Reverse Flush Cooling System

[bill buttermore]

Here is a way to reverse flush the engine, radiator and heater core separately. 95 SLE is described, others similar.

FLUSHING MUST BE DONE WITH A COLD ENGINE TO PREVENT SERIOUS DAMAGE

Drain coolant from the radiator and part of the engine by undoing the splash shield and the lower radiator hose. Loosen the radiator cap to provide a vent. Catch and contain the first flushes from each component when the concentration of coolant is high. Don't leave puddles of coolant on the ground. Dogs and other animals can ingest the sweet tasting stuff and die from it. Check with your local municipality for proper methods of disposal of used coolant.

Engine: Remove the thermostat, then install the top radiator hose and thermostat hose fitting back on the engine with the radiator end of the top hose disconnected. Remove the lower radiator hose from the radiator. Wrap a rag around the hose nozzle and flush the engine through the top radiator hose until the water from the lower radiator hose runs clear.

Heater core: Remove the hoses from the tensioner assembly and flush through the bottom hose until the water from the top hose runs clear.

Radiator: Remove the top and bottom radiator hoses from the thermostat and the water pump. Wrap a rag around the hose nozzle and flush through the bottom radiator hose until the water from the top hose runs clear.

System: Run engine briefly and repeatedly to stir up sediment: Install a flushing tee in the top heater hose by disconnecting the hose from the top fitting and using a spare piece of hose to connect to the tensioner assembly. Reconnect all but the top radiator hose at the thermostat. Fill the system with water at the thermostat opening, and then the radiator. Install a drilled thermostat. With the radiator cap removed, flush through the flushing tee, periodically starting the engine and allowing it to run for only 7-8 seconds at a time. Flushing must be done on a cold engine and the engine must not be allowed to get warm. Cold flushing water will crack hot engine castings. Depending on how cruddy the engine is, it may take 5 or 10 engine "mixes" until the water runs clear after the engine is run.

Filling: Remove the lower radiator hose from the radiator to drain the water from the radiator and partially from the engine. Remove the flushing tee and both heater hoses from the tensioner assembly and blow the water out of the heater core and hoses by mouth or by gentle air pressure. Reconnect the lower radiator hose. Hold the ends of the heater hoses at the same level and pour straight "mixes with any color" coolant in one hose until it begins to run out the other. Reconnect the heater hoses. Fill the engine at the thermostat opening, and then the radiator using straight coolant. Considering the water remaining in the engine, that should give you at least a 50/50 mix. After cleaning it, fill the expansion tank with 50/50 mix. The system holds about 13 quarts, so you will need to add 6.5 quarts of pure coolant to get a 50/50 mix.

Bring engine to operating temperature and bleed air from screw on thermostat top radiator hose fitting.

[Pontiacdad]

This procedure works great for 2000+ as well.
On the 2k's it might be tough to remove the lower rad hose without a long reach set of needle nose pliers, you can also pull the drain plug on the rad, it uses a 3/4" wrench and is on the drivers side.

[gonzo4191]

whats a flushing tee?

[bill buttermore]

Prestone sells a flushing kit for about $5 that includes three different size plastic T fittings. The straight legs of the T are connected to the heater hose line and the branch is threaded to fit a special adapter for your garden hose. By installing the 5/8" T in the heater hose, you can flush the heater core, engine, and radiator simultaneously while running the engine. Running the engine briefly operates the water pump which helps to stir up any sediment in the engine and helps to flush it out.

This is all that most people do to flush the system. It works okay, but is not as thorough and effective as isolating and reverse flushing each component as described above.

[gonzo4191]

not to dig up old thread, but i needed to do this, and had a hard time finding it, can we put this is techinfo or sticky it?

[bill buttermore]

not to dig up old thread, but i needed to do this, and had a hard time finding it, can we put this is techinfo or sticky it?

I'll go ask da boss.