73 340 RR Back to life

[Builderguy]

Not sure which booster and MC you went with but since they are not original to the car you may want to check the push rod measurement. Mine was all the original parts so I didn't check it but if I remember it right, there should be very little space between the rod and and the pocket. Maybe an 1/8" max. Too much space and you will get a "soft" pedal. Some rods are adjustable and others have to be shimmed. Just a thought.

 

[YY1]

I'll add-

are you sure the power booster is working?

are the rear brake shoes adjusted properly? having them not engage correctly can cause a "no air in the lines but have to pump" issue.

not sure if anyone mentioned the rod from the pedal to the booster, should be adjustable and might need it.

 

[MoparJimT]

Hmmm. This is the classic: Nothing is wrong but something is. Happens to me all the time, unfortunately.

First, I would say it sounds like you have air in your lines "Only way to stop is to pump the pedal hard". I would also concentrate on your front disc brakes, since they provide most of the stopping power. If they worked the car would absolutely stop.

Some other questions and thoughts:

1. In know, a very basic question: Are your bleeder fittings at the top of the calipers? They must be at the highest point. Some people have mounted the calipers on the wrong sides and that leaves air in them.
2. What is the bore of your original master cylinder vs. you new one? They should be the same. An incorrect bore size could cause issues.
3. You say your brake warning light is on. This switch is in your proportioning valve, so that is telling you something is wrong there. Either it is still plugged, or has air in it, etc. On my 70 Road Runner, I disassembled it carefully, cleaned it, and then put it back together. It really is not that hard, so that might be something to try.
4. Are your brake hoses new? Some hoses collapse on the inside. You can't see it, but they then inhibit fluid moving through them.

And, please be super careful with brake fluid. Be SURE you protect your paint; it will eat your new paint very quickly: Ask me how I know (I screwed up the paint on my 70 Limelight Road Runner TWICE due to issues. Grrrrr.....)

Maybe a picture or two of one of your calipers will help as well.

Hope some of this helps,

Hawk

Thanks HawkRod,
I will check on the caliper positions never thought of that.
I think the bore sizes were the same but I did not measure them. I will check if I take it off. I will check the new one I just bought verses the original.
I agree on the Brake Light, I tapped on the valve as I was bleeding thinking trapped air. Question on the disassembly, is there a kit out there with new o rings? I was afraid if I took it apart and tore one I would be toast. I am thinking I will do that next instead of the MC.
All brake hoses front and back are new.
Yes thanks for the concern on the brake fluid, I will be very careful. I have seen the damage it can do.
Lastly new info,
I noticed that if I press the pedal, when it goes down to a certain point it feels like something is binding then when I let up you feel a little bump in the release. In other words it is not a smooth action from start to floor and return to normal. I took lots of pics when I took the booster and linkage out but could I have put it in wrong and could this be a concern. I feel like if the brakes had the proper pressure I would not push the pedal that far to the floor. It happens at maybe the last 1/3 or 1/4 to the floor.
Thanks!! I will try and get to it today, unfortunately I have to work on some other stuff today.

 

[MoparJimT]

Not sure which booster and MC you went with but since they are not original to the car you may want to check the push rod measurement. Mine was all the original parts so I didn't check it but if I remember it right, there should be very little space between the rod and and the pocket. Maybe an 1/8" max. Too much space and you will get a "soft" pedal. Some rods are adjustable and others have to be shimmed. Just a thought.

Thanks Builder Guy, Since I ordered both replacements for the car I did not check any measurements, I also did not notice if it had an adjustable rod. Is there a way to check this with everything in the car? I will do some research to check on a procedure and review my disassembly pics to see if I have any of the actual rod.
Good stuff to check that I was not familiar with. Thanks!!!

 

[MoparJimT]

I'll add-

are you sure the power booster is working?

are the rear brake shoes adjusted properly? having them not engage correctly can cause a "no air in the lines but have to pump" issue.

not sure if anyone mentioned the rod from the pedal to the booster, should be adjustable and might need it.

It feels like the booster is working, but even if it is not I thought I should have pedal pressure. Is there any way to test a booster. I tried to research because I wanted to keep the original parts on the car. It was going to take a lot of money, and time I did not have to get both the Booster and MC rebuilt and back to me so I went the rebuilt route to get the car on the road. I plan on sending both in at some point, get them rebuilt and reinstall them.
I just do not know how to test the booster. Any thoughts anyone?
I did adjust the rear brake so they should be good but not opposed to checking them again.

Thanks!

 

[HawkRod]

Here is a picture of my 1970 Road Runner proportioning valve in "exploded view". Note yours will be different since it is for a disc brake car, but it should be similar.

I don't think there is anything special about the O rings, and you can likely reuse them if they are not bad.

Something YY1 said that I want to expand on: First, if the rear brakes are even close to where they should be, putting the drum on shouldn't be too easy. Adjusting the rear brakes should be done so you have just a tiny bit of drag on the wheel when it turns.

Having said that, even with NO rear brakes your car should be able to stop OK on just the front brakes. This is why I am focusing on things that could affect your front brakes.

Hawk

 

[Nxcoupe]

Sounds to me like your differential pressure valve is stuck turning on your brake light, however, if that was the case, either front or rear would have no fluid coming out of it when you bled them. When bleeding brakes, fluid should really shoot out, if it barely dribbles out, you have a restriction.

 

[MoparJimT]

Here is a picture of my 1970 Road Runner proportioning valve in "exploded view". Note yours will be different since it is for a disc brake car, but it should be similar.
View attachment 1163851
I don't think there is anything special about the O rings, and you can likely reuse them if they are not bad.

Something YY1 said that I want to expand on: First, if the rear brakes are even close to where they should be, putting the drum on shouldn't be too easy. Adjusting the rear brakes should be done so you have just a tiny bit of drag on the wheel when it turns.

Having said that, even with NO rear brakes your car should be able to stop OK on just the front brakes. This is why I am focusing on things that could affect your front brakes.

Hawk

Thanks HawkRod. I think I am going to check out the combination valve first. I did have some drag on the rears but still am not sure if the fronts are even moving. I will keep you posted

 

[MoparJimT]

Sounds to me like your differential pressure valve is stuck turning on your brake light, however, if that was the case, either front or rear would have no fluid coming out of it when you bled them. When bleeding brakes, fluid should really shoot out, if it barely dribbles out, you have a restriction.

Well i would not say they are gushing but fluid is coming out on all 4 corners. The valve is the only thing that i was not able to replace or refurbish so i am going to start there.
Thank NXcoupe i appreciate it.

 

[Nxcoupe]

Metering blocks can contain multiple functions. One is tge obvious and what most people mistakingly call them, which is the proportioning valve. If this is clogged up or stuck that could cause an issue. It limits the amount of fluid the rear brakes see in a disk drum setup. It also allows pressure to go to the rear brakes first, then as the pressure builds, it is allowed to go to the front brakes. This is why pedal height is affected by rear drum adjustment.
Next is the differential pressure valve. Introduced in 1967, thos slides to either front or rear, which ever has the loss of pressure. It blocks that side off so that a pump of the brakes restores pedal pressure to whichever side is still sealed.
There is also a residual pressure valve on some, that keeps a small amount of pressure on the drum brake wheel cylinder seals to keep them from sucking air and moisture past the seal. These were phased out as the springs were put to keep the lip seals of the cup expanded.
Sorry to ramble just want to share all this info which may help you or others.

 

[Nxcoupe]

Well i would not say they are gushing but fluid is coming out on all 4 corners. The valve is the only thing that i was not able to replace or refurbish so i am going to start there.
Thank NXcoupe i appreciate it.

Welcome. When I bled the brakes on the last vehicle I worked on, it shot out about 4 feet out of the rears. The calipers I was very cautious with because I didn't want to spray fluid in the wheelwell but it made a nice, solid arch up and about a foot from the bleeder.

 

[YY1]

Disconnect the vacuum hose from the power booster (plug it) and see if the feel changes.

It should be a dramatic difference.

 

[Builderguy]

Ask and you shall receive. One brake booster test procedure video.
https://www.bing.com/videos/search?...02416E72CF91CCEEFD1702416E72CF91CCE&FORM=VIRE

 

[MoparJimT]

Well does not look like my post from yesterday survived the outage. So here is the update.

Thanks to all the help from BuilderGuy, HawkRod, YY1, NXcoupe and the rest of the members that responded to my dilemma. Here is what you guys were able to help me fix.

Calipers were on wrong so I switched sides and the bleeders are now on top.
Bled the brakes and had much better results but still had a problem with the master cylinder. I was making a very strange sound when you let off the pedal.
So out it came, checked the rod length and sure enough it was shorter than the one on the old Booster, it was adjustable so I got it to the correct length and installed the new master cylinder I bought the other day. It was a new unit not rebuilt. Does not match the original unit so I still plan on sending it in to get sleeved and rebuilt along with the original booster.
Bench bled it in the car and it expelled a ton more air then when I did the rebuilt unit in a vise so I know I did not get it right the first time.
Bled all 4 corners, no more gurgling from the Master cylinder and had a firm pedal.
On the combination valve, I see the valve moving in the body so I know it is not stuck. I compared it to my buddies 73 E-body and his did the same thing so at least I know it is not stuck. Plus all 4 corners did bleed.

So here's the bad,
Looked at the calipers in the am and there was a drop of fluid from where the hose mounts to the caliper. I check the tightness and it is good so it is either the hose, which was new, or the washers. There are 2 brass or copper washers 1 on each side of the hose mounting block. Is there a way to seal them or do I just need to get new ones and is there a better washer made from a different material to use? Checked again this afternoon and it is definitely leaking.
Took it for a test drive and the brakes seem to be working now but the brake light is still on but does go out when I depress the brake pedal to stop. I let off the pedal and the light comes back on.
Transmission is still not right.
I adjusted the kickdown linkage according the the instructions in the shop manual check the fluid and it still struggles to move the car. I have to really rev the motor so something is not right. Car seems to roll freely so it is not the brake keeping it from going. Feels like it goes from park to reverse to drive correctly, back into park with no clunks or harshness.

Thanks Again all the Great Members of this forum for getting me to where I am at today, as I said before I could not have done this without your help!!!

I feel like every day is one step closer to getting this car on the road.

 

[Nxcoupe]

My post didn't survive either. I usually just crank the bolt down more when a washer is leaking. They are copper so as you tighten, they compress and squish out, which usually seals them. If you think dirt could get in there, then remove clean and install, then tighten up til leak stops. If you want new ones, any auto parts store has them in the back in a cabinet usually.

 

[YY1]

Not supposed to reuse those copper washers but I've done it.

Look at them closely as well as the surfaces they seal to for any burrs or debris.

You can crank them down pretty darn tight.

Does the car move if the selector is in 1st gear rather than D?

Fluid level is good and has the correct dipstick?

Fluid not milky or burnt?

Does the torque converter whine excessively?

 

[ckessel]

Some of the washers are hard. Get the soft ones if possible. They'll conform better. I would imagine that if you get the ones for brake and not drain plug you should be fine. Some imports use soft copper crush washers too.

 

[MoparJimT]

Not supposed to reuse those copper washers but I've done it.

Look at them closely as well as the surfaces they seal to for any burrs or debris.

You can crank them down pretty darn tight.

Does the car move if the selector is in 1st gear rather than D?

Fluid level is good and has the correct dipstick?

Fluid not milky or burnt?

Does the torque converter whine excessively?

1st works but not sure if it takes the same RPM to get the car moving as in R or D. I will pay closer attention on the next test.
Fluid is good and red not burnt or discolored. Dipstick and tube are original to the car and trans.
There is a whine but it seems like it is when I am in gear not in park or neutral. I feel like it gets louder as I add RPM and the car starts moving. Almost like the clutches are not fully engaging or the bands are slipping. Just not sure.
I am not able to do pics or videos since the camera on my phone makes the files too big. I am trying to get an app that works to reduce them without distortion so I can post them.

 

[Nxcoupe]

Sounds really low on fluid, hence the pump whine. Or the filter is clogged

 

[MoparJimT]

Finally got some time to work on the car. I nstalled the tti headers, mid pipes, mufflers and tail pipes. This will get me to the exhaust shop so they can get new tail pipes bent and everything aligned properly.
I thought I would have to fight with the header but they actually slipped in very easy. The instructions are very clear and right on. I did not have to do any modifications to them and they cleared everything fine. You will need to make some adjustments to the transcooler lines. I took mine out for the installation though that was the one thing not mentioned in the instructions. IMO tti's are worth the money, I am very happy with them.

Still struggling with the trans. I spoke to the shop that rebuilt it and they think there is a lack of oil pressure. They gave me a few tips to try and test. They are willing to honor the warranty but since they are in AZ and I am in CO I am trying to troubleshoot it here.
Symptoms are, takes a lot of rpm to move the car 3000 to 3500 forward or reverse. The converter is a stock 2200 to 2400. I can shift from park to D and R and all other gears and it feel normal. Tried back and forth between P,N and D about 20 time to see if something would free up. This actually work on a Turbo 350 that was stuck in 1st gear. Wishful thinking I guess.
I am back at it today, going to go buy a line pressure kit and test the line pressure at the servo at the right rear of the trans. This was suggestion by the shop.
Any thoughts from the bbody team is appreciated.