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1996 E7-427 exhaust noise and high pyro


Deere Mack
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Hello everyone, it's been a while.  I hope everyone's doing well.  My 1996 CH613 E7-427 started out making a noise that sounded like a bad exhaust leak, then in a good pull the pyro would jump up to 1200+/- quickly and running at around 900 but will drop on down at idle.  No noticeable lose in power but I was paying more attention to the noise before I parked it.  Can't seem to find any leaks and was wondering about the engine brake? Anyone have any input? 

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40 minutes ago, Mack Technician said:

Sounds like you already solved it. Add another two scoops of determination in finding the leak. You got a pressure tester for CMCAC?

Thanks, good to hear from you! No I don't.  Could this make the "exhaust leak" noise?  What part of the Jake do you think is failing, just sticking, solenoid?

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Right back atcha. 

You have no dead holes.....power is good....pyro is high......engine makes a “pich” “pich” “pich” as if it’s a single cylinder and not a constant hiss of steadily escaping boost.... 

The intake has a small square pipe plug with, I believe, 1/8” NPT threads. Run a 1/4” airline compression fitting in and run it into cab window so you can check boost under load. 

let it cool and spray soap water on the exhaust manifold legs to head. Run it and apply more.

Did you extract the active code blink? 

CMCAC-chassis mounted charge air cooler.

Edited by Mack Technician
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Check the little hose at the compressor inlet and under the inlet manifold! those often burst! its a one inch  steel line that runs behind the engine

Edited by fjh
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when I took it on the last drive, I took my father in law. He's not much of an mechanic but a retired over the road trucker.  He thinks it's an injector.  I'm not sure now because it's worse with an overall loss of power and it seemed to have an rough idle that kind comes and goes.  Pyro is still quick to hit 900 especially in higher gears and I'm sure if I were loaded it would climb back to the 1200 mark.

I have checked for leaks with soapy water but I did not pull the codes or boost. I will this morning.  The noise it's making sounds like a blown exhaust gasket to me, but it's not, no exhaust or intake leaks at all.

 

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4 minutes ago, fjh said:

Check the little hose at the compressor inlet and under the inlet manifold! those often burst! its a one inch  steel line that runs behind the engine

Good morning and thanks for tip.  I did a visual on that hose and didn't notice anything, but it might take some pressure before that would show up?

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Pull your valve covers, maybe you have a bent exhaust valve not closing all the way. With engine running, apply pressure to each rocker and see if somebody isn't working right... A quick visual comparison can quickly rule out potential mechanical failures. A valve not closing would also let combustion continue in the exhaust pipe, which would be hotter than completed combustion. And it'd probably sound like an exhaust leak. Because it kinda is.

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On 6/22/2019 at 8:13 AM, Deere Mack said:

when I took it on the last drive, I took my father in law. He's not much of an mechanic but a retired over the road trucker.  He thinks it's an injector.  I'm not sure now because it's worse with an overall loss of power and it seemed to have an rough idle that kind comes and goes.  Pyro is still quick to hit 900 especially in higher gears and I'm sure if I were loaded it would climb back to the 1200 mark.

I have checked for leaks with soapy water but I did not pull the codes or boost. I will this morning.  The noise it's making sounds like a blown exhaust gasket to me, but it's not, no exhaust or intake leaks at all.

 

Did you check the intake with pressure or just with soapy water?

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14 hours ago, JoeH said:

Pull your valve covers, maybe you have a bent exhaust valve not closing all the way. With engine running, apply pressure to each rocker and see if somebody isn't working right... A quick visual comparison can quickly rule out potential mechanical failures. A valve not closing would also let combustion continue in the exhaust pipe, which would be hotter than completed combustion. And it'd probably sound like an exhaust leak. Because it kinda is.

 

9 hours ago, OldRedMack said:

Did you check the intake with pressure or just with soapy water?

I went ahead and took it to my mechanic. I didn't have the time to pull the covers but I'm leaning toward a bent valve or something to do with the Jake.  The drive is about 45 min and the warmer the engine got the worse it ran.  The cold start was  good. Made me think might of had a stuck valve that unstuck but the further I got down the road the worse it got.

I did not use soapy water on the intake side.  It was more of a visual, touch and feel, and not to mention the old dollar bill for vacuum leaks.

I'll post what he finds when I hear something. As always I appreciate everyone's help.

 

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Extra temps caused by the charge cooler maybe caused manifold studs to loosen a little, causing the exh manifold gasket to leak? My old 2 valve endt676 motor is notorious for having the exhaust manifold nuts loosen. Been a while since the truck has had the lock tabs on it. Glad you're running again!

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6 hours ago, JoeH said:

Extra temps caused by the charge cooler maybe caused manifold studs to loosen a little, causing the exh manifold gasket to leak? My old 2 valve endt676 motor is notorious for having the exhaust manifold nuts loosen. Been a while since the truck has had the lock tabs on it. Glad you're running again!

Exactly my thoughts! 

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On 7/2/2019 at 3:42 AM, JoeH said:

Extra temps caused by the charge cooler maybe caused manifold studs to loosen a little, causing the exh manifold gasket to leak? My old 2 valve endt676 motor is notorious for having the exhaust manifold nuts loosen. Been a while since the truck has had the lock tabs on it. Glad you're running again!

 

On 7/2/2019 at 3:44 AM, JoeH said:

Great looking dog too!

Thanks!  I agree with you too.  It only makes sense.Wished I'd thought about some lock tabs, at least all my studs came out and I got some new ones back in.  Might pick up some locks later and put em on.

  Happy 4th of July to everyone!  God Bless America!

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