98 Windstar Braking Problem

[Ulsterman]

Fresh from curing an engine problem by replacing the fuel pump I'm back to the original braking problem that has been plaguing this van for a couple of months or more.
The brake pedal feels spongy like there's air in the lines and will travel all the way to the floor anytime the engine is running. I bled at all four wheels yet again today after rebuilding the rear brakes with new wheel cylinders, shoes, adjusters and hardware. I checked everywhere and followed all of the brakes lines out to the wheels but it is not leaking fluid anywhere that i can see as the constant level in the reservoir suggests. I have tried bleeding from the wheel farthest from the master cylinder and also starting with the wheel closest but to no avail.
On previous occasions within the last couple of months I've fitted new front pads and checked the calipers, a new master cylinder and pressure switch and bled all four wheels on numerous occasions both myself with a mittyvac and traditionally with an assistant.
When driving and I hit the brakes there is an initial grab as normal but then the pressure seems to fade and the pedal travels down until I chicken out and pump to get the vehicle slowed or to a standstill. Could this be an ABS fault in an controller, valve, hydraulic circuit or wheel sensor? there is no warning light coming on.

[workstar]

I'm from the old school and have never worked on the ABS part of the brake system, so I've never bothered to study it, or the power assist for that matter. Have you checked the thickness of your discs (or diameter of the drums)? If they are worn too far, one stroke of the master cylinder piston may not be quite enough.

Other than that, and assuming as you say that the system has been bled sufficiently, I would say you have a bad master cylinder. After you get them pumped up, does the pedal stay firm, or start going down again?

ken

[Ulsterman]

I'm 'old school' as well workstar and never seen anything quite like this. I've already replaced the master cylinder and followed all the pre and post installation bleeding procedures.
The front rotors were replaced less than 30k miles ago, pads are brand new and the calipers work fine. I haven't checked the diameter of the drums but the wheel cylinders and shoes are new and the brakes appear to function normally when I have the wheels off the ground and an assistant press the pedal. Handbrake works fine but then it's cable operated. Everything is very well bled with clean fluid now right through the system.

[Ulsterman]

Meant to say it's the 'feel' when the pedal travels down that has me thinking ABS problem. Initial grab and ok braking then fade.... pedal travels down and then a lesser grab when it's right near the bottom. Alternatively initial grab then fade then release and reapply gives grab again but fade again and repeat with lesser effect. Pedal ends up almost on the floor by the time the van is stationary.

[Ulsterman]

Well short on ideas and really trying to get this van running well and safely for my wife and the three little ones I went to Autozone today and bought replacement front calipers. I fitted them this evening and bled clean fluid through but as I thought no improvement in braking. Symptoms remain as set out above.
Now I've renewed front pads and calipers, master cylinder, rear shoes and wheel cylinders with all new hardware.
Ideas appreciated on what to try next.

[searcherrr]

Originally Posted by Ulsterman

Meant to say it's the 'feel' when the pedal travels down that has me thinking ABS problem. Initial grab and ok braking then fade.... pedal travels down and then a lesser grab when it's right near the bottom. Alternatively initial grab then fade then release and reapply gives grab again but fade again and repeat with lesser effect. Pedal ends up almost on the floor by the time the van is stationary.

I haven't read the other posts in here yet.

On my 95 I have replaced the HCU (hydraulic control unit) once, but the bad one only caused the ABS light to come on not affecting braking function at all aside from the ABS function itself on fast stops. Though a fault in the HCU will not cause a soft or dropping pedal. Usually thats from deteriorated rubber brake lines or a leak.

Also my rear wheel cylinders have been replaced twice (were leaking) and 1 time unusually enough the Proportioning valve was leaking as well. You might check those areas as they were/are at least trouble spots on my 95.

Possible too are severaly worn pads or more likely severely worn rotors. When my rotors were at their very end of life the pads would "clap" onto them at times though the only other symptom I experienced was shuddering/shaking when coming to stops.

Also possible and could be likely is that your calipers are sticking which is causing your rotors to heat up dramatically. In my other car I had horribly gummed up slider bolts and then another time I lubed the slider bolts with the wrong grease (supposed to use specific slider bolt grease and a VERY thin film of it too). In either situation this keeps the calipers from backing off the pads/rotors causing heat up and exactly what you describe happens..... have to push it to the floor hard to get it to stop.

Hope that helps.

[searcherrr]

Quote: "When driving and I hit the brakes there is an initial grab as normal but then the pressure seems to fade and the pedal travels down until I chicken out and pump to get the vehicle slowed or to a standstill."

That is precisely what was happening to my car when the calipers were sticking/frozen keeping the pads rubbing onto the new rotors. I would bank on this if they are all 4 original calipers. I haven't looked at Windstar brakes specifically, but on other cars there are rubber boots surrounding the slider bolts. If you've ever been in standing flood water etc.. the water gets in the slider bolt bores during brake use in that water and eventually rusts out the holes and causes debris to get in too. I took mine apart and cleaned them out well and then twisted some "moderate to fine" grade sand paper in there enough times till it was rust free and smooth again and then of course recleaned it. You could perhaps use a dremel tool with a long driver extension with one of those sanding ends on it too if that exists.

Believe me this problem bewildered me for a very long time as I rebuilt my entire braking system all the way to the Master Cylinder on my car only to be met with disgust and surprise when my brakes did exactly what you describe cause of the stuck slider bolts. Autozone sells lil packets of slider bolt grease at their desks and Advance Auto sells Permatex slider bolt grease. The autozone packets have instructions on them. What you have to be really careful with is the amount of grease you use. All of the details are here for when I did it on my car: http://www.3si.org/forum/f41/slider-...oblems-410439/

Also, I just read that you replaced the front calipers. I doubt you bought the ones with the caliper bracket which on my 3000GT is where the slider bolt bores are. The good news is that you can do this without breaking open the fluid lines again (at least on my 3000GT) assuming the brakes are very similar on the front of the Windstar at least. Its IMPERATIVE you use the proper amount (no less or more) of slider bolt grease. The Autozone packets are .14oz and do 1 AXLE. That means that .08oz PER brake caliper which amounts to just a thin film of grease around the bolts. This job is tedious as you have to be "CLEAN" when reassembling the slider bolts and greasing.

Also, you WOULD get a brake light and/or CODE if there was air still in the lines. I believe this is kicked off by the HCU in most cases.

Aside from that I would think you'd have idling trouble if this is the case, but the brake booster is assisted by the engine vacuum. If there is a leak in the brake booster line chances are you will see the idle change a good bit when you press and release the brakes in Park. If you don't and have tried the slider bolts proper greasing method then if you've rebuilt everything else.... including the MC... then if it were me I'd try replacing the brake booster. I did this however on my 3000GT before knowing about the slider bolt greasing technique and replacing the brake booster did nothing for me as apparently they are like SUPER DOOPER heavy duty and long-lasting.

GOOD LUCK and post back your fix. You are almost there as there isn't much left to the brake system as you've ironed out everything else.

[searcherrr]

Forgot to tell the most important thing:

The slider bolt test: You should be able to (by hand) expand and contract the caliper either without the disc/rotor in place or disc in place and caliper piston(s) retracted into the caliper body. The caliper should move freely along its guide/slider bolts and even bounce back a bit after retracted. If it does not then it needs relubing/greasing especially if they don't move at all "by hand" (this is a "free" movement too... not one you should have to force).

Use brake parts cleaner to get the old gunk out, do the twisted sand paper thing if the bores are rusted inside, clean the bolts themselves till they are like new (mine I had to use a drill attaching rouded wire brush to get all the debris off them while holding the bolts at their head with a pliers or vice grip), also clean/inspect the bolt boots and if cracked anywhere replace them and if not cracked then clean them out thoroughly as well.

[Rotorman]

Originally Posted by Ulsterman

Well short on ideas and really trying to get this van running well and safely for my wife and the three little ones I went to Autozone today and bought replacement front calipers. I fitted them this evening and bled clean fluid through but as I thought no improvement in braking. Symptoms remain as set out above.
Now I've renewed front pads and calipers, master cylinder, rear shoes and wheel cylinders with all new hardware.
Ideas appreciated on what to try next.

Ulsterman, On mine 96 windstar I replaced all the lines in the rear of the vehicle, with a couple in the middle of the van. Let me tell you what a job was it to get a firm brake pedal.The trick is your patience and a lot of brake fluid. In your case I would jack up all 4 wheels and bleed using the trickle method. I would run min 2 pints of fluid in each wheel into a jar. Because you have a couple of air bubbles in the line, usually there in the rear lines. Hint I never used them, but I will next time is speed bleeders for wheel cylinders and calipers. This will aid in quick bleeding of the system ( about $10.00 bucks ea.). When you start bleeding the calipers I would use a rubber mallet to tap on them gently to loosen any air bubbles.After your done on each wheel tighten ea. bleeder tight but don't overdo it. This worked for me and I didn't have an assistant.

[12Ounce]

There are several good ideas already posted. I would re-emphasize lubrication of caliper bolts and rear-shoe-to-backing-plates.

Make sure the rear pistons are not stuck in place. You should be able to slide the piston assembly forward-backward with your fingers.

Its hard to better the old "assistant method" of bleeding brakes.

After installing a master cylinder, it is wise to bleed it ... right there at the firewall ... by loosening the tube nuts on the master cylinder body, just as you would with a wheel bleed screw ... of course, using the assistant. After the master cyl is done ... then do the wheels.

The ABS is not your problem.

[Ulsterman]

Thanks for all the replies guys. I accept it's a straightforward 'air in the system issue' and will go back to first principles and bleed from the master cylinder on out to each wheel.
Rained off today in MD so I'll get back to it after work during the week.

[kevink1955]

I think you have covered all the bases. I do not think it's air, if it was you would not have the initial high pedal that drops off. It would go right to the point where the air was compressed.

Does the pedal also start high and drop off when the vehicle is parked with engine runing?? If it does there are only 2 things that can cause it. A bad master cylinder (I know it's already been replaced) or a leak. You say you are not loosing fluid so it's not a leak.

To rule out the master cylinder remove the lines and plug the outlets on the master cylinder. start the engine and stand on the pedal, if it drops away the master is bypassing internaly. Caution: leave the vehicle in park when you try this because hard pedal or not you will have no brakes with the lines disconnected.

[searcherrr]

Originally Posted by Ulsterman

Thanks for all the replies guys. I accept it's a straightforward 'air in the system issue' and will go back to first principles and bleed from the master cylinder on out to each wheel.
Rained off today in MD so I'll get back to it after work during the week.

I will be very surprised if it is "air" in the system at all unless you are not bleeding the system correctly. On my import car there is a specific order to do it and its not always the same on other vehicles. I do not know what it is on the Windstar, but even still you have bled the system multiple times with no success.

My money is on the guide/slider bolts; IE: stuck/frozen calipers and your rotors heating up and why this makes sense is that you reported that the pedal gradually gets worse "as you drive" .... as you drive the heat builds and makes the brakes almost usless and the bummer about that is that if you keep it up you'll ruin/warp your NEW and OLD rotors possibly beyond repair of a resurface.

If its not that then I'd bank on old rubber lines having lost their firmness, but this is much less likely cause they'd have to be changing size dramatically as you push the pedal to cause what you are saying.

Good luck. Report back !

[Hyguy]

Ulsterman,

I have a 98 windstar and I currently have the exact problem you have been chasing.

To date, new drums and shoes, new pads, rotors and calipers. Most of the lines have also been replaced.

As I had to have the vehicle certified, I left most of the bleeding honors to a mechanic. He bled the brakes repeatedly but never corrected the problem. At last we spoke he wanted to replace my master cylinder but I had some lingering doubts and didn't want to spend the big $ for a master cylinder until I had a chance to do some research.

I have suspected that air has been my problem all along as I have checked the rear wheel cylinders (pretty much the only other thing not to have been replaced at the corners) and rear adjustment, all are good.

I too need the vehicle safe and reliable for my wife and babe.

I think I will pursue the brake bleeding issue further...

Perhaps we can compare notes here shortly.

[Ulsterman]

Thanks for all the replies folks.
I can rule out the stuck caliper pins right away Searcherr, I've had them out they're as new and greased up and sliding freely. I can watch each caliper move the pads and grab the rotor when an assistant presses the brake pedal.
I appreciate your views Rotorman and 12Ounce and others about patience and bleeding and running a lot of fluid through and I intend to continue this process once MD dries up a little after two days rain. I returned the old calipers to Autozone yesterday and picked up speed bleeders for the front calipers (they claimed they didn't have ones for the rear cylinders) but I'll check against the old units this evening. Patience is not something I'm noted for so I'll have to force myself to take time over this.
Hyguy just watch this post and I'll update once I get a dry evening here. I'd welcome hearing of any progress you make.

Overall I actually like this van. It looks good, has a good safety record and drives a treat and we've had good service from it. I did the lower intake manifold gaskets 3 years ago and last week replaced the fuel pump. We look forward to another few years with a bit of luck!