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Don Knight
Don Knight, ASE Certified Technician
Category: GM
Satisfied Customers: 1736
Experience:  40+ years all makes & models
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2005 Chevy Tahoe: properly flush the cooling system

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2005 Chevy Tahoe, 5.3L V8. How do you properly flush the cooling system? My Hayes manual assumes I have a radiator cap, so it's useless. I have no radiator access and no drain plug, so draining from lower rad hose is messy. Discharging from upper radiator hose would seem to completely bypass radiator.

I have the Prestone Flush Kit, but is it necessary? Also can't tell which hose goes to the heat core. I have two hoses to the firewall, and both come from the water pump.

Is the flush chemical really necessary? Some say yes, others say just flush with water.
If your coolant was clean when you did the water pump job then you really dont need to flush the system.Check the reservoir for any sign of ginger(that brown stuff) if the reservoir is clean then you dont need to flush the system.You can remove the drain plugs on the side of the engine but I really dont think that is nessary.Just fill the cooling system with a 50/50 mixture of antifreeze and you will be good to go,Don
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Customer: replied 6 years ago.
The Dealer did a flush, or at least said they did, about 100K miles ago. Not sure how they did it when the system isn't set up like older model vehicles. My surge tank is fairly clean and the fluid seemed clean when doing the water pump change, so I'll just refill and call it good. Replaced thermostat and coolant temp sensor while I was in there for good measure too, as I'm at 177K miles and this is the first issue I've had.

For future, how do they do the flush so I'll know the correct method for this model? I'm used to splicing into the heater supply hose with the flush Tee, and discharging from the radiator cap. I have no rad cap, and have two hoses from water pump to firewall. One of those hoses tees into the water pump (right at thr pump) via the surge tank line to the water pump; I'm assumng that's the hearter return? The other hose goes directly from pump to firewall, so I'm assuming that's the hose I'd Tee into. But then where would I discharge the flush water from with no rad cap access?
With no radiator cap the best way is to remove the upper radiator hose and run clean water from the reservoir till the discharge is clean and clear.Then disconnect the lower radiator hose to drain the system.Then connect every thing and fill the system.