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Little red carAs safety precaution , pump the brakes several times before you drop the car in gear and take off .
You can also use flammable break clean to hunt for leaks .
God bless
Wyr
As safety precaution , pump the brakes several times before you drop the car in gear and take off .
You can also use flammable break clean to hunt for leaks .
God bless
Wyr
I typically use starting fluid or brake cleaner to find vacuum leaks. Start the car, and spray the lines, go slow and don't spray anything that is hot or sparks. If you hit a leak in the system, the car idles up. If you suspect a spot, you can immediately go back over it and it will idle up again.
I've been reading the thread. But it sounds like you are mostly covered with possibilities.. But since my first post i the thread (#6) i said check for vacuum leaks. So I am glad you are.
Will do WyrTwister. Last night I did pump the brakes with the engine off and the pedal was harder to push as it should. Turned on the engine and pedal goes down. I tried duplicating the problem and no results. Fluid level on the master cylinder is good and no signs of leaks. I did see your post petrified.rabbit but I used a spay bottle with water to check for vacuum leaks. Did find one and fixed it but it was at the PCV valve connection. I soaked the booster hose and the other ones but I couldn't hear anything. I'll report back with my findings with the propane one. I may even try it with carb cleaner. Yesterday I went to Harbor Freight and picked up a vacuum gauge just to measure how much vacuum I am getting off the engine. I might even try to hook it up to the car between the engine and booster and tape the gauge to the windshield. Then I will drive the car around for week. Of course this is if I don't find any leaks and having the same problems after replacing the hoses. There could be a chance that the engine is not producing enough vacuum. So if and when I exhausted all my options then I will install a electric vacuum and tie it to the booster. This is of course the last resort lol..
Just in case anyone needs it here is the routing for the vaccum hoses on my 2005 Aveo LS Hatchback. I see that there is a vacuum hose to the climate damper? Is that like the air blender that blends the air from inside and outside? I have no idea what that is.
If the engine is running OK , vacuum should be max ( more or less ) at idle . As you open the throttle , vacuum should fall ,Originally Posted by jamesd
proportionally .
I have read that observing a vacuum gauge can reveal a lot of useful info .
God bless
Wyr
The engine ( green ) is pulling air in , past the throttle plate ( yellow ) . This restriction , by the throttle plate , results in a vacuum in the intake manifold ( Blue ) .
The climate control ( brown ) does use vacuum from the intake manifold ( blue ) .
As does the brake booster ( red ) .
This diagram does not show any check valve in the brake booster system . It may have one built in ?
Until you get the problems corrected , I would make it my SOP to get into the car , start it & pump the brakes until they are OK , before I put the car in gear and drove off .
The valve cover and connecting hose ( purple ) I am guessing represent the PCV system ? I think you said you worked on that ?
The vacuum tank may or may not have a check valve in that system ? Check the tank for cracks / leaks , also .
The last major system I see is the evap control system . You could also have leaks there or valves that are not opening or closing properly .
God bless
Wyr
If you pump the brakes , with the engine off , you quickly dissipate any vacuum stored in the brake booster & it revert to pretty much what it would be w/o power brakes .
Power assist will not be restored until the engine is started and vacuum is restored , from the running engine .
God bless
Wyr
Last edited by WyrTwister; 05-24-2016 at 08:32 PM.
Wow that's pretty cool how you highlighted them! Thanks! Yeah last time I found a vacuum leak at the hose end of the PCV valve. I might replace the PCV valve when I do the valve cover gasket job. It's leaking oil all around the valve cover. More like seeping but still I need to fix that. I got the valve cover gasket for free at Autozone. I cashed in my reward points lol..
Last edited by jamesd; 05-24-2016 at 09:46 PM.
Just used Paint .
A PVC valve is suppose to all a specific amount of air ( and fumes ) to be sucked from the engine and burned . That way it is not just vented to the atmosphere . They usually rattle when you shake them . But , as inexpensive as they are , if in doubt , replace .
I have the impression the new vacuum booster is behaving the same as the old one ?
Just wondering what the ID of the new vacuum hose to the booster is ? And if you can find an inline check valve to fit ?
My late Dad had a Ford LTD we put an after marker cruse control on . The car was geared high and when climbing a long steep hill , the cruse control would not hold speed .
In those days , the cruse control was electrical / vacuum . What was happening was , as the cruse opened the throttle , manifold vacuum would fall . It would reach the point where vacuum dropped to the point where there was not enough vacuum to operate the vacuum servo , to open the throttle any more , to maintain speed up the hill .
I did one or both of 2 things . Added a vacuum reservoir or added a check valve in the line connecting the system to the intake manifold . This solved the issue .
But that vacuum hose was maybe 1/4" ID . Looks like your hose to the booster is more like 1/2" ? Not sure you can find a check valve that large . For an acceptable cost ?
God bless
Wyr
PS When I was working on our 91 Caprice , I received a rewards card in the mail , from O'Reilly Auto Parts do something like $ 5 .
Last edited by WyrTwister; 05-24-2016 at 10:34 PM.
A 1/2" or at least larger check valve should be easily had, as most brake boosters have them (of some sort).
I just re skimmed the thread:
We are certain now this is all on the booster side, the car always stops, it just take more pressure to the pedal to do so, correct?
If you replaced the both the booster and master cylinder (did you do it together?) check for leaks around where the master cylinder bolts to the booster, I wish there was also an easy way to check the pedal side, but spraying propane or brake clean in the interior of a running car is just bad...
You might need the seal between your two new pieces to be gasketed, RTV, something. It could also be a bad, or wrong booster. I don't have access the gm parts database. But on some cars a NON abs booster is different than an ABS booster. Sometimes th cheaper aftermarket parts say them fit all kinds of things when they really don't. Even though they go it.
If you have a vacuum gauge now, do you also have a vacuum pump? I would pull vacuum through the check valve to the booster and see if it leaks down. If it does, it might narrow your problem. Unfortunately you can't reverse pressure to see if it blows out, because the tight damage the diaphragm.
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2016 Chevrolet Aveo