3GM30F-Coolant drain placement?

[toddt]

The coolant in my 3GM30F is looking pretty sorry. My Seloc "bible" doesn't show where the block and heat exchanger coolant drains are for a 3GM30F. I found one petcock at the back of the heat exchanger but I think it's for raw water. Also, are the drains petcocks or plugs? I have the feeling the drain is on the back side of the engine. (bolts) Any help is certainly appreciated. Thanks in advance. Todd

[toddt]

I think I found the block drain the port side of the engine near the front. Any tips on the heat exchanger? I'm no mechanic.....is there a fresh water drain for the heat exchanger?

Thanks

Todd

[Liberty28]

Worse comes to worse, pull a hose off and blow out the system that way.

[never monday]

bottom of the heat ex and side of the block in the same area

[Badsanta]

There are several drains on the 3gm30f. To change your Engine antifreeze open them, or remove a lower coolant hose as liberty stated. If it looks that bad, drain it and refill with water run and drain till clear. Them drain and refill with a premixed antifreeze that is compatible with iron and aluminum. Most of the modern ones work. While your there change your oil and filter. To protect your fresh water cooling exchanger.After you refill your engine antifreeze, turn off your fresh water sea cock and connect that intake line to or stick it into several gallons of RV antifreeze. The cheep pink stuff at $4 a gallon start your engine till the pink antifreeze comes out your exhaust. Please use only the antifreeze for drinking water lines in the fresh water side of the heat exchanger as the automotive type will kill you and not good for the environment. You need both types of antifreeze for your motor. If you don't protect your heat exchanger you may have to replace it in the spring.