Proportioning valve leaking, of course.

opihinalu

Active Member
Feb 10, 2021
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Florida
My brake fluid has been leaking for a while now but has just recently got much worse. It used to be a slow leak and I had to fill up on fluid every 2 months or so, but 2 days ago I filled the fluid up and it is already completely empty after about 2 hours of driving. I looked for the leak and I found it was leaking out of the front of the proportioning valve where the nut is with the hole in it. It is leaking out of the center hole. Pretty much the same problem I am seeing on a ton of posts on these cars. Is there any recommendations to fixing this (even temporarily) without taking too much time or spending too much money?? This car is a daily driver and my only car so I really need to be able to drive without filling up fluid every other day. Would it be possible to fill the hole up with something or cover it up some how??
 

Mustang5L5

Put lubricant all over the balls
Mod Dude
Feb 18, 2001
39,184
15,082
224
Massachusetts
Need to replace the plug. Unfortunately these plugs are only available used.


There's this plug, but It's to be used when "gutting" the stock PV and installing an adjustable prop valve on the line to the rear.

I assume you are on a stock brake setup? Any plans to ever add rear disk? If so you might just want to be proactive and buy the aftermarket plug, pull the PV rod out, and install an adjustable on the firewall brake line


Yes, expensive solution to fix a simple problem, but the alternative is hopping on ebay and finding a used valve and rolling the dice. Unsure of if i have any as i do have a few junk prop valves but not sure i have all the parts.
 

opihinalu

Active Member
Feb 10, 2021
178
19
28
19
Florida
Need to replace the plug. Unfortunately these plugs are only available used.


There's this plug, but It's to be used when "gutting" the stock PV and installing an adjustable prop valve on the line to the rear.

I assume you are on a stock brake setup? Any plans to ever add rear disk? If so you might just want to be proactive and buy the aftermarket plug, pull the PV rod out, and install an adjustable on the firewall brake line


Yes, expensive solution to fix a simple problem, but the alternative is hopping on ebay and finding a used valve and rolling the dice. Unsure of if i have any as i do have a few junk prop valves but not sure i have all the parts.
Thats unfortunate. Yeah I have cobra discs in the front but the rear is stock. I do plan on doing a rear disc swap eventually but probably not for a while. If I were to buy the plug from LMR, the valve wouldn't work how properly correct? To be honest to me it sounds like it is going to be buying an adjustable valve. Would that be a hard install?? If you do have the part I would be willing to buy it from you.
 

opihinalu

Active Member
Feb 10, 2021
178
19
28
19
Florida
Need to replace the plug. Unfortunately these plugs are only available used.


There's this plug, but It's to be used when "gutting" the stock PV and installing an adjustable prop valve on the line to the rear.

I assume you are on a stock brake setup? Any plans to ever add rear disk? If so you might just want to be proactive and buy the aftermarket plug, pull the PV rod out, and install an adjustable on the firewall brake line


Yes, expensive solution to fix a simple problem, but the alternative is hopping on ebay and finding a used valve and rolling the dice. Unsure of if i have any as i do have a few junk prop valves but not sure i have all the parts.
Can I install something like this:
and skip out on gutting the valve and removing the old one at installing this by itself?
 

Mustang5L5

Put lubricant all over the balls
Mod Dude
Feb 18, 2001
39,184
15,082
224
Massachusetts
If you have cobra disks up front, you should be installing the adjustable valve and gutting the stocker anyway.


You can certainly buy and install the above valve, but it won't directly swap in. That valve uses all 3/8-24 inverted flare ports, but the stock fox valve uses both 3/8-24 and 7/16-24 Inverted flare. So would need adapter fittings on two of the ports.

Your call which way to go.
 

opihinalu

Active Member
Feb 10, 2021
178
19
28
19
Florida
If you have cobra disks up front, you should be installing the adjustable valve and gutting the stocker anyway.


You can certainly buy and install the above valve, but it won't directly swap in. That valve uses all 3/8-24 inverted flare ports, but the stock fox valve uses both 3/8-24 and 7/16-24 Inverted flare. So would need adapter fittings on two of the ports.

Your call which way to go.
I'm going to go the route of gutting the old and plugging it up. Thanks for your help
 
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Mustang5L5

Put lubricant all over the balls
Mod Dude
Feb 18, 2001
39,184
15,082
224
Massachusetts
The plugs sold today do not come with an O-ring, so you must use the old one. Hopefully your o-ring is in good shape and it's the center plug that is leaking.

O-rings are standard sizes, so you can measure and get a new one if you want to replace it.
 
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opihinalu

Active Member
Feb 10, 2021
178
19
28
19
Florida
The plugs sold today do not come with an O-ring, so you must use the old one. Hopefully your o-ring is in good shape and it's the center plug that is leaking.

O-rings are standard sizes, so you can measure and get a new one if you want to replace it.
One more question, could this small of an opening cause such a huge leak? I worry that there is something else leaking because it is leaking like crazy and it just started like this.
 

Mustang5L5

Put lubricant all over the balls
Mod Dude
Feb 18, 2001
39,184
15,082
224
Massachusetts
It doesn’t take much to cause a big leak with brake fluid. When you hit the pedal, significant pressure builds in the system.

Also, make sure you clean the brake fluid off. Brake fluid is hydroscopic so it will collect and retain moisture and cause damage to your frame rail.