coolant flush

[eddiedaina]

I have a 99 gmc 2500 7.4 that has a leaking heater core and want to flush the system before i replace it and put appropriate coolant what is the best way to flush out all the old coolant?

[00Silverado4x4]

The only way I know how is to drain the system, remove thermostat and reinstall cover. Then refill with straight water, run the truck until it warms up, drain the system, repeat and then reinstall a new thermostat and refill with coolant of choice.

[MMC]

The block has two drains in it on the side remove them and flush out, you can also blow out the core with compressed air. Did you try bars leak to seal up the core?

[eddiedaina]

Thank you guys for the advice! I thought about using some Sort of sealant for the core but it looks like a very eeasy one to get to, no need to pull the dash! Do you guys think its a good idea to run prestone flush through the sysystem and flush it through one of the heater hoses??

[00Silverado4x4]

Yes, I'd say run some flush through the heater hoses. I don't know which hose is which so I'd run it both way to make sure you get as much crud out of the system as possible.

[diyer2]

If you did not do regular recommended coolant drains and new coolant refills, then flush it. Remove radiator cap and look inside for build up on the end of the radiator tubes.

Try this drain coolant into a container by opening pit cock on bottom of radiator and removing radiator cap.

Put hose in radiator and refill with water, start motor and let run until clear water comes out of the pit cock on bottom of radiator,

Do not let radiator get low on water or it will starve the water pump.

Good Luck

 

Edit run with heater on high.

[eddiedaina]

Hey there my chevy/gmc buddies! I got the flush complete first i ran a flush through the system theni disconnected the heater hoses and took the t stat off and ran water with a garden hose through both top and bottom hoses until water was clear! Previous owner neglected the cooling system it came out jet black Thank God i flushed it put heater core and so far so good just need to pray nothing else goes out never know when you buy used vehicles ! Thank you all for advice God bless!

[StepsideGMC]

So when you have completed a water flush, do you close the drain plugs off and leave the water in there with descaling agent, or leave the plugs open while it runs and just flush everything through?

 

When you drain the water at the end, do you wait until the block is cold or can you drain water out of a warm block and immediately add your new 50/50 dexcool?

 

If someone could number the steps on here that would be awesome. I am thinking of replacing my thermostat as well in the process.

 

Thanks,

Evan