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Old 08-13-2012, 08:51 PM   #1
Roysneon
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Brake booster leaking vacuum. bad booster or check valve

My brake booster is hissing away, I think it's leaking. The brakes feel just fine, but it's something that's on the list to fix up. Lately the idle is rough. Runs fine any other time. Would the booster leaking rob vacuum from the engine? Is that how it works? Would a bad check valve in the line from the intake manifold to the booster cause that? When I run the car with the intake manifold to brake booster port blocked off the car idles super smooth, but obviously no brake assist.
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Old 08-14-2012, 05:39 AM   #2
jlevie
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A bad check valve won't cause a hissing sound, unless the valve is cracked. You can test the booster with a hand operated vacuum pump/gauge. Once you have vacuum on the booster the gauge should not show pressure increasing.

A leaking booster, hose or check valve is an intake leak and it will make the engine idle rough.
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Old 08-14-2012, 07:26 AM   #3
Roysneon
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Thanks for the insight. As I said, I'm not exactly sure how the system works. I've got a much better idea of it now. Guess the brake booster replacement will have to happen sooner than later.
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Quote:
Originally Posted by mbonanni View Post
I hate modded emtree, I hate modded cawrz, I hate jdm, I hate swag, I hate stanceyolokids, I hate bags (on cars), I hate stuff that is slowz, I hate tires.

I am a pursit now.
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Old 08-14-2012, 08:06 AM   #4
fronton
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assuming this is a 24v swap, you probably have the iX booster? Details would be nice. If you have the iX booster, you'll note that the black plastic pipe fitting that goes into the booster may be as blocked by the strut tower. If it is not in there flush, it will leak. The solution is relocate the booster a few mm toward the passenger side or get the e34 M5/e32 735i booster which is the same as iX but with the vacuum hole on the other side.
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Old 08-14-2012, 09:58 AM   #5
Roysneon
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Yeah, iX booster. May have to look into buying a new/rebuilt 7er booster. I don't think the problem is the grommet where the vac. hose goes in, but I do know what you mean about it being on the wrong side.

I had to remove the bracket between the firewall and booster for it to fit as well as shortening and tapping the rod. I may have broken something inside it when I had it in the vice to do that.
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Quote:
Originally Posted by mbonanni View Post
I hate modded emtree, I hate modded cawrz, I hate jdm, I hate swag, I hate stanceyolokids, I hate bags (on cars), I hate stuff that is slowz, I hate tires.

I am a pursit now.
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