Brake problems after cam swap 5.7/6.4

[f.creek-ranch]

No TUNING QUESTION !

2012 Dodge RAM 1500 LL NGC4

Cam swap to 6.4 and MDS delete.

Brakes are completely new, brakelines, brake booster, ABS block...because of this failure.
Wheel sensors are all same data, so no ABS problem.

The car has ABS ESP but no active brake system.

Problem is, the brake pedal needs only a light foot and it responses quickly, like the brakes are under preload.

When driving under cruise control, the brakes comes lighly in and overheats.

Now my question...

Did the cam this in cause of lower MAP pressure - by wider LSA - and get the brakes in ready conditions ?

Or is it the higher vacuum for the Booster - but I think not, because Ive disabled the booster vaccum once and the brakes didnt release.

[TheMechanic]

Start with this. Was there any contamination in the brake fluid? Did the little rubber seal seem all expanded and mushy?
When the pistons were pushed in on the calipers did they push in smoothly? Did they stick or require extra force?
Did you do an ABS bleed? With a scan tool?
Does it drag on all four? Just fronts? Just rears? just one?
Did you switch to organics?
Was the master cylinder replaced? Did it bolt up without the booster/pedal rod depressing the master cylinder piston?
Did the calipers float nicely after install? Or do you live in a "rustbelt" area that freezes calipers and brake hardware?
Honestly can't see any way low MAP would cause brake drag.

[f.creek-ranch]

All Brakes are working correctly, no issue so far. No air, all bleeded professional by hand and with software twice.
Brake booster replaced twice in cause of a faulty new one - shit happens.

All 4 brakes are involved.

The hole system is inspected again and again.
All lines are inspected, tested and working fine.

Brake switch replaced.
All calipers and rotors are the correct ones, measured all.

ABS is working fine, stoppes like hell.
Ive never seen this before...

[TheMechanic]

The times that I have seen it happen to all four wheels at the same time it has been either contamination (oil, P/S fluid, etc.) in the master, the wrong master cylinder, a improperly adjusted rod, and also on an older vehicle the brake switch under the dash was misadjusted causing the pedal to be pushing slightly on the master. When the brake temps go up the fluid expands, does not have the bypass hole exposed and increased pressure in the system causing application of brakes.
fast check. Remove the caliper lid and have someone inside give a really good hard press on the brakes. When they are released you should see a squirt/movement of the fluid as the bypass hole is uncovered. No release and that may be your problem

[f.creek-ranch]

Contamination - definitely no.
Master Cyl - same failure with the genuine
I be disassembled the master and found nothing - the new comes without the bypass hole and I get a replacement for it - strange, what sometimes happens….
The rod is in placement.
Even under pedals all is in placement.

The bypass is the one I will look at. The calipers opens, when I pull them back, this was the last Ive tested on the ramp, it now its back again.
Why should the bypass work different under driving condition / cruise control?
Maybe I m trying another new master from Mopar.

Shouldnt there be a preload from ABS block when brake lights are on ? This is the reason why I thought about another fault.

The lines are all flushed and free or new.

[TheMechanic]

The bypass is the one I will look at. The calipers opens, when I pull them back, this was the last Ive tested on the ramp, it now its back again.
Why should the bypass work different under driving condition / cruise control?
Maybe I m trying another new master from Mopar.

Shouldn't there be a preload from ABS block when brake lights are on ? This is the reason why I thought about another fault.

The rod that is connected to the brake pedal lever that pushes the piston of the master usually has an adjustment for length. If it is to long is pushes on the piston and can cover the port that is responsible for releasing the pressure in the system.
The reason it can be effected by cruise is that if a light pressure is applied at the pads it will gradually create heat, expanding the fluid. If they bypass hole is blocked from the application of the rod being to long the fluid has no where to go. It will add pressure thereby increasing the application of the brakes. Like an avalanche just gaining momentum/heat making it worse.
As to preload if I am getting your question correct. There is a very slight pressure in the combination/proportioning valve if it has drum brakes. It is used to keep the cups/seals in the wheel cylinders from leaking and introducing air in the system. In disc brakes they do not have this.
Have you personally experienced the condition? Is there a chance that you have a two footed driver? Some like to "rest" their foot on the brake pedal.

[f.creek-ranch]

��
no two feet on the pedal, only for accelerating.but its ok to mention it !

drum brakes only for parking - its a 2012.

The booster has no adjustable rod and is assembled without any pressure from the pedal.

IMG_1346.png

I drove a while today and nothing is happening.

If I couldnt get rid of it by software ( displacement setting for abs) I would try a new Mopar cylinder or try to drill the return hole a little bit?no panic, I also tune weapons, Im careful!

Thank you for your time so far and I will post the reason…one fine day ��

[f.creek-ranch]

I took a look in the tire adjustment.
The circumstance is 2538. The Ram has 275/60-20 since Ive bought it and never gor a problem with the brakes.
I took on new tires on the rear and after a while on the front axle.
Seems the problem appears in this period.
I think the right cir is 2633 and the problem found ?

[LilSick]

that is almost 4" variance in rollout front to rear

dunno what that does to the brakes but the hp75 trans will not like it

[f.creek-ranch]

no, not difference tire sizes…
its all 275/60 20….only change tires, not size.

But maybe it tips the scale.

[LilSick]

My old eyes saw circumference

Good luck

[f.creek-ranch]

…no luck at all.

Brakes are getting warm again…

Change main brake cylinder again.
Brake booster is new, Abs block is new, all brake parts new.
The only old part is Abs control unit.
Abs is initialized and bleeded.
All lines are bleeding perfect.

Brake feel normal and smooth at first.

After a drive they are getting very responsive and warm.

Abs sensors are all the same data by logging

This thing is blow my mind.
Any idea is welcome !

[LilSick]

i know it doesnt make any sense but i had to shorten a push rod once

sure sounds like its long

[f.creek-ranch]

Just have done some things....

Set MBC with shims on Booster...no change.

After a while....

One wheel hub bearing is faulty - replace both with abs sensors because the ABS lamp has flickering sometimes.

After fixing this the ABS pulses sometimes again and I ask myself if there are some Gremlins in this piece of sh....

Today I have overhaul the parking brake on the left side because the left side doesnt have grip anymore.

After cleaning all I have reassemble it and the ABS pulses really a lot and ESP is making a ghost job.

I have lost my course of action in this holy sh.. of problems and ill be sure I never find the reason for the ghost braking now.

But maybe its a multiple problem of sensors and or bearings.

Unbelievable...

[f.creek-ranch]

So after taking a few drive it seems to be a problem of initializing or Voltage drop.
After a start it will happens all the time or never.

So I replace the battery without success.
Next step is resoldering the abs module and place extra ground for it.

[f.creek-ranch]

Little update.

I’ve changed the alternator - replace it with the stronger one from the Cummins. The pulleys diameter is a little bigger, so I have to replace the belt. The 8Rib doesn’t matters, fits perfect and idles a lot better with the OAP coupler.

But no change at all.
The more I try, the more I think it’s a ground problem.
I have done a lot of work on rust protection under an in the truck with different products like Brunox, Mike Sanders and Owatrol.
Never give up !

[Nycamar]

I know this is an old post.
Do you have an update?
Most of the time when I see problems like this it is a stuck caliper slide pin or not proper lubricated.
On a brake job they get neglected a lot.

[f.creek-ranch]

Hey Nycamar,

nothing new here.
I got enough work and the failure comes up seldom.
So I dont give a damn about it untill I get it on the jack for any repair.