Sinking brake pedal

[don340-4]

I need to get some information before I take my truck to the dealer, I have a 2012 Ram 1500 R/T purchased it new has 25000 miles on it, great condition always garaged, for the last couple months it has been scaring the hell out of me, first depression of the brake pedal it will sink to the floor with no resistance, pedal comes up depress again got brakes with a solid pedal. I am really considering getting rid of it, I am an old guy and retired, was hoping this truck would last me the rest of my life, even if the dealer works on it and charges me a bundle I don't think I will ever trust the brakes again. Hey guys anyone have any ideas? Brake fluid is full, pads are original like new, no mods to this truck whatsoever.

 

[McBroom]

Its a vaccum leak on the power booster. Small cheap fix. I wouldn't sell the truck just cause it needs a little service work on it.

Blue Mule

 

[don340-4]

McBroom, Thank you for the information, I will check out the booster. Semper Fi 1955 to 1959 USMC

 

[Tach_tech]

To check the brake booster, start with the truck off and pump the brakes till the pedal is very stiff. This will deplete any vacuum left in the booster. Next, place your foot on the pedal then start the truck. The pedal should drop a few inches as vacuum builds up. If you then shut the truck off you should get a couple presses of the brake pedal before it gets stiff.

 

[don340-4]

Tach tech, Thank you for your reply to my post, I did the booster test as you suggested and it responded exactly as you described, 3 depressions after turning the engine off. This problem is so intermittent it almost seems like an electrical failure in a relay or switch, does the brake light switch have any effect on the antilock system? or is there a relay involved, I know this problem is not going to occur when I take it to the dealer, they will tell me the brakes are fine, they will fail after I leave the dealership.

 

[Tach_tech]

Brake light switch won’t have anything to do with it.

It could be an issue with the master cylinder itself as well, or there is air in the system.

Make sure the vacuum line to the booster isn’t cracking or brittle as well.

 

[co-pilot]

I agree with the above post.....either a bad master cylinder or booster

I wouldn't get rid of the truck because of it, parts sometimes go bad.....

I had a bad master cylinder on a year old Chevrolet

 

[Octane]

You could have a bad master cylinder.Check the vacuum booster lines valve,the little one way valve that plugs into the booster also

 

[McBroom]

McBroom, Thank you for the information, I will check out the booster. Semper Fi 1955 to 1959 USMC

Semper Fi
88-01
0317

Blue Mule

 

[don340-4]

Ok guys here is the latest, took my truck to the Dodge dealer where I purchased it back in 2012 new, they had the truck for a week, flushed the system, bled the brakes twice, then they told me the brake booster was bad and needed to be replaced, so they replaced the booster and told me all fixed, $750.00 later brakes still fail as before pedal goes to the floor once with no resistance second pedal press got brakes, does this mostly when hot in stop and go traffic. Scary! How much $ is it going to take to fix this thing.

 

[NJMOPAR]

It still has the original pads & rotors after 8 years?
That might be your problem right there.
Everything is so thin the caliper pistons are going way out on first press, then filling with fluid for the 2nd so pedal's higher.

 

[don340-4]

Thanks NJMOPAR, true my truck is 8 yrs old, just has 25000 easy miles, service advisor told me I had 80% left on the pads.

 

[averageguy]

Before the dealer smooth talks you into a new truck and gives you $2000.00 trade in on your garage kept 25,000 mile truck, I'll take it off your hands for a cool $2500.00 to help you out.

 

[don340-4]

I appreciate your offer, can you do a bit better?

 

[Burla]

OEM brake fluid is not terrible good quality, and when it gets hot it gets thin, and can cause this issue even with new fluid. If you get a brake fluid similar to redline 600 the fluid stays thicker when hot, so keeps the back pressure good. It isn't a waste that they flushed you system, that cleaned the system out, and you can do a fluid upgrade redline 600 15 bucks x 4. Or other fluids, look for high dry and hot boiling temps, here is a list. You want dot 4, i think dot 3 works and may be what the application asks for, but bottom line dot 3 and 4 are compatable/interchangeable and dot 4 performs better. Just get 400 wet boil and 600 dry boil, thus is why they call it redline 600. You need 4 pints, you can even do it with tires on. If you are gonna do this let me know, I'lll give you more info.

 

[Burla]

It doesn't sound like pads or rotors, or even caliper. So it is something with the internals, master cylinder, vacuum or abs or something, possibly fluid. If you are local to sonoma, I can do that flush for the fun of it.

 

[huntergreen]

It doesn't sound like pads or rotors, or even caliper. So it is something with the internals, master cylinder, vacuum or abs or something, possibly fluid. If you are local to sonoma, I can do that flush for the fun of it.

Damn nice of you to offer that.

 

[huntergreen]

Ok guys here is the latest, took my truck to the Dodge dealer where I purchased it back in 2012 new, they had the truck for a week, flushed the system, bled the brakes twice, then they told me the brake booster was bad and needed to be replaced, so they replaced the booster and told me all fixed, $750.00 later brakes still fail as before pedal goes to the floor once with no resistance second pedal press got brakes, does this mostly when hot in stop and go traffic. Scary! How much $ is it going to take to fix this thing.

Don, just my 2 cents, but why aren't you taking this to local independent mechanic with a good trout ? It would be cheaper and most likely fixed on the first attempt.

 

[Burla]

Some things are just fun to do, now if wanted a cam swap, barking up the wrong tree

With him being out 750, I think the dealer should make it right.

 

[don340-4]

Wow you guys really gave me a lot of things to think about, Buria thank you for your offer, I am in So. Cali. nowhere near Sonoma, huntergreen no local mechanics I would trust working on my truck. I am leaning towards replacing the ABS pump, seems to be a bad hombre.