Lifter ques
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Senior User
Joined: Nov 2008
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From: Sorrento BC, Canada
Lifter ques
My truck has a chuffing noise through the exh. I have done 2 separate compression tests done at operating temp, and found that the highest cylinder is 495, and the lowest is 410-420 (the rest were 450-490). This tells me that an valve couldn't be leaking due to good compression in all cyls. I have also done a glow plug resistance test while running and found all cyls but number 8 at 16.7 ohms. Number 8 was at 13.4 ohms, this tells me #8 is weak. Could the chuff and weak cyl be caused by a bad lifter(s) opening the exh valve late causing compressed gases by way of the piston compressing the gases alittle before the valve opens to rush out causing a chuff? The engine also has a tick that is present when off or on the throttle. Thanks.
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Joined: Apr 2007
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From: Conway, AR
Anything is possible, but most likely youve got one or more bum valve guides. They get pretty hammered over time , especially if it's a 7.3 with the original positive seals all around. they have a habit of eating valve guides This might not show up in a compression test as you are only at cranking speed, sometimes the valve will seat and sometimes walk around a little.
If you have a comp gauge, it is easy to rig it into a leakdown tester and put air pressure to the cylinder and listen for it coming out the exhaust or around the valve guides
If you have a comp gauge, it is easy to rig it into a leakdown tester and put air pressure to the cylinder and listen for it coming out the exhaust or around the valve guides
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Joined: Jan 2005
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My truck has a chuffing noise through the exh. I have done 2 separate compression tests done at operating temp, and found that the highest cylinder is 495, and the lowest is 410-420 (the rest were 450-490). This tells me that an valve couldn't be leaking due to good compression in all cyls. I have also done a glow plug resistance test while running and found all cyls but number 8 at 16.7 ohms. Number 8 was at 13.4 ohms, this tells me #8 is weak. Could the chuff and weak cyl be caused by a bad lifter(s) opening the exh valve late causing compressed gases by way of the piston compressing the gases alittle before the valve opens to rush out causing a chuff? The engine also has a tick that is present when off or on the throttle. Thanks.
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Senior User
Joined: Nov 2008
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From: Sorrento BC, Canada
How would i make my compression tester into a leak down tester? Also if it was a valve would it definitely leak with shop air on it (135 psi)? Would you be able to hear it at the end of the exh pipe? Thank you.
Senior User
Joined: Apr 2007
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From: Conway, AR
If you want to measure the leakdown, youll need to plumb in a shutoff valve and a gauge
Senior User
Joined: Apr 2007
Posts: 315
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From: Conway, AR
And yes, you can hear it leaking out teh end of teh exhaust pipe. Even with a clogged muffler it reverberates as it comes out, makes quite a racket. and listening at the intake manifold with the cdr blocked if n/a will tell you if it's leaking past an intake valve
