Locating brake fluid leakage

[my name is alex]

Thanks east302!

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It's leaking from that nipple in the middle of the picture above the black plastic covering. I'm wondering if there's something I can adjust?

With the car off, light pumping makes the nipple lightly ooze, while a good hard stomp elicits a full drop or two.

I'll have to look at mine again in daylight to see if it's the same as yours. I feel like my pic is the backside in your pic. I guess it's the bpmv that I'm having the issue with.

 

[east302]

That is on the combination valve. The bpmv is the part with 12765501 stamped on it.

Here's a picture of mine with and without the rubber cover. There's a similar nozzle on the opposite end of the manifold where the lines connect. It also has a rubber cap but has a pin that extends and retracts when the brake pedal is pushed. I would guess that you lost the cover some time ago and that dirt and grime have since contaminated it and messed up some internal seal or something.

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You could always try to clean it off with a toothbrush or something and see if that helps. Otherwise, you'd probably need to replace the combination valve or look for a complete ABS assembly and drop it in.

 

[my name is alex]

It looks like I'll just need to start looking for a combination valve replacement. I see a new one on Amazon for 140. Thanks again for your help east302.

 

[east302]

Probably a good idea. My repair manual says to use new transfer tubes (#13 in that schematic a few posts up) when replacing the valve. Those are GM part number 12548294. Three Allen bolts connect the valve to the bpmv. Manual says to tighten them to 6-ft lbs and then 12-ft lbs.

You'll need to bleed the ABS system afterward. A shop or dealer will use a scan tool to run the automated bleed procedure. They would probably charge around $100 if you went that route and you'd be done. Or, you may be able to get away with slamming on the brakes a few times on a gravel road. That should activate the ABS and purge the air out of the abs unit and into the brake lines. You'd then bleed the lines from the caliper/cylinder bleeders like normal.


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[my name is alex]

Probably a good idea. My repair manual says to use new transfer tubes (#13 in that schematic a few posts up) when replacing the valve. Those are GM part number 12548294. Three Allen bolts connect the valve to the bpmv. Manual says to tighten them to 6-ft lbs and then 12-ft lbs.

You'll need to bleed the ABS system afterward. A shop or dealer will use a scan tool to run the automated bleed procedure. They would probably charge around $100 if you went that route and you'd be done. Or, you may be able to get away with slamming on the brakes a few times on a gravel road. That should activate the ABS and purge the air out of the abs unit and into the brake lines. You'd then bleed the lines from the caliper/cylinder bleeders like normal.


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I'll probably source the parts myself and then have a shop to the install. I've never actually bled brakes before and it sounds like a PITA to my low patience self.

 

[df2x4]

I'll probably source the parts myself and then have a shop to the install. I've never actually bled brakes before and it sounds like a PITA to my low patience self.

Good call! Trust me, you'll be happy you had a shop do it. I've had my brakes bled by a shop without a proper scan tool ONCE in my red truck, never again. It's a night and day difference in the pedal when they're bled properly.

 

[my name is alex]

Good call! Trust me, you'll be happy you had a shop do it. I've had my brakes bled by a shop without a proper scan tool ONCE in my red truck, never again. It's a night and day difference in the pedal when they're bled properly.

Sweet. Thanks for validating my laziness!

 

[my name is alex]

I went to the two mechanics I'm currently using today, and they were both a bit lost as to what exactly needed to be replaced and where to find the part.

I think I've found the part here. It's actually called a brake proportioning valve from what I can tell online.

If I were to do the install myself, but then drive the truck to the shop for a proper bleed...would this be feasible? That is, would the brakes work well enough to get me to the shop, which is about 5-10 minutes away?

 

[east302]

That's the part. It's usually called the combination valve because it incorporates both the metering and proportioning valves in one unit.

Did you try a dealer?

I replaced mine and got most of the air out on my own. You'd be better off by bleeding it as well as you can before driving it.




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[east302]

Here's the installation procedure for a 1998 K1500. It looks like your truck has the same part. Hope it helps...

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1. Install the new transfer tubes(13) into the combination valve (12).
2. Install the combination valve (12) onto the BPMV (4).
3. Install the three alien bolts (11) that fasten the combination valve (12) to the BPMV (4). Tighten the three allen bolts to 8 Nm (6 ft. lbs.), then to 16 Nm (12 ft. lbs.) .
4. Install the front and rear brake pipes (from master cylinder) to the combination valve (12).
5. Tighten the three brake pipe fittings to 30 Nm (22 ft. lbs.) .
6. Connect the electrical connector (10) to the combination valve (12).
7. Connect the negative battery cable.
8. Bleed the brake system.
Important: Verify that the combination valve metering rod is depressed during bleeding.

It looks like the part that you linked from Amazon does include new transfer tubes.