I need a little guidence here about 'Dump valves' Please.

[JTWard]

I read so much about the "Isolation / Dump Valve" or "Disc Brake Proportioning valve" that In my head I have one wheel in the mud and the other spinning in the snow. In this pic of my brake MC and 'Valves' do I have either valves on my 1990 Chevy 1500 Silverado 2WD 305 V8 ?

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Can anyone tell me what I have attached to the underside of the MC ? Thank you !

After all the work I've done and had done, I can't get rid of the weak soft pedal which everyone says is normal but if the brakes don't stop so well empty what the heck is it going to do with 1000 pounds of cargo in the back or towing a 5000 pound trailer ? I'd be pulling my hair out if I had any !

 

[kennythewelder]

Welcome JT, good to see you here. If you don't get an answer, bump the thread in a day or so.

 

[someotherguy]

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Richard

 

[JTWard]

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Richard

Hi Richard, I got the soft/sloppy brake pedal syndrome that most people tell me is normal ? Now granted, this 1990 Tenn. Hardtop isn't my 2014 GMC Terrain, But I'd be damn scared of putting 1500 pounds in the bed and feeling comfortable coming to a light and someone in front of me jamb on their brakes. They feel like air in the system but the shop says no and I'm still mystified that GM built all these truck from 1988 to 1994 and no one else felt a little squirrely about the braking ability ? What do you think looking at my brake combination ? Thank you !

 

[wally]

If your back brakes are adjusted right more than likely there is air in the rear wheel anti lock)black box). Some where I read the older, earlier one could be bleed I have a 95sbss that has the same problem I have to take it to the dealer and get mine bled . I did the same as you ,my master cylinder was leaking. If you do a search you will find the info here . good luck

 

[JTWard]

If your back brakes are adjusted right more than likely there is air in the rear wheel anti lock)black box). Some where I read the older, earlier one could be bleed I have a 95sbss that has the same problem I have to take it to the dealer and get mine bled . I did the same as you ,my master cylinder was leaking. If you do a search you will find the info here . good luck

Thanks wally,

I'm presently first trying the swap from a GMT 400 to a GMT 800 MC, and since it's apart to that point, I'm putting on a new brake vacuum booster, new pads in front and a multiple power bleed/s. If you drove it, it really feels like air in the system. I want a final fix and I'm not sure that throwing money at it is going to fix it ? Thank you

 

[JTWard]

Hi Kenny, Thank you for the welcome. I called the shop and they broke off a bleed valve, so their waiting on a replacement (I'm assuming it was a wheel cylinder), so I might get it back today, with the GMT800 MC new brake Booster, new front drilled & slotted disc ( Yeah, They have nothing to do with the problem but I just wanted to put them on) I'm a disable veteran so almost all of the work has to be done by my local shop, But the owner is a really smart guy and he knows I'm limited in what I can do. Right now I hoping like all heck the new MC is going to get rid of 3/4 if not all of my braking mushy pedal feeling.

To me, I don't know why we can't open all the bleeders valves and rig up a gallon of DOT3-4 brake fluid inverted and get some lawn chairs and I'll buy a case of beer and we'll let gravity do it's thing, or just do a really good power bleed on my brake system. Hydraulic system are basically steel and brake fluid and once it all steel, rubber seals and brake fluid and no air that's it. That's as good as it gets. I frustrates me that any air can find places to hide while doing a power bleeding. Thank all of you who offer technical knowledge to my problem. Thank you !

 

[kennythewelder]

I am glade I could help a little. Thank you for serving. Sooner or later I will do the GMT 800 MC swap on mine. I have seen you truck on GMtruckclub.com for some time now, and it is beautiful, very, very nice job. I'm glad to see you here also. There is a lot of GMT 400 info here.

 

[wally]

Jt 1st let me say thank you for your service . I have a 91 gmc long bed work truck and a 95 short box . The 91 I have complete service records and I knew all parties involve and never other than calipers and wheel cylinders The brakes system has never been broke open other than to flush this truck has a pretty good peddle . That being said my 95 has had the m/c replaced both rear cly replaced . I have owned this truck since it was a few years old it had a pretty good until I change the master cly after that mush city . From what I was told I need to take it in to have the abs module bleed due to air in some of the dead ends in it that only get exposed If the abs gets activated . Please let us know what you find also would like to hear the feed back on the conversion was giving it some serious thought

 

[JTWard]

GMT-400 to GMT-800 MC conversion

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Thank you Wally, I went ahead and installed a new 1990 Chevy 1500 Brake booster and a 174-1003 MC and all I can say as to the remedy of the mushy brake pedal is Hell Yes. I now have brake pedal travel of about 2" and then it's rock solid and you can lock up the front brakes on a dry surface. I also put on a set of drilled and slotted 1" front rotors from a Canadian parts ( I don't have the F44 chassis) but the brakes are now fantastic. I posted this somewhere else, but if you do this you can get the GM MC 174-1003 from a number of places, I paid $139.95 for it, but it was defective and I had to buy one from a local parts house @ $250.00 and Rockauto.com won't take it back because it is meant to go on a 2000 and later Chevy 1500 ? But blowing almost $400.00 on MC pain is numbed by the fact that this mod works so well I couldn't be happier. I put on new Raybestos semi-metallic brake pads as well. But now I have a truck the really does have "Power Brakes" I can't recommend it more.

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Now in the third picture from the right, you'll see the new MC , the RWAL module and right below it on the right is the proportioning valve and right next it on the left, that is the 'Isolation/dump valve' and it has a bleeder valve on top of it. Don't know what it does, but in the shot of the mounted new 174-1003 master cylinder, you'll see a little electric port, just forget about. only late model 1500's had some electric plug that attached into it.