Write-Up: Flushing Radiator Coolant

ibmoses wrote:

One thing that would be easy to overlook or to not notice when servicing the radiator is to be sure and verify that the drain pipe inside the radiator overflow reservoir and the hose that goes from the reservoir to the radiator are not clogged. That little metal tube inside the overflow reservoir is easily clogged and it only takes a few minutes to remove and clean the reservoir. While you have it off check the hose to make sure its not clogged.

Bert

Oh yeah, definately. I took out the reservoir tank and cleaned it with a power washer. I should have mentioned that I also replaced the thermostat, rad hoses and overflow tube.

deekster_caddy wrote:

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.

Derek, I'm curious. You let everything drain out the bottom of the radiator, and it only comes to a gallon? The total capacity is 3 gallons, and I can't see the dash holding very much...

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.

Rickw wrote:

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.

Well, per the "electronic" GM SPO manual the 3.8 litre coolant capacity is 13 quarts, which is just under 3 gallons... As I've said, my memory is crap, but I think I put a gallon & a 1/2 of anti-freeze and an equal amount of distilled water in my motor when I converted...

Eldo wrote:

deekster_caddy wrote:

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.

Derek, I'm curious. You let everything drain out the bottom of the radiator, and it only comes to a gallon? The total capacity is 3 gallons, and I can't see the dash holding very much...

It takes about 1-1/2 gallons total. Not enough for a full 2. 1 gallon of DexCool, 1 gallon of distilled water. I mix pour in about 1/2 gallon of each, then pour the other 1/2 gallons into each other so I have a 50/50 mix, then I can pour the rest in as needed, pre-mixed.

The engine and heater core hold quite a lot of coolant. If you want all the rest out, you need to take the supercharger off... then the heads and tip the block over... and I can assure you there is a LOT more coolant in there than the radiator holds.

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.

Eldo wrote:

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.

The next time you have your stat out or are replacing and drilling a new one, if you could take a pic of where the holes are drilled and post it on here it would be appreciated. I know it is a simple procedure, but I'd like to see where, how many and the diameter of the holes in relation to the flange.

Eldo wrote:

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 understand the perceived benefits of a drilled thermostat, but you do live in a warm climate, and there is some reason they didn't do this for all cars. A drilled stat DOES affect warm-up times.

So you think you know more than every engine manufacturer who specs out a non-drilled thermostat? Some of the old V8s even have a bypass to keep coolant flowing around the block... (think buick 350 and 455) but why did they stop doing that?

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.

Rickw wrote:

The next time you have your stat out or are replacing and drilling a new one, if you could take a pic of where the holes are drilled and post it on here it would be appreciated. I know it is a simple procedure, but I'd like to see where, how many and the diameter of the holes in relation to the flange.

Looking at a ruler, I'd say they were a bit under 1/8". If you think of the bail that runs across the top of the stat as 12 and 6 o'clock, then the holes are at 3 and 9.

deekster_caddy wrote:

Some of the old V8s even have a bypass to keep coolant flowing around the block... (think buick 350 and 455) but why did they stop doing that?

I think that it's stupid in the summer, when I want ice-cubes to come out of the A/C, but the answer to your question is that we don't have shut-off valves in the heater hoses anymore. Ergo, the heater core loop provides the recirculation that the hose on the front of the engine used to...

AA wrote:

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.

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.

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.

You'll note that none of the reasons I gave were for hot cooling performance, I'm not talking about that kind of flow. And a pair of sub-1/8-inch holes are not going to make the engine "never get up to temperature".

As far as the opening of the stat, surely you've stood around with the engine running, the radiator cap off, waiting for the thermostat to pop so you could top off the coolant... Growing up in a garage, I've done it scores of times. When that 'still' water behind the stat finally gets heated by conduction instead of flow, the stat does open rather quickly. If it had a wide temperature range, it wouldn't be able to keep the operating temp in such a narrow one. And remember, when you're driving, the coolant in the radiator is being kept chilled by the rushing air.

For purging, you got me on the semantics. I should have written "helps when you are purging air from the system." I simply meant that when you're trying to purge the system, air, like water, will flow out to the radiator before the stat opens.

We'll just have to agree to disagree on this one, at least until I can see how it runs at Tahoe in mid-winter.

Eldo wrote:

but the answer to your question is that we don't have shut-off valves in the heater hoses anymore. Ergo, the heater core loop provides the recirculation that the hose on the front of the engine used to...

Never thought about that. Ah Hah moment.

Quote :

When that 'still' water behind the stat finally gets heated by conduction instead of flow, the stat does open rather quickly. If it had a wide temperature range, it wouldn't be able to keep the operating temp in such a narrow one.

I don't doubt that the t-stat responds quickly; I'm saying it doesn't go straight to open from closed. It opens gradually, so it's not at full flow when it first begins to open. It's not a "pop" thing, nor is it an on/off thing. There's a 10 degree range in which the t-stat operates (between 190-200ºF).

At 190º, the thermostat cracks open, as designed. It starts letting coolant pass at a slow rate at first, then opens wider as temps increase. In 40ºF ambient temps, it takes 5 minutes for the engine to warm up to 190º. Drilling holes will delay the t-stat in cracking open. Obviously the larger the holes, the longer the delay. My point is, if your holes are small enough that they don't matter much, then they really don't matter much (there are guys out there drilling multiple 1/4 holes in their t-stats).

Do the "jiggle pins" in most t-stats performs the same function as a hole drilled into the flange?

I think the jiggle pins do the same thing as drilling holes, but I don't see them in "most" thermostats, only high performance racing types.

I've never noticed that pin in any of the thermostats I've bought in recent memory.

AA wrote:

I think the jiggle pins do the same thing as drilling holes, but I don't see them in "most" thermostats, only high performance racing types.

The t-stat by "motorad" that is recommended for the Riv, has 'em.

I've seen these pins on certain thermostat designs for installation "clocking" which means that if oriented in any other way, coolant flow can be affected.

BKRIV wrote:

I've seen these pins on certain thermostat designs for installation "clocking" which means that if oriented in any other way, coolant flow can be affected.

Could be. I did notice that the second stat pictured is asymmetrical... The 'guts' are offset to the right.

I bought 3 containers of the 50/50 Dex-Cool today. Is that enough?