....the leak does seem all fixed with the new sending unit, but short of refilling the reservoir, how would I bleed the system?-g
To bleed the system you'll need:
Paper Towels
Wrenches
Mechanic's gloves
Spray bottle with Distilled water
ground cover/drip pan/fluid catch system
To bleed the system:
Locate the radiator hose that enters the head, next to the cam housing and intake manifold and up/behind the distributor cap. On top of the hose flange that the hose is fitted on is a 12M or 13M bleeder bolt. Be sure the wrench you're using fits the bolt properly. Place the drip/fluid catching system under the front of the car. don't let the coolant/water run onto the ground and into the street. Surfers don't like the taste of ethylene glycol, and it's now a crime to knowingly discharge fluids into the storm-water system. (Note: there are water-narc's everywhere. Be environmentally consciensious.)
Be sure there is plenty of coolant/distilled water in the reservoir. Start the engine and let it warm up to operating temperature; I wait until the fans cycle on once.
Carefully stuff the paper towels around the radiator hose and cam housing, and under the intake manifold to absorb coolant as it's being bled. With the engine running, loosen the bleeder bolt slowly until coolant/air (hopefully) squirts out. Use a towel over the bolt if it's squirting aggressively. Tap the hose and hose flange (where the bolt lives) to ensure any trapped air is dislodged. Close the bleeder bolt.
I used to open the bolt for about 5 to 8 seconds to bleed the system. That may not seem like much time, but when hot fluid is squirting/spritzing everywhere, five seconds is an eternity! The mechanic's gloves will help prevent any hot fluid from irritating your hands. I also have used Nitrile or Playtex gloves. The idea is to protect your hands from 180-degree fluid. Try not to let the fluid get into or behind the timing/balance shaft belt cover. Timing belts don't like ethylene glycol, either (I think they go surfing when you park the car
).
If you think you have more air in the system, open the bleeder bolt for another 5 seconds. Check the reservoir. Still plenty of fluid in it? Good. As long as you have fluid in the reservoir, you can repeat the bleeding process. No fluid? STOP! Wait for the engine to cool down, and add more distilled water to the reservoir (never use tap water in your coolant system).
Do not open the reservoir cap when the engine is hot. It is pressurized!Turn off the engine, remove any wet paper towels, take the spray bottle with distilled water and clean off everything nice and dry. You want to make sure all the discharged coolant is cleaned up to reduce odors when driving, and prevent any long-term corrosion from old coolant ponding around the head and cam housing.
Be sure the bleeder bolt is tight.
You're done. Have a beer and relish the peace of mind only a shade-tree DIY mechanic can have.
Good luck!