Question about brakes and ABS... help please

[tysamigo]

PROBLEM:
When I press down on the brakes now, I have to press them almost all the way to the floor. There is WAY to much give in the pedal now.

WHAT HAPPEND:
I sent off 2 ABS modules to that company on eBay that rebuilds them. Just this weekend I had my current/bad ABS module replaced with one of the newly refurbished ones. The ABS light went out without having me to reset it, which is good. The tech said he bled all air out of the lines. 2 lines on the ABS had air and the other 2 didn't. He bled all lines and the master cylinder. He says that he thinks my Master Cylinder is bad because there is no air in the lines and it has to be the Master Cylinder. I told him, well my brake pedal wasn't doing this before. The only thing was that I didn't have ABS and my ABS light was on.

So, advice? What's going on? Did he do something wrong, or is is this a coincidence that the Master Cylinder is now bad on the exact day that he replaced the ABS module?

Help please?? I don't know what to do

Ty

[tom4bren]

According to the shop manual (page 5C-7) Excessive Brake Pedal Travel is caused by:

Air in hydraulic circuit

Level of brake fluid in reservoir too low

Master cylinder push rod clearance excessive

Leakage in hydraulic system

I'm confused though. Why did the Tech open the hydraulic system anyway? I was under the impression that the rebuild kits only dealt with the electronic portion of the ABS. Replacing that does not require opening the hydraulic system.

The Tech should also not have had to do anything that would have damaged the Master Cylinder ... but it's also unlikely that the Master Cylinder would go bad at the same time as working on the ABS.

The likely scenario is that the Tech did not properly bleed the brakes. It's a fairly involved process on the VX. The instructions for bleeding the brakes is on page 5C-9 of the Shop Manual (I'll try to post that in a moment). The first thing you should ask the Tech is if he removed the 40A ABS fuse during the bleeding process. If he looks at you funny or says that's not standard operating procedure then tell the boss to have a different Tech repeat the bleeding process.

[Mile High VX]

x2 with what Tom said.

When I had my brakes done I took this with me and gave it to them. They shop manager said he was glad I did because they would have just done it like every other vehicle that they service.

[tom4bren]

I've gotten mixed results from taking in specs or instructions. Sometimes they appreciate it & sometimes they take offense. I'd absolutely take in these instructions if I were getting brake work done that includes bleeding the brakes.

BTW Ty - you may want to take a look at your brake pads before going too far down the rabbit hole. When my brakes got really mushy it was because I have a sticking caliper (RR) that eats up pads in about 6 months ... I'm just sayin!!!

[tysamigo]

Thanks guys soooooo much. I printed out the instructions and will take them back to him. Yea he probably serviced my VX just like any other vehicle. I'll tell him to redo the process using these instructions. Hopefully by doing that, it will fix the problem.

[tom4bren]

Yah, I'm not used to leaving the car running whilst bleeding the brakes (or pulling a fuse). I rekin I'm just old school.

[8695Beaters]

Since the VX is a semi-GM engineered vehicle, check if your mechanic has a scan tool that can electronically bleed the ABS module. I know a lot of GMs can be bled this way (and in fact HAVE to be bled in this manner). I'm not sure if it works for Isuzus too, but it's worth a try. The mechanic at the shop I used to work at had a Snap-On scanned that could do the ABS bleed (he said it cost him $10,000 and seeing what it could do, I'm inclined to believe him). Basically it cycles the ABS system and will pull fluid through the ABS unit. I wouldn't try jump-starting the ABS module with a battery to replicate this effect though: you could easily fry the system.

Another brake bleeding tip is if you are replacing a master cylinder, make sure you fill it with fluid and bleed it BEFORE you install it into the vehicle. Many MCs have a small pocket behind the brake line fitting that can trap air and will leave you with a spongy pedal. It's a bit messier but saves a lot of time.

I know the manual says things differently, but remember the VX is now 15 years old. Times move on. But there's no excuse for any shop to not be able to bleed brakes properly.