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Old 09-02-2014, 11:09 PM   #1
JerrittB08
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Weird sound turning truck off

I have a 72 c10 350v8. Sometimes when I turn it of the engine will make a shhhhhshhshh sound. it dosent do it every time, maybe every 7th or 8th turn off. Does anyone have any ideas what this is?
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Old 09-02-2014, 11:14 PM   #2
Lee H
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Re: Weird sound turning truck off

Run on maybe?
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Old 09-02-2014, 11:36 PM   #3
no1udknow
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Re: Weird sound turning truck off

Sounds like vacuum bleeding off. Could be a leak in the diaphragm for the brakes if you have a booster. Or maybe in the HVAC system
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Old 09-02-2014, 11:47 PM   #4
Crazyduck
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Re: Weird sound turning truck off

A/c compressor will do it too, If you have it.
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Old 09-03-2014, 12:07 AM   #5
zeldman
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Re: Weird sound turning truck off

Hard to tell without hearing the noise. Could be PCV is stuck.
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Old 09-03-2014, 12:38 AM   #6
JerrittB08
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Re: Weird sound turning truck off

It not a hose or anything, it sounds like the whole engine turning over. What do you mean by a run on
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Old 09-03-2014, 07:25 AM   #7
no1udknow
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Re: Weird sound turning truck off

The only other suggestions I have is a vakve that may be too tight or not seating properly letting compression leak back in to the intake or a loose spark plug, but thats only if your sure it is coming from the engine. You could check both by pulling power from the coil/hei and bumping the engine a little at a time and see if you start to hear it.
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Built not bought!
My dad always tried to convince me HEI was pointless!
Welding is a lot like sex, you don't have to be great with the rod as long as you thoroughly prep the surface and your good at grinding
My build : 68 C10 Short Bed Conversion
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Old 09-03-2014, 07:32 AM   #8
dfrank
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Re: Weird sound turning truck off

Too much timing can sometimes cause a run on. Double check your timing. It could be as simple of a fix of just turning the distributor a little. Good luck.
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Old 09-03-2014, 09:23 AM   #9
luvbowties
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Smile Re: Weird sound turning truck off

Having idle speed set too high can cause it. If it keeps on after all our suggestions & it worries you, try cutting it off while still in gear--assuming it is an automatic.

Luck to you,
Sam
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