Where's My Vacuum Reservoir?

ford
mustang

#1

I’ve got a 1989 Mustang with the 2.3 and AC. My heater/AC control stopped working. The fan runs fine, but none of the doors that select where the air flows seem to be working. Now everything blows through the defroster vents. Also, I don’t hear the vacuum noises when I switch between any of the selections. The vacuum hoses looked OK under the hood. My guess is that the vacuum reservoir rotted through. Does anyone out there know where Ford hid it? I’m guessing in under one of the fenders, but it’s not obvious - both have various hoses and wires running through them.


#2

Find the main vacuum port on the intake manifold or behind the throttle body and follow it to the reservoir. Usually, they are tucked in the R/F (passenger) fender…


#3

Do you have power brakes? If so, I doubt it’s the reservior. It’s probably the blend doors or the hoses behind the dash.


#4

I don’t know what you are used to Greasy, but Ford used separate reservoirs for the brakes (inside the brake booster) and the AC (in the 80’s it would have been a metal can).


#5

I have replaced these before. I’ve actually gone to the supermarket and picked up a can of juice so I could use the can for a replacement reservoir. I just can’t find the darn thing! I’ll try to pull the wheel well cover off the passenger side. Its got to be under there.


#6

Oh, never mind then. I was figuring if they were coming from the same reservior than a leak that affected one would affect the other.


#7

Odds are the problem is not the vacuum resevoir.
It’s more than likely either a faulty one-way valve (usually located on the firewall and inline with the vacuum hose entering the interior of the car) or there’s a faulty vacuum pod.

This car should have several pods in the dash and odds are it’s the one behind the glove box. Remove the glove box, operate the controls, and verify that vacuum is reaching the pod and that the arm on the pod moves.
Those pods are little canister shaped widgets a couple of inches in diameter and about 3" long.