Hard brake pedal

[rreegg]

Past few weeks I’ve been getting a stiff brake pedal after the truck sits for a few hours. After start up the brake pedal had returned to its normal feel.
Earlier today I noticed the brake pedal started to feel a bit hard to press while driving.

This brake booster and master cyl are new as of a couple years ago and about 10k miles. Replaced these parts because previously the brake pedal was hard and would take a few minutes to get soft again.

From what I’ve read these symptoms are either brake booster, vac leak, or vac pump.

Anyone have tips on trouble shooting steps to determine what’s going on now? Not quite sure which vacuum lines to remove to check for pressure.
If anyone has pointers or other threads o check out it’s much appreciated!

 

[rreegg]

Just pulled the vac line from the top of the brake booster and it pulls/suck on my finger pretty good. Don’t have a vac gauge but it seems to be working alright at least.
Was doing some brake work the past few month and not sure if I damaged the booster or something in that process.
No brake fluid leaking anywhere or fluid level dropping from what I can tell

 

[rreegg]

Ended up getting a vac gauge and the line at the brake booster reads ~25 inHg so am assuming the vac pump is good. If issues persist will probably see if I can get a warranty replacement on the brake booster/master cylinder unit as it’s from Oreilly’s (Órales).

 

[IDIBRONCO]

That's good vacuum. I would guess that it's your booster. This is why I like to have a vacuum gauge permanently installed in my truck.

 

[rreegg]

That’s a great idea and I understand the importance of that now.
Was able to fish up the receipt at the store and turns out the booster is reman so less a surprise it’s going out now.

The brake quality has deteriorated dramatically in the last 20 or so miles driven. Was starting to double guess myself but the pedal being hard after sitting overnight was kind of an obvious symptom

Gonna try to leave the master cylinder be for now and see how things go

 

[mf7lakes]

What about the check valve on the brake booster to which the vacuum line is attached ??? Does it hold vacuum ?

 

[frankenwrench]

And did you pull vaccume values just before the brake booster? Had a similar issue on a few of my trucks and it turned out to be a leak in another vaccum on one truck, easy fix replacing a rubber hose, and the other was the plastic vaccume junction had a Crack in it, which I stole one off of one of my other non running parts wagons. Both simple and free to check now that you have a vaccume guage

 

[rreegg]

Thanks for the suggestions this morning. I swapped the booster last night and it didn’t really change anything. So… will keep looking into things.
Brake is still firm at startup after sitting overnight. Not sure if there’s some environmental thing happening now it’s hot out, but just driving on the freeway for an hour the brake pedal is super firm, more so than it was last night after swapping the booster. But the braking action is real good, but pedal seems really firm not sure what’s up.

Will look more into the check valve and vac system

The brake pedal doesn’t seem to emit the wheezing sound when pushed now though, but seems that’s kind of a common thing for healthy brake system.
Honestly can’t really make heads/tails of the brake system on this truck, it’s the only part of the truck that’s given me grief and still can’t get it consistently solid

 

[Cubey]

I wouldn't worry about firm from sitting overnight. unless it's randomly or totally firm when driving (no power brakes from no vacuum) it's probably fine, booster wise.

I've had vac pumps die twice and leave me with a hard pedal, in a 27ft motorhome, while towing. That's when you stomp with both feet and lifting your butt off of the seat to apply pressure. I don't weigh a lot (150ish) so yeah that was certainly interesting. Downshifting can help too, with extra engine braking.

 

[rreegg]

Yeah wasn’t worried about the firm pedal initially and was just keeping an eye on things. The parking brake works OK but not perfectly and one time the truck rolled back a few feet and into a tree while I was starting the engine with clutch in… so it is a safety concern. Usually chock the tires or use a curb when possible but not always and was just caught off guard that one time.

 

[rreegg]

Plus I’ve a habit of forgetting chocks around and driving off but that’s purely operator error. Have considered putting a long lanyard or rope around them to be able to remove them from the cab but..

 

[IDIBRONCO]

Plus I’ve a habit of forgetting chocks around and driving off but that’s purely operator error. Have considered putting a long lanyard or rope around them to be able to remove them from the cab but..

Just use rocks or tree branches. That way it's no big seal if you leave them behind and there's plenty of replacements.

 

[rreegg]

Just use rocks or tree branches. That way it's no big seal if you leave them behind and there's plenty of replacements.

Haha definitely keep some spare rocks in the cab surprisingly never leave those or 2x4s behind for some reason