Vacuum leak

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Apr 21, 2019 | 12:45 PM

Dweber85rc

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Fleet Mechanic

Joined: Mar 2019

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Vacuum leak

I have an 01 excursion with the v-10 and have what appears to be a vacuum leak. Now the heat or ac coming out of the vents will stop and switch to defrost when you give it some throttle. Are there any common spots on these to look for?

Apr 21, 2019 | 02:49 PM

WE3ZS

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From: Media PA

Check the under hood vacuum lines for something obvious first, then look over the electro mechanical vacuum switch for the Front hubs mounted to the pass side inner fender just rearward OD the battery. Those switches are becoming a common leak source.

May 10, 2019 | 08:22 AM

Dweber85rc

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Fleet Mechanic

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Does anyone have a diagram for the vacuum system or a list of the different size tubing? I have not been successful in finding the leak and am just going to start by replacing some of the tubing

May 10, 2019 | 10:08 AM

wae

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Joined: Mar 2005

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This may not be helpful, but I had an E150 a while back that used what appears to be a similar blend door actuation system and it had the exact same problem that you're describing. As I understand it, when there's no vacuum the blend door system fails to the defrost position since it's safer to drive cold or hot versus blind. My vacuum leak was caused by a failed check valve that I think was between the vacuum reservoir and the blend door actuator. When they build the vans, they hang the whole HVAC system in the air and then assemble a van around it so I never went through the effort to replace it. On the Ex, if you pull the glovebox out, much of the system should be readily accessible to be able to put a Mityvac on the hoses and test for function, leaks, and if the check valve is checking.

May 10, 2019 | 02:08 PM

90limited

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Joined: Nov 2018

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Mostly likely the auto locking hubs. That is where mine was. Pull the vacuum line that goes to the auto hub control solenoid and plug it. Bet the problem goes away. It is on the passenger side just forward of the vacuum canister and is mounted on the fender. My solenoid was cracked...