Hydroboost Question

[bfr57]

I found a hydroboost out of a 2005 Tahoe. I opted not to take the MC from donor and get a new one. I've done a HB swap in my hotrod and it works great, so getting this one mach'd up in my '72 for better brake performance. When I saw this one in the Tahoe, it had a return line from the MC reservoir to the HB; it was just a standard rubber line. This line went from the bottom of MC reservoir to the return line on the HB shown in the pic. Got it mounted and then it dawned on me that the brake system is combined with the PS system. What the heck? How does this work? I'm positive that line went from MC to HB. I know I can find another MC reservoir without the nipple and add a return fitting from HB to the PS pump, but just trying to wrap my head about the 2 systems combined?

[mongocanfly]

Obviously anythings possible, but I've not seen one plumbed that way...interesting...I would think you could just cap it off

[mongocanfly]

I found this pic

[mongocanfly]

Does your new hydro have all 3 lines coming from it?

[bfr57]

Originally Posted by mongocanfly

Does your new hydro have all 3 lines coming from it?

It does. The HB has the regular 3 connections. It's that low pressure return line that was connected directly to the MC that has me confused.

[bfr57]

Originally Posted by mongocanfly

I found this pic

Yup, that's what it looked like.

[mongocanfly]

Does seem odd
Was the master reservoir doubling as a reservoir for the power steering pump...I know some ps pumps have remote reservoirs..

[SCOTI]

Interesting. New to me as well.

[Richard]

Maybe the vehicle was a manual transmission and that nipple/hose runs to a clutch master cylinder. Personally I do not know of any consumer type vehicle that uses hydraulic brake fluid in the power steering system. While a hydroboost brake system does use the power steering pump, the brake fluid and power steering fluid are two separate circuits.

[mongocanfly]

05 tahoes wernt manual trans...all autos
the LS3/TR6060 i pulled from a camaro did use a shared reservoir for the brake and clutch
after a whole lotta searching , i found where that hose hooks to some sorta canister that has another line coming from the proportioning valve ...
it dont hook to the power steering though.

[mongocanfly]

found it ....
part # 3 is called (brake pressure modulator valve)..part of antilock brake system

"The Brake Pressure Modulate Valve is a part of your vehicle's anti-lock braking system(ABS).
It is a device that is controlled by the electric signal that is generated by the ABS module.
The brake pressure modulate valve regulates the pressure that is supplied to each ABS controlled brake in the wheels."

https://chevroletforum.com/forum/tah...id-part-78138/

[Richard]

Originally Posted by mongocanfly

found it ....
part # 3 is called (brake pressure modulator valve)..part of antilock brake system

"The Brake Pressure Modulate Valve is a part of your vehicle's anti-lock braking system(ABS).
It is a device that is controlled by the electric signal that is generated by the ABS module.
The brake pressure modulate valve regulates the pressure that is supplied to each ABS controlled brake in the wheels."

https://chevroletforum.com/forum/tah...id-part-78138/

Congrats on finding that. Was thinking it may have something to do with the ABS myself. I did find evidence that the Tahoe could be ordered with a manual trans.

[mongocanfly]

(did find evidence that the Tahoe could be ordered with a manual trans.)
Really..??...
I thought the last manual trans stopped long before 05...that's interesting

[v30crewcab]

my tahoe has factory hydroboost. that line from the brake reservoir feeds the anti-lock brake setup.

[bfr57]

Thanks all! Could've sworn that line from MC went to the HB, but obviously wrong! So, now I'm curious where the low pressure return line on the HB went on the Tahoe? I'm going to weld in an -6 AN return fitting into the PS reservoir and get a reservoir without that fitting and be done. Got an education lesson on this one!