Coolant Replacement

[grubby65]

I have been having some issues with cooling my 500/400 stroker. When the motor was built a thermostat was not installed so I decided to put a high flow 180 degree one in. I wanted to remove as much of the old coolant as possible because I was going with a distilled water/anti-freeze 50/50 mixture so I drained the radiator and pulled the plug on the block. I got everything put back together with the new thermostat and started it up. I let the car idle in the garage and the temperature did not get above 150 degrees with the radiator cap off. I turned on the heater and the air was warm. I got to worrying about having a large air pocket in the motor and not having hot water up to thermostat so it would not open. It was getting late so I shut it down for the night. From what I drained out and what I put in I'm about 1 gallon low of coolant. There is no bypass around the thermostat, I was going to drill a 1/8" hole in the thermostat plate before I installed it, but forgot. I guess my question is the block back fed through the water pump when you initially fill it? Should I be concerned or should I just take it out and drive it until the thermostat opens and then let it cool and fill it up with coolant. I don't want to hurt the motor.

 

[Yatzee]

I have been having some issues with cooling my 500/400 stroker. When the motor was built a thermostat was not installed so I decided to put a high flow 180 degree one in. I wanted to remove as much of the old coolant as possible because I was going with a distilled water/anti-freeze 50/50 mixture so I drained the radiator and pulled the plug on the block. I got everything put back together with the new thermostat and started it up. I let the car idle in the garage and the temperature did not get above 150 degrees with the radiator cap off. I turned on the heater and the air was warm. I got to worrying about having a large air pocket in the motor and not having hot water up to thermostat so it would not open. It was getting late so I shut it down for the night. From what I drained out and what I put in I'm about 1 gallon low of coolant. There is no bypass around the thermostat, I was going to drill a 1/8" hole in the thermostat plate before I installed it, but forgot. I guess my question is the block back fed through the water pump when you initially fill it? Should I be concerned or should I just take it out and drive it until the thermostat opens and then let it cool and fill it up with coolant. I don't want to hurt the motor.

At 180 degrees the thermostat will open and the pump will push coolant through all the passages. If you leave the cap off with the top tank of the rad about 1/3 full, you should be able to see the air come out the upper hose and flow through the rad. It will actually look a bit like foam. Do not raise the engine rpm's. Now you can start slowly adding glycol until you are up to the bottom of the fill neck. Make sure your overflow bottle is about half full, put the cap on and take it for a drive. Let it cool down and check your overflow bottle, it should now be lower. Recommendations are for a 16 lb. cap to get enough pressure in the system to prevent air pockets at the walls of the block. You will notice fluctuations in the level of the overflow bottle until all the air is dispelled and remember coolant expands about 6% when hot so don't let this fool you into thinking there's too much fluid in the overflow bottle. Always note the level with a cold engine.

 

[khryslerkid]

At 180 degrees the thermostat will open and the pump will push coolant through all the passages. If you leave the cap off with the top tank of the rad about 1/3 full, you should be able to see the air come out the upper hose and flow through the rad. It will actually look a bit like foam. Do not raise the engine rpm's. Now you can start slowly adding glycol until you are up to the bottom of the fill neck. Make sure your overflow bottle is about half full, put the cap on and take it for a drive. Let it cool down and check your overflow bottle, it should now be lower. Recommendations are for a 16 lb. cap to get enough pressure in the system to prevent air pockets at the walls of the block. You will notice fluctuations in the level of the overflow bottle until all the air is dispelled and remember coolant expands about 6% when hot so don't let this fool you into thinking there's too much fluid in the overflow bottle. Always note the level with a cold engine.

That would be instructions for a "closed" system.

If the op has a standard system, (without a recovery bottle) you need to have the radiator fluid level about 3/4" to 1" below the fill neck.

Don't install the cap until the thermostat opens and you see coolant moving through the radiator tank on either system.