Proportioning valve: symptoms of being bad

[ProwlerGT]

Drivability test 2 - Today I went out again by myself and paid closer attention. Windows down I can hear the brakes scrapping the rotors the entire time while going 10 - 35mph. Comparing the braking to a 2001 maxima which has the same engine size, a dodge charger 2006, and my 95 Windstar the braking is just better on all 3. I did several panic stops today from 30 or 35mph and measured the temps of the rotors with an infrared thermometer with a laser pointer.

35 mph run and quick stops:
Front Rotors: Low 300's F variance of about 15 degrees between the two.
Rear Rotors: Low 200's F variance of about 10-15 degrees between the two.

Highway drive to 70mph:
Front Rotors: High 300's F near 400F; variance of about 20 degrees between the two.
Rear Rotors: High 200's F near 300F; variance of about 10-15 degrees between the two.

Now what I don't know is if ANYONE is gonna know if those temps are within some kind of decent normal range. I was happy to see that they all seemed relatively close in temp to each other, but thats all I can say. Dunno if thats too hot or what.

I still also after all this time feel some kind of strange "popping" when I press the pedal all the way down. Before I replaced a single thing on the brake system I sought to eliminate this popping sound/feeling and after replacing everything, but of course the prop metering valve. I can't think of what else would be causing the scraping and this popping as I have bled the lines repeatedly.

So without further adue I've ordered a new proportioning valve which as I was saying somewhere before is actually listed as a metering valve as well and if a metering valve is bad it will cause loss of braking power. When I replace this damn thing if my issues aren't resolved then there's a demon in the car who's chosen to only live in the brakes.

[ProwlerGT]

Drivability test 3 - Took the car out for its first "real-life" event since Katrina. Went to the grocery store for some regular driving. Brakes seemed the same (stopping power not good; "not all there"), but I could stop when I wanted to this time without seeming like they were fading. I still religiously hear the brake pads scrapping the discs though. Gonna jack the car up tomorrow and see which wheel(s) is/are doing it.

Wondering now about booster push-rod to master cylinder clearance. Using my hand and a small ruler it seems as if the push-rod is not engaging the master cylinder until the pedal is pushed 3/8" downward. Adjusting pedal height will not resolve this. I think if I check the specs and its off (which I think it must be cause 3/8" seems too much) I'm gonna have to pop the MC off to adjust it I do believe.

[SOHC3000GT]

Interesting....

[ProwlerGT]

AH HA!!

LITTLE TEST: With my sister's help I had an idea for a new test to see if the push rod clearance is good. I had her watch the brake fluid reservoir with the top OFF of it. Brake fluid at max line. Use a flashlight. I went in the car and gently gently gently with both hands for "control of the push" pushed the brake pedal down slowly slowly slowly .... merrily merrily merrily life is but a dream.. oopps i trailed off sorry.... I noticed an initial bump when pushing the pedal accounting for brake pedal play and then noticed a second bump as if the push rod was engaging late.

From the moment I pushed the pedal to the moment of the 2nd bump the brake fluid reservoir level did not move up or down AT ALL! What's this mean? It means that the push-rod to master cylinder clearance is WAAAAAY off in terms. From the pedal to the brake pads should be like the same type of response you get from a limb on your body. This space between the rod and the MC (about 3/8") accounts for not only not being able to use all the power in your brakes, but for late braking (milliseconds to seconds which count a great deal on the road) and for YOU GUESSED IT ... DRAGGING BRAKE PADS!

Check it out:


Don't have time tonight, but tomorrow the first thing I'll be doing is popping the MC off and adjusting that clearance. I bet you this nabs the damn brake demons and that I ended up ordering that Prop valve for nothing!

The specified space shown on the graphic accounts for what can be described in English as maybe the width of a sharpened pencil tip. This is damn near touching the MC back plate which is how it should be.

For adjustment, it would seem that you should get the push-rod out enough to where it touches the MC back plate lifting it barely off the booster mounting surface and then successively back the rod off in 1/4 turns till you have it right.

This also explains why I had thought that my 1st stock booster was bad and why the 2nd used OEM booster did the same exact thing cause this means my original booster push-rod and the 2nd used less mileage booster I bought were BOTH incorrectly adjusted too far back. Unfortunately and GOOD to know at the same time this may mean that all NA booster push rod's over time back themselves off from extended usage. This should be checked by everyone at least with an NA car.

I'm soooo excited.... and I just can't hide it.... I know I know I know I know....I want brakes... I want brakes ! YEAH! cheese cheese cheese... lol

[ProwlerGT]

The proportioning valve is on national backorder so my order was canceled. Dunno if they plan to make more. I guess this is another one of those parts we can all add to the "no longer made" list.

So I hope when I get around to the push-rod adjustment that it fixes my issue otherwise I gotta do a hunt for a low miles used one.

[Polygon]

Just grab one from a part out thread.