NBS/Astro knuckle brake upgrade.

[Schurkey]

MichaelGot reported.

 

[Kevco2]

This is awesome. I purchased the knuckles on ebay. I'll get bearings and brakes there too likely. Good call on the connector difference, I can get a new pigtail from Rock Auto for 07+. I'm already set on wheels, I'm running 18s from a '13 Z71. The only unknown at this point is a brake line adapter, but I think I can work that.

How did you make out with this swap?
I ran into that terrible roadblock that is Winter before being able to complete all the work on my truck.
What did you manage to do for the brake line fittings?

-Kevco

 

[Kevco2]

I finally got everything installed and swapped over on my truck
It is still up on the lift, but I have run into the strangest issue
The front calipers spun completely free at first and everything seemed great
Now the two sides alternate building pressure and locking up after releasing the brake pedal
We are COMPLETELY stumped and it is wicked demoralizing

I have 05 Astro brake hoses and Calipers
Could it be some issue inside the Kelsey Hayes ABS box?

 

[CrustyJunker]

I finally got everything installed and swapped over on my truck
It is still up on the lift, but I have run into the strangest issue
The front calipers spun completely free at first and everything seemed great
Now the two sides alternate building pressure and locking up after releasing the brake pedal
We are COMPLETELY stumped and it is wicked demoralizing

I have 05 Astro brake hoses and Calipers
Could it be some issue inside the Kelsey Hayes ABS box?

That's creative. Silly question, are you using new brake hoses? Saw that once before on a 1-ton. Acted like a caliper locked up, replaced it, same thing with the new caliper. Pressure would go into the calipers when you hit the brakes, but the hoses would collapse inside when you let off the pedal (like a check valve). You could literally mash the brakes harder, but still would not relieve pressure. It also exhibited that uneven side-to-side behavior - just an idea!

I know those Kelsey-Hayes ABS boxes can give you spongy brakes, but I don't think they can give you the behavior your seeing.

 

[Kevco2]

That's creative. Silly question, are you using new brake hoses? Saw that once before on a 1-ton. Acted like a caliper locked up, replaced it, same thing with the new caliper. Pressure would go into the calipers when you hit the brakes, but the hoses would collapse inside when you let off the pedal (like a check valve). You could literally mash the brakes harder, but still would not relieve pressure. It also exhibited that uneven side-to-side behavior - just an idea!

I know those Kelsey-Hayes ABS boxes can give you spongy brakes, but I don't think they can give you the behavior your seeing.

Everything is new. Brakes hoses, calipers, CV axles. There were no Astro vans in the junkyards for 500 miles

 

[CrustyJunker]

Hopefully someone else chimes in, not sure what else would cause that.

 

[Kevco2]

My thought process is leading me towards the ABS unit having something gummed up and needs to be run with the fancy scan tool OR the combination of AC Delco GMT400 master cylinder with Rock Auto vacuum booster has something out of whack.

I bled the Kelsey Hayes unit as much as possible with the port under the black cap too

 

[stutaeng]

My thought process is leading me towards the ABS unit having something gummed up and needs to be run with the fancy scan tool OR the combination of AC Delco GMT400 master cylinder with Rock Auto vacuum booster has something out of whack.

I bled the Kelsey Hayes unit as much as possible with the port under the black cap too

What if you just pull out the ABS fuse? That will rule out the EBCM I'm pretty sure. I don't think it would be problem though, but simple enough to try.

 

[Kevco2]

What if you just pull out the ABS fuse? That will rule out the EBCM I'm pretty sure. I don't think it would be problem though, but simple enough to try.

Worth a shot. The truck is still on the lift. I have not even put it in gear since starting this upgrade conversion 8 months ago

 

[Kevco2]

The valve on the ABS unit is now stuck out and won't budge. That is how I found it with a bit of fluid inside the black cap
Maybe that has something to do with my issues
Hopefully the whole module isn't wrecked

I just ordered the Autel MaxiCheck pro scan tool because it can supposedly run the ABS function tests