Vacuum leak??

daccrow86 · 10-17-2003, 10:00 AM

my carb on my 66 mustang is making A spitty air noise like it is a vacuum leak we have check all the vacuum lines and nothing is it possible to have a leak somewhere like in the engine. my car has alot of power in the engine when it is in park but when you put it in gear (reverse, drive , or low) it always dies but will idle in park or nutreul. where could the leak or leaks be, and is it evan a leak. because it is getting plenty of gas. what could my problem be.

Thanks

Rev · 10-17-2003, 02:49 PM

Put a vacuum gauge (any auto supply) on a manifold vacuum port. A stock 289 should show 15-17 in hg. vacuum. If it's a stock engine and it's alot less, then you do have avacuum leak.

A leak can occur at the head/intake manifold interface or at the intake manifold carb interface. Also a leak can occur in the carb itself where the butterfly shaft works in the carb body (loose fit from wear).

You pretty much need a vacuum gauge to diagnose the problem. For $30 it's not a bad deal. You'll need it over and over again anyway as the years go by.

Rev

HotRoddin · 10-18-2003, 03:59 PM

Ditto what Rev said .... I would pay careful attention to the intake manifold gasket, especially in that engine, they had a tendency to spit them out. Replace the intake manifold gasket and the carb to manifold gasket, those are two very cheap very easy fixes on your engine and you will have ruled out 60% of the things that could be causing your problem.
In the old days to check for a leak in the intake manifold gasket they would take an oil can and squirt heavy oil along the top edge of the intake manifold ... if there was a small leak there, the oil would seal it for a second and the idle would noticably change ... if the leak were large you could see it suck the oil down into the intake port ... its messy and sometimes smokey but it does work. Another way is to take a length of 1/4" or so rubber fuel line, put one end in your ear and run the other along all the gasket edges where you suspect a leak ... the tubing picks up only the sound very near its tip, so when you get near a vacuum leak you'll hear the hiss like its amplified ... that one isn't so messy but you do look like a goofball with the tubing in your ear

daccrow86 · 10-20-2003, 10:16 AM

Quote:

Originally posted by Rev
Put a vacuum gauge (any auto supply) on a manifold vacuum port. A stock 289 should show 15-17 in hg. vacuum. If it's a stock engine and it's alot less, then you do have avacuum leak.

A leak can occur at the head/intake manifold interface or at the intake manifold carb interface. Also a leak can occur in the carb itself where the butterfly shaft works in the carb body (loose fit from wear).

You pretty much need a vacuum gauge to diagnose the problem. For $30 it's not a bad deal. You'll need it over and over again anyway as the years go by.

Rev

Sorry that i forgot to mention that it is a straight six and not a 289 what is the hg. vacuum.

sorry
thanks

daccrow86 · 10-20-2003, 10:25 AM

yeah one of my friends tryed something similar to that instead of oil we used w-d 40 and there was a leak around the bottom of the carb so we changed the gaskets and checked it again and there was no more leaks. and the problem persisted. yesterday we got it running it was running great we drove it all over town it was all good we got home turned it off went inside got a drink got back in the car turned the key it wouldnt idle. we were bak in the same old boat again. my next step is to take it to the shop and see if they can fix it. if they can fix it i will probably sell it.

10-17-2003, 10:00 AM	#1
daccrow86 Registered Member Join Date: Sep 2003 Posts: 11	Vacuum leak?? my carb on my 66 mustang is making A spitty air noise like it is a vacuum leak we have check all the vacuum lines and nothing is it possible to have a leak somewhere like in the engine. my car has alot of power in the engine when it is in park but when you put it in gear (reverse, drive , or low) it always dies but will idle in park or nutreul. where could the leak or leaks be, and is it evan a leak. because it is getting plenty of gas. what could my problem be. Thanks

10-17-2003, 02:49 PM	#2
Rev Registered Member Join Date: Nov 1998 Location: Houston, Tx. Posts: 3,887	Vacuum gauge Put a vacuum gauge (any auto supply) on a manifold vacuum port. A stock 289 should show 15-17 in hg. vacuum. If it's a stock engine and it's alot less, then you do have avacuum leak. A leak can occur at the head/intake manifold interface or at the intake manifold carb interface. Also a leak can occur in the carb itself where the butterfly shaft works in the carb body (loose fit from wear). You pretty much need a vacuum gauge to diagnose the problem. For $30 it's not a bad deal. You'll need it over and over again anyway as the years go by. Rev __________________ '66 Coupe, 306, 350-375 HP, C-4, 13.07 e.t., 104.8 mph, 1/4 mi. O.B.C. #2 '66 coupe

10-18-2003, 03:59 PM	#3
HotRoddin cranky old man Join Date: Sep 2001 Location: Longview Texas Posts: 683	Ditto what Rev said .... I would pay careful attention to the intake manifold gasket, especially in that engine, they had a tendency to spit them out. Replace the intake manifold gasket and the carb to manifold gasket, those are two very cheap very easy fixes on your engine and you will have ruled out 60% of the things that could be causing your problem. In the old days to check for a leak in the intake manifold gasket they would take an oil can and squirt heavy oil along the top edge of the intake manifold ... if there was a small leak there, the oil would seal it for a second and the idle would noticably change ... if the leak were large you could see it suck the oil down into the intake port ... its messy and sometimes smokey but it does work. Another way is to take a length of 1/4" or so rubber fuel line, put one end in your ear and run the other along all the gasket edges where you suspect a leak ... the tubing picks up only the sound very near its tip, so when you get near a vacuum leak you'll hear the hiss like its amplified ... that one isn't so messy but you do look like a goofball with the tubing in your ear __________________ Under Construction: 64 Falcon 372 cu in. stroker 1:72 rod ratio 6.250" rods (long rod), Comp Cams XE274 230/236 520/526 @ .050, Scorpion Rollers, Roush 200 irons, 10:1 Keith Blacks, Hedman long tubes, 750 Holley DP, Edelbrock Victor Jr., C4 3500 stall, gears and tires to be anounced.

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10-20-2003, 10:25 AM	#5
daccrow86 Registered Member Join Date: Sep 2003 Posts: 11	yeah one of my friends tryed something similar to that instead of oil we used w-d 40 and there was a leak around the bottom of the carb so we changed the gaskets and checked it again and there was no more leaks. and the problem persisted. yesterday we got it running it was running great we drove it all over town it was all good we got home turned it off went inside got a drink got back in the car turned the key it wouldnt idle. we were bak in the same old boat again. my next step is to take it to the shop and see if they can fix it. if they can fix it i will probably sell it.