Bleeding Master Cylinder

[Brian Conway 264]

Another long shot; the 69 brake booster push rod connecting to the brake pedal is different than the 70 brake booster push rod. The 69 has a turn down and the 70 is straight. Poor picture but all I got. Brian

[mark69sportsroof 31]

I did remember today that I did measure the boost rod before installing the last mc.  The car originally had drums all around.  The local mustang store has over1500 mustangs in their junk yard.  That is where I also bought the car.  I purchased all original type equipment.  The only used parts are the front spindles and the brake boost.  It is a 69 boost with the bent brake pedal push rod.

 

The car was an automatic so I purchased a used brake/clutch pedals.  I cant remember if it was from a 69 or 70.  Is there a difference between the two years?

 

Everyone here has been a great wealth of information and for that I am grateful.

 

Mark     

[Brian Conway 264]

I suggest you go back to page two and study the Mustang Steve site information. Take a look at the pedal supports as well. You may discover what the problem is. Brian

[RPM 1,190]

Yes, please follow Brian's advice. The power brake pedal is different from the manual pedal. It also mounts in a different location.

[RPM 1,190]

This is a manual brakes w/auto trans pedal. Just fyi so you can compare.

[1969_Mach1 333]

I believe the 69 and 70 brake pedals for power brakes are different.  I don't know what the difference is.  But I always see repro brake pedals listed to fit 1968 and 1969 Mustangs.  1970 is not included in the years covered.

 

Do you know what year car your pedals and the other disk conversion parts were from?  Was the booster rebuilt before installing it?

[mark69sportsroof 31]

I will check tomorrow and make sure I have the correct brake/clutch set up.  I have seen mustang Steve's website before.  It will be a good double verification.  I know I have the right brake boost.  It was professional rebuilt locally.

 

I will do the brake boost check also.  

 

Todays high was 17 and light snow and more of the same this weekend.   Sounds like fun.

 

Thanks Mark

[mark69sportsroof 31]

Another update.  I believe I have the 70 brake/clutch pedals.  I have checked Mustang Steve's website.  The easiest way is to measure the clutch pedal bolt holes but that does not work in my case.  I have the Modern driveline clutch cable setup.  With that you have to cutoff the top part of the clutch pedal so I can't measure to see if it 4.5" or 5" from the center of the 2 bolt holes.  I remember about 4 years ago I got the setup off a coupe but don't know if it was a 69 or 70.  No paperwork or way to tell now.  After reviewing the overall brackets that's where I think it appears more like the 70.

 

I took off a rear wheel trying to verify if I had the correct wheel cylinder on the correct side.  It appears by the metal brake line position to be correct.  I was hoping to have a number to verify it against but no luck. 

 

I put my foot on the brake pedal which went down about 11/2" - 2" and started the engine.  It moved about the same distance and almost to the floor. 

 

What affect would a 70 brake/clutch pedal setup be with the 69 curved brake rod from the brake boost? 

 

Thanks Mark

[Brian Conway 264]

Mark this is a picture of my pedal support. At the top of the support, center of the picture, is a nut and bolt. That is the Brake pedal pivot. No measuring involved either your pedal is using that hole or not. Brian

[mark69sportsroof 31]

Thanks I will check mine to verify

 

Thanks Mark

[buening 63]

A 70 pedal will result in more pedal travel compared to a 69 pedal.

[SA69mach 39]

Hey Mark, seems like you are having troubles with the brakes.  I have some experience with brakes, and the different parts on the 69 and 70 Mustangs, but I am not the big expert.  I changed out drums to disc on my 70, and then later added power booster to them - with the predictable problems.

 

I studied Mustang Steves website and talked with Dan at Chockostang.  Those guys are the experts, so much of what follows is what I learned from them, and from fixing my own brakes.  I am surprised no-one has detailed the main issues yet, so here goes...

 

The 69 cars have the in-line proportioning valve, usually found in the metal brake line leading to the rear brakes,  Usually just past the firewall.  It is separate item from the 'distribution block' on the 69.  In 1970 model the proportioning valve is incorporated in the distribution block.

There are some great  videos and information about rebuilding them on the West Coast Cougar website.  Worth a look... as they point out, these valves gunk up over time, and are often overlooked when you get brake issues.  Usually it manifest in locked on rear brakes, or non-operational rear brakes, which does not seem to be your problem.

 

Important - The 69 booster MUST have the 69 brake pedal.  NOT the 70 pedal.

Likewise -  The 70 booster MUST have the 70 pedal.

 

The reason is there is a half inch difference in the positioning of the pushrod stud between the two year-models.  The booster on the 69 has the 'down-turned' push rod, which fits exactly onto the stud, which is 5 inches from the top pivot.  If you use a 70 pedal it will fit on, but push the rod at the WRONG ANGLE, damaging the booster, and the rod, and potentially, the Master cylinder.

I think this might be causing you the grief, and the leaking MC's, and poor brakes.  I would say your booster is most likely toast by now.

 

This is a frustrating issue, for sure, but you must get a matching set of brake pedals and booster parts.  The hardest parts to find, in my recent experience is the 1970 power brake pedal, for manual transmission cars.   This part is not readily available in aftermarket suppliers.  The 69 pedal is, so you are in luck in that regard.

The other obvious difference between the 69 and 70 pedals is the curve of the pedal.  1970 cars had the thicker steering column, so the curve is bigger.  I have seen guys try bending a 69 pedal to suit.  It ends up shorter at the foot pad.

 

I urge you to pull the pedal box out of that car, check exactly what you have, and install the correct, 1969 pedals, and rebuild the 69 booster.  I know it is a pain, I have done it a few times myself now.  But it seems pointless and frustrating, and expensive, to keep replacing MC's when this is clearly not the issue.

 

If you find you are able to bleed the rear brakes, and getting clear fluid, as you would expect, then check that the rear drums are not staying locked on, or not working, when applying pedal.  That is a fair indication that your proportioning valve is 'OK'.

 

My amateur opinion is that the booster pushrod has now become skewed, and not operating the pushrod in the MC properly, perhaps even jamming the MC pushrod at an angle, causing damage to the seals, and then leaks....and no brakes, and low pedal.  I also think the bleeding is working for you while the car is not running, because the booster is not powered up when you do the bleeding process.  Without the booster powered, it probably allows for semi-normal operation of the master cylinder.  I hope that makes sense.

 

I wish you luck, and can assure you that brake systems are very robust, very reliable, when assembled correctly and with appropriately sized and matched components.  if you have very poor brakes, there is something very basic that is at fault.  1969 Mustang brakes are as good as any cars from that era, and work just fine.  Manual or boosted, drum or disc, they all work well.

 

I know Dan is worth a call, for parts or advice, or both. 

[gsxrken 21]

I have a 69 auto power pedal, booster and front disc distribution/prop valve all original just removed from driving car. Master was a FLAPs rebuild but doesn't leak.

PM me for a very sympathetic quote if you end up needing to go this route.

Ken

[gsxrken 21]

Btw love the bit about the 83 year old MIL brake bleeding assistant. How can you yell at your assistant when they left up too early when they're 83 years old? ;-)

[mark69sportsroof 31]

OK thanks.  To the best that I can tell I have the 70 brake/clutch pedal set up.  It is hard to tell 100% with it installed.  Using pics I'm thinking its a 1970.  I know the the brake boost push rod is curved and is a 69.  The brake boost is correct and rebuilt.

 

I have ordered the wilwood adjustable proportional valve.  It will be here on Wednesday.  I made arrangements with a local Mustang shop to install the new valve and they will relocate the position of the brake boost rod up 1/2" or so up.  They just did a all drum conversion to power disc up front and rear drums.  I fell very comfortable in their knowledge and quality.  I'have seen their work for the last 6-7 years.

 

AlsoIi have a few wiring bugs to resolve and their wiring guy will clean them up also.  So in about 2 weeks i should have normal brakes and all working electrical.

 

I will keep everyone updated.

 

Mark 

[mark69sportsroof 31]

Hey everyone, just an update.  It's been 4 months since anything has happen.  I've been waiting for 6 months for a local mustang shop to fix it.  Well I got tired of waiting with no time frame.  So I took it back the shop that has worked on it before.  The owner had bleed the brakes and tried different remedies but no brakes.

So after 5 master cylinders and 4 proportional valves I FINALLY have power disc brakes that work.

 

So I bought the wilwood adjustable proportional valve.  The shop put it on and again no change.  I had to pump the brakes 3-4 times to get 60% or so of braking.

Then he pinched off the front disc brake rubber hoses and pressed the brake pedal and it was hard.  

 

He said he thought the front calipers need to be switched.  About an hour later he called and said I have brakes.  The body/paint shop put on the calipers but I had no engine yet.  Another guy doing my wiring said they were incorrect.  I did several searches and looking at the internet pics and they appeared to be incorrect.  So I had him switch them.  Later I got the engine and found my brakes were not working.  So its been a long, costly and painful 8-9 months.

 

I have learned a lot about the braking system which is very educational.  I received great advice of helpful hints from the members here.   So thank you all very much.

 

Mark 

[RPM 1,190]

Glad it's been fixed. So when you say the calipers needed to be switched, is that side to side?

[Rsmach1 71]

Well I bet you feel like a huge weight came off your shoulders when you pressed the brake pedal and it worked. It's a fairly common mistake if you're not familiar with these calipers (why I mentioned it early in this thread). The important thing is it's fixed, it stops, and you're smiling now. Go enjoy your car :)