Brake Question - Normal behavior?

[anhizer]

I had the truck (its a 1998) in the shop for an alignment and the tech noted that the brakes felt very soft. I mentioned something about electronic boosters on the 100's and he said 'he drives them all the time and these felt soft'.

I paid close attention to the brake feel and noticed this:
- first get in the truck (off) and press the pedal it goes to the floor, maybe a little resistance at the bottom of the stroke. This seems to happen after the truck has sat for a few hours.
Turn the truck on and it starts to get firmer, i think i can hear the booster running.
Pull away and 1/2 a block later hit the brakes and they feel firm. Typical of other cars i have.

Sitting at a stop light the pedal is -FIRM- half way down. It feels "normal" to me. If I MASH on the pedal (After i have come to a stop) i can get it to go to the floor, but I have to push quite hard, much harder than i would under normal usage. I don't sense any pedal droop either.

Is this normal? Im thinking the tech noticed the pedal feel at start-up and didn't pay attention after that, but maybe im wrong and i need to fix something? At minimum ill probably get a fluid flush performed. The pads and calipers visually look fine and have quite a bit of material left on them.

 

[Traskew3]

Mine is a 98 and does the same thing!! I always notice it!! When I first got it the dealer adjusted the rear caliper pins and that helped some...

 

[TXLX100]

I'm not sure exactly what your 100 is doing, but sounds like the issue I'm having. The pedal in mine is soft and have to go to 3/4 depressed at least to really get it to stop. If I depress the pedal, let off and then depress again the brakes are firm all the way to a stop.

I bought a new master cylinder and some other bits that looked like could be replaced. I haven't rebuilt it yet, but hopeful it will solve the problem. See this thread and search the forum for loads of brake information.

https://forum.ih8mud.com/threads/master-cylinder-rebuild-diy.406533/#post-5791308

 

[anhizer]

I don't know that my truck has the two pump issue, but it might be in the early stages of it. From what you describe it seems like yours is exhibiting the master cylinder leak by which is fixed with a rebuild.

On my 100 I don't think i see a significant difference between brake application #1 and brake application #2 as im pulling up to a stop. If im travelling at 35mph and need to stop i just gradually apply the brakes until i stop. At this point the pedal is approximately half way down and is firm. I can force it to the floor, but that takes quite a bit of effort.

The only thing that its doing that i consider possibly questionable is the loss of pressure when its sitting not running. Braking seems to be fine otherwise.

 

[TXLX100]

Could be nothing is wrong at all. You could say 100 brakes are soft, especially if you compare them to a car. The 4runner we had definitely did not have soft brakes and took a minute to get use to. I'd definitely get the fluid changed if it's been a couple years or unknown when last done. Brake fluid doesn't deteriorate fast, but you'll know when it's toast.

 

[Traskew3]

It was the first "issue" I noticed when I test drove it and made me pull into a repair facility with the auto brokers assistant with me! Granted, I had never driven a 100 series before but I have had plenty of rentals and other cars to know that the brakes felt softer than what I was used too...

 

[anhizer]

Just wanted to follow up on this. I continued noticing a very soft pedal after the truck had been sitting. I decided to take it to a local shop to have them check it out. They confirmed that the master cylinder was bad. I opted to replace it, though i saved the old one to rebuild so i can have a spare. It never got to the point where the brakes needed two pumps to get a firm pedal, but knowing how these behave with a bad MC if the booster goes out i figure better safe than sorry.

 

[nnnnnate]

How far does the pedal travel before you start to feel resistance and the vehicle starts to slow?

 

[anhizer]

After letting the truck sit overnight the pedal starts to get firm at around 1/2 way down. It doesn't seem to ever get hard like it would in a traditional master cylinder. When the truck is running the pedal gets hard in the first 1/3 of pedal stroke but if I really push I can still make the pedal go to the floor. Hope that helps.

 

[dnp]

Both of the GXs we've had have had sort of a weird pedal feel, and my 80s have had a mushy pedal from time to time, but I've never experienced anything but a nice, firm pedal in a 100 (and I've had several of them). If the pedal feels mushy or has a long travel, that's not normal, and I'd get it diagnosed.

 

[nnnnnate]

I've got some travel before it seems like the brakes engage. Once driving I get used to it but when going from another vehicle to the 100 it take a bit to get used to the feel. It usually makes me jam on the brakes rather than have it be a smooth engagement. The pedal doesn't dive to the floor it just takes a little before anything happens.

 

[TXLX100]

^You might try putting a new piston in the master cylinder. It worked for mine.

There is a rebuild thread here and a write up in the FSM.

 

[OG 91 LC]

From my experience:

1. Brakes feeling hard to push down? Needing to use both feet to stop the vehicle?

You need a new brake booster.

2. Brakes are feeling squishy; spongy; pedal goes way down?

You may need a new master cylinder.
Check brake fluid levels. If brake fluid levels are low there may be a leak in the system. Check brake lines. Def have it diagnosed.

I drove my 80 a few weeks back with brake booster on its way out. Scary stuff.