After doing the radiator removal/cleaning/fin straightening, I went ahead with the coolant swap. Gave up on the thermostat for now...just couldn't quite get wrenches on it. Anyway, the coolant was really dark. There is no oil in it nor water in oil, so I am happy. I did not drain the block and have started flushing with distilled water but only draining the radiator. I am running the heater. How many gallons is this going to take? Should I be worried about the black coolant? Thanks!

 

it sounds like someone never changed the coolant... what does it smell like? if it just smells like old nasty coolant i think you will be just fine as long as you swap it out. might have to do it a few times though.... might want to flush the block as well

 

What year is the car? The block should have one or two O2 sensors depending on the year. I would remove the sensor(s) and keep running tap water through the cooling system until water comes out clear. Don't run the motor; just let water flow through for awhile.

While the FSM doesn't really recommend the use of flush chemicals, you may want to get a bottle and add it (or half of it) as part of the flush once there is clean water coming out.

Once everything is closed up, fill the system with water and the flush stuff. Let the engine idle for 5-10 minutes and keep an eye on the coolant temp. Leave the heater temp on HOT. Put the pressure cap on so pressure builds up. Let everything cool down some and then drain the system again opening up the block. Let water run through for a minute or so.

Then re-fill with water, run the engine, stop, drain and repeat.

Then you can drain for the final time (again with draining the block). Use some anti-seize on the O2 sensor and re-install. For coolant, use what is recommended for the year (green or Dex). Add two gallons of concentrate followed by two gallons of distilled water.

If your car has an LT1 motor, make sure you open the two bleed valves; one should be on the thermostat housing and the other is on the TB. The L98 cars don't have them.

Add the liquid, start the engine, and when the thermostat opens and the coolant level drops, run the engine at about 1100-1200 RPM and continue filling to the top. Replace the cap and watch the temp. If the temp climbs above 230 or so, shut the engine off, let it cool, and then add more coolant. This may take a couple of tries to fully fill the system.

Make sure you clean out the plastic overflow bottle and add fresh mixed coolant to the proper mark.

 

I think you meant the KNOCK sensors....not the O2 sensors.
Or do you want to flush the exhaust? On the other hand, never underestimate a clean exhaust pipe.....

 

Yep, knock sensors.....

 

I know I'm going to have to drain the block now. I am never going to get things fully right until I can remove all of it. Last car I did was a full rebuild on a Ford 302, so it was just a matter of filling and burping.