Vaccum Whistle
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Freshman User
Joined: Feb 2005
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From: Tucson, AZ
Vaccum Whistle
I've got an 85 F150 stepside I've been trying to put back together. It was in pretty good shape to begin with but I can't seem to get to the "ahead" part when I seem to be constantly fixing the old stuff that's dying off. At the moment I'm replacing the exhaust/intake manifold (4.9L 6Cyl). New exhaust manifolds are easy to find but intakes, that's a different animal. Had to settle for a used one from Alabama! I get this noise like a "vaccum whistle" (very loud) at express way speeds and sometimes around town only in the morning hours. I've checked everything and it seems to come back to the intake. I've replaced the gasket twice in 3.5 years. I think at high vaccum the gasket is acting like a reed.
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Freshman User
Joined: Feb 2005
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From: Tucson, AZ
Thanks for the info. That is why I bought a new exhaust manifold. The only new intake I found was either a fuel injected style or a polished aluminum Offenhauser for $250.00. Hopefully the sed one coming is in good condition.
Fleet Mechanic
Joined: Sep 2003
Posts: 1,279
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From: savannah,ga
take some carb cleaner and spray differant
spots that may be your leak
if idle changes then you found the leak
when installing new gaskets it is important to
retorque after 5 or so heat cycles
especially a 6 cyl. with this style of exh. and int.
manifolds siamesed together
I have had many problems with the carb to egr to manifold seals
spots that may be your leak
if idle changes then you found the leak
when installing new gaskets it is important to
retorque after 5 or so heat cycles
especially a 6 cyl. with this style of exh. and int.
manifolds siamesed together
I have had many problems with the carb to egr to manifold seals
Posting Guru
Joined: Jun 2002
Posts: 2,091
Likes: 3
From: Suffolk, VA USA
Vaccum Whistle
I've had this issue with at least two 4.9s. It's a chronic problem with these engines. Both times I've been able to take the intake to a machine shop and have it trued.
Bill,
86 F150 4x4 5.0
Bill,
86 F150 4x4 5.0
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Freshman User
Joined: Feb 2005
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From: Tucson, AZ
Originally Posted by mhg
take some carb cleaner and spray differant
spots that may be your leak
if idle changes then you found the leak
when installing new gaskets it is important to
retorque after 5 or so heat cycles
especially a 6 cyl. with this style of exh. and int.
manifolds siamesed together
I have had many problems with the carb to egr to manifold seals
spots that may be your leak
if idle changes then you found the leak
when installing new gaskets it is important to
retorque after 5 or so heat cycles
especially a 6 cyl. with this style of exh. and int.
manifolds siamesed together
I have had many problems with the carb to egr to manifold seals
I will keep in mind the retorque suggestion. Thanks and thanks for the reply.
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Freshman User
Joined: Feb 2005
Posts: 40
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From: Tucson, AZ
Originally Posted by ri_truck_guy
I've had this issue with at least two 4.9s. It's a chronic problem with these engines. Both times I've been able to take the intake to a machine shop and have it trued.
Bill,
86 F150 4x4 5.0
Bill,
86 F150 4x4 5.0
Thanks for the reply,
CJS
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Posting Guru
Joined: Jun 2002
Posts: 2,091
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From: Suffolk, VA USA
I don't know how much truth there is to this, but I've been told from a couple of sources the problem has to do with the way the intake and exhaust bolt together in the center. I've never tried doing away with that coupling, but would be curious to hear if anyone has tried it.
Bill
86 F150 4x4 5.0
Bill
86 F150 4x4 5.0
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Thread Starter
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Freshman User
Joined: Feb 2005
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From: Tucson, AZ
Originally Posted by ri_truck_guy
I don't know how much truth there is to this, but I've been told from a couple of sources the problem has to do with the way the intake and exhaust bolt together in the center. I've never tried doing away with that coupling, but would be curious to hear if anyone has tried it.
Bill
86 F150 4x4 5.0
Bill
86 F150 4x4 5.0
