Do i need to drain any coolant to replace the thermostat? the housing being on the top of the engine, i was curious if there are any cheats to doing it without needing a drain, as i live in an apt (lot parking), and it'd just plain be easier to not have to drain fluid.

Well when your engine is cold the thermostat will be closed. Once you pull off the Thermostat housing you are going to get some coolant that is sitting on top of the thermostat. So basically if you drained the coolant out of the radiator, you are still going to have some coolant that is trapped on top of the thermostat because the stat is in it's closed position.

Just have a few rags close by because the coolant will spill out onto your intake manifold a little bit.

Na, you won't have to drain the coolant. Some will spill out when you pull the hose and housing off, but only a little. May have to add some coolant though, but it's better than trying to either filter your old coolant or buy all new. After the job is done, wash it off with a garden hose if you want.

just drain it down about 6" below the top of the radiator. if you are careful, you can catch all the coolant you drain with a drain pan. do it when the engine is warm enough for the thermostat to be open, but not so hot that a lot of pressure builds ups.

You will probaly lose a little coolant no matter how hard you try not to, so spread some newspaper underneath. Wait until its cooled off. The pressures will equalize between the upstream and downstream of the the thermostat. Its not a perfect seal when its closed, and anyway there is a small opening in the valve designed for this purpose. So leave the rad cap on and place a suitable container under the petcock. Wide shallow containers minimize the chance of dripping on the ground, but are very difficult to handle and drain without spilling. If you use a wide shallow container, drain in stages and transfer to another container for refilling the system. A clean plastic gallon milk container works fine for this. Need a funnel of some kind.

The petcock is left-hand thread to open if I remember correctly. open the rad cap and petcock and Drain it down to lower than the thermostat housing level. Remove the two capscrews holding the thermostat housing and give it a few taps sideways to loosen and remove it. No need to remove the hose. Clean and smooth both surfaces--the thermostst housing and manifold. If they are flat, clean and smooth, no sealer is necessary, just the gasket. Be sure to put the new thermostat in same sas the old one came out, so watch it and take a snapshot if necessary. Best replacement thermostat housing for the money are the cast iron 4 Seasons and other brands.

Refill the radiator and let it gurgle for a few minutes and start it up and check for leaks. You can leave the cap off and watch the level in the radiator and see the flow to start when the thermostat opens. Shut it off and let it cool down and fill to brim if reservoir equipped, or to one to one-and-a-half inches below the top if no reservoir. Fill the reservoir to the cold line. I've heard of air locks and "burping" the system, but never seen it since I started doing this stuff in 1960.

Works for me; my $0.02