RiglerTKE
Joined:
Jul 2002
Richmond, VA
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Not sure if you guys remember me since it has been a while since I have posted, but I was converting to non-ABS before non-ABS conversion was cool, about 4 years ago. Well I am still not cool. Just to remind you- when I purchased the car there was no fluid getting to the back brakes. Unfortunately I had pulled the ABS MC prior to finding you guys. I was told by 2 shops and a Ford dealership that the MC was bad and needed to be replaced. Probably not true but that is all water under the bridge and about $350 dollars worth of BS advice (but I am not bitter).
Progress to date:
1. I swapped out the ABS MC and replaced it with a used MC from a non-ABS '87 t-bird with booster. I have since then replaced it with a new non-ABS '87 t-bird MC.
2. I have placed a prop valve inline to the rear brakes.
3. Replaced the rear brake lines from where they curve under the firewall to the rear discs.
4. Replaced all four calipers and pads.
5. Replaced the flex hoses to the rear brakes.
6. And gone through about a million gallons of brake fluid.
Buttttttttt.....I(the car) still ha(s)ve issues.
I stopped adding it up but guess that I have well over $2000 tied up in this thing and have driven it about 30 miles with 15 getting it home.
Recently I decided that I was going to give it one more try. So I did the brake lines and put on a brand new MC.
I can now get good fluid pressure to all four wheels and a solid pedal when the car is off. Turn the car on and I get a pedal that will pump up and slowly creep to the floor.
If I pull the vacuum line off of the booster with the car running I get the same solid pedal as with the car off.
So my question is this- WTF is wrong?
Do I have a bad booster?
Do I have a vacuum issue to the booster? It is run into the vacuum tree on the upper firewall.
Do I have crap that I need to part and get it out of my life?
Any suggestions, but please do not explain to me how to bleed brakes. I have done that- I have good pressure and solid brake with car off.
Todd Rigler
87 TC Stock except for brake swap.
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DonH
Joined:
Jun 2002
Central Massachusetts, USA
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The service manual says that the distance from the floor (sheet metal) to the to the center of the pedal pad should be 6.3 to 7.3 inches with the engine running and the maximum pedal travel should be 3.1 inches. Are the brakes dragging when the pedal goes to the floor? Was there an adjustable push rod on the booster and is it set to the proper length, .98 to .995 inches? Is the pedal assembly worn and are the bushings installed and in good shape?
It is normal for the pedal to drop when the car is started and the pedal is usually pretty close to the carpet. That seems to show the booster is working properly. How far does the pedal drop from the no booster position to the booster on position? The pedal may be too low to begin with. I don't know if there is any difference in pedal push rod length between the ABS system and the vacuum boosted system but that may be something to look into. Possibly the push rod is too long.
1987 TC stock except ATR 2.5"
1983 Pontiac Transam T-top 5.7 T56 [email protected] top speed: 176mph
1978 Fairmont 2.3 4-spd Big-top S/W
1946 Willys CJ2A 134.2ci L4 No-top
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RiglerTKE
Joined:
Jul 2002
Richmond, VA
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The pedal slowly creeps down to the floor from high up. The pedal feels as though it is not set too low, the numbers you provided (DonH) sound right. With the car on and the pedal depressed, it just sinks, it never really hits a solid point. Normally I would say that it is the MC but this has happened with two differnt MCs used and new. This one is new not refurbished and holds with the car off or the booster not supplied with vacuum, so I don't think that it is the MC or the pedal too low or even the bushings.
I suspect that it is the booster but why? What could cause this. The vacuum set up is relatively simple and I have replaced everything but the booster.
Could the diaphram have a hole in it?
After posting this I did a little more research. I hooked a vacuum gauge to the line that is coming from the vacuum tree to the booster(that way I could elimate the chance that the line is crimping or calapsing) and I have 20 pounds of pressure. So I am getting more than enough vacuum to operate the booster.
The pedal will pump up and then sink to the floor with the engine on. The solid pedal with the car off makes me eliminate the MC and air in the lines.
How to I test the booster?
The booster blowback valve only allows air one way so I am sure that it is good.
I put a mity vac and pumped to 5 lbs from the hose that goes to the vac tree and it held. Is that a decent test or is ther something else?
Todd Rigler
87 TC Stock except for brake swap.
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DonH
Joined:
Jun 2002
Central Massachusetts, USA
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I meant to say "Possibly the push rod is too short." in my post above.
My experience with brake boosters has been that they generally always work or fail completely. The only problems related to boosters that I have experienced has been the booster filling up with brake fluid due to leaking MCs and incorrect pedal height caused by mis-adjusted push rods. The brake pedal will not normally rise when the engine is started. With your foot on the pedal when starting the car the pedal should go down perhaps an inch. I can't say why this is happening and thinking about how a booster normally operates cannot come up with a scenario as to why this is happening as you describe.
The test with the Mity Vac may show that the booster case and diaphragm don't leak but the usual test is as above, put your foot on the pedal and start the car, the pedal drops a short distance. Other tests involve noise from the booster, mis-adjusted push rod, and brakes dragging, mis-adjusted push rod. Having failed the foot on pedal test the Ford dealer would replace the booster.
1987 TC stock except ATR 2.5"
1983 Pontiac Transam T-top 5.7 T56 [email protected] top speed: 176mph
1978 Fairmont 2.3 4-spd Big-top S/W
1946 Willys CJ2A 134.2ci L4 No-top
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RiglerTKE
Joined:
Jul 2002
Richmond, VA
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Quote: Incorrect pedal height caused by mis-adjusted push rods.
I will do more investigation on this. I don't think this is it but will give it a more indepth check.
Quote:With your foot on the pedal when starting the car the pedal should go down perhaps an inch.
I have tried this and the pedal just slowly sinks.
Quote:Other tests involve noise from the booster, mis-adjusted push rod, and brakes dragging, mis-adjusted push rod. Having failed the foot on pedal test the Ford dealer would replace the booster.
When I pump the pedal a get a pretty loud whoosh which I thought was normal. I will compare to my truck and see if it is more dramatic.
Do you recommed the booster being changed? That is really the only thing in the car that is not new or refirbushed. It came of a tbird junker. Don I appreciate you help.
Todd Rigler
87 TC Stock except for brake swap.
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DonH
Joined:
Jun 2002
Central Massachusetts, USA
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You shouldn't notice any noise from the booster and comparing it with a known good unit is the proper procedure. If it is noisier than your truck check the booster to MC push rod length. If it is adjustable set it to the length mentioned above and try it out. If it is already set correctly or adjusting it doesn't work or the booster is not adjustable replace the booster. The service manual shows two types of booster on these cars, one adjustable and one not, but it is not clear which is used on what car.
1987 TC stock except ATR 2.5"
1983 Pontiac Transam T-top 5.7 T56 [email protected] top speed: 176mph
1978 Fairmont 2.3 4-spd Big-top S/W
1946 Willys CJ2A 134.2ci L4 No-top
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RiglerTKE
Joined:
Jul 2002
Richmond, VA
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I HAVE BRAKES! Thanks Don H. I twisted the booster pushrod out and it seemed to work. Who would have guessed that it was something like that. I did not even know that would be an issue. Now for all of the other problems.
Todd Rigler
87 TC Stock except for brake swap.
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DonH
Joined:
Jun 2002
Central Massachusetts, USA
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Happy to help.
1987 TC stock except ATR 2.5"
1983 Pontiac Transam T-top 5.7 T56 [email protected] top speed: 176mph
1978 Fairmont 2.3 4-spd Big-top S/W
1946 Willys CJ2A 134.2ci L4 No-top
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