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Toyota Service
Toyota Service, Toyota Expert
Category: Toyota
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I'm bypassing the proportioning valve on a 94 Toyota base

Customer Question

I'm bypassing the proportioning valve on a 94 Toyota base pickup with an adjustable proportioning valve and need to identify which line going into the stock valve is the rear brake line, and which is the booster line going back to the front brakes. I plan to remove the rear brake line to the stock proportioning valve and install it into the hose to the tee for the rear brakes mounted on the axle, then plug the booster line gong back to the front brakes.
JA: Thanks. Can you give me any more details about your issue?
Customer: With no load, the rear brakes are locking before the front brakes. My research shows that Toyota pickup proportioning valves are problematic, and most DIY owners have successfully installed an adjustable valve to correct the problems.
JA: OK got it. Last thing — Toyota Mechanics generally expect a deposit of about $20 to help with your type of question (you only pay if satisfied). Now I'm going to take you to a page to place a secure deposit with JustAnswer. Don't worry, this chat is saved. After that, we will finish helping you.
Submitted: 10 months ago.
Category: Toyota
Expert:  Toyota Service replied 10 months ago.

Hello. Welcome to Just Answer. Please allow me to assist you. I would caution you on this idea. The whole reason for the load sensing proportioning valve )"LSPV") is to keep the rear brakes from locking up too soon. If you send full brake pressure to the rear brakes via a tee, you are going to lock the rears up and, I would not be surprised to see if the back end breaks loos and spins the vehicle out. This is dangerous, to say the least.

The LSPVs are problematic. This is because people neglect them. They will develop rust internally and seize up. The rear arm that manipulates the LSPV seizes up at the rear axle, or sometimes falls off.

If I were you, I would invest in a new LSPV and install it. Makes sure that the control rod has free motion as the vehicle bed moves up and down. Then make sure that the rear brakes are adjusted properly. Lastly, make sure your front calipers are not sticking, causing the rear brakes to activate before the fronts.

Expert:  Toyota Service replied 10 months ago.

Please confirm that you have received my input. If you have any questions, please feel free to ask.

Customer: replied 10 months ago.
I believe I figured it out earlier on Sunday -- the ports are marked on the cast housing of the stock proportioning valve.
Expert:  Toyota Service replied 10 months ago.

Ok. Good.

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