melition

Well ive been beaten down on this truck as well as some fellow techs at the dealer. I work at a dodge dealer so i cant hook up scanners, etc..

I purchased this truck used and did a cam swap pretty quickly due to dod lifter issues. Only drove this truck maybe a month before the swap, and since then i have dealt with brake problems.

I get about 14 inches of vacuum at idle and running the stock converter. When coming to a stop 10mph or less, my pedal will sink to the floor and my truck comes to a sudden stop. They work everywhere else normally and firmly and very rarely do they get too hard to stop. I have gotten service brake system soon and the code was C0299.

Since then ive messed with my tune, flushed my brake system, bled my brake system. Checked for leaks and a leaky master and no progress has been made.

Has anyone else has this odd sinking pedal issue after a cam swap?

91LT16SpeedFormula

iTrader: (35)

Possible hub,harness or ebcm?

melition

Well the brakes work fine otherwise, but just randomly does this. Sometimes it stops fine, sometimes it doesnt. Cold or hot, heavy braking or light.

I did just find out my truck has active brake control. It has the jl4 rpo code and i have seen my cluster say service stabliltrak and service brake system soon.

With this info i think i can rule out the master and probably say its the hcu. Guess ill wait until it gets worse and diag it better.

Edit: looks like the brake assist system is built into the booster on this truck and applies mechanical pressure when low vacuum is detected. So no real issues here other then low vacuum from cam causing the brake system to freak out.

310reaper

I have the same issue. I've been at it for two weeks now, and everything points to needing a higher stall and bringing the idle up even more. The tune shop and I have been pushing up my idle(im at 900 now). I have a factory stall I run 14sh at idle. I pulled specs and service manual from Alldata and it’s saying needs atleast 15-20 at booster.

_zebra

iTrader: (5)

that's what i was gonna ask - how much overlap does the cam have, are y'all pulling enough vacuum at idle?
some of the hot-rodder types end up adding a belt-driven vacuum pump to assist the brakes. or you could try a hydroboost conversion.

MikeGyver

iTrader: (5)

Do you have active brake management, and a GMT 900?

wardlws

Your brake pedal is suddenly easy to push (and sinks to the floor), because your ECBM thinks that you have lost too much vacuum boost assist and is using the pre-charged ABS unit to assist / boost your braking.

Either, you have a vacuum leak somewhere (including your vacuum brake booster), or you are not producing enough vacuum at idle.

I recommend switching to hydraulic brake booster: https://www.performancetrucks.net/fo...g-hose-559297/,

or at least tricking the sensor to think you have the proper vacuum levels throughout braking: https://www.performancetrucks.net/fo...-c0299-559296/