Water Leak - A/C Evaporator/Heater Area
Article No. WATER LEAK - A/C EVAPORATOR/HEATER AREA 87-6-3
MERKUR 1985-87 XR4Ti
ISSUE: Some Merkur XR4Ti vehicles may have water leaking into the passenger compartment at the front footwell and tunnel area. This article is intended to assist in diagnosing the source of the water and to outline corrective action.
ACTION: There are two primary sources for this water entry and in some cases more than one source may be applicable, particularly when prior service attempts have been unsuccessful. The two sources are condensation from the air condition system and outside water from rain or car washing. In both cases the water will be seen dripping at exactly the same area. The only exception to this is when the fuse box cover is loose or missing, in which case external water will wick through the wire harness and drip in the left footwell above the brake pedal. Whenever external water is suspected, proper installation of the fuse box cover should be checked first.
Before beginning the diagnosis, it should be understood that a water leak from condensation is the result of a nonfunctioning evaporator housing drain system. External water entering is the result of improper evaporator housing sealing. In both cases the water enters the vehicle through the same opening in the body, but from different causes. For this reason, all three of the following tests and applicable repairs should be conducted on concern vehicles in the order they are shown.
Test #1 - Duct Hoses
A disconnected or missing air duct hose, especially the center register hose, decreases blower motor resistance and increases the blower motor speed. The increased speed creates a vacuum at the evaporator fresh air inlet which can draw rain water into the air distribution system whereupon it collects in the heater housing and leaks on the tunnel area.
1. To check, place the air distribution lever in the "panel" position and close all instrument panel vents. Turn the blower switch to low speed in the outside air mode and open each vent individually and check for air flow. If no air flow
is detected in one or more of the vents, refer to the Merkur XR4Ti Shop Manual, Section 36-01 and connect the duct or ducts as required.
NOTE: If it is determined that the center duct is not connected, do not attempt to connect it by removing the center register. The center register can only be reinstalled by removing the instrument panel from the vehicle.
Test #2 - Water From Condensation
The evaporator housing drain system works on the principal of a balance of gravity and internal vacuum pressure. Any fault with the system or components will result in water being drawn to the blower motor and forced into the air distribution system rather than into the drain hoses.
Figure 2 - Article 87-6-3:
1. To check, operate the air condition system on maximum cold for approximately thirty minutes (or less depending on humidity). If water is observed dripping on the tunnel area, turn the system off and check the drain hose and check valve assemblies. The hoses protrude into the engine compartment on either side of the engine (Figure 2). The hoses are a slip fit on the evaporator drain tubes. When removing, note the side (right and left) for proper reinstallation. The hoses and valves must be clean and free of foreign material. The check valve rubber flap must face outward, be snug but have just enough clearance at the center pin to allow it to be freely rotated. It cannot have any holes or gaps at the outer edges. If a fault is detected, clean or replace the hose assemblies as appropriate and retest the system.
NOTE: The check valve and hose are serviced as an assembly (E5RY-19858-A/C).
Figure 3 - Article 87-6-3:
2. If no fault was detected in the drain hose assemblies and/or if condensation water is still dripping into the interior of the vehicle, refer to Section 36-01 of the Merkur XR4Ti Shop Manual and remove the evaporator assembly from the vehicle. Remove the upper case half and inspect it for warpage or damage and replace it if necessary. Similarly, inspect the lower case half. The ribbed drain area beneath the evaporator core and the drain channels leading to the hoses must be open and clean
(Figure 3). The plastic covers over the drain channels must be tight to the case body. On some vehicles these covers have been found to be loose and/or warped. When this occurs, blower motor vacuum draws the water out of the channels and into the heater ducts. If this condition is found, secure the covers with a suitable plastic cement and a light bead of butyl sealer. Use caution not to block the channels.
3. In a few cases a combination of tolerance stackup and slight warpage of the lower case half may have decreased the clearance between the case bottom and the evaporator core. This restricts the air flow that normally pushes water into the drain channels and allows some water to flow back towards the blower motor. To correct this condition, shim the evaporator core up from the case bottom 1/8 inch (4 mm) as shown in Figure 3. Use a suitable material compatible with aluminum placed across the case bottom ribbed area. An example would be two lengths of brazing rod. Do not use steel or wood. It is recommended this step be done on all concern vehicles whenever the housing is being serviced.
Figure 4 - Article 87-6-3:
4. When assembling the case halves, apply a bead of sealer in the "V" groove of the mating joint and the opening for the blower wires (Figure 4). Before installing the assembly in the vehicle, inspect the plenum seal at the recirc door and replace it if it is damaged (E5RY-18B623-B). The lower gasket between the housing and air distribution opening (E5RY-18583-A) must be replaced. This is a compressed seal gasket that remains compressed after use and is likely to leak if reused.
Test #3 - External Water Entry
1. With the exception of a loose fuse box cover as previously noted, external water can enter the evaporator housing in several places but entry into the interior of the vehicle is always through the air distribution opening in the body beneath the blower motor (Figure 4). To facilitate water testing, remove the plastic insulator cover at the cowl to expose the evaporator assembly to water flow. Set the air distribution lever on the
"floor" position and activate the blower motor on high speed. Direct a liberal flow of water across the windshield in a manner that allows water to flow over the center cowl area and the evaporator housing. It should be noted that water entering the vehicle is first absorbed by the foam rubber gaskets at the heater housing and does not start to drip until the gasket is saturated. Therefore, a minimal leak may not be observed until approximately thirty minutes of continuous water flow after starting the test.
2. If water is observed entering the vehicle, first check to ensure the blower resistor, the top inspection plate, grommets and the blower wire opening (see Figure 4) are secure and sealed. If a fault is found with these items, repair/seal as necessary and retest. If no fault is found or if water entry is still present, remove the evaporator assembly from the vehicle as outlined in Section 36-01 of the Merkur XR4Ti Shop Manual.
3. Remove the upper case half and apply a bead of sealer in the "V" groove (Figure 4). Discard the lower gasket and replace it with a new gasket (E5RY-18583-A). Inspect the plenum gasket and replace it if necessary (E5RY-18B623-B). Reinstall the assembly in the vehicle and retest.
NOTE: Use caution when reinstalling the assembly as the lower gasket may catch on the mating surface and not seat properly.
PART NUMBER PART NAME CLASS
E5RY-18583-A Gasket C
E5RY-18B623-B Seal C
E5RY-19858-A Hose Assembly - C
A/C Drain (R.H.)
E5RY-19858-C Hose Assembly - C
A/C Drain (L.H.)
OTHER APPLICABLE ARTICLES: None
WARRANTY STATUS: Reimbursable within the provisions of the Warranty and Policy Manual
OPERATION: SP870603A
TIME: 5.3 Hrs. DLR. CODING: Basic Part No. 19860 - Code: 47