Proportioning Valve blow out

[JeepGuy]

There I was...

About 1 1/2 cups of coffee into my morning planning the attack of my usual "honey do" list which included taking the Bronco out for a spin to pick a few things up. Doing my normal walk around and see this:

Of course the normal "what now" thoughts start going through my head and I was crossing my fingers that I simply forgot to put some bottle of something away after placing it on the inner fender... but nope! Go up top and look down and I can tell the high end paint (Rusotoleum Black) was peeling up off the top of the frame rail. Uhh Ohh... At first I couldn't tell where it was coming from but was pretty sure it was brake fluid... duhhh... So I pop the cap on the master cylinder and sure enough, the front brake reservoir is almost empty. Still couldn't see anything obvious so I had my daughter jump in a push the pedal. Bronco is off, so this just normal pressure, and fluid is coming out from all angles around the very front of the proportioning valve around the metering valve cylinder. In this picture you can barely see a drip on the bottom of the valve:

Seem like a pretty straight forward failure to me, but now I'm wondering why? This valve was bought to match the front brake conversion set up through the same vendor the brakes came through and I'm pretty sure it was all at the same time. I did notice there is an additional front bake line connection port on the bottom of the proportioning valve, and I'm not sure if that is just there so you have the option to run the line from the bottom instead of the top, or if this proportioning valve is supposed to have two front brake lines from the valve, and there is potentially too much pressure with only one line. Of course, the way these Bronco brakes systems are set up, that makes no sense, but it does have me asking the question?

Who knows, I guess it's time to replace yet another very new part with maybe a little over 500 to 600 miles of use

 

[jeffncs]

I have bought the Amazon PV2 brake dist block with relative success. (I don’t want to jinx myself!). They have always had the extra front port which I just plugged.

Reality is that, unless your m/c is pushing too much fluid at one end of the other and the piston was forced out of center, you may just have a faulty piece.

All taken with a grain of salt and 1 persons experience.

 

[69_Sport]

This is fairly common. Bad Chinese crap.

See this thread. Simple fix.

https://classicbroncos.com/forums/threads/proportion-valve-leaking.319033/

 

[JeepGuy]

This is fairly common. Bad Chinese crap.

See this thread. Simple fix.

https://classicbroncos.com/forums/threads/proportion-valve-leaking.319033/

Thank you for that info. Saved me a bit of time surfing the net, and the part you ordered is still available from Summit #CLP-PVMVK-T. It did double in price, but I'll give it a 40 dollar shot at correcting the problem before I buy a complete replacement.

 

[JeepGuy]

Update:

Thanks to this community I got the part from Summit without issue. Inspected it, double checked the condition of the washers and O-rings and got to the swap. Very easy to do, and it was a huge bonus to not have to undo all the brake lines and remount everything.

The swap took maybe 5 minutes with a small break in between to wash my hands, grab my phone, and snap the above picture.

After getting the old parts out I noticed some very hard build up caked in the spring. There was a noticeable difference between the spring travel on the new one and this one which I guessing helped further along the failure of the seals. Old spring barely moved. No idea where that material came from as all of the brake lines, calipers, and master cylinder were new, and the brake fluid is still very clean. I wasn't able to see it upon removal, so I don't know if it is positioned at the top port or bottom port of the front brake line attachments. Just something interesting I discovered.

Tomorrow if time permits it will get a quick rebleed then test drive.

 

[DirtDonk]

Great to hear! Luckily, you only have to bleed the front brakes.

 

[JeepGuy]

Update. Massive improvement in braking at this point. Pretty sure this has been my primary issue with my brakes. Kind of odd, I'm wondering if I didn't have this issue, would I have ever discovered the short plunger portion at the booster, or would it have been masked the whole time. Either way, this community with all its knowledge is AWESOME.

 

[Slowleak]

Good to hear that you got it resolved. A few days ago I installed a new booster just to try out while I refurbish my original Bendix. I did not like the pedal feel of the new one so I started experimenting with different reaction disks.
Just a slight difference in the density and thickness of that disk can make a HUGE difference in pedal feel and performance.
I made 4 or five different disks out of various density’s of rubber and tried them out. With a thin soft disk, the brakes would practically throw you thru the windshield. A soft thick disk would provide a slower and smoother engagement and firm one would give a more sensitive and quicker engagement. I even tried one with soft and firm layers combined until I got one just right.
It also provides a means of adjusting pedal height. Never even knew this little disks were in there until it fell out of my booster when I pulled the rod out.