Hey everyone, I was told it’s possible to flush the heater core and block of any remaining coolant in case there are different types lingering. You might have to open each image to see the arrows - sorry I couldn’t get better pictures. It’s currently green coolant, but never was sure if red, pink or orange was actually what needed to be used. I have the lower radiator hose pulled and I poured distilled water through to flush until it ran clear. I’m wondering if the two red arrows point to the correct square-headed bolts that allow you to flush the block - also, does anyone know what to torque these to afterward and if you should use something like black silicone on them? I believe that a 3/8” 8-point socket will loosen those bolts, right?

Also, to flush the heater core, would you pull the hose by the clamp shown with the green arrow or yellow arrow? I’m guessing that’s how this is done - pull the hose by the clamp and pour toward the heater core and let it flush. I know most people pull the lower radiator hose, then fill a few times, pull the hose again and keep doing that until they think it’s mostly clear, but I’m thinking that while the vehicle is up on jack stands and I can access these bolts, it might be good to flush everything in case I need to use a different type of coolant instead of the green stuff. I know many use green since it’s sort of an old American motor, but for whatever reason they used some other type from the factory. Is it OK to flush this while the front end is lifted up or does it need to be lowered to flush it, then raised to get the plugs back in? Is it a problem if coolant drains out and gets into some other areas? Hopefully it won’t get into the crank case or bell housing - by the way, anything necessary to clean the bell housing while it’s open or can it be cleaned later if needed without removing the sump? I’ve covered it while working, but hopefully no dust or spiders got in there. Not sure if any fluid runs through there normally that gets flushed or if it’s just lubricated at the factory and that’s it. Thank you

 

You can simply flush the heater core by disconnecting those two lines above the passenger side valve cover and just use a garden hose. Flush it one way until it runs out clear and then flush it the other way just to make sure until it also runs clear with a good flow. Engine block yes you would loosen those two plugs and coolant would flow out of them if you had a garden hose in the reservoir.

 

Thanks, any idea how tight the bolts should be torqued and would you use silicone on the threads to help them seal?

The water here is very hard - is it OK to use that for flushing? I have a few gallons of distilled water and I could try to get enough pressure through the heater core and block if the hose water is no good. Will it be an issue that the front of the vehicle is lifted up while flushing?

 

Use tap water to flush then put everything back together and run the disco up to temp up with distilled water. After that do the full drain the minerals in hard water to not cause problems instantly.

Or get a a cheap pond pump and use that to push the distilled water through the heater

 

Thank you, but I’m starting to think I better try to flush using the fill, run, dump, repeat until clear method. I might have to try these engine block plugs and heater core hoses another time, but it’ll be best if I stick to the more common method after all.

I know tons of coolant threads are out there and I’ve read them, but many are old and there are lots of opinions. I’ve heard that green Prestone concentrate is a good option. I have the generic oreilly brand green concentrate since I was told I can use anything green, but wondering if it’s best that I exchange it and get Prestone instead just to be safe with this.