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I have what sounds like a pretty wicked vaccuum leak on the drivers side some where. I cant seem to find it but it sounds like its coming from around the back spark plug. When i step on the brake before i put it in gear it gets quieter but comes back after a second. I can put it in drive and it idles ok and sometimes i can put it in reverse and it will idle ok for a few mintues before it dies out. I have recently run seafoam through everything and i have double checked the throttle body to be clean. I rechecked valve lash and doublechecked the head bolts and all the spark plugs were tight. I sprayed carb cleaner all around the hoses and didnt notice any difference in idle. I am stumped and dont know where else to look. This motor came from a 01 tahoe its a 5.3l with a 4l60e. anyone have any ideas?
i sprayed some carb cleaner around the intake all the way around and didnt notice any difference in idle i tried snugging the intake bolts up as well but i did reuse the intake gaskets so that might be it. I just dont know how else to tell. I am running at about 30kpa at idle so it seems normal.
Only other thing I can think of is to use a stethoscope (one made for automotive use). They come with a metal probe...so you can poke around and listen to the internals while the motors running. I'd think if your leak is loud enough...you'd here it when you get close.
__________________ '68 GMC short/step- Comp LSr cam'd '09 LY6, .650 dual spring kit w/titanium retainers, Dynatech 1 7/8" x 3" headers, GMPP 4L85e w/2200 stall, 12 bolt 3.73 posi, 4/5 drop w/big sway bars f/r, etc '06 TBSS - our LS2 powered 13 sec grocery getter...with a radix in its future.
i had a long piece of fuel line i stuck in my ear and it sounded like it was coming from the #7 spark plug? I tightened it down and snugged up on the intake and exhaust manifold bolts back there as well as checked the vaccuum hoses that i could see but nothing seemed to help or change anything. And as soon as i put it into gear it dies. I remember it doing the stall before when my NSS was not adjusted properly. Any chance i am looking at two seperate problems here?
well did you plug the vacum boster connection at the rear of the Intake or hook it up in what ever it swaped into??? Is the Fuel pressure regulator vacum source hooked up??? When you had the gaskets out for the intake was the rubber still protuding past the plastic??? If not they need to be replaced...
Brake booster line from the manifold is hooked up to the brake booster in the truck. That line isnt leaking. The FPR line is hooked up as well. It has been a while but i am pretty sure the gaskets for the intake are good as well. I keep looking at the vaccumm lines and stuff but the noise keeps me looking around where the head meets the block behind and around #7. I had an old TPI motor that didnt like to keep the #1 plug in the block, and it almost sounds like the plug is coming loose but it is as tight as i dare go with the aluminum....
pull the plug and see if the threads are ok. also id put a compression gauge on it, make sure you have enough compression. if its coming from the back check the PCV in the rear of the driver valve cover that goes to the top of the manifold. it shouldnt keep the truck from running but itll cause a leak if those rubbers are bad or the hard plastic line is broken.
it sounds like its that PCV in the valve cover not a head gasket. can you video it for us?
1 7/8" headers, 4" exhaust
4" cai, 90mm tb, ud pulley
Yank Pro Truck 3600 triple disc
Driveshaft specialist 2 piece
Tick Performance custom cam upgrades in the works Built Not Bought