Replaced Brake Booster... Trapped Air Somewhere Issue
 

Still trying to figure out my problem with my brakes on my 97 Blazer LS. Replaced the brake booster, bled the master cylinder (bought the bleeder kit), bled all four brakes (so there is fluid flow to all brakes.....proportional valve is releasing fine), did the pressure on brake pedal and hold..... key on and off 10 times, start engine and lose pedal so air is somewhere. Was told to use a pressure bleeder....... Mity Vac ....... my blazer has the odd rectangular master cylinder that has the black lid that snaps on so any ideas without buying a pressure bleeder? I did the one person and 2 person bleeds (bottle/fluid with hose). Got to be an easier way. I have air trapped somewhere...... brake pedal has resistance with engine NOT running..... start engine and very little pressure and it goes to the floor. Leaning toward air in the ABS area. I could gravity bleed but I don't think that will work. Suggestions????

Need to know year, make, model.

I edited it and added information I forgot....... thx

Why did you bleed it after booster replacement? It's not necessary to bleed it unless the hydraulic system is opened. Booster replacement does not require opening the hydraulic system.


Most likely there is air trapped in the solenoids of the ABS unit. You can try gravity bleeding each wheel, one at a time. Could take several minutes at each wheel before the fluid exits the bleeders with no bubbles. After they all have been bled, if the pedal is still mushy, it will need to have the automated bleed performed with a capable scan tool. The scan tool operates each solenoid and pushes the air into the steel lines. Each wheel then needs to be gravity bled until the fluid comes out clear, (no bubbles). Then bleed each wheel the same as you would on a vehicle without ABS. DO NOT allow the master cylinder to run low on fluid at any time during any bleed process.

I bled it because I had to remove the brake lines from the master cylinder to make room to remove the booster.... I didn't have enough room to pull the master cylinder out of the way WITH LINES ATTACHED in order to clear the booster. So with that said..... I will try the gravity bleed but I don't think it will work. Never hurts to try and then it will be fixed once I have the scan tool put on it.....thx

ive always had really good luck when changing master cylinders of just bleeding the lines directly at the master. so instead of having someone pumping and holding the brake pedal and you cracking the bleeders, pump and hold the brake pedal then open the lines where they meet the master cylinder. you can try that but might be to late if you tried bleeding out the tires

After everything said, I believe the air problem is around the ABS and I'm putting it up for sale. Nice solid truck but it reminds me of my ex-wife....... starting to be a real bitch and getting nowhere!

Cap'n...got a link to the gravity bleed how-to?

https://www.google.com/search?q=grav...006&gws_rd=ssl I find it very odd that people don't use Google to answer many of their questions (in general). Sure there are times like mine with brakes and I have Googled and went through allot of info and my problem is still unsolved..... with that said........ I Googled for ya and there ya go. In the future, Google everything first....... no matter if its how to wipe your butt properly! SERIOUSLY......GOOGLE IT!

I think Bagherra was simply asking Capt Hook if he had the link to the description Capt Hook has given on the gravity bleeding procedure...

I bet the Capt has a big list of macro buttons taped up by his computer monitor to make it easier for him to keep answering the same questions over and over;)

Here is an option to bleed the abs system without a scanner. If you own a controlled gravel area such as a driveway or parking lot, gravity bleed to get all the air out, then CAREFULLY activate your abs system. I think you can figure out how to do that. However, please don't be stupid using this approach... Then gravity bleed them again. Seriously, the emphasis here is don't be stupid...

I was playing with my new to me scanner the other day and did the automated bleed just for fun. It was pretty cool...