I do not have the FSM out to where I can give you the values..
but it is a matter of sticking one probe into the coolant and one to the car .

I wasn't sure if you stuck two leads into the liquid or the method you described.

So it's a simple conductivity test. I wonder how much the resistance changes with time and depletion of the corrosion inhibitor?

Enough to eat through your heater core and cause you big headaches....
LOL

Or does it measure the effect of corrosion, indicating a depleted corrosion inhibitor package?

My impression is that... like dissimilar metals in contact... there is too much difference .. thus causing transfer of metal to the liquid... like a plating tank ... or unplating as the case might be....

Good points. I do not know if you are measuring a decrease in conductivity as the chemical is consumed or an electrochemical phenomena due to the difference in chemical potential of the various materials in contact with each other and the fluid.

After all of this I'm going to take a look at my radiator!

Just the opposite.

I used test strips on a semi I owned that would tell me the ph balance of the coolant. Then if it tested corrosive you would add pencool to even it out. The previous owner learned the hard way by not checking it and he had to put in new sleeves. I beleive not sure though that you should use the test strips even if you flushed and changed just to make sure its ok. Somewhere I read the subaru engines had massive trouble with this because the battery was too close to the radiator and would somewhat charge the coolant, make it highly corrosive and hence all the head gasket replacements at 80k.

That would have to violate a LOT of PHYSICs laws to happen that way....

Yep, you're right.

I had a couple subarus before and digging around their forums before I found this.


"How does a battery effect head gaskets you ask? Without getting to far into the scientific end of it, the battery is located very close to the radiator. The electrical system in the car is grounded to the engine block on the left side of the engine, as the ground circuit resistance increases (from corroded battery cables), the voltage found in the cooling system will also increase, this is what causes electrolysis. Coolant can become very corrosive as a result."

"A battery that is covered in battery acid and corrosion will add to the level of corrosion in the cooling system, by increasing the resistance in the vehicle ground circuit which can lead to higher levels of electrolysis. This corrosion can eat away at metal gaskets, seals and metal that it comes in contact with. On a 2nd generation 2.2 and 2.5l it is almost always the left side head gasket that leaks coolant externally and it is also the cylinder head gasket that is the closest to the battery. Odd, no? A properly serviced and healthy battery will decrease the possibility of the battery adding to the corrosion level of the cooling system.

As the battery vents out acid and the cooling fans come on some of the vented acid can make its way into the coolant overflow bottle, not a lot in most cases but how much is too much? The overflow bottle catches coolant from the cooling system as heat and pressure cause expansion of the coolant from the radiator into the overflow bottle as the engine cools the coolant is then pulled back into the cooling system form the “expansion tank” or “overflow bottle”. In some cases you can look at the inside of the hood of your Subaru and see white acid all over the hood liner, if that is your car you are pulling a tiny amount of acid into the overflow bottle past the tube and from there into the radiator, remember as the engine cools, coolant is pulled back into the radiator via the vacuum that is created as pressure decreases, so there is a small vacuum pulling at particles surrounding the coolant overflow bottle.

The health of the electrical system is a contributing factor. We know that corrosive coolant is part of the problem, we know that electrolysis is a result of increased voltage levels in the cooling system as a result of poor grounding , we know that a poor ground can be caused by resistance in the primary electrical circuit. We know the coolant is the same in the entire engine, and the gaskets the same left to right the only difference is the fact that the ground is at the left side of the engine and that if there is voltage present in the cooling system it will always travel the shortest path to ground and the ground is on the same side of the engine as the gasket that always fails the most via external coolant leaks."


http://www.rs25.com/forums/f190/t100250-head-gasket-problems-explained.html

I know this is for a subaru but just came to mind while I was reading the posts.

People are allowed to make up all sorts of good stories concerning "causal " relationships which are not true when they can not figure the true reasons something happens.... And they can post them on the internet.
One hint about this one.... those things require a complete circuit... and the positive side of the equation is pretty well wrapped in rubber to isolate it from the negative side... so that the completed circuits happen only where they are supposed to... like the filaments in the lights...
I owned several Subaru's and love them... but they follow the same physics as everyone else.

I certainly don't mind being corrected, as if I did it would be hard to learn new things and it would greatly detract from the enjoyment of grad students when they get they chance to correct professors. I do mind being told I am incorrect when our two statements were pretty much identical.

.

It is always possible to agree with someone without saying they are incorrect. The more the merrier, I hope to have half the knowledge about MBs as the people here do.

Actually, the explanation was not inaccurate, perhaps not fully explained with bond stretch and electron density clouds, but more accurate than yours stating that inter-molecular forces have no affect on bond length. The use of either of those statements as a basis for expanding ones knowledge is probably best evaluated by an individual on their own.

Interesting thread. I've a question for you guys: Is there a good way to tell whether the coolant in my engine is protecting it against cavitation? If not, what kind or what additive should I get? There was a good thread here posted by Whunter but it disappeared...
(By the way, I did do a search on Cavitation on the forum with the following result: "No Thread specified. If you followed a valid link, please notify the administrator")

Did you notify the administrator ?

And how do you define cavitation ?