What just happened with my brakes?

Posted By: SPWC

What just happened with my brakes? - 04/27/10 04:49 AM

Was driving my 73 Dodge D200 around last fall,maybe for a week when I first got it.I parked it about a week after I got it,as it was running rough and I didnt want to mess with it at the time.I was going through the truck recently and came across the fact that my gasket for the brake master cylinder was all kinds of torn up.

This fact led me to believe that this vehicle had been driven like this for who knows how long and that the master cylinder didnt have a tight seal and likely sucked air into the system

I got a new seal,installed it and bled the master cylinder on the vehicle. I had my daughter help me bleed the wheels.

I started the truck up to take it for a test drive and first thing I see is that the brake warning light is glowing(on).I also noticed the brakes didnt function very well.

I drove the truck through the neighborhood and into my alley where I needed to unload something. I left the truck idling in PARK while I unloaded my stuff.I got back in the truck and noticed the brake warning light was off,and now my truck stops on a dime.

How could the truck just go from having the brake warning light on and poor brakes,to having hair trigger brakes with the brake warning light off,just by sitting and idling a few minutes.

Could I have had a stuck brake proportioning valve? Dont get me wrong,Im happy the truck stops properly now but im puzzled as to how this occurred in this manner.

Any thoughts? Should I attempt to rebleed the wheels?

Posted By: HealthServices

Re: What just happened with my brakes? - 04/27/10 04:57 AM

Probably

Posted By: Kern Dog

Re: What just happened with my brakes? - 04/27/10 05:09 AM

An old timer once said if your brakes are bad, all you really need is a manual transmission and a loud horn.
Your symptoms are odd. I have had a soft pedal with new brake pads that stiffened up as the pad material compressed, but your situation .... It will be interesting to see what others write.

Posted By: 1_WILD_RT

Re: What just happened with my brakes? - 04/27/10 05:42 AM

Likely an air bubble in the M/C found it's way through the fluid port... The engine heat & slight vibration from the engine may have been just enough to cause it to move... That wouldn't cause the light to go out but as soon as you hit the brakes one time now there would be equal hydraulic pressure on both sides of the safety switch so the spool valve would center & the light would go out.... This is why they tell you to bench bleed a master cylinder... It's very hard to push an air bubble out of a master cylinder through the fluid passage & brake lines it can hang in the fluid chamber causing a spongy pedal... It's not uncommon for a bubble to clear itself by floating out through the fluid in the M/C reservoir but it will only do this when the brake pedal is fully up uncovering the passages from the reservoir to the fluid chambers of the M/C...

Posted By: mcmopars

Re: What just happened with my brakes? - 04/27/10 10:25 AM

Quote:

Was driving my 73 Dodge D200 around last fall,maybe for a week when I first got it.I parked it about a week after I got it,as it was running rough and I didnt want to mess with it at the time.I was going through the truck recently and came across the fact that my gasket for the brake master cylinder was all kinds of torn up.

This fact led me to believe that this vehicle had been driven like this for who knows how long and that the master cylinder didnt have a tight seal and likely sucked air into the system

hows the vibration?

I got a new seal,installed it and bled the master cylinder on the vehicle. I had my daughter help me bleed the wheels.

I started the truck up to take it for a test drive and first thing I see is that the brake warning light is glowing(on).I also noticed the brakes didnt function very well.

I drove the truck through the neighborhood and into my alley where I needed to unload something. I left the truck idling in PARK while I unloaded my stuff.I got back in the truck and noticed the brake warning light was off,and now my truck stops on a dime.

How could the truck just go from having the brake warning light on and poor brakes,to having hair trigger brakes with the brake warning light off,just by sitting and idling a few minutes.

Could I have had a stuck brake proportioning valve? Dont get me wrong,Im happy the truck stops properly now but im puzzled as to how this occurred in this manner.

Any thoughts? Should I attempt to rebleed the wheels?

Posted By: chett

Re: What just happened with my brakes? - 03/03/11 11:51 PM

I am having no luck trying to find a brake proportioning or metering valve for my 1984 Dodge B front 250 VAN.

Also do not know if it has a distribution valve separate or integral.

Please advise as to possible contacts on this subject and include any tech info you think I WILL NEED IN YOUR ANSWER.
I have also been asked to determine if mine is a B 1,2 Or 3 fro correct application.

Posted By: RapidRobert

Re: What just happened with my brakes? - 03/04/11 01:43 AM

Quote:

master cylinder didnt have a tight seal and likely sucked air into the system
I got a new seal,installed it and bled the master.I also noticed the brakes didnt function very well. Any thoughts?

You mean the M/C neoprene seal under the lid?, that keeps br fluid from absorbing moisture from the atmosphere over a period of time and obviously stops spillage but does not affect air in the lines. Define didn't function very well. I'd drive easy/light around the block for a few days and right now check underneath for any leaks & I think you're good but post how they were acting (b4 the miracle).

Posted By: 70Cuda383

Re: What just happened with my brakes? - 03/04/11 01:54 AM

the brake light is normal...during bleeding, you end up moving the safety switch because as one wheel cylinder is open, you release all pressure in that half of the system, but still have pressure in the other half...so when bleeding the rears, the rear has zero pressure, the front has brake pressure because it's all sealed up still. this makes the safety switch THINK there is a leak, and will trigger the brake warning light, until you use the brakes, and with pressure in both halves of the system, center out the safety switch.

as for the soft/spongy pedal that's now firm...could have been air that bubbled up like already said, or with the pressure released from the brake system, your brake shoe return springs pulled them all the way back in, fully compressing the wheel cylinders, and your pedal was spongy until you pumped the brakes and re-filled them.

Remember--drums have a residual pressure valve to prevent this, otherwise the return springs would pull the shoes all the way back in, fully compressing and draining the wheel cylinders--opening the bleeder screw would bypass the residual pressure valve, which is normally located up in the master or in the distribution block

good for a race car...bad for street driving!

Posted By: GO_Fish

Re: What just happened with my brakes? - 03/04/11 02:08 AM

Quote:

Quote:

master cylinder didnt have a tight seal and likely sucked air into the system
I got a new seal,installed it and bled the master.I also noticed the brakes didnt function very well. Any thoughts?

You mean the M/C neoprene seal under the lid?, that keeps br fluid from absorbing moisture from the atmosphere over a period of time and obviously stops spillage but does not affect air in the lines.

Should not affect air in the lines unless the fluid sloshed out enough to get really low and uncover the ports in the floor of the master cylinder.

You need to flush all the old brake fluid out, regardless, to get the moisture out of there. Otherwise your system will seize up from the water in the fluid and you'll be in there again. Check your wheel cylinder/ caliper function, one or more may already be seized. My '68 had poor braking, and found that the rear brake cylinders looked new on the outside, but both had froze solid with no rear brake function.