Intake Manifold Leak
Instructor
Joined: Apr 2007
Posts: 136
Likes: 0
From: Fountain CO
If you meant to say a vacuum leak then a propane torch with the gas on (do not light 
) with the car running. It will raise the rpms if you find a leak. Just move it around the suspected area.
) with the car running. It will raise the rpms if you find a leak. Just move it around the suspected area.
Last edited by TOMS93; May 23, 2007 at 10:15 PM.
Thread Starter
Team Owner
Joined: Feb 2006
Posts: 24,460
Likes: 7
From: sw Ohio
I dont have a propane torch, and I have absolutely no idea where it might be leaking. I dont see any fluids and dont hear any hissing, but the dye test sounds like it might work.
Instructor
Joined: Apr 2007
Posts: 136
Likes: 0
From: Fountain CO
I'm not a mind reader here, give us some details....
Thread Starter
Team Owner
Joined: Feb 2006
Posts: 24,460
Likes: 7
From: sw Ohio
I've checked all the obvious like vacuum lines, fuel lines, and electrical connections. I've also checked the timing, cap and rotor, coil, IAC, MAF, 02 sensor, and fuel pressure. Their all good. I mean it HAS to be a leak somewhere in the intake right?
Instructor
Joined: Apr 2007
Posts: 136
Likes: 0
From: Fountain CO
If it's hunting then the IAC is doing it's job trying to correct an A/F issue.
Go buy a torch. Every garage should have one any way. Home Depot has them for like $18. It beats trying to fart in those tight areas
. If you have a vacuum leak, it will help you find it.
Other than that it could also be a O2 sensor, but I see you tested that too.
Go buy a torch. Every garage should have one any way. Home Depot has them for like $18. It beats trying to fart in those tight areas
. If you have a vacuum leak, it will help you find it.Other than that it could also be a O2 sensor, but I see you tested that too.
Last edited by TOMS93; May 23, 2007 at 11:15 PM.
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Thread Starter
Team Owner
Joined: Feb 2006
Posts: 24,460
Likes: 7
From: sw Ohio
If it's hunting then the IAC is doing it's job trying to correct an A/F issue.
Go buy a torch. Every garage should have one any way. Home Depot has the for like $18. It beats trying to fart in those tight areas . If you have a vacuum leak, it will help you find it.
Other than that it could also be a O2 sensor, but I see you tested that too.
Go buy a torch. Every garage should have one any way. Home Depot has the for like $18. It beats trying to fart in those tight areas
. If you have a vacuum leak, it will help you find it.Other than that it could also be a O2 sensor, but I see you tested that too.
Instructor
Joined: Apr 2007
Posts: 136
Likes: 0
From: Fountain CO
This might help with the O2 test.
http://www.forparts.com/o-21.htm
I usually bench test it in a vice and a good quality Fluke multi meter. But the in car method is a more accurate test, INMO. Taking it out allows me to inspect it.
http://www.forparts.com/o-21.htm
I usually bench test it in a vice and a good quality Fluke multi meter. But the in car method is a more accurate test, INMO. Taking it out allows me to inspect it.
Le Mans Master
Joined: Apr 2005
Posts: 8,077
Likes: 4
From: Scarborough ONTARIO
If u have small small leak than its waaay hard to detect that, find out whose mechanic shop has a smoke detector machine, they will remove ur MAF and in pace they will block this, and than from brake booster hose mahine will through smoke, if u have any leak smoke will come out from there, 1/2 an hr job probably 20-30 bucs at the most he might charge u, in this way u can find vacum leaks too.
Safety Car
Joined: May 2006
Posts: 4,290
Likes: 140
From: Salem NH
LOL, I know your not a mind reader. I just put new heads on it roughly a month ago. I followed all the directions for putting the intake manifold, runners, and plenum back on. Torque settings are correct. It ran fine for about 2 weeks and then I got a leak in the fuel rail where the cold start valve connects. I replaced the O-ring and all is well again, runs just fine. The next day, it runs like crap, idle is "hunting" and will eventually stall out unless you keep giving it gas, even then it stalls out sometimes. When I put it in drive, it stumbles on acceleration, but is good once I get going. I cant even make it out of the driveway now though.
I've checked all the obvious like vacuum lines, fuel lines, and electrical connections. I've also checked the timing, cap and rotor, coil, IAC, MAF, 02 sensor, and fuel pressure. Their all good. I mean it HAS to be a leak somewhere in the intake right?
I've checked all the obvious like vacuum lines, fuel lines, and electrical connections. I've also checked the timing, cap and rotor, coil, IAC, MAF, 02 sensor, and fuel pressure. Their all good. I mean it HAS to be a leak somewhere in the intake right?
This happens immediately on startup? Well then you can rule out 02.
Your first leak, it was a fuel leak then eh? Maybe you have another one you cannot see. Get a small fuel pressure gauge, about $25 and put it on the rail. See if you leak down after you turn the key off.
Next, check for vac leaks. Forget the propane. Instead, get a $3 can of throttle body cleaner. Hose each bank, and every component down a little at a time. If you find a vac leak, you WILL hear it. the car will stumble, race, etc.
Check your valve lash. I don't like the way any book describes how to set valve lash. Especially older tired motors with roller lifters. You should do a running valve adjustment. Get it HOT, back each rockr off until it ticks (thats the lash), Then tighten until it stops ticking and you FEEL a little preload, then go 1/4 turn. (1/4 turn on a 3/8" x 16 stud = about .050" preload).
Check your plugs! How do they look? Oil fouled? Water? Fuel? Lean? (white and blistered).
-- Joe
Melting Slicks
Joined: Jan 2001
Posts: 2,940
Likes: 5
From: Chesapeake VA
+1 on the smoke technique.
Get some tubing ($3 for a 10' roll from Lowes/ Home Depot), some duct tape and a smoker.
Remove the snorkle from the MAF to the throttle body and put the tube in the throttle body and tape it up real good with the duct tape.
Have the smoker exhale into the tube for a few minutes. It will take a while for the engine to fill up with smoke.
Once the engine is full any vacuum leakes will apear as smoke will come out with each exhale.
Use a flashlight and exhale speed to pinpoint the leak.
Get some tubing ($3 for a 10' roll from Lowes/ Home Depot), some duct tape and a smoker.
Remove the snorkle from the MAF to the throttle body and put the tube in the throttle body and tape it up real good with the duct tape.
Have the smoker exhale into the tube for a few minutes. It will take a while for the engine to fill up with smoke.
Once the engine is full any vacuum leakes will apear as smoke will come out with each exhale.
Use a flashlight and exhale speed to pinpoint the leak.
Race Director
Joined: Jun 2004
Posts: 13,957
Likes: 706
From: WI
Aye good write up. I did that during the day and had to look sideways across the engine because of the sun. Having it darker with a light would make it much quicker. It was easy to do. I had a small leak under the plenum, the MAT sensor, this was a long time ago now. The smoke even came out downward there, I had to watch as he exhaled into the tube though, it was such a small leak.
Instructor
Joined: Apr 2007
Posts: 136
Likes: 0
From: Fountain CO
This happens immediately on startup? Well then you can rule out 02.
Your first leak, it was a fuel leak then eh? Maybe you have another one you cannot see. Get a small fuel pressure gauge, about $25 and put it on the rail. See if you leak down after you turn the key off.
Next, check for vac leaks. Forget the propane. Instead, get a $3 can of throttle body cleaner. Hose each bank, and every component down a little at a time. If you find a vac leak, you WILL hear it. the car will stumble, race, etc.
Check your valve lash. I don't like the way any book describes how to set valve lash. Especially older tired motors with roller lifters. You should do a running valve adjustment. Get it HOT, back each rockr off until it ticks (thats the lash), Then tighten until it stops ticking and you FEEL a little preload, then go 1/4 turn. (1/4 turn on a 3/8" x 16 stud = about .050" preload).
Check your plugs! How do they look? Oil fouled? Water? Fuel? Lean? (white and blistered).
-- Joe
Your first leak, it was a fuel leak then eh? Maybe you have another one you cannot see. Get a small fuel pressure gauge, about $25 and put it on the rail. See if you leak down after you turn the key off.
Next, check for vac leaks. Forget the propane. Instead, get a $3 can of throttle body cleaner. Hose each bank, and every component down a little at a time. If you find a vac leak, you WILL hear it. the car will stumble, race, etc.
Check your valve lash. I don't like the way any book describes how to set valve lash. Especially older tired motors with roller lifters. You should do a running valve adjustment. Get it HOT, back each rockr off until it ticks (thats the lash), Then tighten until it stops ticking and you FEEL a little preload, then go 1/4 turn. (1/4 turn on a 3/8" x 16 stud = about .050" preload).
Check your plugs! How do they look? Oil fouled? Water? Fuel? Lean? (white and blistered).
-- Joe
. I like the smoke idea better though. It sounds a lot safer than propane or throttle body cleaner 
.I doubt it's his valve lash since it worked good for 2 weeks. Unless little tiny gremlin's with wrenches came in after midnight and did their own tweaking.
I agree with 02 as well, however he didn't give us that info. So I offered that as a possibility.
Safety Car
Joined: May 2006
Posts: 4,290
Likes: 140
From: Salem NH
Nothing wrong with propane . I like the smoke idea better though. It sounds a lot safer than propane or throttle body cleaner .
I doubt it's his valve lash since it worked good for 2 weeks. Unless little tiny gremlin's with wrenches came in after midnight and did their own tweaking.
. I like the smoke idea better though. It sounds a lot safer than propane or throttle body cleaner .I doubt it's his valve lash since it worked good for 2 weeks. Unless little tiny gremlin's with wrenches came in after midnight and did their own tweaking.
I've seen all sorts of scenarios. I don't rule anything out anymore.
-- Joe
Instructor
Joined: Apr 2007
Posts: 136
Likes: 0
From: Fountain CO
