Subaru ff-1/1300/1400/1600/1800/Brat 1970-1984 Repair Guide

Cooling System



A quality ethylene glycol coolant, containing corrosion inhibitors should be used. A 50/50 mixture of water and coolant is recommended. Antifreeze concentration should be high enough to maintain freezing protection down to -34°F (-37°C).

When draining the coolant, keep in mind that cats and other animals are attracted by ethylene glycol antifreeze, and are likely to drink any that is left on the ground or in an open container. This can prove to be fatal in sufficient quantity. Always drain coolant into a suitable container. Coolant may be reused unless it is contaminated or several years old.


Never add coolant to a hot engine. Stop the engine and allow it to cool. Then, start it to circulate coolant uniformly through the block and add coolant slowly as the engine idles. Otherwise you risk cracking the block. Coolant can be added to the radiator. NEVER REMOVE THE RADIATOR CAP UNTIL THE ENGINE HAS HAD AMPLE TIME TO COOL TO BELOW OPERATING TEMPERATURE.

ff-1 and 1300G Models

These models have a sealed cooling system with two radiators and separate thermal expansion tank.

On 1300G models, it is not necessary to remove the cap to check the coolant level, because the expansion tank is translucent plastic. The coolant should be replenished if its level falls 3 / 8 in. (9.5mm) below the line molded in the side of the tank.

On ff-1 models, the cap must be removed from the expansion tank in order to check the coolant level which should be flush with the top of the pipe inside of the tank.

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Fig. Fig. 1 Checking the coolant level-ff-1 and 1300G models

If, on either model, the level in the expansion tank is lower than it should be, check the coolant level in the main radiator, as well.

The cap on the main radiator is not a pressure/vacuum safety cap. Never remove it when the engine is hot. Always remove the cap on the expansion tank first, after depressing the black button on it to release the pressure in the cooling system.

On both models, fill the main radiator to the bottom of the filler port. On the ff-1 models, fill the expansion tank so that the water just covers the pipe inside it. On 1300G models, fill the expansion tank up to the mark on its side. Add a good brand of an anti-corrosive ethylene glycol coolant, and water, in a 50/50 mixture.

Never add cold coolant to an engine which has overheated because of a low coolant level. First allow the engine to cool, and then idle it while adding the fresh coolant slowly.

Except ff-1 and 1300G Models

These models use a conventional crossflow radiator. Check the coolant level with the engine cold. To check the coolant level:

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Fig. Fig. 2 Checking the coolant level-except ff-1 and 1300G models

  1. Depress the black button on the top of the radiator cap to allow the pressure to escape from the cooling system.
  3. The coolant level should not fall more than 1 / 2 in. (12.7mm) below the plate welded inside the tank. Add a good brand of an anti-corrosive, ethylene glycol coolant and water (preferably distilled) in a 50/50 mixture.
  5. Install the radiator cap.


  1. Remove the radiator and recovery tank caps. Run the engine till the upper radiator hose gets hot. This means that the thermostat is open and the coolant is flowing through the system.
  3. Turn the engine OFF and place a large container under the radiator. Open the drain valve at the bottom of the radiator. Open the block drain plugs (If equipped) to speed up the draining process.
  5. Close the drain valves and the block drain plugs and add water until the system is nearly full.

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Fig. Fig. 3 Loosen the petcock to drain the cooling system

  1. Add a can of quality radiator flush to the radiator, following any special instructions on the can.
  3. Turn the engine ON and idle the engine as long as is specified on the can of flush, or until the upper radiator hose is hot.
  5. Turn the vehicle OFF and drain the system again. There should be quite a bit of scale and rust in the drained water.
  7. Repeat the draining and filling process several times, until the liquid is nearly colorless.
  9. After the last draining, fill the system with a 50/50 mixture of ethylene glycol and water.
  11. Run the engine until the system is hot and add coolant, if necessary. Install the caps and check for leaks.

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Fig. Fig. 4 After the last draining, fill the system with a 50/50 mixture of ethylene glycol and water