Threadlocker Replacement Part: · ACDelco GM Original Equipment Vacuum Pump -- P/N 12669488 (I bought it from gmpartsgiant for about $130 shipped) Step 1 – Prep the Workspace: Park the truck on a level surface Lock steering wheel about 1/16th of rotation right of center Disconnect the negative battery terminal Remove the plastic skid plate/shielding from below the engine compartment (four 10mm and two 15mm bolts) Place the drain pan on the ground below the vacuum pump Pull the air intake tube away from the throttle body to give access to the crank pulley from above Disconnect the two crank case vent hoses from the intake Disconnect the intake from the throttle body by loosening the clamp and pulling it back Pull the intake up and toward the passenger side. Secure it, out of the way, using a bungee cord Cover the throttle body intake with a plastic bag, secure with a rubber band Step 2 – Remove the Lower Steering Shaft With the paint pen, mark the steering shafts at the connection points between the intermediate steering shaft and the steering gearbox input shaft. This will be used for reference at reinstallation. With the steering wheel locked about 1/16th of a rotation right of center, the upper bolt (closest to the firewall) of the lower steering shaft easily accessible. Using a 15mm socket, remove the bolt. Note: The upper bolt is secured with a collared nut that wraps around the shaft. When the bolt is completely removed, you should be able pop the nut off the shaft. Moving down the shaft, there is an 11mm bolt that fastens the lower steering shaft to the steering gearbox input shaft. I was able to easily access this bolt by unlocking the steering wheel and slightly moving the wheel toward center. Remove the 11mm bolt. With both bolts removed, remove the lower steering shaft from the steering gearbox input shaft by pulling upward. Once the lower steering shaft is separated from the input shaft, slide the lower shaft down and toward the front of the vehicle to separate the lower shaft from the intermediate shaft. Step 3 – Remove the Vacuum Pump Place the stretch belt removal tool on the vacuum pump pulley. Using the 1/2-in drive 24-in breaker bar, 24mm socket and 5-in extension, turn the crank pulley until the belt slips off the vacuum pump pulley. Follow the vacuum line from the brake booster to the vacuum pump. Using the plastic pry tool, separate pressure fit fasteners holding the vacuum line in place. Additionally, remove the pressure fit fastener securing a wire loom to the pump Using the hook pick, carefully remove the retaining clip where the vacuum hose is attached to the vacuum pump. Note: There is a heatshield around this fitting the will need to be carefully peeled back. Separate the vacuum hose from the pump and rotate the hose out of the work area. Four bolts secure the vacuum pump in place. Using a the 11mm socket and a combination of the 3/8-in drive extensions, loosen all four bolts. While holding the vacuum pump in place, finish removing all four bolts and separate the pump and gasket from its mounting point. Note: About 1/4 to 1/3 of a quart of oil will leak out into the drain pan during this process. Lift the pump out while rotating it around the wire looms and belts (this will take some finagling). Step 4 – Install the New Vacuum Pump Coming from the top, rotate the new pump into position. Note: The pump I bought came with four new bolts and a new gasket. While ensuring that the gasket is firmly in place, use the 11mm socket and extensions to finger tighten the four bolts. With the 3/8-in drive torque wrench, torque the four bolts to 23 ft/lbs. Note: I called my dealership service department and was told the torque specs over the phone. I have no documentation showing the specs Rotate the vacuum hose back into location and attach to the pump. Snap the retaining clip back into place and put the heat shield back into position. Push the pressure fit fasteners back into position Using the reverse process of removal, reinstall the belt. Note: if you are reusing the same belt, be sure to check that it is in acceptable condition for reuse. Step 5 – Reinstall the Lower Steering Shaft Lining up the paint pen marks, slide the lower steering shaft back onto the intermediate steering shaft. Once the lower shaft and intermediate shaft are together, slide the lower shaft onto the steering gearbox input shaft. Apply the threadlocker to both bolts. Reinstall each bolt (15mm and 11mm) and torque to 35 ft/lbs. Note: I called my dealership service department and was told the torque specs over the phone. I have no documentation showing the specs. Step 6 – Reinstallation of Workspace Items Reinstall air intake tube using the reverse process outlined in step 1. Reinstall the plastic skid plate/shielding from below the engine compartment (four 10mm and two 15mm bolts). Connect the negative battery terminal. Check engine oil. Refill as needed (1/4 to 1/3 quart)