98 Windstar Braking Problem

[12Ounce]

Have you adjusted the gap between the master cylinder and the power assist unit? I think I remember some critical small clearance there that must be maintained ... but I have not replaced a master cyl on a Winnie so this may not be the case.

Just slinging out a thought.

If there is such of an adjustment ... its usually corrected by a nut and screw clevis mounted right on the brake pedal arm.

[Ulsterman]

I was thinking along those same lines today 12Ounce i.e. is there any way I can adjust the brake pedal height and maybe reduce some of the travel.
I have a Hayes manual which talks about being able to adjust the pushrod length on some brake boosters with the master cylinder unbolted and moved out of the way. I of course simply swapped out the master cylinder about a month ago now thinking I had the culprit right there.
I'll inspect and try this once we get a dry evening again here in MD.
I also intend to remove and clean the front ABS wheel sensors and generally see what sort of shape they're in. A while back I had them replaced on my chevy truck under a safety recall and it improved braking as a result - just a thought. I cleaned the rear ones when I had the drums off but haven't touched the front ones.
The saga continues...

[searcherrr]

After trying and replacing virtually everything else I would bet on the proportioning valve especially if its a "metering" valve (combination valve) as well. I am going through this with my car right now. All 4 calipers are in TIP TOP condition now and I have replaced EVERYTHING else and yet the brakes don't feel new as they SHOULD feel (IE: braking power is probably at least HALF effective). The proportioning valve is the only thing I haven't replaced and it IS responsible for loss of braking power when its also doing a Metering valve's job. There is very little information about these valves on the web because they are believed to be HULKS and are very rarely replaced though that is on a brake system that is taken care of routinely. I knew very little about brakes till I did all the work on my car and without a flush of the lines way long after it was due the fluid of course was sludge. I imagine this ate away at the proportioning valve especially with tid bits of water in the lines I'm sure from driving in flood waters in the past.

You may experience loss of power as I said with a bad proportioning (metering) valve as well as possibly brakes dragging and/or possibly vehicle pulling to one side. The best info I've seen yet on this is here at Babcox: Brake Valves: Operation and Service
I find that Babcox has a lot of good information that isn't normally covered so well other places.

Dunno if I said this too already, but I did have to replace my proportioning valve on my Windstar when I first got it. Thats where the "SAGA" began.

Also, note that a function (probably the main one) of the proportioning valve is to provide proper power/pressure to the rear brakes in the event of a "PANIC" braking due to weight transfer/momentum etc... Its on that Babcox page, but it says if this wasn't in place the rears would lock up or attempt to. If you think about it if you are an aggressive or "ahemmm" defensive driver (which I am) you may be using the proportioning valve more often than most vehicles do which may be a reason why it fails faster (besides not bleeding when you should) on some vehicles vs others aside from design or location on the vehicle (corrosion).

[searcherrr]

You do not need to adjust the push rod if you can tell its hitting the MC as soon as you press the pedal. Test with your hand and just push the pedal slightly (maybe 1/4 of an inch at most). You can gauge how far the rod is from the MC by sensing the "bump" or "thud" feeling you get when the rod hits the MC. If there is no small bump felt I would think your push-rod is perfectly as close to the MC as possible.

Adjusting the brake pedal height is likely not necessary though if you did adjust the bolts that move the brake height when you installed the brake booster you may have inadvertently changed the brake pedal height. In any case adjusting the brake pedal height is really a workaround rather than a fix and will probably lead to much more degraded brake performance later on if you don't nab the real cause. The brake pedal height should be set to what the factory wants it to be at all times. Changing this could cause an accident especially if you raise it cause your foot will bump it when switching from the accel pedal.

Trust me man, I went through this too on my car when I thought I found my brake pedal was too low. Turns out it was a misprint in the manual and I spent weeks wondering why things didn't feel right cause of belief in the manual.

[12Ounce]

The proportioning valve is a good candidate for a trouble source. Had a friend who was never able to "bleed" his brakes properly on his Chevy S10 until this valve was replaced.

Quite frankly, I didn't even realize the Windstar had one.

[Ulsterman]

I've been bleeding and bleeding and yesterday I fitted new rear brake drums with one very slight improvement to brake performance with the pedal still travelling 3/4 way down. I looked at pedal height and at the master cylinder to pushrod contact and concluded there was nothing to adjust.
I've read everything I could find on ABS and since there's no warning lights and the fuses and the lights on ignition come on as normal I gave it the ok too.
I'll find and replace this proportioning valve as quite frankly this braking issue is driving me crazy. I've been driving and working at vehicles for 30 years and I swear I've bled more brake fluid through this one than all the others put together with little success!

[rick_gator]

Ulsterman,
You mentioned " initial grab as normal but then the pressure seems to fade"
I have had the exact same experience with my 1999 Windstar. I first noticed the problem a few days after replacing the brake pads and rotors(front).
Two weeks ago I replaced the master cylinder but no improvement.
Today I replaced the brake booster and the problem was solved. No more fade.
I got a reman A1 Cardone booster. It was very easy to install.

RickC

[12Ounce]

Good info, RickC.

[Ulsterman]

Thanks for the advice RickC. I'd reckoned the brake vacuum booster was ok since I'd ran through the checks listed in the Haynes manual but I called my local Advance AP and they have one in stock so I'll pick it up on the way home today.

12Ounce I'm also picking up a proportioning valve from Ford on the way home so either it or the vacuum power booster, being all there is left to renew, should get me a result. otherwise I'll tell my wife to post the obituary on here!

[Ulsterman]

Well over the course of today I fitted the new proportioning valve and bled the master cylinder and all four wheels but no change in braking performance.
Tomorrow it's the vacuum booster being the only thing, apart from ABS equipment, that I haven't changed to date.
We'll see!

[workstar]

May the light of success shine brightly on your back. Don't want any obits. now, do we? Good Luck and let us know.


ken - sittin here on the group w bench

[Ulsterman]

This morning I installed a Cardone reman brake booster. The pedal feels stiffer i.e more force required to press down and there is some improvement in braking. There is still too much pedal travel and the stopping power is not nearly as good as it has been in the past with this van despite all the new components and hours of bleeding.
I'll drive it to work this week and see how things settle in.

[Jerry Irons]

Ulsterman,

When the car is cold, and you go out, start it up, and just press on the brakes, do they still travel 3/4 way down? (without driving it)

-Jerry

[Ulsterman]

Jerry,
After I fitted the power booster today I started it up from cold and the pedal travels way down before braking occurs.
I took it out to go shopping with the family on board and it's exactly the same as it was last week before changing the proportioning valve and power booster; only difference is the pedal is stiffer i.e it takes more force to move it down than before due to the new power booster I'm assuming. My wife hasn't driven it today but she may not be happy with the force now required to work the brake pedal. .
When moving the brakes stop better if I go down fast on the pedal and then the braking force fades off as previously. There is still some braking power left but it's right near the floor and usually I have pumped i.e. released and reapplied before then.
If it's sitting idling like at traffic lights or in park and I keep pressure on the pedal it will slowly go right to the floor.
It's very frustrating as everything else is running so well.

[rick_gator]

I was certain that our head scratching would be over by now.

So the new booster requires lots of foot pressure. Can you double check that the vacuum hose is properly connected to the booster and that the hose is in good condition.

Have you verified that the drums and shoes are within tolerance?

A previous poster mentioned disconnecting the rear circuit brake line from the master cylinder. Your local parts store should have a brass plug that you can screw into the master cyl port. With the engine running in PARK, check brake pedal feel. If it does not sink to the floor, then you may have isolated the problem to the rear brakes.


RickC