I found this out today while I was behind someone on the freeway. The guy didnt turn as quickly as I thought so I had to hit the brakes a couple times in a row.

The brake pedal got hard and braking power was greatly reduced (I almost hit him).

I tested this out on a deserted road later, and found that the brakes work normal when used normally, but fade when they are hit repeatedly.

This is not brake fade from overheating. I think it is a vacuum problem.

 

I think this is normal for our trucks. We have a vacuum power brake booster and since a diesel makes no vacuum it has to have a seperate external vacuum pump to supply vacuum for the brakes and heater/AC system. When you "pump" the brakes at idle it uses up all of the vacuum and the brakes go hard.

There is also a vacuum check valve that you can check. Follow the link below and you can find information on how to check if your truck has the proper vacuum brake booster check valve.

http://dodgeram.info/tsb/index.html
and
http://dodgeram.info/tsb/1999/05-11-99.htm

 

can this be fixed by adding a bigger vaccum resivoir? I found this out too when offroading. or maybe some kind of addon electric vacuum pump?

 

I was having similar issues,

Read my last post on this matter, and i strongly suggest u check these three connections, and try my "fix"

https://www.dieseltruckresource.com/...763#post733763

Thanks! and hope that this helps..

Tx

 

Dodge offers an auxiliary vacuum reservoir to correct the not enough vacuum at idle problem but it's over $100 for a little plastic tank, some hose and a tee.
You can buy a vacuum tank from many parts suppliers for under $20 or make your own from a short length of 4" pvc pipe with two caps glued on and a 1/8" port drilled and tapped into it.
Just one small hose teed into any vacuum line finishes it. Most trucks even have an unused leg on a tee that is capped up under the hood seal.

Personally just knowing that it's going to occur braking while idling is enough for me, I just rev the engine up.