coolant system flush question

trik-99 · October 6, 2015

I recently bought a 99 Silverado 5.3 with 101,000 miles on it.

Since I don't know how long ago, if ever, the cooling system was flushed, I would like to flush the whole system using one of those Prestone flush and fill kits.

I have used these kits successfully before on my older vehicles. Have any of you ever used this kit on one of these trucks and if so, which heater hose did you splice the flush tee into?

I have always heard bad things about Dexcool coolant in the past but maybe it's a lot better now. Would you all suggest staying with Dexcool after the flush or changing over to a green colored coolant like regular Prestone used in older vehicles?

Thanks for your input on these questions!

CapitalTruck · October 12, 2015

If you have no issues with the cooling system I probably wouldn't do the flush tee thing. I've never trusted those things leak wise. I bought a bunch of Dex-Cool antifreeze pre-dilute, drained radiator (let it keep flowing...it takes a while), refilled with predilute, ran engine, drained radiator again, added pre-dilute. That exhanges most of the antifreeze, at least enough to keep the PH good and safe. Dex-Cool is fine now. The reason I used the pre-dilute is that it takes care of the water question (mineral content in tap water).

Drain the radiator, fill with water, drain, refill with water, drain and do this until it runs clear. If you flush until it runs clear, use concentrated Dex-Cool and add 1/2 the cooling system's capacity (I think you'd be adding two gallons). After you get the two gallons in, use water to fill up the system to the fill line. This will ensure you have a 50/50 solution.

txab · October 12, 2015

If it came with Dex, replace it with Dex. Nothing wrong with it

Gurrzt · October 12, 2015

After doing what is prescribed above, I would use a 50/50 mix of Dexcool and distilled water, also adding an additive like "purple ice" or "water wetter", whether some say it works or not, for $8 to $11 more it won't hurt.

trik-99 · October 12, 2015

Capital,

I'm not really having any issues with the cooling system. It's just that since I recently bought the truck from a dealer and don't know the history of the truck I just thought it might be a good idea to flush the cooling system and put in new anti-freeze, especially since I don't know how old it is.

I have used the Prestone flush and fill kits numerous times on several older vehicles and never had a problem with leaks from the part you splice into the heater hose lines. It make flushing the system sooooo much faster and easier than repeatedly draining and refilling like you mentioned, plus it backflushes the whole system including the heater core, radiator, and engine block.

If you are happy and confident of the way you do yours that's fine. I just like this system a lot better and asked my questions because I was not sure which heater hose to splice into since they are arranged a little differently than an older vehicle system is.

I wasn't sure about using the dexcool antifreeze either because of all the horror stories I heard about it when it first came out years ago. You guys seem to think it's OK now so they must have made some changes and improvements in it over the years.

Anyhow, thanks for all you guys comments and opinions. I do appreciate it.

waumo1 · October 12, 2015

I think the Dexcool "horror" stories were related to people mixing regular antifreeze with it (whether they knew it happened or not). I've had GM vehicles since they started using Dexcool and never had a problem with it in any vehicle except my stepfather's 98 S10. I'm almost certain someone topped it off with regular antifreeze setting in motion a long term mess.

WilliamBos · October 12, 2015

The original Dex formula was propylene glycol, if left low and once air entered the system, it got nasty. GM switched the formula to Ethylene glycol and there have been no more issues. Buy a new thermostat and housing and change both. The housings hsve been known to break.