ERAChas - A Simple Coolant Math Problem

[patrickt]

Chas, RodKnock's engine is now two years old and he knows he needs to change the coolant but doesn't want to hassle with burping the notorious FE air pocket that always develops, flushing the the heater core, etc. so he came up with a wonderful "simple" method for changing the coolant the "EZ way." Rod is going to simply open the petcock at the bottom of the radiator and drain one gallon of old coolant in to a catch basin while simultaneously filling his surge tank with one gallon of new coolant so that it is always full and no air gets in to the system. Just one gallon, mind you; no more. He will then take the car for a ride to thoroughly circulate the coolant, let the car cool, then drain another gallon of old coolant out while simultaneously replacing it with a new gallon. But Rod is smart, he realizes that his system holds four gallons and that while the first drain and fill replaced 25% of that old coolant with new coolant, the second drain actually had one quarter of a gallon of new coolant in it, so he was really only replacing three quarters of a gallon of old coolant. After two "drain and fills" he now has a system with two and one quarter gallons old coolant and one and three quarters new coolant. Rod says he will be happy if he can replace 90% of his old coolant with new coolant. How many times will he have to repeat his "drain one gallon while adding one gallon and then drive" task in order to achieve his goal of a 90% coolant change? Show your work for full credit.

[mr0077]

Four gallons = 512 ounces of liquid. If he wants to change out at least 90% of the old fluid, he can allow 10%, or 51.2 oz of old fluid left in the system. Each time he changes 1/4 of the fluid he leaves 3/4 (75% or 0.75) of whatever is in it. If he did this routine 8 times, he would have 512 x 0.75^8 of old fluid. 0.75^8 = 0.1001, roughly 10%, so 512 x 0.75^8 = 51.2578 oz, slightly more than 10% old fluid. Therefore he has to do this change 9 times to have 10% or less of the old fluid (he would have 7.51% old fluid and 92.49% fresh fluid, or 473.5566 oz of fresh fluid and 38.4434 oz of old fluid.

Why did I just do that?

[patrickt]

Originally Posted by mr0077

Each time he changes 1/4 of the fluid he leaves 3/4 (75% or 0.75) of whatever is in it.

The ratio of good to bad coolant changes on each iteration. It is not a 1/4 to 3/4 constant.

[RodKnock]

The problem is specious. The fluid in the coolant system was changed March 2009 at the same time a coolant recovery tank was added.

Heater core? Puh-leeze. I didn't mark PS, AC, PW, PB, PDL and convertible top on the option sheet either.

And no. I don't have cupholders either.

[patrickt]

Originally Posted by RodKnock

The problem is specious.

True, but only because Chas will not be able to figure it out.

[ERA Chas]

Originally Posted by patrickt

True, but only because Chas will not be able to figure it out.

Nooooooo...because Chas will not be stupid enough to dignify child games with a reply as poor Ken realized he had done.

Pat-did you get bounced off the Harry Potter Forum? Ran out of broken parts to flood us with macro digital full-color close ups? Slow night over on FE?

Well Rod, our precocious child is at it again. This is why he has 11,059 posts (ELEVEN THOUSAND FIFTY-NINE). I wish Keith, Barry, George, Clayton, Acton, Tom, Kincade and Mike had 11,000-(they don't have that many combined). We would all learn far more about our cars and motors and not Readers Digest popcorn games.

What's next to entertain we children Mr. Wizard-find the rabbit in the maze pictures?

A valuable help to any hands-on guys is this tip: block drains. Put brass petcocks in place of the block drain plugs, attach tubing to reach into your drain pan. When changing, drain from the lower rad hose, and both petcocks. You get a complete purge that way and refill through the temp sensor boss on the intake.

Now that's something people can use.

[Bob In Ct]

He's walking halfway to the wall. BTW - the answer is 8 times.

Bob

[RodKnock]

BTW, no traditional coolant either. A little bottle of Water Wetter and Pencool and the rest is distilled water.

[elmariachi]

Finally, proof of the infinite monkey theorem.

[patrickt]

Ahh, the road to Hell... All I try to do is help RodKnock change his coolant and what does it get me.

[ERA Chas]

Originally Posted by elmariachi

Finally, proof of the infinite monkey theorem.

A perfect explanation of our 'clever' counselor...

[patrickt]

Originally Posted by ERA Chas

A perfect explanation of our 'clever' counselor...

Isn't it past your bed time?

[ERA Chas]

Originally Posted by patrickt

Isn't it past your bed time?

NAAAAhhhh-I enjoyed watching the Mets beat the crap out of your team while I beat the crap out of you here

[RICK LAKE]

ERA Chas I figured that you would have told Pat that it takes 2 gallons of coolant and 2 gallons of distilled water and about 15-20 minutes to complete this problem. The mixture will be about 95% new and not have the heavy stuff in the block floating around to clog other parts. As far as ways to do this,

IF you have a SOLID camshaft and can idle the motor for 10 minutes we have a in line exchange machine that hooks to the upper hose. Emptys on one side and fills on the other side. When done, top off.

Other way is a vacuum setup that suck out about 80% on the coolant and refills itself with the vacuum. This is good also for checking for leaks in the motor too.

My last thought was adding petcocks to the back of the intake manifold on both sides and using them to remove any air pockets. Bleed offs.
Not sure but a min of 4 gallons of coolant plus 8 gallons to get rid of sound like alot of work. The only plus is the drive for 8 times.
Small side note, it's a long season and we know how the Mets fell into the playoff last year? or was it the years before?? Rick L.

[PANAVIA]

At least he's not running dex-cool

[RICK LAKE]

PANAVIA Steve What's wrong with Dex, Safer than Green for the country. Seals aluminum motors better than Green, Last more then twice as long. I have it in all my cars but 2. Both are over 100K on miles and don't like mixing the 2 different coolant togeather.
The only problems I found with Dex is, It can cause a chemical reaction with waterwetter and higher pressure in the radiator. Removing heat from the motor is about 5% less than green. This is a 50/50 mix for both. We are told that it's safer for the enviroment and the green stuff. Green does kill. Other issue is getting rid of the stuff, We are storing millions of gallons of the stuff and send millions more over to India. They clean it and sell it back to us. Orange can be freshen with a booster kit. So can the green, but still only half the life or orange. I have run dex and now have to run just water at some tracks with wetter due to cleanups and fines.
If I was running more on the street and long trips in the car with an ALL Aluminum motor Dex would be my first choice. Dex doesn't seam to eat aluminum as fast as green stuff either and in some motors that have intake gasket failure the dex seals the leak and extends the life of the motor where green doen't and in most cases means bearing wash from combo of green and water. Dex is about 10-15% better at having a motor last long with a coolant leak if you check. I see this all the time over the years. It depends on the application more IMO Steve. Rick L.

[patrickt]

Originally Posted by RICK LAKE

PANAVIA Steve What's wrong with Dex, Safer than Green for the country. Seals aluminum motors better than Green, Last more then twice as long. I have it in all my cars but 2.

That's interesting. Before my last flush and fill this summer, I tried to wade through the coolant literature. All I wanted was a simple answer to "what is the best coolant to use on an iron block/aluminum head engine?" But with that question I had a couple of caveats: I don't care how long it lasts, I don't care whether it's poisonous or not, and I don't care about the mineral level of the water in Europe (because I use distilled water). As best I could gather, the answer was conventional green coolant with all the additives that they put in it -- it beats red, orange, yellow, etc. but it doesn't last as long, it's poison, and, of course, you should use distilled water with it. Now, mind you, I am not positive that I got to the best answer. There's a lot of bogus BS that is floated around on coolant, so I'm really not 100% sure. BTW, I bought AutoZone Conventional Green at nine bucks a gallon, and distilled water at the grocery store is a dollar a gallon. I also added WaterWetter, mostly because Bob P. told me to....

[dcdoug]

Originally Posted by patrickt

I bought AutoZone Conventional Green at nine bucks a gallon, and distilled water at the grocery store is a dollar a gallon. I also added WaterWetter, mostly because Bob P. told me to....

So what % mix do you run? Do you flush every year or every second year?

[patrickt]

Originally Posted by dcdoug

So what % mix do you run? Do you flush every year or every second year?

50/50 mix, and a flush/fill every two and a half years.