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Excessive vacuum in crankcase, 07 f150 with a 5.4l.. once it…

Excessive vacuum in crankcase, ...

Excessive vacuum in crankcase,

Mechanic's Assistant: What is the model/year of your Ford?

07 f150 with a 5.4l.. once it warms up it starts whistling trying to suck in enough air , the pcv was replace and no change

Mechanic's Assistant: Do the vents feel cold? Is there a coolant leak?

No coolant leak that I can tell. Very low compression in #1 cylinder though

Mechanic's Assistant: Are you fixing your F150 yourself? What have you tried so far?

Yes

Mechanic's Assistant: Anything else you want the mechanic to know before I connect you?

About to pull the motor to see why I have almost no compression in one hole

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Answered in 5 minutes by:
3/18/2018
Gary
Gary, ASE Certified Technician
Category: Ford
Satisfied Customers: 1,915
Experience: Senior Technician
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Hello! My name is Gary.
Welcome to JustAnswer.
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I would pull the valve cover on bank 1.

Perhaps you have a broken inlet rocker, then that cylinder has low compression, and pulls a vacuum on the crankcase while running.

Gary

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Customer reply replied 4 months ago
Thanks, I'll try that

If you have replaced the pcv valve and the fresh air hose is clear, then the vacuum and compression loss has to be related, so my suggestion is very rare, but can happen.

So hopefully you see something amiss after pulling the valve cover, and running the engine, before you pull it out.

Gary

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Hello again,

Do you need any further help?

I hope my advice has been of assistance to you.

Kind regards

Gary

Gary
Gary, ASE Certified Technician
Category: Ford
Satisfied Customers: 1,915
Experience: Senior Technician
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