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2008 Sentra brakes lock temporarily


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Caseyjones
New User

Oct 5, 2020, 5:49 AM

Post #1 of 9 (189 views)
  post locked   2008 Sentra brakes lock temporarily  

2008 Nissan Sentra 60,000 miles. Brakes locked up after driving for 20 minutes. Stopped, waited a few minutes, and drove home. Two days later the same thing happened. I disconneted the vacuum hose that powers the booster. With my mouth, not an air hose, I can't blow air into that hose, nor can I suck any air out of it. All mechanical parts of the brake system at each wheel look ok.
Various sorces said to check the brake booster check valve. Various parts stores do or don't list them, but online (questionable?) sources show how to replace it. Nissan doesn't have one nor do they admit that it has one, but a Nissan dealer said it is internal to the to the booster. So, in conclusion, do I need to replace a $280 booster because a $20 check valve went bad?
Casey


Tom Greenleaf
Ultimate Carjunky / Moderator
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Oct 5, 2020, 6:03 AM

Post #2 of 9 (171 views)
  post locked   Re: 2008 Sentra brakes lock temporarily  

? Not sure which way you are blowing or sucking to see if a hose is clear? Toward engine or booster? Doesn't totally matter for a second here brakes are NOT meant to lock up if you meant stuck in BRAKING mode as in locked? Many defaults that wouldn't happen up there could from one and feel like that and free up when cooled down??
I doubt the booster at all for right now still would want to know check valve works. Just turn engine off and exhaust the vacuum in it. Now pedal is harder or will be pump it a few times. Hold brake pedal and start engine feel it power up foot lowers towards floor some more.


BRAKES work without boost just really hard to push if that's the trouble is more of a bad booster problem but also leaking vacuum I would think most or check valve really clogged.


Other is if hose to vacuum source is bent, full of oil sludge or not clear to source (most intake manifold vacuum) just removing that when running engine would stall out.


Very few known to me use a vacuum pump to source vacuum haven't noticed if doing that again.


More likely for now a problem with a hose at a wheel locking a caliper noticed lots more if a front would/could lock brakes and be intermittent that wheel would be hot only maybe two of them check and go from there if so.


Sorry for lots to read if the brake fluid was topped off with an oil this also could be the problem so if that's possible say so! Tom



Caseyjones
New User

Oct 5, 2020, 6:28 AM

Post #3 of 9 (169 views)
  post locked   Re: 2008 Sentra brakes lock temporarily  

Toward the booster. If the check valve is ok I should be able to suck air out of it be cause that's what the engine does. I shouldn't be able to blow air into it because the check valve is preventing it. That little valve allows the brakes to work for a time or two if the engine should suddenly stop running. I have no idea why that check valve would be able to apply the brakes suddenly, as in "lock up", but that's what the customer said and that's what I "learned" using that "often suspicious, sometimes reliable, occasionally funny" source called The Internet". Am I being reckless because of that? Perhaps. But then I've been fixing cars, and about everything else, for more decades than you might think. I've not run into every kind of problem, but there has never been one like this.
Casey


Tom Greenleaf
Ultimate Carjunky / Moderator
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Oct 5, 2020, 6:45 AM

Post #4 of 9 (163 views)
  post locked   Re: 2008 Sentra brakes lock temporarily  

OK: So it's what a "customer" say to YOU. The word "lock up" has us in a twist. I would take that as brakes are ON hard like can't move the thing but may mean "feel" is hard like no boost. Your check is correct IDK for sure how assorted check valves MIGHT only allow vacuum more than your mouth isn't much - no puns please it's serious.
Yes, the idea is checked vacuum does NOT leak out unless pedal is touched by rights holds a "charge" of vacuum for days or longer? If not where did it go?


Other things is it has moving parts inside once were rebuildable if you've been at this diaphragms leaked could crimp in a new one!


One rare bird is the gap of pedal "lash" or free-play isn't adjustable to anything anymore you might get a vehicle with a WRONG master or rod so it thinks brakes are dragging not returning fluid back, heats up and self applies brakes! When it cools they are fine for a while - this happened once since the dang 60s to me non adjustable but new master wasn't made properly ended up why.
Other is bent, broken or who knows of mechanical pedal and how it pivots??
Now perhaps get a better description from driver/customer as to what really happens if it's otherwise fine to you a mess up of use of words misunderstood.


Last: If any brake fluid in reservoir doesn't wash off a finger (AYOR use glove?) with plain water it's contaminated! Oil wouldn't now the chance of rubber everywhere bloating OMG you don't want that - a disaster! Tom


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Oct 5, 2020, 8:16 AM

Post #5 of 9 (144 views)
  post locked   Re: 2008 Sentra brakes lock temporarily  

I think you're barking up the wrong tree.

It's very easy to find out if the booster is the problem. Simply shut the car off. If the booster is the problem, the brakes will release.

It could be the adjustment of the push rod or contamination of the fluid.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Double J
Veteran / Moderator
Double J profile image

Oct 5, 2020, 8:24 AM

Post #6 of 9 (142 views)
  post locked   Re: 2008 Sentra brakes lock temporarily  

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My query to you is , Can you duplicate it?
If so, are all 4 locking up?
A quick look at the Nissan Parts shows what appears to be a check valve in the booster but no part number
Must not be serviceable separately.
I would have to see it in person not just a generic image from Nissan
If it has one, ,run down to a U Pull and snatch a used one from a junk car
I'm not convinced yet that's your problem


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Oct 5, 2020, 8:29 AM

Post #7 of 9 (136 views)
  post locked   Re: 2008 Sentra brakes lock temporarily  

One more RARE something: Is firewall bent? Did customer NOT tell you something? Shouldn't be this much trouble, Tom


Caseyjones
New User

Oct 6, 2020, 7:06 PM

Post #8 of 9 (105 views)
  post locked   Re: 2008 Sentra brakes lock temporarily  

Oooops, the driver mis-reported the problem originally. The star wheels in the rear drums were worn to the point that the automatic brake adjuster didn't automatically adjust at all. Losing that function eventually made the rear brakes basically useless. Braking with only the front brakes placed a lot of responsibility on the traction for each wheel being equal. More traction on one side than the other (on wet pavement) put the car into an interesting path not intended by the driver. To the driver, a wheel (or wheels) sliding felt like the brakes had stuck, thus the erroneous report. Adjusting those brakes fixed the problem but not for too long as those star wheels need to be replaced.
Casey


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Oct 6, 2020, 7:44 PM

Post #9 of 9 (100 views)
  post locked   Re: 2008 Sentra brakes lock temporarily  

The DRIVER misreported?

So, you were trying to fix a condition that you never even saw. Sure didn't sound like that when you asked the question.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.







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