K1500 Suburban Coolant Flushing

[SUBURBAN5]

I’m getting ready for the same project on my 98 K1500 Suburban so I’ll add my couple of questions here. For doing a good flush, do you just need to have the rear heat on to have it cycle the whole system? Remove thermostat or leave in? Do you install a flush T (if so where), or just stick a hose in the radiator cap, or just just drain top off repeat? I’ll be replacing heater hoses anyway since I’m getting a leak somewhere around the regulator that sends coolant to the rear heater (replacing that and the plastic T connections also).

Mostly I’m trying to make sure I know if the rear heat complicates things.

Thanks! Hopefully also helpful to the OP

Rear heat doesn't complicate things imo unless your trying to cap off or buy new hoses to the rear. Otherwise @Coveman has solid advise. I technically have 474k miles on my front heater core and rear. I should be replacing both but I've done several flushes through out the time of owning my burb. Also I've heard front to rear heater hoses or discontinued. Idk if it's TRUE. Now I put coolant flush in my radiator and overflow tank drove around 2 days at different speeds. Ran my heater just to circulate coolant to both. And then I drain it and I ran water to flush out as much as I could. Let it drain and hooked it back up and installed new thermostat drove around and checked it 1 more time to ensure coolant is at its recommended level. I'm now replacing all my hoses and fittings except for rear lines, for preventative maintenance.

 

[Char]

Suburban5, that’s the same plan I’m thinking of. Prestone coolant flush for a couple days, then drain and run garden hose through it all. Then drain and fill with Prestone “all vehicle”. I’m avoiding DexCool given all the bad things I’ve read about it when it’s not used in a closed system

My suburban has 197000 km / 122000 miles, not sure how old any fluids are. Coolant seems old given the sludge. Not sure if the radiator is stock, given the strange drain plug?
A 6mm Allen wrench fits perfectly in the plug, I think it might be a quarter-turn similar time one I found on google for a corvette

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I will give it a try when I get some time and report back!

 

[Pinger]

I recommend fitting isolation valves in the heater lines before they exit the engine bay so that the heaters can be isolated in the event of a leak aft of the bulkhead. Let me know how it goes - and inspire me to do the same to mine (still on my to-do list - sadly!).