Vaccum Leak?
#1
Join Date: May 2005
Location: MI
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Vacuum Leak?
When i first start my truck up and go down the road, my brake pressure is crap. If i "get on it" (upon acceleration - 4-5grand), then come to a stop, my brake pressure is much better. If i drive on the expressway for 15+ miles, the brake pressure also gets alot better - even better than accelerating like crazy.....Any ideas? Im probably going to have to check my vacuum lines..
Im thinking this *might* have something to do with that HUMM noise i ONLY have had in the summer as well...
https://www.ranger-forums.com/forum2...ht=vaccum+leak
Im thinking this *might* have something to do with that HUMM noise i ONLY have had in the summer as well...
https://www.ranger-forums.com/forum2...ht=vaccum+leak
Last edited by 01xltranger4x4; 01-22-2007 at 07:00 PM.
#3
#4
To summarize:
poor brake assist after an engine start;
improves after a high vacuum decel:
improves after a medium vacuum cruise.
How about a leak in your brake booster? It has a fairly large volume that has to be "pulled down" by engine vacuum. In a healthy truck, you can feel that happen through the brake pedal right after the engine starts. If there is a leak in the booster diaphragm or a leak/restriction in its supply hose, it will take longer to build the vacuum necessary for power assist.
poor brake assist after an engine start;
improves after a high vacuum decel:
improves after a medium vacuum cruise.
How about a leak in your brake booster? It has a fairly large volume that has to be "pulled down" by engine vacuum. In a healthy truck, you can feel that happen through the brake pedal right after the engine starts. If there is a leak in the booster diaphragm or a leak/restriction in its supply hose, it will take longer to build the vacuum necessary for power assist.
#5
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Originally Posted by rwenzing
To summarize:
poor brake assist after an engine start;
improves after a high vacuum decel:
improves after a medium vacuum cruise.
How about a leak in your brake booster? It has a fairly large volume that has to be "pulled down" by engine vacuum. In a healthy truck, you can feel that happen through the brake pedal right after the engine starts. If there is a leak in the booster diaphragm or a leak/restriction in its supply hose, it will take longer to build the vacuum necessary for power assist.
poor brake assist after an engine start;
improves after a high vacuum decel:
improves after a medium vacuum cruise.
How about a leak in your brake booster? It has a fairly large volume that has to be "pulled down" by engine vacuum. In a healthy truck, you can feel that happen through the brake pedal right after the engine starts. If there is a leak in the booster diaphragm or a leak/restriction in its supply hose, it will take longer to build the vacuum necessary for power assist.
I did check this vacuum line a few days ago and everything appeared to be fine - plugged in, etc. So how could i tell if there was a leak in the booster or a restriction in the supply hose?
Thanks for the help
#12
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Location: MI
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Originally Posted by rwenzing
To summarize:
poor brake assist after an engine start;
improves after a high vacuum decel:
improves after a medium vacuum cruise.
How about a leak in your brake booster? It has a fairly large volume that has to be "pulled down" by engine vacuum. In a healthy truck, you can feel that happen through the brake pedal right after the engine starts. If there is a leak in the booster diaphragm or a leak/restriction in its supply hose, it will take longer to build the vacuum necessary for power assist.
poor brake assist after an engine start;
improves after a high vacuum decel:
improves after a medium vacuum cruise.
How about a leak in your brake booster? It has a fairly large volume that has to be "pulled down" by engine vacuum. In a healthy truck, you can feel that happen through the brake pedal right after the engine starts. If there is a leak in the booster diaphragm or a leak/restriction in its supply hose, it will take longer to build the vacuum necessary for power assist.
Before i started the explorer, i put my foot on the brake pedal and fully depressed it. I then started it and the pedal felt like it depressed even more, even felt a little squishy as this happened.
Tried it in the ranger and the first time i started it with the brake pedal fully depressed, nothing happened - pedal didnt depress more or feel squishy. But the second time i tried it, the pedal did depress down a little but not like my moms explorer. The pedal did feel a bit squishy as it depressed but only depressed 1/2 as much as the explorer.
I guess i could still have a vacuum leak in the booster, just a minor or 'unpredictable' one?
#13
There is a check valve in the booster that tries to maintain full vacuum in the booster even though the vacuum varies in the intake manifold. Maybe a small amount of vacuum was trapped in the reservoir on the first start and didn't have time to leak out before the second start. Just guessing though.
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