Puzzling brake problem

Sounds like you're talking about the Proportional valve and it's not working for you as it should. There is a trick to bleeding with one, there's a part that you push/pull at appropriate times while bleeding the front and rear. This device controls the difference in line pressure which is necessary because the front brakes are designed to do more of the braking than the rear brakes. This is more prevalent when the front brakes are disc and the rear are drums. You should get a manual for your vehicle to explain it better than I can via e-mail.

-PapaRick

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Henry Hansteen wrote:

Sounds like you're talking about the Proportional valve and it's not working for you as it should. There is a trick to bleeding with one, there's a part that you push/pull at appropriate times while bleeding the front and rear. This device controls the difference in line pressure which is necessary because the front brakes are designed to do more of the braking than the rear brakes. This is more prevalent when the front brakes are disc and the rear are drums. You should get a manual for your vehicle to explain it better than I can via e-mail.

-PapaRick

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Henry Hansteen wrote:

Thanks for the info, Rick. The part they replaced wasn't the proportional valve, though - it was a part of the ABS system, but I can't recall the name. Anyway, I'll ask the service manager about the bleeding procedure. Sure feels like air in the system to me. Henry

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I can't lay my hands on the article now, but I have seen several postings and read in my local paper about folks with that Ranger having rear end accidents because the pedal went to the floor and braking action was missing. Ford refused to admit liability. In some cases the problem was intermittent so the brakes appeared OK when Ford checked them.

First off it's a truck....

They do not stop like cars.

Second if you can lock the rear brakes up in a truck, the brakes are broken and need to be replaced.

Locking up the rear wheels in a truck will make you spin 360's faster than you can blink and way back in the 70's at least in Jeeps they started putting a combination or proportioning valve in to prevent rear wheel lock up as a safety feature.

Then you have ABS and that just plain won't let you lock up the brakes period!

This usually means a lot longer stopping distance and a soft spongy pedal, especially on snow and ice as you seem to have noticed.

Hey, but you can still maybe steer it into the ditch with the ABS, if you can't avoid hitting the vehicle in front of you....

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

Henry Hansteen wrote:

The brakes are most definitely not working properly. When they were working properly, the truck stopped *very* well.

I pulled the ABS fuse, so the rear wheels should most definitely lock up, especially when I apply them on hard packed snow or ice. The parking brake will lock the rear wheels, so the brake pedal certainly should.

That was meant as silly joke, I hope....

The pedal was high and firm before the brake system developed this problem. There is definitely a major problem with the brakes on this truck. I'm pretty much convinced that there's air trapped in the system somewhere. Seems the proper bleeding procedure is more complicated than I thought for this ABS system. I'm waiting to hear from the shop to find out if they're aware of it and followed it.

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No sir, they are two independent systems. One is a cable, the other uses hydraulics and a proportioning valve still to make sure the rear wheels don't lock up on you.

Most definitely not!

Try it sometime on snow/ice and just lock the rears with the e-brake. Make sure you have lots of room...

Having the rear brakes lock up on a truck or SUV or station wagon is big time bad news unless you are using the e-brake when ice racing so you can do right angle corner slides.

You are likely right from that description.

Mike

Maybe I missed it, but have the rubber hoses been checked or replaced? They could cause a spongy feel and if on the rear, it may prevent the rear brakes from ever building enough pressure to grab (I don't know how the proportioning valve works, but if it is volume based, the rear brake system could use up the fluid it is provided by expanding the pads to touch the drums and then swell up the rubber hose). I thought the brakes were "properly adjusted", so the brake shoe travel shouldn't be the problem, but if there isn't any air in the system and the master cylinder is functioning corectly, the fluid is going somewhere...

If the d'ship cannot cure it, try 'gravity-bleeding the brakes: open the bleed screw just enough to allow fluid to ooze via gravity. Ensure MC is full on both reservoirs. Let it sit several hours, keeping MC topped off. Tighten bleed screws. Manually adjust the rear shoes. (I'm assuming disc on front with drums on rear & with anti-lock on the rear only.) If you aren't sure when rears are tight enough by feel, get a mechanic who is familiar to help. This procedure alone could--could--reduce pedal travel and alter the "feel". This should at least allow for air to be bled AND for rears to have correct travel. With all else good, "good feel" should be restored. HTH & good luck. sdlomi PS: ENSURE you are using quality (repeated, "QUALITY") pads and/or shoes. El cheapos can give a weird 'feel'. And remember: good brakes are cheap insurance! They deserve professional service!

"Rick Colombo" wrote in message news: snipped-for-privacy@Ameritech.net...

If you can find and of that info, I sure would like to have a look. The dealer has now put $1200 worth of parts on my truck, and the brakes still suck. The pedal travel is way too long, it won't even skid the rear wheels on packed snow, and they're trying to tell me it's normal, and the brakes work fine.

I was under the truck today while someone pushed the brake pedal. I watched all three flex hoses hoping to see one of them expand, but they seemed solid.

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Why not open a bleeder while the brake pedal is pushed? That's much more conclusive.

What would that conclude?

It would conclude that fluid is reaching the rear brakes. What can you conclude from an expanding brake hose?

That it would. Fluid is reaching the rear brakes, but under very low pressure.

That would have told me that the hose is damaged, and instead of the fluid expanding the brake shoes, it's expanding the hose.

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The brake hose could obstruct the flow of fluid without expanding. Further more, the usual symptom of a restricted brake hose is the brake not releasing. Have you opened a bleeder yet?

Yes, but I doubt that would give me excessive brake pedal travel and weak bakes on all four corners.

Yep. I bled them before I took it to the dealer, and the dealer claims to have bled them four times. My brakes release just fine - problem is they don't build enough pressure.