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Hello all! A few months ago I purchased a 2006 Silverado 2500 with the 6.0 Vortec engine. My coolant is slightly discolored and there seems to be a little scale inside the tank. I would like to backflush the system, but I am not entirely sure how on this truck. My Chiltons manual says to remove the thermostat and reinstall the housing by itself, then hook up a garden hose to the radiator and backflush. 2 chapters later, the same manual says that the thermostat is part of the housing and cannot be removed! Any advice?

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You won't know for sure until you remove the housing and look. Original pump had separate thermo and housing, replacement pumps often required a one piece housing/thermo.


Flushing the radiator by itself easy to do. Then you could flush the rest of the system

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I'm no sure on your truck, but the 5.3l you can buy a radiator fairly cheap. If I had to pull mine, I believe I would replace it before I paid someone to flush it. Might be just a little bit more for a new one. Rock auto  has a Delco for about $220 and a Sepectra for about $120 for the truck you described.

Edited by Retiredmastertech
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  • 2 weeks later...
I'm no sure on your truck, but the 5.3l you can buy a radiator fairly cheap. If I had to pull mine, I believe I would replace it before I paid someone to flush it. Might be just a little bit more for a new one. Rock auto  has a Delco for about $220 and a Sepectra for about $120 for the truck you described.

If I was gonna pull it, I'd replace it.

That being said , here's how I did my 06 5.3:

Drain radiator via petcock.

Remove t-stat, replace housing, don't stress over a little leakage, you're gonna replace the gasket later anyway.

Dump one gallon of distilled h2o and one bottle of "ZEP Acidic Toilet Bowl Cleaner" (available at HD/Lowe's/etc) in to the system (stay with me here); fill with distilled h2o.

Run until hot with heat on high to circulate thru heater core as well.

(I actually drove my Burb for a coupla days like this to really circulate the solution and give it time to work on any rust, corrosion, lime scale or whatever other crud has build up in there, especially if regular tap or hard h2o had been used previously.)

When ready to drain, run engine for a few minutes, shut down and drain by d/c'ing lower radiator hose.

Fill with straight distilled h2o. Run until hot with heater on high (again to circulate thru heater core).

Repeat 1-2 more times.

You are essentially rinsing the cleaning solution out of the system including all the water jackets, etc.

The last time, I drain via the petcock to make sure there is nothing obstructing it.

Wipe everything down to absorb any spills or leakage.

Replace t-stat and housing gasket. Make sure hoses are all secure.

Wipe and dry again.

Fill with correct mixture of your chosen flavor of coolant and distilled h2o.

Roll on...


FWIW, I did NOT use DexCool. I planned to use traditional "green" coolant but stumbled across a coupla gallons of Rotella ELC NF on clearance at WallyWorld. zep-toilet-cleaners-zuatb32-64_1000.jpege5e24e538a78410e122c3beef6e3fda5.jpg

Sent from my moto g(6) using Tapatalk

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