Still trying to get a decent pedal on my '03. My Chevy guru mechanic and I are both getting frustrated. At this point (because it was time), the entire braking system has been cleaned up and/or renewed- calipers, pads, a couple of brake lines, etc. Since the system was opened, we did the complete manual and scan-tool bleeding according to factory specs. The scan tool is one that reads the VIN from the diagnostic port, and tailors the guidelines accordingly.

The scanner refers to two "hidden" bleeders on the pressure modulator and we think that's where some air is trapped, but we can't find those bleeders. There are a couple of rubber plugs on the valve that look promising (see photo), but my guy said they were not what we were looking for. Any forum members have info on this?

 

You did not specifically mention replacing the master cylinder. Does your cleaned up/renewed statement include a new master cylinder? I am not familiar with any hidden bleeders, nor does your attached picture look like anything I have come across on any of my blazers. Mine are all 98 and 99 though. My experience is bench bleed the new master and bleed the system rear to front ( I have used a pressure bleeder and gravity bled ) and presto, hard pedal. The only time I have had issues such as you describe are a bad master cylinder. If you did replace it, maybe you got a bad one. Try another maybe

 

The master didn't need replacing, it tests out fine. The pictured part is part of the ABS system, sits on the top of the left fender, next to the master- maybe your Blazers don't have ABS?

I'm hearing that these systems on the later S10 Blazers can be a real problem to bleed completely, even the FSM alludes to that.

 

I don't recognize that part, but on my 98 and 2000 blazers I have had air get into the abs module and give me issues with bleeding the rear brake system. There is a valve inside that distributes fluid between the front/rear brake systems.the air in the abs unit kept it from moving one way and wouldn't put any pressure to that system.

The way I got the air out of the abs unit was by cracking/tightening the outlet lines that come out of the unit and and using them as a bleeder to get the air out of the unit itself.

In the front and rear of the abs unit there are rubber caps you can take off, and when you hit the brakes, there is a little pin that should push out, both front and rear. If there is air in it, and it's blocking the valve- the pin will not push out of one(or both ) side(s)

 

To bleed the ABS module you need a capable bi-directional scan tool to open the valves inside the abs unit to get all the air bubbles out

 

How did you test the master cylinder? I think the part pictured is from a 2003 TrailBlazer, not a 2nd gen S10 Blazer. Could you take a picture of that exact part on your vehicle? Any of the 2nd gen S10 Blazers I have seen, including the five I have in my shop have pumps that look like this:





Neither pics are of mine. Mine are much dirtier!!

What kind of scanner does your friend have? Like richphotos said, not all scanners can activate the abs pumps. It sounds like your friend's can though.

I take it that this increased travel of the brake pedal is a new occurrence? Did you replace the ABS pump when you were renewing all these parts?

Yes, my understanding is that these systems can be finicky during the bleeding process, but I figure if I can do it so can anyone!

I still question the master cylinder... Maybe the abs pump is bad?

 

Thanks to all who replied.

Some followup info- as far as I can tell, the modulator valve unit pictured is used on m/y 2003-2005 Blazers and S10 pickups, older ones have a different configuration. And yes, the photo shows the correct part, no mistaking it. Don't know what other GM vehicles might use this part. The ABS pump is within this unit, thus the search for these two "hidden bleeders" mentioned by the tutorial on the scanner, and displayed on the screen after the scanner read the VIN thru the diagnostic port.

Can't cite the details on the scanner, but I know it's capable of manipulating the ABS function. The scanner walks you thru the automated bleed procedure, same as the GM Tech unit, but works on non-GM as well.

As far as the low pedal issue is concerned, it has been more or less a problem for a long time, finally decided to look at it in the course of a general rejuvenation of this limo, since I plan to keep it indefinitely. It currently has just 84k miles.

 

Good luck

 

Thanks. BTW, I should have mentioned that my friend who's working on this is not an amateur- he has run his own independent shop for about 30 years now, and I have known him about as long. He has a couple of good guys working for him, too.

 

Looks like we've put this issue to bed. After bleeding the bejeezus out of it, manually and with the scanner, we were at an impasse. Then we tried pinching off the rear brakes- pedal still went to the floor, no answer there. But when we released the rears and pinched off the fronts, we got a good firm pedal. This clue directly implicated the new front calipers.

Since new Delco calipers are no longer available, and the front calipers had turned into rusty paperweights, we had used aftermarket units, NAPA's best. But, when we replaced them with rebuilt Delco's we were rewarded with a nice solid pedal.

This is not the first time I've seen an issue with new aftermarket calipers, but sometimes you have to learn a lesson more than once for it to stick. Thanks to all who weighed in on this problem. Think I'll go for a ride...