Master Cylinder Cap Broken

Was having a strange issue where the brakes were normal and then randomly they would become rock hard with only about an inch of travel. Discovered today that the master cylinder cap broke so that it wouldn't sit flush on the cylinder anymore. I did some quick searching online and couldn't seem to find a place to just buy the cap. Every place I went online doesn't sell the cap, just the whole master cylinder, which I don't need. Anyone know of any places I can find just the cap? Or am I screwed here.

 

the cap just keeps it from splashing out, it does nothing to hold or build pressure so it sounds like you have some other problem going on besides the cap. it should work fine even if you used a baggie and rubber band as a cap.

 

Ok, so what do you think it could be? I tried bringing it to a brake place but it wouldn't act up for them. When the pedal is rock hard, if I tap the brakes, it feels as though I'm applying 50% pressure

 

just guessing, maybe the brake booster.

check the hose connections and its getting good vacuum.

I honestly have no idea how to test or troubleshoot a brake booster but does the truck run rough when the brakes act up? if so I might be losing vacuum to it.

unplug the booster hose and see if that what the brakes feel like, if so you need to determine if you are losing vacuum to it somehow, if not all I can think of is its internally bad and swap it for one from salvage yard.

 

Nah it idles fine when braking.

 

what you describe sure sounds like the brake booster stops working on you.

to simulate pump the brake with the truck off and the pedal gets hard as a rock, start engine so it gets vacuum and its soft and easy again, so you can see this is a logical cause to look at for your issues.

also without the booster you have no power for the power brakes so in fact you have manual brakes so they wont stop very well

 

I stop pretty well, just having that random hardness issue. Was afraid you'd say it was the booster

 

I agree, it sounds like a brake booster problem.

As far as the reservoir cap, you can get a new one from Toyota for $10-15. Just put your VIN in on an online Toyota parts dealer and look in the Brake Master Cylinder section, or go to a local dealer. This won't solve the hard brake pedal problem, but you don't want to contaminate the fluid with dirt or dust from a broken cap.

 

Brake vaccum line has a check valve in it.

Much more likely the failure (failing?) point than the actual booster, particularly since it's intermittent.

 

How do I check it through the valve?

Update: Went to the car wash after work. As I'm sitting in line for the car wash and the brake pedal was hard. Went through the car wash, and the pedal was normal again. But after a while, it did get hard again.

 

That's what she said
Seriously, as said previously it sounds like a booster.

 

Haha i was waiting for someone to say something. I'll do an inspection before I replace the booster as money is kind of tight. Still have a carrier bearing and u-joints to replace.

 

http://www.classicperform.com/TechBook/BrakeTroubleshoot.htm#testbooster

 

Thank you good sir!

 

For the good of the order, be sure to let us know the resolution please.

 

Sure thing. I'm going to do these tests tomorrow after work