Moved from brakes suspension and steering section....

First post, hope to learn alot from you guys....

Heres my problem.

Intermittent power brakes, happened while driving. Noticed there is power when brakes are applied while engine is above idle, but when it idles down while driving, no power assist.

Troubleshot with girlfriends dad. Hooked vacuum pump directly to brake booster, (disconnected vacuum manifold from system), and still no power at idle. I feel vacuum from line from pump is on my finger. He suggested that I replace booster, just want to see what you guys think.

I know the pump is creating vacuum, just dont know how much! Is there a spec as to what the pump should produce? Should I test it with some kind of gauge before I go replacing parts?

The booster itself has no visible cracks, holes, or corrosion, thats why her dad suggested replacing booster. Told me the diaphram inside can wear out letting vaccum pass.

I notice that on the pump the round thing, I guess its where the pump gets its air, is greasy. Figure its power steering fluid getting sucked up from the area where the resivoir is. Girls dad said that isnt the problem.

May or may not help, but the cruise has been intermittent sine I bought truck. Sometimes it works, sometimes it dont. Sometimes it even turns off while driving, figured it was a vacuum problem, just never dug into it.

Thanks for any input in advance, I got to fix it this weekend, and dont want to make a handfull of trips to the parts store!

Higgy

 

its your vacuum pump more than likely. Minimum vacuum is 18 in hg. It will still feel like vacuum but its not enough. a boost issue won't change with idle unless its a small leak.

 

I guess I will drive it to the parts store and see if I can borrow a vacuum gauge and test it before I buy a part. Thanks again.

 

x2 what Tim said, Vacuum pump.

Your CC is probably the sensor on the end of the master cylinder. They are prone to failure. Unplug it and see of there is fluid in the connector cavity. It should have continuity on it all the time...it opens when you step on the brakes. I would just replace it because they were re-called for starting fires on gas engine vehicles. No fires on diesels that I know of.

 

Just to throw something in here. My CC shuts off when I use my blinker. My diagnosis is the Multi function switch since sometimes when I turn on the left blinker the inside and front blinker don't blink but the rear does. Strange huh? just my .02

I agree start with the sensor at the end of the master cylinder first. They are cheap.

Also Welcome to FTE.

 

Neal on your MFS remove it from the truck and hose it down really well inside and out with brake cleaner. It will probably work like new after you blow it clean with air and put it back in.

 

REALLY ??? I didn't think of that. I just assumed the contacts were going bad or getting worn thru. I will try that, Thanx Tim.
I assume brake cleaner or contact cleaner will work.

Sorry for the Hi-Jack

 

yes either will work, I think brake cleaner is a little more harsh but thats what I have used in the past with good results. Not really out anything if it doesn't work.

 

Yes that is true. Thanx. Reps sent.

 

Thanks again for the input guys!
I'll report back tomorrow or sunday!

It's cool about the hijack, Neal. I learned something from your question too!

 

Thanks to those who pointed to the vacuum pump. I ONLY had to go to 5 different parts stores to find the part, all city driving without power brakes! To top it off, I didn't have the right kind of puller to swap the pulley, so I had to run up to a local shop and get it swapped, no charge, so that was cool. Thanks again everyone!

 

Glad you got it fixed Higgy .... no brakes is not fun.

I ditched mine and went hydroboost a while back. No more pumps die'n for me.