My Dodge Ram uses vacuum for brake assist. A couple of days ago I drove to town and all was well. On the return trip shortly after starting up I drove out on the highway and applied brakes and no brake assist. The pedal was rock hard and very little braking. This had happened once before and it was a vaccum line that burned through on the exhaust. Since it was raining really hard I just nursed the truck home. During the drive home, the brakes never returned to normal.

The next day I checked all the hoses and could not find a leak. I started the truck and the brakes once again worked ok. I started the truck several times and all ok. I have driven the truck a few times, constantly checking the brakes and all is operating ok. I have no clue as to the cause of this problem.

1. I read somewhere that there is a check valve in the system. What does this valve do and could a stuck valve be the cause of my problem?

2. How much of a vacuum reading does a new pump pull?

3. Is this a sign that the vacuum pump may be failing?

All comments and troubleshooting recommendations will be appreciated. ET

 

There is a check valve in the system. It's right at the pump and is used to prevent oil from getting into the lines. It is located right at the pump where the main line connects on mine. I have never heard of the valve hanging up though.

 

The check valve was part of a recall, not sure which years.
Unless you had the recall done you may not have a check valve.
I would suspect you have oil or water in the lines.

 

Recal #720

http://dodgeram.info/tsb/recalls/720.htm

 

Well, thanks for the info. I checked the TSB and my truck has the external check valve installed. I have checked the system again and I find no problems. The brakes have been working fine for the past week with no failure. I guess I will drive it very carefully and see what happens. Now, I frequently check the brakes and am ready to apply the emergency brakes and use the engine and clutch to stop the truck.