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Old 07-16-2018, 03:16 PM   #1
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Pacbrake PRXB barely working!

I upgraded to a Pacbrake PRXB 2 years ago. Worked great! I also installed a gauge on the dash to tell me how much back pressure I get. It usually reads about 58 lbs when braking.

Well, it all of a sudden started barely working? Only about 2-5 lbs backpressure?

The pneumatic cylinder is opening all the way, and I pulled it and bench tested it to make sure the butterfly was closing too.

I also checked that gauge, and it is accurate.

There is no apparent exhaust leak that I can detect, although I know a cracked manifold could cause this condition.

Any suggestions?
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Old 07-16-2018, 04:17 PM   #2
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Are you 100% Sure that the pacbrake is actually being activated while driving?
If it is working properly as you state, a loss of all but 2 lb’s of backpressure would indicate a major leakage I.e. cracked manifold, block or stuck valve. All of those would cause a marked change in engine sound.
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Old 07-16-2018, 04:22 PM   #3
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Quote:
Originally Posted by Dsallach View Post
Are you 100% Sure that the pacbrake is actually being activated while driving?
If it is working properly as you state, a loss of all but 2 lbs of backpressure would indicate a major leakage I.e. cracked manifold, block or stuck valve. All of those would cause a marked change in engine sound.
100%. I laid on bed watching while son-in-law drove. Everything looks and sounds normal. That's why I am so baffled.

Now, I am pretty hard of hearing, but I figured an exhaust leak of that magnitude would be easy for even me to hear!
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Old 07-22-2018, 11:27 AM   #4
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I am still hopeful that someone may have some suggestions on where my problem might be.

I called Pacbrake and they agreed that it sounded like my problem was an exhaust leak. Maybe a cracked manifold or bad gaskets. I checked the best I could, but I can not see or hear any signs of any exhaust leak.

I also have exactly the same boost pressure I have always had, about 24 psi. Shouldn't an exhaust leak affect my boost pressure significantly?

Any ideas would be greatly appreciated.
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Old 11-29-2018, 01:46 PM   #5
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I took the brake off and tested everything I could. I couldn't find any problem. I put it the brake back on, and everything was working fine. No problem.

I suspect the clamp that hold the brake on to the exhaust manifold must have been leaking and I simply got lucky when I put it back on and it sealed.

Anyway, the brake is working fine again, and has been for 1500 miles.
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Old 11-29-2018, 03:33 PM   #6
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Glad to hear it's working. I'm still having a problem with mine - hopefully will get it sorted out in the next few weeks.
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