I recently tore down my 140K engine which has had dexcool 100% of the time. I thought the plastic LIM gaskets were _slightly_ warped, but not bad and certainly not leaking. I drain and refill my radiator with fresh coolant every year. (not a full system flush)

It takes about a gallon, and that way the contents don't become overly acidic or whatever.

I suppose I could do exactly the same procedure with the green stuff and I'd never have any problems with that either, so there's really no benefit to using one over the other.

When I drained/refilled the radiator and removed/cleaned/refilled the overflow it required just a fuzz less than two gallons of the 50/50 mix of Dexcool/distilled water.

Bert

I've never had to add more than 2 gallons after a flush and complete draining of the system. IIRC.
I remove thermostat housing , radiator drain plug and pull the lower hose.
I do believe the system is empty after that.
Eldo, are you sure about the 3 gallons?
Maybe you have the "Extra Capacity" option.

That's exactly what I do with the water & coolant, too.

One last question: is your thermostat drilled?

No. I won't run a drilled thermostat, I need to use my heat in the winters.

I've never understood why anyone would want to run a 180* drilled thermostat on the street.

Track use only along with careful monitoring of coolant temps and pressures.

Well, there are several reasons...

- The size of the holes that you can drill on these tiny stats is quite small, not enough to appreciably hurt warm-up. They certainly can't pass enough coolant to affect running temp.

- Having a couple holes there keeps the stat from vacuum-locking the cooling passages when you are trying to drain all the coolant from the engine, which is why I asked Derek...

- The holes help purge air back out of the system.

- Mostly, my father taught me to drill the stats so there was always some coolant moving thru the engine during warm-up, so in turn the heat doesn't have to move slowly through still water to make its way to the thermostat on the first opening cycle. That makes the water in the engine get hotter than desired, and then hits the engine with a cold shock when all that water in the radiator finally rushes in. If you watch closely, you'll see it on the gauge. I don't mind waiting an extra minute to reach operating temperature if it opens smoothly, instead of going past the stat temperature and then falling below it when it opens, and then settling down.

I'm with Deek - I wouldn't do it. With drilling holes, warm-ups can take longer (increasing engine wear), and you may never get up to proper temperature (also increasing engine wear). The better way, imo, is to tune your fans to cool the radiator properly, and letting the t-stat do its job. Mine warms up fast, then stays between 180-190º at all times.

The biggest reason I think most people drill t-stats is the misconception that t-stats open & close suddenly, rather than gradually. But nothing could be further from the truth. When you understand how sensitive the operation of a t-stat is, the need for drilling holes for a gradual stream of coolant becomes less concerning.

I don't think the coolant inside the engine gets hot enough on start-up (before the t-stat opens) to have a damaging effect, and automotive engineers seem to agree. If anything, it helps quicken the warm-up process to decrease engine wear. This is part of the reason we try to warm up a car during a relatively long period, to make sure we don't superheat the coolant to a boil before the t-stat opens. This way the engine heats up evenly, including the coolant in the engine.

I also don't believe the engine gets a shock when "all that water in the radiator finally rushes in". As mentioned, the t-stat doesn't open suddenly; it opens very slowly, letting a small amount of coolant through. It's a progressive valve, so in a way it acts like a drilled t-stat, but only when temperature demands it from the t-stat. By drilling, you make the t-stat less effective at its job, less dynamic. It would be the same as a t-stat that's stuck open a small amount. Remember at times the t-stat's job is to heat the engine in addition to cooling it.

I understand how a hole would help keep air from building up behind the t-stat, but how exactly does it "purge air back out of the system"? Where does the air go?

I do think a very small hole drilled in the t-stat wouldn't cause any problems, but it also won't do much to help performance. A larger hole or holes changes things, but I'm not convinced it's good things, especially for those in colder climates.