94 B250 What's the best way to find a vacuum leak - DodgeTalk : Dodge Car Forums, Dodge Truck Forums and Ram Forums
 
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#1 Old 04-17-2009, 08:06 AM
BAMAVAN
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94 B250 What's the best way to find a vacuum leak

I've traced all the tubes but can't see it visually.

Thanks for your help.
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#2 Old 04-17-2009, 08:21 AM
alloro
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What is making you think that you have a vacuum leak?
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#3 Old 04-17-2009, 09:57 AM
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My air keeps swithing back and forth from the defrost to the front vents. Also my AC compressor is kicking on for about 4 to 5 seconds and then off for 4 to 5 seconds. I've checked the freon and I have good pressure.
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#4 Old 04-17-2009, 07:38 PM
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There's a vacuum hose that comes off the passenger side of the intake manifold. That hose is the one that feeds the vent actuators. If the vent/defroster switch happens when accelerating or climbing long hills, it might just be a leaking check valve (1-way valve). The check valve is in the hose I mentioned above, about 4" away from the intake. You can test the check valve by blowing through it. Air should only go one way but not the other. If it's not the valve then you'll have to follow that vacuum hose and find the leak.
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#5 Old 04-18-2009, 09:59 AM
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A hand operated vacuum pump that you buy from the auto parts store for between 30 and 40 dollars will help with this-Some will have a brake fluid recovery jar as well. Especially if you have good ears to hear the hissing sound that some leaking parts will make, though not all of them will. I found the hose to the evap canister was not full on the canister causing a leak on my van. Just had to push the hose on to the canister tighter.

1977 Chevrolet Impala Sedan, 5.0L, TH200, 2.56:1, 106K miles, 37 Lifetime Warranty Parts.
1989 GMC Sierra Extended Cab 5.7L, 5 Speed, 3.08:1, 327K miles, 0 Lifetime Warranty Parts.
1997 Dodge Ram B2500, gone.

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