I put new front rotors, pads and calipers on my brother in-laws 2005 Venture mini van. The brakes didn't seem to bleed correctly with the engine on or off. With the engine running if I start to push the brake pedal it makes a whooshing sound and the pedal goes to the floor with almost no pressure on it. I unhooked the booster vacuum hose and plugged it off still zero brakes. It all worked prior to installing the new parts however the pads were non-existent and the metal backing was running on the rotor and the rotor was worn to almost paper thin on one side. This van is an absolute piece of junk with 248k miles but it is all he has and I just dropped $200 on the brake parts. Any advice would be much appreciated.

 

Hello.Air may have entered the system.You need to start pumping from the rear right wheel.Next is the rear left.Next is the front right.Next is the front left.It takes two people to bleed the system.One person presses the pedal several times and keeps it pressed.The second person unscrews the nipple on the brakes.As soon as the pedal is weak, you need to close the nipple.Then press the pedal again several times... and so on.You need to do this several times until no air (or air bubbles) comes out.Somehow...

 

My brother in-law pumped the pedal for me the 1st time I bled the brakes but he has dementia so I can't rely on him doing things correctly. I bled all the brakes a 2nd time using my wife as the pedal pumper. They pump up and hold pressure when the van is turned off but when the engine is started and you push the brake it goes to the floor with almost no effort. I'm considering buying a master cylinder and giving that a shot as the booster is 3x the money and is buried behind all kinds of stuff. Booster replacement is probably beyond my mechanical skill level and he doesn't have the $$ to hire it done anyway. Any suggestions?

 

Hello .The amplifier rarely breaks down.Only if all the liquid has leaked out of the amplifier.But....Perhaps the master cylinder is not working...or there is a leak in the line.It's difficult to advise anything.For pumping I can recommend this - pump for pumping brake fluid on a car .These pumps are not expensive.From 10 to 30 $.Perhaps someone else can advise...
Link to a site where you can read how to properly replace the brake fluid and master cylinder.Montana and Venture are identical cars.

https://www.2carpros.com/questions/b...er-replacement

 

Thank you for the responses. I have ordered a new master cylinder since it is the cheapest and easiest possible fix. It will be about a week before it arrives. I'll post back when it arrives and I get it installed. Thanks again.

 

Good luck to you.

 

I had similar issues on my 1996 C1500, and replaces the master cylinder. Still had the issue, and it turned out just being TONS of air in the lines. Once I did the proper bleeding procedure and order (back-right, back-left, front-right, front-left), things got much better. But it still SOMETIMES goes down to the floor when the engine is running, and gets stuck, to where I gotta slip my toe under the brake pedal and pull up hard. Then it will act fine again. Suspecting a flakey brake booster, but just not sure.

I guess my point is - be sure you bled all that air out of the lines before replacing the master cylinder. You certainly will need to bleed them after you do. I got a "self bleeding" kit, basically hose that fits onto the bleed screw at the wheel, and you run it into a jug of brake fluid, so that no air can suck back in. I pump-pump-pump, then go to see if there is air in the clear hose. Once all the air is purged, no more bubbles, I close the bleed screw, and go to the next wheel. Be sure to keep topping off the master cylinder so it doesn't run dry.

First time I did it, I think I went through 2 quarts of brake fluid before I got all the bubbles out, and the brakes worked much better.

Be aware that it's not super hard to replace the brake booster, as there is usually just one vacuum line that pops off, and 4 bolts. The nuts are above the brake pedal under the dash.

 

Ok, I'll try and cover everything here. I replaced the master cylinder, bled the MC with a syringe prior to installing it. Bled all 4 wheels again in the proper order and didn't see any air bubbles at all. Don't know if this matters but I used my scantool to actuate all of the ABS solenoids. When the engine is off the brakes will pump up and hold without falling. With engine running the pedal goes to the floor if any pressure is applied. I don't hear any leaking type noise when the brake pedal is held down with engine running and no fluctuation in engine idle that would indicate a vacuum leak.

For jfmorris: this is a mini van and the booster is located well up under the cowling(?) with AC lines and the ABS module located in front of it. I suspect the wipers, wiper actuating arms, cowling etc would all need to be removed just to get enough space to pull the booster out. Looks like a lot of work and about $100 for the booster so I'm in no hurry to go there unless I know that is the problem.

EDIT: I unhooked the vacuum line from the booster and plugged it off, started the van and the pedal feels close to normal, no longer going to the floor though I haven't tried driving it yet.

Any suggestions would be greatly appreciated.

 

Yeah, mini van's and vehicles with transverse mount engines are a whole nightmare to work on. I've not owned a front wheel drive in 22 years, so had forgotten how bad it can be up under that hood.

I am kinda watching your thread here, as I have a 1996 C1500 doing very similar things, and I did the same things as you (short of using a scan tool to command the ABS during the bleed).

 

I want to preface this post with the fact that I am 65 years old and nobody in my entire lifetime has ever called me a mechanic. (for good reason I guess)
I discovered that I had both calipers mounted upside down, thus the left caliper was on the right side of the car and the right caliper was on the left side of the car. This put the bleeders at to low a position to evacuate all of the air. Once I switched the calipers to the correct sides the bleeder valve was in a higher position and I bled the front brakes and got a ton of air out and now have a hard pedal.
I was at my wits end and was ready to take it to a shop. Thankfully that didn't happen and I was spared the embarrassment of looking like a moron.