Okay for the last couple weeks I've been getting an intermittent brake/ABS light on when I'd hit the brakes but would go out right quickly. The last couple of days I've been getting a hard brake pedal upon initial startup and occasionally while sitting at a stop light idling with my foot on the pedal. Well yesterday the light came on and stayed on and I popped the hood and opened the cover on the master cylinder and the rear brake reservoir was empty! So I filled it up and I still have the lights and hard brake pedal issues. It's currently blizzarding outside and not really motivated enough to give it a thorough inspection but it kinda looks like the left rear brake drums are greasy looking. Is this probably a blown seal on a wheel cylinder or do I have multiple things going wrong here? These brakes were all completely rebuilt this summer (supposedly) by a local shop.

 

I am a little confused, Is the rear compartment of the master cylinder empty? If so, that services the front brakes and, obviously, the front compartment services the rear. So, if it is the rear compartment, the problem is with the front brakes or the cylinder itself. You may have a leak in a caliper. The hard pedal could be low vacuum to the booster or a problem with the booster itself. Air in the system will cause the RWAL brake light to come on. This brake system is vexing and the same problems keep cropping up with a lot of folks, so I am going to go out on a limb and say they are crumby brakes for such an otherwise good truck. I feel your pain and good luck, you'll need it...Mark

 

Another thing is that many times greasy rear wheels are the result of a leaking rear axle seal. You may want to check the rear end oil level also...Mark

 

As mentioned, I also think your warning lights and hard pedal were caused by a low vacuum situation. While the lights are on steady, you can verify this by disconnecting the low vacuum switch connector. If it was the cause of the lights, they will go out when you disconnect the switch. Now you can look for the cause of the low vacuum. The most common cause is a leak, it's fairly rare to have low vacuum caused by the vacuum pump itself.

 

Front compartment of master cylinder was empty which services the rear brakes.

Where might the low vacuum warning switch be? Is it the one on the drivers side inner fenderwell just below the hood hinge?

 

Yup, it has the smaller vac line going to it...Mark

 

I had this exact issue to the T. Before I had my truck shipped to England with me, my pedal would randomly go hard and barely want to stop and my lights would go on and off. Well, when I picked up fromt he VPC in England, the lights were on and wouldnt go off, I had maybe 5% braking power and my front resevoir was bone dry. The lights came up because the proportioning valve detected an extreme imbalance of pressure. I filled the front reservoir, ghetto bled it, and the lights went out and I got my brakes back. I found I have a pretty bad leaky left rear wheel cylinder. Ordered them nearly a month ago and still waiting on them to come in I still dont know what possessed me to bring a D-350 Club Cab DRW to England

 

I sold a porsche 912 to a guy from London last year and when he came over to get it I showed him my big 68 implala ss. He had no interest in it, so I asked him if he didn't like big American muscle cars. He said they're ok, but I wouldn't be able to drive one in London traffic or on London roads, that's why he was so thrilled with the little Porsche (besides the fact that it was loads of fun to drive anywhere)...Mark

 

Luckily I live in farm coutry and far away from the city and my drive to work is all on Major roads. But that still doesnt make it any easier since these major roads are worse than some of the back roads in the states. Thats why I also bought a little tiny Renault Clio...lol. Right now Im just trying to get the truck to pass the road safety test. So, Ive ordered like 1k dollars worth of crap. Whats worse is when I bought the truck it had 1 tiny soft spot in the drivers floor pan. Well, it is now a 1 foot gapping whole behind the pedals and completely separated from the rocker So I gotta fix that before they will even give me a plate. All this headache just to turn around and restore it in the summer.

 

That would be the MOT right? The guy was thrilled also by the fact the the car was rust free. He said that it was the first car that he had ever bought that was rust free and ready to drive. It was unusual because Porsche did not start galvanizing the steel until 1974 and it was a 1966...Mark

 

Back to the topic........

You have 2 issues. Fluid leak somewhere in the rear brake circuit, and a vacuum leak or weak vacuum pump. Don't worry about the vacuum switch. It's working as it should, lighting the brake light when vacuum is low. That switch also notifies the ABS controller of a fault and that lights the ABS light. All perfectly normal.

Test the vacuum pump. If it's good, you then have to find the leak. Could be the brake booster, or anywhere in the heater controls.

 

Thanks! As soon as I get my plow bracket fabbed up I'll start troubleshooting the brake system.

 

just to update this post I found out that the brake boosters on our trucks and others that can survive hundreds of thousands of miles have brake boosters that are subject to deterioration over time causing hard pedal. What I did was pulled the 3 vacuum lines off the top of the booster and put a vacuum pump gauge on each to check for leaks. one comes from the pump, one goes to the cruise control (if you have one) and the third goes to the firewall to run your heater controls. All 3 of these held vacuum so I knew that the only thing left was the booster. Because I have nearly 200k on my truck I decided to replace both the booster and the master cylinder allowing the opportunity to paint them if needed. It cost about $150 and about an hour and a half of my time for the swap. Brakes work like new again! Yay!


Once again thanks all for the help!