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I recently acquired a 2007 Ram 1500 4.7L truck. The brake pedal is 'spongy' (almost to the floor) on the first pump but I get a firm and solid brake pedal with accompanying stopping power on subsequent pumps.

I've bled all four corners and checked the vacuum hoses for leaks. There are no weeping or outright leaks in the master cylinder to (4) disk brake calipers.The master cylinder visually appears to be in good shape but I haven't torn it apart yet.

The rear brakes use a disk brake for stopping power and a drum brake for the parking brake. My wandering mind is starting to think that this may be the problem area.

Before I rip out and replace everything from pedal to all four tires, I'd like to ask if I'm missing something a little less obvious.

fwiw, this is a 4.7L 6 speed manual

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  • Classic symptom of air in the system, bleed it again. Only other one I have ever ran into that bleeding could not cure was a 2001 chevy pickup that had a bad abs unit.
    – Moab
    Commented Sep 24, 2019 at 15:26

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I agree with what @Moab said in the comments: This appears to be a bleeding problem.

I'm not sure what method you are using to bleed your brakes, however I've recently found the virtue of using a vacuum operated brake bleeder. This is the type which you plug one end onto the brake bleeder fitting and then suck the fluid through to a reservoir (you can pick one up from Harbor Freight for around $20, IIRC). As long as you have a decent air compressor, it works really well. The reason I'd suggest using this is, I had to bleed my son's clutch system as it WOULD NOT bleed manually (I tried for over four hours to get it to bleed without any luck). With the auto brake bleeder, it took me longer to setup everything up than it did to bleed it, and it did it the first time. It was amazing to me how well it worked. The reason I believe it did, is because the bubbles (or air in the system) will follow the vacuum source. If you cannot get the thing to bleed manually, using one of these is a very good choice.

As for your other thought, while the disk brake system and e-brake system are on the same rotor, they are completely separate systems (on most vehicles, which includes your Ram). There's no reason in my mind why one would cause problems for the other, except if it's so screwed up the rotor is out of sorts. It'd have to get really ugly before that'd happen.

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