While I was replacing a heater hose today, I shut the truck off after testing and heard what I thought was a vacuum leak. A small buzzing sound that petered out after 20-30 seconds. Since my '88 F-250 460 has a maze of vacuum hoses on top of the engine, is there any easy way to locate it?

Thanks in advance for any help you can give,

Paul

 

plug off or apply soapy water to any suspected lines, where ever the line bubbles its a leak.


John Floyd
South Mills,NC
'86 F150 2wd 300 6
Crane Cam 260/272
stock manifolds, w/ staight pipe

 

Hi, if your truck has a/c it is a normal thing to hear a hissing sound right after the engine is shut down it is all the vacume in the heaterbox to open and close the various doors.
JOHN (FATFORTY)

 

Also , Some of the vacuum solenoids make that noise after the engine is shut off .

 

Paul, this may sound strange, but take your old heater hose and clean off one end. Start your engine, put the clean end next to your ear and use the other end to listen for the leak. If you have a leak you'll find it.

Good Luck

Kevin

 

 

Thanks for the tips all. Due to a rough idle, I suspect the leak may be large, since it's pretty cold around here and I don't have a garage, I'll check it next time it warms up.

Thanks again, Paul

 

Hi, one other thing you might check that would cause a rough idle is where the power brake vacume hose is hooked up it could have been jarred loose on the engine or it could be at the booster itself but that will cause a buzzing sound and a rough idle. JOHN FATFORTY

 

Being as this is associated with the replacement of the heater hose, I would begin my search by checking the vacuum cannister that sits on the fender under or next to your heater hose. The cannister builds up a reserve to run the vacuum controled heater or a/c doors. It's very easy to knock the vacuum hose off the cannister and cause a leak.

'82 F150 2WD w/351W (orig 300 I6)
Slik