Vaccum Leak! PLEASE HELP!

[Midnight]

FOLKS! i have a vaccum leak somewhere.... my AC will go to defrost when i make a minor accelleration, and a rough idle while in gear.. stopped... i took it to my mechanic.. my pcv valve looked a little cracked so i replaced the whole assembly for the staggering 33$. but my mechanic checked everything and couldnt find the problem

does anyone know of any vaccum leak issues... my friend had the same problem with his marauder and its at a control valve for the AC..the one right underneath the glove box. HELP!!!!!!!!!!!! AAAH!!!! :bows::bows::bows::bows::bows: :bows::bows::bows::bows::bows:

[fastblackmerc]

Check all the hoses and the vacuum canister (small square box on the left front fender). With engine running, spray carb cleaner on all the vacuum connections, when the engine RPM's change you've found the leak.

[Motorhead350]

Check the little hose that is to the passenger side of the intake manufold. The connection is curved to a 90 degree angel. When I put on my blower that kept coming off and I thought the engine was screwed at first, then I just put a clamp on it and the problem was solved.

Check it out!

[Midnight]

But has anyone experienced an issue with that ac control? Has anyone had a leak and could tell me where it was. I checked all the hot spots. Ill try to cap that control valve and see what happens

[Wires]

Sounds like the Electronic Air Conditioning Control module. The O-rings in the valves inside go bad, causing a vacuum leak and the symptoms you describe.

I think there's a sticky somewhere, or maybe someone who is better at searching than I am can link to the thread showing how to fix it.

I got lazy and had my mechanic install a re-built one.

[Wires]

Mine became an altimeter. The blower would output from the dash vents under 4000 feet. From 4000-6000 feet, any acceleration at all would send the air to the defrost vents, but it would return during cruise. At over 6000 feet, it would stay in defrost. It was NOT a fun trip to North Carolina!!!!

[Midnight]

so what did you do wires?

[Midnight]

and also, its "electronic" so why would it cause a vaccum leak?

[Richy04]

My bet its the EATC as well, your vac leak is in the car, not outside. As the other poster said, the heater is flip flopping back and forth on accel and deccel, a sure bet the eatc is losing vacuum.. The post is easy to find related to eatc repair.


Found it, here is the post.........


http://www.mercurymarauder.net/forums/showthread.php?t=36922

[Richy04]

and also, its "electronic" so why would it cause a vaccum leak?


It is electronically controlled, but the a/c and heater servos are vacuum operated, meaning vac from your engine is stored in a can (amplifier) the unit then bleeds off this vacuum to pull the diaphragm in (or out) to move the doors to divert the heated or cooled air to the appropriate vents.

The controller is electronic, but it distributes vacuum to the servos that need to be opened or closed. The eatc has passages that use O-Rings to seal them and they go bad, get hard,shrink or tear. The vacuum is then lost and the vents dont work properly, air then rushes in and you have a vacuum leak. Your engine will run funny since the leak is after all of your engine controls which monitor vacuum.

[Wires]

^ what he said. With no vacuum, it's in "defrost" mode, for safety. You need vacuum to cause the positive air pressure to move the various diaphrams to direct the air elsewhere. With a bad valve or two, the air leaks in and you get defrost.

I ended up paying my great Ford mechanic to install a re-built one. I should have done it myself, but I had to go to Atlanta (Marietta) anyway, and he had it ready to go sooner than I could have changed the o-rings myself.

[Midnight]

does anyone know where the solenoid is?

[RF Overlord]

Midnight, read the sticky at the very top of the Shop Talk forum...it will explain everything.