vaccum leak?
Thread Starter
|
Junior User
Joined: Nov 2002
Posts: 74
Likes: 0
From: albany ga
vaccum leak?
i have a 390 and it has developed a sound like it is trying to suck air into the engine. could this be caused by a vaccum leak? the engine was rebuilt a few months ago and it has had no power loss. so any help would be great.
Senior User
Joined: Aug 2000
Posts: 407
Likes: 0
vaccum leak?
Sounds like it may well be a vacuum leak. Put a vacuum gauge on it and see what your readings are.
A likely source of a leak that would be loud is the brake power booster. With the gauge connected read the vacuum with the booster line connected and then disconnected and the connection on the engine plugged. If the booster is leaking there will be a noticeable differece in the readings. If that isn't it then use some carb cleaner and start spraying around the cab base, intake manifold to head union, and any other areas that are suspected. If there is a leak the rpm's will go up momentarily when the cleaner is sucked in.
You can also take a piece of heater hose about two feet long and use it as a stethoscope to find the source of the noise. With one end of the hose on your ear move the other end around areas that you suspect and you will easliy hear the difference in the sound when you come upon the leak if it is a loud one.
Good luck,
Mark
A likely source of a leak that would be loud is the brake power booster. With the gauge connected read the vacuum with the booster line connected and then disconnected and the connection on the engine plugged. If the booster is leaking there will be a noticeable differece in the readings. If that isn't it then use some carb cleaner and start spraying around the cab base, intake manifold to head union, and any other areas that are suspected. If there is a leak the rpm's will go up momentarily when the cleaner is sucked in.
You can also take a piece of heater hose about two feet long and use it as a stethoscope to find the source of the noise. With one end of the hose on your ear move the other end around areas that you suspect and you will easliy hear the difference in the sound when you come upon the leak if it is a loud one.
Good luck,
Mark
Junior User
Joined: Jul 2003
Posts: 61
Likes: 0
From: Bothell, WA
vaccum leak?
I just eliminated a few leaks this weekend.
The rubber seal around the PCV valve on the passenger side was letting air in. I fixed that by plugging the hose that goes to the manifold and re-routing the vent hose to the air filter, just like the drivers side is.
I also used small cable ties to snug down the vacuum hoses on the distributor and transmission, plus the other ends of those hoses where they join the carb, or manifold tee. That seemed to sort things out.
I noticed an immediate improvement in idle and starting with these things fixed.
Good luck
Kevin
The rubber seal around the PCV valve on the passenger side was letting air in. I fixed that by plugging the hose that goes to the manifold and re-routing the vent hose to the air filter, just like the drivers side is.
I also used small cable ties to snug down the vacuum hoses on the distributor and transmission, plus the other ends of those hoses where they join the carb, or manifold tee. That seemed to sort things out.
I noticed an immediate improvement in idle and starting with these things fixed.
Good luck
Kevin
New User
Joined: Jun 2003
Posts: 13
Likes: 0
vaccum leak?
FE motors are known for vac leaks. Check around your distributer and front and back of your intake. I just did my 75. It started and ran great but had the vacuum cleaner noise Dodges are known
for. You can use a carb cleaner to help locate your leaks. spray
all around your carb and intake listening for engine pitch changes.
In my case I ran my hand around the distibuter and found it.
Hope this helps.
Mike
for. You can use a carb cleaner to help locate your leaks. spray
all around your carb and intake listening for engine pitch changes.
In my case I ran my hand around the distibuter and found it.
Hope this helps.
Mike
Thread
Thread Starter
Forum
Replies
Last Post
FitchBanjos
FE & FT Big Block V8 (332, 352, 360, 390, 406, 410, 427, 428)
13
Mar 5, 2008 06:05 PM
reamer
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
5
Nov 9, 2004 06:31 AM
