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Strange hissing?

5K views 24 replies 9 participants last post by  PSD 2004 
#1 ·
A couple of days ago I laid into the throttle and out of no where I hear a loud hissing from under the hood. At first I thought I may have a boost leak but im still hitting 28psi (at intake elbow) at wot. There is no cel all the guages look good and no noticable coolant loss yet and the truck runs great. I just cant stand this loud hissing. Any ideas im trying to get the truck ready for the trip to TS and I cant afford any problems.
 
#2 ·
Might be your degass bottle hissing, from what ive read on here, a new degass cap might be in order. Thats all i can think of, im sure someone can come up with something else.
 
#3 ·
beware of that sound. It might not be just the degauss bottle. On my dads dually it did that sound for a long time. He tried different degauss bottle caps and it still did it. Finally started blowing white smoke on startup and he was adding about 20oz of coolant every couple of weeks. Ended up being the gaskets were trashed. ARP studs, new gaskets, new heads, old ones were warped, EGR delete uppipe and EGR blockoff and it seems to have fixed the sound! LOL
 
#4 ·
:whs: If its not the degass bottle, then it could be the head gaskets, if this happens to be the problem, might as well stud her while shes apart and make sure to have the heads machined. Also an EGR full delete kit might be in order as well, FCDP has the best kit IMO.
 
#6 ·
Take the degas bottle cap to the local stealership and have it tested. Should hold 16 lbs. If not, get a new one, which is an updated part. If that's not the issue, look for coolant leaks, and check all ring clamps for an exhaust leak.
 
#7 ·
Thanks for the info guys. Im doing an oil change and installing a colant filter tomorow so ill take a better look then but I havent seen any leaks so far. I think ill replace the degas cap just to be shure hopefully its not the head gaskets.
 
#13 ·
Adam does
 
#14 ·
should be 450 for the studs then find someone to install if u cant get the money right lol
 
#17 ·
Like adam says check your up pipes, thats where my hissing noise was coming from higher chance there. Also if it was your boost tubes it probably would have blown off like mine did at 20 psi cause it was loose.

If ARP are on back order look at H-11's just another option its what Im running.
 
#18 ·
ANOTHER SIGN THE UP PIPE BELLOW IS BAD IS BLACK SOOT ON THE FIREWALL INSULATION..
 
#25 ·
Hmmm. Just finished my egr delete last night and when i started it, it started making this pulsating hiss noise. Sounds like a boost leak, but its not constant, which leads me to believe its from something else.
 
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