Why does it take a while for my brakes to work properly?

[Dino]

Power drums, will not brake all too well when cold, brake system light goes on when giving the pedal decent pressure.  It seems that once it warms up enough the light stays out and the car stops fine but that means it doesn't stop fine before I reach that point.  I was on my way to work and was driving for about 15 minutes before the light finally didn't come on and the car stopped as it should.  Pedal feel does not change throughout, I just need to push a bit harder when it's cold.  Last night I went for a short drive and the brakes worked fine after only a minute or two, the difference would be that I was driving a bit 'sporty' as opposed to my slow cruise into work.

Is this a vacuum issue? 

[bobs66440]

It sounds like it will stop only when hot which could be a few things. Could be worn/glazed shoes/drums or the wrong compound shoe material. I had this same issue with brand new brakes on a '70 Mustang and it turned out to be the wrong pad material. I changed to the std Autozone pads and it stopped perfectly, no other change.

Are these new brake shoes/drums or old? New master cylinder? Booster? A little more info would be helpful.

[Dino]

It sounds like it will stop only when hot which could be a few things. Could be worn/glazed shoes/drums or the wrong compound shoe material. I had this same issue with brand new brakes on a '70 Mustang and it turned out to be the wrong pad material. I changed to the std Autozone pads and it stopped perfectly, no other change.

Are these new brake shoes/drums or old? New master cylinder? Booster? A little more info would be helpful.

It's all old, very very old, nothing has been done to the brakes in at least 10 years.  I have a front disc brake kit but I'm unsure when I'll have the time to install it.  I also bought a new master cylinder for the kit and have a prop valve.  I do intend to use the drum booster unless I can find something better I can afford but I don't see why this wouldn't work.

I thought somehow this would be related to oil pressure as the brakes seem to work fine once the pressure is up.  With my gauges all being off it's hard to tell though, oil pressure gauge will only go up to 10-20 instead of the usual 50-60.  It's the gauge though, I know that much.

[bobs66440]

It sounds like it will stop only when hot which could be a few things. Could be worn/glazed shoes/drums or the wrong compound shoe material. I had this same issue with brand new brakes on a '70 Mustang and it turned out to be the wrong pad material. I changed to the std Autozone pads and it stopped perfectly, no other change.

Are these new brake shoes/drums or old? New master cylinder? Booster? A little more info would be helpful.

It's all old, very very old, nothing has been done to the brakes in at least 10 years.  I have a front disc brake kit but I'm unsure when I'll have the time to install it.  I also bought a new master cylinder for the kit and have a prop valve.  I do intend to use the drum booster unless I can find something better I can afford but I don't see why this wouldn't work.

I thought somehow this would be related to oil pressure as the brakes seem to work fine once the pressure is up.  With my gauges all being off it's hard to tell though, oil pressure gauge will only go up to 10-20 instead of the usual 50-60.  It's the gauge though, I know that much.

Your oil pressure has nothing to do with your braking. I would say you need new shoes and drums. It seems the old ones have seen their last days. You may be able to get away with turning (resurfacing) the existing drums, but it depends if they have been turned before or not. There is a minimum thickness spec for the drums (not sure what it is for your car, sometimes it's marked on the drum) and they shouldn't be made any thinner than that. I would replace all the hardware and check the wheel cylinders for leaks and replace as needed.

[Dino]

Sounds like a plan.  I'll replace the rear shoes, cylinders and drums if needed.  Thanks! 

[bobs66440]

Sounds like a plan.  I'll replace the rear shoes, cylinders and drums if needed.  Thanks! 

FYI, the front brakes do most of the work stopping the car. Why replace just the rears? If your rear brakes are working better than the fronts, it can be a very dangerous situation if the rears lock up while the fronts are not working. The car will not stop well and you risk losing control. I would replace all the brakes, but definitely the fronts first...unless of course you will now be installing the disc setup.

[Dino]

Yes I will install the front discs as well when I redo the rears.  I don't intend to do the rears only for the reasons you stated.  I better make this brake job a priority before it gets worse!

[Musicman]

If your brake light is coming on, that means the shuttle valve for the idiot light is moving which is not a good thing.

When you change out the brakes, also be sure to flush the "entire brake system". Your old fluid is obviously contaminated which is part of your problem.

Change all the brakes front and rear... It's true that Front brakes absorb the initial shift in the vehicles center of gravity so they tend to wear a little quicker than the rears, but in the end all four brakes stop the car. Stopping a car is no different than stopping a bicycle.. if your front brakes lock up first, your ass end will end up in front of you. Thats why they put a metering (hold off) valve on cars with front disc's and rear drums, to insure that the rear drums grab first, before the front disc's are applied.

[68 RT]

If your light is coming on your master cyl is bad, you have a leak in the system, or system is not bled properly.   

[Dino]

I'm thinking it's a combination of things here, the system is old, has not been worked on in a decade or more and it's simply all degrading.  When I start work on the brakes I will redo the whole thing.  Install the front disc kit, the new m/c, get new shoes for the back, rebuild the pumps and flush the lines.
I'm a bit hesitant to start because I've never bled brakes before, nor do I have a clue where and how to install the prop valve so I'll have to check with Mr. Google again. 
I'm always a bit careful with tearing into the car as it could end up sitting on stands for a while.  I get anxious when I can't drive it for a week!

I need 15" wheels....not sure if the discs and calipers will fit my 14" wheels.

[Musicman]

If you're doing a Disc/Drum setup you will need a "Combination Valve" which is a Metering (Hold Off) Valve, Proportioning Valve, and Hydraulic Safety Switch (Shuttle valve) all in one. A very common item which is very often (99.9% of the time) wrongly referred to as a Proportioning Valve by those who don't know what the F@#! they're talking about or what it is their selling.
You can also buy these components individually, as was often seen in some of the first vehicle applications before combining them into one unit. Many folks actually prefer having the Prop valve separate because it allows for fine tuning.

[Dino]

If you're doing a Disc/Drum setup you will need a "Combination Valve" which is a Metering (Hold Off) Valve, Proportioning Valve, and Hydraulic Safety Switch (Shuttle valve) all in one. A very common item which is very often (99.9% of the time) wrongly referred to as a Proportioning Valve by those who don't know what the F@#! they're talking about or what it is their selling.
You can also buy these components individually, as was often seen in some of the first vehicle applications before combining them into one unit. Many folks actually prefer having the Prop valve separate because it allows for fine tuning.

Good info, thanks!  The one I have is from Wilwood, I'll look at the number tonight and post it. 

I'd like to have every single piece ready to go before I tackle this job so when I have a chance I'll take a look at all that stuff and list what I have.

[Dino]

Why is the part you need always hidden best....

Finally found the prop valve.  It's Wilwood # 260-2220.  So what is recommended?  Keep this one and buy an additional metering valve and safety switch or combo, and if so whch ones, or forget about the prop valve I have and get an all in one? 

[bobs66440]

What you have there is a proportioning valve only. It's designed to limit the pressure to the rear drum brakes so that they don't lock up before the front discs. Under braking, weight is transferred from the rear of the car to the front making the rear very light and prone to easily locking the rear wheels. As musicman said, you can fine tune the front/rear brake proportion so it suits your needs. But for most applications, an appropriate combination valve is all you need...similar to these...but double check for the correct application.

http://www.summitracing.com/search/Department/Brake-Systems/Part-Type/Brake-Combination-Valves/

[Musicman]

Sorry, I've been away for a couple of days... As bob said, the Proportioning valve keeps the brake line pressure to the rear drums in check under hard or sudden braking to prevent lock-up... Under normal day to day braking conditions however they are dumb as a post and do nothing at all to regulate pressure... In short, they are reactionary valves.

As I said earlier... Valves can be purchased separately, together, or in almost any combo thereof (1, 2 or all 3) from any number of online vendors.

[Dino]

Thanks gentlemen.  I'll leave the proportioning valve in the box and will look for a combination valve.  This car gets driven a lot so I want something that'll work out there.  I've got around 800 miles on it since I got it back last month.

EDIT:  There's too mcuh out there!  Which one do I need? 

So since I have a 4 drum system right now there should be a distribution block in there right?  Do I add a combo valve to it or do I get rid of the distribution block and install a combo valve in its place?  What about a residual valve?  Do I need one of those?

This is what I have so far:

It was a 318 car with power drums.  Everything drivetrain related on that car has been replaced with a 71 squad car drivetrain but I doubt they changed the brake lines.  Master cylinder brake lines enter on the fender side, not the engine side.

Booster is original drum booster.

Wilwood front disc kit, forgot the number but it's been new in the box since 2000-ish.  It's the basic kit with 10.75" vented rotors and billet 4 piston calipers.  I think they changed the kit later to cast calipers.  I have all the parts to bolt onto the drum spindles.

New master cylinder Raybestos MC36283 with inlets on fender side.

[bobs66440]

Thanks gentlemen.  I'll leave the proportioning valve in the box and will look for a combination valve.  This car gets driven a lot so I want something that'll work out there.  I've got around 800 miles on it since I got it back last month.

EDIT:  There's too mcuh out there!  Which one do I need?  

So since I have a 4 drum system right now there should be a distribution block in there right?  Do I add a combo valve to it or do I get rid of the distribution block and install a combo valve in its place?  What about a residual valve?  Do I need one of those?

This is what I have so far:

It was a 318 car with power drums.  Everything drivetrain related on that car has been replaced with a 71 squad car drivetrain but I doubt they changed the brake lines.  Master cylinder brake lines enter on the fender side, not the engine side.

Booster is original drum booster.

Wilwood front disc kit, forgot the number but it's been new in the box since 2000-ish.  It's the basic kit with 10.75" vented rotors and billet 4 piston calipers.  I think they changed the kit later to cast calipers.  I have all the parts to bolt onto the drum spindles.

New master cylinder Raybestos MC36283 with inlets on fender side.

With a 4 drum system, you should just have a distribution/safety shuttle valve/brake light switch unit now. With a disc/drum setup, you would replace that with a new appropriate combination valve that handles all that plus the proportioning to the rear. And you will not need a residual valve. Those are mainly used for systems where the master cylinder is lower than the calipers/wheel cylinder and there is danger of the fluid draining back into the master cylinder. They act as a check valve and keep the fluid where it should be and hold slight position/pressure at the shoes/pads. I would call Wilwood, explain the setup you have and let them recommend a combination valve.

[Dino]

Thanks gentlemen.  I'll leave the proportioning valve in the box and will look for a combination valve.  This car gets driven a lot so I want something that'll work out there.  I've got around 800 miles on it since I got it back last month.

EDIT:  There's too mcuh out there!  Which one do I need?  

So since I have a 4 drum system right now there should be a distribution block in there right?  Do I add a combo valve to it or do I get rid of the distribution block and install a combo valve in its place?  What about a residual valve?  Do I need one of those?

This is what I have so far:

It was a 318 car with power drums.  Everything drivetrain related on that car has been replaced with a 71 squad car drivetrain but I doubt they changed the brake lines.  Master cylinder brake lines enter on the fender side, not the engine side.

Booster is original drum booster.

Wilwood front disc kit, forgot the number but it's been new in the box since 2000-ish.  It's the basic kit with 10.75" vented rotors and billet 4 piston calipers.  I think they changed the kit later to cast calipers.  I have all the parts to bolt onto the drum spindles.

New master cylinder Raybestos MC36283 with inlets on fender side.

With a 4 drum system, you should just have a distribution/safety shuttle valve/brake light switch unit now. With a disc/drum setup, you would replace that with a new appropriate combination valve that handles all that plus the proportioning to the rear. And you will not need a residual valve. Those are mainly used for systems where the master cylinder is lower than the calipers/wheel cylinder and there is danger of the fluid draining back into the master cylinder. They act as a check valve and keep the fluid where it should be and hold slight position/pressure at the shoes/pads. I would call Wilwood, explain the setup you have and let them recommend a combination valve.

Perfect!  I'll give them a call.

[Musicman]

OK... lets save a little time & typing here... Read this, here's a couple of sites that have everything you need to know concerning brake systems valves.

http://www.piratejack.net/index.php?option=com_content&view=article&id=10&Itemid=17

http://ecihotrodbrakes.com/brake_facts.html


Typical setups...
http://www.piratejack.net/index.php?option=com_content&view=article&id=11&Itemid=18
http://www.piratejack.net/index.php?option=com_content&view=article&id=12&Itemid=19

You know, I was just looking around at a few vendors sites for some of this stuff, and I have to tell you I am just amazed at how many vendors out there are just "absolutly clueless" when it comes to brake systems, as well as their own product line.

[Dino]

OK... lets save a little time & typing here... Read this, here's a couple of sites that have everything you need to know concerning brake systems valves.

http://www.piratejack.net/index.php?option=com_content&view=article&id=10&Itemid=17

http://ecihotrodbrakes.com/brake_facts.html


Typical setups...
http://www.piratejack.net/index.php?option=com_content&view=article&id=11&Itemid=18
http://www.piratejack.net/index.php?option=com_content&view=article&id=12&Itemid=19

You know, I was just looking around at a few vendors sites for some of this stuff, and I have to tell you I am just amazed at how many vendors out there are just "absolutly clueless" when it comes to brake systems, as well as their own product line.

Tell me about it!  I've been trying to get a straight answer regarding barrier hoses so I can replace my old a/c hoses and I'm not getting anywhere.  The last guy flatout asked me why I would want to change my 40+ year old r12 hoses even after I to;ld him I was going to run r134a.  WTF?

Anyway, thank you much for those links, that was really helpful.  To be safe I will add a 10 lbs residual valve as I do not believe my mc has one and I don't want to take the chance of having a spongy pedal.  The article says it doesn't hurt to have one even if you don't need it.

I found this one for a good price, trying to find out if it has all I need.  ACDelco 172-2243 combination valve.

[Musicman]

Here's a better price 

Here's a Mopar style one... which uses the original wire connector.
http://inlinetube.com/Prop%20Valves/VML104.htm

This is a universal job... a few bucks cheaper
http://www.piratejack.net/index.php?page=shop.product_details&flypage=yagendoo_flypage_1.tpl&product_id=178&category_id=30&option=com_virtuemart&Itemid=6

... and the wire connector for it
http://www.piratejack.net/index.php?page=shop.product_details&flypage=yagendoo_flypage_1.tpl&product_id=227&category_id=30&option=com_virtuemart&Itemid=6

[Dino]

Here's a better price 

http://www.piratejack.net/index.php?page=shop.product_details&flypage=yagendoo_flypage_1.tpl&product_id=178&category_id=30&option=com_virtuemart&Itemid=6

... and the wire connector

http://www.piratejack.net/index.php?page=shop.product_details&flypage=yagendoo_flypage_1.tpl&product_id=227&category_id=30&option=com_virtuemart&Itemid=6

Hey not bad, but I can buy the acdelco one for $6, brand new!   

[Dino]

That's the one and apart from this picture there's not a lot I found out about it.  It looks to have all I need though.  What do you think?

[Musicman]

I can't find any info on that one outside of the cost $133
The electrical connection is different, appears to be 2 wire...

[Dino]

There's one on ebay for $6 but that's not going to last.  I even talked to the ACDelco guys and they couldn't tell me what it is so I'll let it be and find something else, like the one you posted.  I don't care for originality seeing I'm installing a Wilwood kit so whatever works for a good price will be my next order.