Please save your self allot of time and know how to Flush, back flush and, flush your heater core properly. As I quote from the 1991 Escort Tracer Shop Manual
some one sticky this cause its importantWARNING: NEVER REMOVE THE RADIATOR CAP UNDER ANY CONDITIONS WHILE THE ENGIE IS OPERATING. FAILURE TO FOLLOW THESE INSTRUCTIONS COULD RESULT IN PERSONAL INJURY AND / OR DAMAGE TOTHE COOLING SYSTEM OR ENGINE. TO AVOID HAVING SCALDING HOT COOLANT OR STEAM BLOW OUT OF THE RADIATOR, USE EXTREME CARE WHEN REMOVING THE CAP FROM A HOT RADIATOR. WAIT UNTIL THE ENGIEN HAS COOLED, THEN WRAP A THICK CLOTH AROUND THE RADIATOR CAP AND TURN IT SLOWLY TO THE FIRST STOP. STEP BACK WHILE THE PRESSURE IS RELEASED FROM THE COOLING SYSTEM. WHEN YOUR ARE CIRTAIN ALL THE PRESSURE HAS BEEN RELEASED, PRESS DOWN ON THE CAP (WITH A CLOTH), TURN AND REMOVE.
Coolant Drain Procedure
With the engine off and sufficiently cool, remove the radiator cap, open the drain-cock and allow the coolant to drain. A 9.5mm (3/8-inch) hose may be attached to the drain-cock discharge orifice to direct coolant into a suitable container.
On 1.9l (Second generation; I don't know about 1st or about the 3rd generation SPI.), some coolant may remain in the cylinder block and can be drained by removing the headless pipe plug in the center of the block at the front of the vehicle using a 3/16-inch Allen wrench. Prior to installation of the pipe plug, apply Ford Pipe Sealant with Teflon (R) D8AZ-19554-A or equivalent. (Who knows what's equivalent to that?)
On 1.8L engines, the remaining coolant also may be drained by removing the bolt and copper washer located at the front of the cylinder block near the transaxle mounting surface. NOTE: there are two drilled and tapped bosses at this location. The coolant drain bolt is located in the upper boss the lower boss connects to the engine oil system and should NOT be used for this procedure. (Hmm coolant and oil lines for a turbo?)
Coolant System Flush Procedure
1. Drain the cooling system as outlined in this section
2. Install the block drain plug, if removed, and close the radiator drain-cock.
3. Slowly add water until the radiator is full and wait several minutes. As the water level in the radiator drops, continue to slowly add water until the radiator remains full.
4. Idle the engine for 3-5 minutes.
5. Turn the engine off and drain the water by opening the drain-cock.
6. Repeat Steps 1 through 5 as many times as necessary until nearly clear water is drained from the radiator.
7. Allow the remaining water to drain, then close the drain-cock.
8. Disconnect the overflow hose from the radiator filler neck nipple.
9. Remove the coolant recovery reservoir from the fender apron and empty the fluid. Flush the reservoir and over flow hose and clamp to the radiator filler neck.
10. Fill the cooling system as outlined in this section.
11. Start the engine and check for coolant leaks.
Cooling System Back Flush
1. Back flush the radiator. Be sure the radiator cap is in position. Turn the radiator upside down. Position a high pressure water hose in the bottom hose location and back-flush.
CAUTION: The Radiator's internal pressure must not exceed 138kPa (20PSI)
2. Remove the thermostat housing and the thermostat, as outlined in this Section.
NOTE: The ignition coil pack on the 1.9L engine and the distributor on the 1.8L engines are located near this area. Wrap them with a clean shop rag to prevent any water from entering the components.
3. Back-flush the engine. Position a high-pressure hose into the engine though the thermostat location and back-flush the engine.
4. Install the thermostat and housing as outlined in this section.
5. Fill the cooling system as outlined in this section
6. Start the engine and check for coolant leaks.
Heater Core Back flush
Back-flushing the heater core should be a separate operation to achieve the required reverse coolant flow.
1. Disconnect the heater core outlet hose that connects to the water pump. Install a clamp on a garden hose female end fitting and connect it to the heater core outlet fitting.
2. Disconnect the heater core inlet hose and position the hose to allow suitable draining.
3. Back-flush the heater core until the water runs clear out of the heater core inlet hose.
4. Remove the garden hose and reconnect all of the hoses.
5. Refill the cooling system as outlined in this section.
6. Start the engine and check for coolant leaks.
Coolant Refill Procedure
With the entire cooling system drained, the following procedure should be used to ensure a complete fill.
1. Install the block drain plug, if removed, and close the drain cock. With the engine OFF, add 50/50 Glycol water premix solution. Add the coolant until the radiator remains full (approximately 10-15 minutes are required to fill the system).
CAUTION: Less than 30 percent, approximately 2 liters (2.1 quarts) of coolant concentrate (-15C [4F] freezing point may cause engine corrosion and overheating.
2. Install the Radiator cap to the first notch to keep spillage to a minimum.
3. Start and idle the engine approximately 2 minutes.
4. Carefully remove the cap and top off the radiator with water.
5. Repeat Steps 3 and 4.
6. Securely install the cap on the radiator.
7. Fill the coolant recovery reservoir to the FILL HOT mark with the specified coolant 50/50 mixture. This will ensure a proper mixture and level in the coolant recovery bottle. Check for leaks at the drain cock and the block plug.