vacuum leak
08-07-2010, 04:56 PM
#3
thanks, so what about the vacuum leak? I dont know why my car sputter under intense acceleration just at high rms and its a light power loss. and my breaks dont work near as good as they should, im kinda scared to go too fast and not be able to stop fast enough.
08-07-2010, 07:42 PM
#4
TECH Regular
Join Date: Apr 2007
Location: Kempner, TX
Posts: 420
Likes: 0
Received 0 Likes
on
0 Posts
THESE ENGINES ARE EXTREMELY SENSITIVE TO VACUUM LEAKS.
First thing I'd do is connect a vacuum gage to the idling, fully warmed engine to see what reading I get.
Whatever it is, it should be relatively stable. The actual number may differ from other engines or stock engines because of the mods you've made but I'd say no lower than 12 in order for the brakes to work well.
The check for a leak, there are several different ways to go about it; each guy who has done this before probably has his own favorite. I've tried almost all of them over the decades and, yes, I have my favorite.
I check ALL the vacuum hoses for being tightly connected and not leaking from being old and brittle. I replace any that are suspicious, put a clamp on others, whatever it takes to make sure the fitting is tight and leak free.
I then go over all the intake manifold bolts to see if they've remained tight (35 lb/ft).
In the actual checking some like to spray the idling engine with carb cleaner, others use an un-lit propane torch, others like using smoke, on and on and on. For me I want to see and hear a change in idle as I spray water to all thoses areas where vacuum could be leaking.
Yes, I use just plain old water out of my garden hose directly it AWAY from the electrical connections. If there is a leak, at some point water will get sucked into the leaking area and the idle will object. A small amount of white smoke (steam) may exit the muffler or it may not but in any event the idle quality will briefly worsen. Wherever you were spraying when the worsening happens is your leak spot.
I'm not timid about applying the water either. No, I don't flood the engine with so much water that I'd need a bucket to bail it out but I flow enough to insure results should a leak be there, somewhere.
Hope this helps.
Jake
First thing I'd do is connect a vacuum gage to the idling, fully warmed engine to see what reading I get.
Whatever it is, it should be relatively stable. The actual number may differ from other engines or stock engines because of the mods you've made but I'd say no lower than 12 in order for the brakes to work well.
The check for a leak, there are several different ways to go about it; each guy who has done this before probably has his own favorite. I've tried almost all of them over the decades and, yes, I have my favorite.
I check ALL the vacuum hoses for being tightly connected and not leaking from being old and brittle. I replace any that are suspicious, put a clamp on others, whatever it takes to make sure the fitting is tight and leak free.
I then go over all the intake manifold bolts to see if they've remained tight (35 lb/ft).
In the actual checking some like to spray the idling engine with carb cleaner, others use an un-lit propane torch, others like using smoke, on and on and on. For me I want to see and hear a change in idle as I spray water to all thoses areas where vacuum could be leaking.
Yes, I use just plain old water out of my garden hose directly it AWAY from the electrical connections. If there is a leak, at some point water will get sucked into the leaking area and the idle will object. A small amount of white smoke (steam) may exit the muffler or it may not but in any event the idle quality will briefly worsen. Wherever you were spraying when the worsening happens is your leak spot.
I'm not timid about applying the water either. No, I don't flood the engine with so much water that I'd need a bucket to bail it out but I flow enough to insure results should a leak be there, somewhere.
Hope this helps.
Jake
09-20-2010, 03:50 PM
#5
Launching!
iTrader: (6)
Join Date: Feb 2010
Location: St Petersburg, Fl
Posts: 239
Likes: 0
Received 0 Likes
on
0 Posts
Its a pretty loud leak, and I can hear it more on the driver side rather than the passenger. I checked my hoses with WD40 to see if the idle would object, but got no response.
I thought it could have been a fuel issue like a injector, but someone mentioned that it could be my intake manifold.
Do LT1's have issues with intake bolts backing off? Or worse case, could my intake be cracked?
What would cause the bolts to back out or the intake to maybe crack? Time/ware and tare, overheating?
