Brakes 5 Lug Conversion Brake Proportion Valve Bleed Tool


Active Member
Nov 29, 1999
Note: cars without the pressure switch on top of the PV / Combo Valve need to find another solution to lock the valve in place, 1987+ I believe) If you want to buy an 86 and earlier model PV ? Combo valve and install it - then get the (LPV) switch on the top you can have both brake warning systems active. Low Fluid Level and Line Pressure Valve circuits. Just connect the two purple wire to the 86gt switch, either way as they are ground looped.

Getting ready for my 5 lug conv. brake bleed job on my 86GT, (I found that many were having or had issues getting their system bleed down correctly; especially so when doing a lot of "Pedal Bleeding."

After a bit of research, I discovered most had not considered using the PV/Combo Valve Bleed Tool to lock the Line Pressure Valve in place. What can happen is: the line pressure valve, located inside the Combo Valve can shift inside, shutting off one half of the brake line system. This will make it almost impossible to bleed the brake correctly because fluid and trapped air cannot get past the LPV. Or, it may partially shift and you end up with air bubbles just sitting there in the combo valve to later possible work its way down into the rest of the system....hopefully not during a time when you need brakes the most!

Another piece of the puzzle solved: Use this tool when doing a full brake system with line change and Combo / PV gutting modification - if you can find one to fit the Fox / SN95!!!
86 Mustang GT Brake PV Bleed Tool 2.jpg
86 Mustang GT Brake PV Bleed Tool.jpg

86 Mustang GT brake Proportioning Valve Cutaway.jpg

I looked everywhere for one of these tools known to fit the 86GT Combo Valve - and I got nowhere! I decide to make one! Below you can see a photo of what I came up with.

Here's the deal: Find a Brake Line Fitting with 3/8-24 thread, this is the sizing for the Pressure Switch on the 86GT Combo Valve. (may be the same on other Fords) Leave a piece of the flared brake line with the bevel in place. I simple cut the fitting off my old lines and left the line stuck in place. You need the line in place because the hole in it is about the same size as the pin prong on the pressure switch that must fit down inside the little hole in the CV body.

Get a screw small enough to thread into the bevel flare of the old line piece and screw it in tight. Using a dremel tool, cut off the head of the screw leaving a snub of thread sticking out. Use the original pressure switch to measure how long to file the screw piece down to the correct, same length as the switch pin that protrudes out. This is the depth needed to lock the valve in place inside the Combo Valvebody. Depending on the thickness of your screw, you may have to file it down to the right diameter to fit down into the hole inside the CVbody. Once you have test fitted everything, you can then use JB Weld to secure everything together, being sure not to get JBW on the threads of the flare fitting. Once it hardens 24hrs you can fine-tune the fitment. All you need to have happen is for the pin to make contact with the LPV slide inside the Valve Body; then it can't move. GM guys use a plastic tool so this metal one should be fine DO NOT over tighten this tool in the Valvebody, a little pressure will do as it won't leak fluid form this location so long as the seals in the Combo Valve are good. A picture is worth a thousand words. see below.

Hope this helps somebody during their brake bleed. BTW, get a pressure bleeder as well to make the whole job go well. I hear they are a must.


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