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Hey all, I got a 2000 S10 Blazer 4×4, 4.3 v6. I just acqiired it it had a soft, spongy brake pedal. I decided to replace the master cylinder. Bled the MC, bled all 4 wheels. The rear i bleed using thr bleeder screws, the fronts i wound up bleeding using the line. I had a real good firm pedal but as soon as I start the engine the pedal goes soft. I dont see any obvious signs of a leak. The truck does have ABS and i dont have the tools to do an abs bleed it. Any suggestions?
Also if the truck sits over 10 or 20 minutes it has a crank no start issue. If i spray some starter fluid in the intake it starts and runs no issues. I suspected a bad check valve on the fuel pump so i tried ETCGs suggestion of turning the key on and off and thus using the fuel pump to prime the fuel system. No joy there. Im wkndering if its an injector or fuel filter issue. But if thats the case wouldnt it affect how the truck runs once it starts?
I dknt have a CEL and no stored codes.
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That might just be the way it is. I had a few chevys with very soft brakes. What you feel when you start the engine is the vacuum brake booster.
Edit, does it have the hydro boost setup they used on diesels? They also used it in a few trucks.
I’m used to the GM soft brakes but mine wont stop the truck and the brake warnig light is on with the ebrake off
You do have the fluid topped off, yes? Usually I think if you have a leak issue, the ABS light will come on with it, indicating a loss of pressure, at least that’s how it goes with most. Normally just having the ebrake light on without the ebrake on indicates low fluid, an issue with the sensor, or some other anomaly; since you have actual pressure symptoms however, it may just be that the leak isn’t enough to trigger the ABS unit fault signal.
Are you losing brake fluid at all? If so, then I’d suggest you jack the vehicle up and go over the lines thoroughly. If you can’t find even the smallest suspect, then move to the calipers and cylinders(and lines) themselves to inspect. It really doesn’t need to be a massive leak to cause a problem.
I just got done patching my F-150’s rear brake lines last weekend and bleeding everything. Rusted out at a hold-down clip on top of the rear axle. Went though near half the master cylinder’s fluid just getting it home, but there was very little evidence at the failure, and only a few drops seemed to show when I tested it a few times. Took me about 15mins crawling underneath following all the lines to find the trouble-spot.
I’d also suggest a FSM, or just a subscription to alldatadiy to go over the layout and procedures of your brake system.
As to the starting issue after 10/20mins, I’d replace the fuel filter just because, and hook up a pressure gauge to see what’s going on when you turn it off, and when you do KOEO. My “guess” would be weak pump in addition to check valve, but I’d get some verification before you throw that part at it.
Greetings again and thank you for the input everyone. I took the truck to the shop this week. They found that the bleeder valves were all bad, I had a bad washer on one of the lines going into tone of the calipers and I didn’t tighten down the lines going into the MC (I didn’t have my flare wrenches so I was worries about rounding off the lines). So they fixed all that and bled the ABS system. I still have a soft pedal but effective braking. The last few day I noticed that intermittently the brakes go ineffective again but usually a few quick pumps brakes return to normal. So I plan on taking it back to the shop next week and see what they say.
The starting issue is also becoming intermittent Ive noticed. There will be a few days I can start it without any starter fluid but once in awhile itll need it.
Since the bleeder valve is at the top of the caliper piston bore and the line is at the bottom and the fact that air rises in brake fluid I suspect that there is still air trapped in the calipers. If you can’t get the bleeders open you could try removing the calipers, install a block of wood between the pads and try bleeding them with the lines facing upwards.
If that doesn’t work you may have to replace the calipers.Your injector poppet nozzles need at least 55 PSI of pressure to open so I suspect either the fuel filter is plugged or the fuel pump is weak. A fuel pressure test is in order.
Hi again. Been a busy beeband havnt been able to get to the computer. Anyway took truck back to the shop. They believe the ABS has an internal leak. As for the fuel issue i found the fuel rail wasnt secured to the manifold correctly and i had a loose connection at the pump. Still has some hard starts at times but havnt had to use starter fluid.
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