Preparing to Change Coolant

1. With engine running, set heater temperature control to maximum. The heater core water valve is not operated if the engine is off.

2. Switch off the engine and leave to cool completely, it must not be warm when changing the coolant.

3. Locate and remove the cold-air duct from across the top of the radiator by undoing the two 10mm nuts at each end, and the hose clip to the airbox.

4. With the engine COLD, locate the black plastic radiator drain stop-cock on the bottom left rear-side of the radiator. Place a catch-tray under the radiator stopcock, open the stopcock, the radiator cap & engine filler cap. Approximately 2 litres of coolant will drain out.

5. The bulk of the coolant is within the engine and will only drain via disconnecting the oil-to-water cooler hoses. Locate the oil-to-water cooler by looking down at the oil filter and noting the two coolant lines above. Place a 5L tray under the cooler hoses and using a pair of large pliars carefully squeeze the ears of the hose clips and slide off the hose. Then carefully twist the hose until it comes off and direct the coolant into the tray. Remove the other hose in a similar manner.

Flushing the System with Water

6. Flush the system with clean water, unless you change your coolant annually in which case it is not required. Coolant becomes acidic in 9 months and so should be replaced annually - we have a galvanised steel pipe running the width of an aluminium engine which will cause electrolytic depletion of the coolant. Clean coolant also prevents scale on heads (hot-spots) and on heater cores (also aluminium, but can still scale up).

7. After flushing with clean water, flush with a 50:50 mix of coolant:deionised water since around 1.5L of liquid will still remain in the engine block. There is a rear coolant block drain (right, lower side of the engine) which requires a new O-Ring to be purchased BEFORE it is removed from the engine and the car to be placed on jack-stands so it can be reached.

8. Syphon the coolant reservoir of old coolant, and refill with a fresh 50:50 mixture of coolant:deionised water until the "F" mark is reached.

Refilling the Coolant System

9. Reconnect cooler hoses ensuring old spring-clips if re-used are fitted in exactly the same place, remembering the coolant system is pressurised to 15psi. Close the radiator drain cock fully.

10. Measure out a mixture of 50:50 coolant:deionised-water and using a funnel trickle at 1L/minute into the engine's coolant filler cap. This pace will avoid air bubbles in the system and thus reducing air bleeding later.

Wash coolant off body work quickly, and dispose off properly (poisonous).

11. When coolant has reached the top of the radiator cap, fit & tighten the cap. Continue filling at the same slow rate until the engine filler-cap is full and tighten that cap.

Testing the system & Air-Bleeding

12. Verify there are no leaks, and oil cooler coolant hoses are secure.

13. Verify the handbrake is on, place the gearbox in neutral & depress the clutch fully. Start the engine and monitor the water-temperature guage. If any ANY point it goes past the usual 1/2-way mark, switch off, allow everything to cool totally and then add coolant to the filler cap again as required. Never undo any coolant cap with the engine hot, steam is dangerous.

14. Run the engine at idle speed until it reaches normal operating temperature, and then at 2200-2800rpm for 5 minutes until the radiator cooling fans turn on and then off again. Monitor the temperature guage throughout.

15. Then turn off the engine and allow to cool completely.

16. With the engine cool, undo the engine's coolant filler cap and add coolant mixture slowly as before until it is topped off. Usually only 0.25L is required if the filling procedure was done correctly. This may need to be repeated with a 0.05L top-up at some later date.

17. Verify the coolant mixture is correct for boiling point as well as freezing point protection using a coolant hygrometer. Canada may require a different mixture to 50:50 coolant:water such as 55:45 - check with your local dealer. If outside temperatures drop below -25oC then a Full Synthetic 5wNN or 0wNN oil must be used to prevent oil starvation on startup.

18. Verify that the coolant reservoir is on the Full mark. Dispose of the used coolant safely.

Notes:

Milky-Oil - coolant in oil or Oily-Coolant, do not even start the vehicle or engine damage will result, have it towed to a Mazda Main Dealer.

If the oil-to-water cooler coolant hoses ever need replacing, extremely long pliars are required to reach the clips deep in the engine block.

Driving an overheating all aluminium engine "that bit further" will totally destroy the entire engine, they are totally intolerant of such compared to old heavy cast-iron engines. At the first sign of overheating the engine must be switched off. Regular coolant changes will prolong the radiator, hoses, coolant-passages & heater core.

Coolant & additives which contain copper (eg, Redline Water Wetter) can cause small particles of brown sludge to appear in oil. It is not oil, but copper displaced which used up a little of the Water Wetter.

Last Upload: 31st January, 2002. V1.50a
URL: http://homepage.ntlworld.com/dorothy.bradbury/probemx/m_p3.htm