Sorry... Coolant Again
I just wanted to clarify one thing.
Coolant/Antifreeze does not have any cooling properties, or ability to keep the engine temp down. The water only does this.

SO: the purpose of coolant/antifreeze is to (1) prevent the water from freezing and to (2) prevent corrosion in the cooling system, and that's it?

I ask this because ever since I put an 80/20 mixture of Water to MB Coolant, respectively and a bottle of Water Wetter, and my coolant temp even rose a little (on average, gets hotter quicker in traffic). Though I am aware that thw WW does not necessairy reduce coolant temp.
After driving for atleast 15 minutes on the freeway with perfect engine temps, the second I come to a stop, temp shoots up to 100 in no time at all. Fans kick in properly and as they should.
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David:

In addition to the 2 areas you covered, coolant also raises the boiling point. Check the back of just about any container of coolant for this type of info.

The whole thing is catch-22 - you use too much and lose heat dissipating capabilities; you use too little and you lower the boiling point and invite corrosion.

I believe the manual typically specifies a 50/50 for optimum freeze protection, although 45/55 concentration of water/antifreeze works a bit better. More than 55% coolant begins to inhibit heat dissipation and anti-freezing qualities.

Although coolant does have a higher boiling point than plain water, from a thermodynamic standpoint, the system pressure is REALLY what allows the coolant to sustain a higher boiling point (ask your mom about her pressure cooker...she can tell you about this).

Boiling over occurs when the temps get high, the pressure in the system increases to a point where the radiator cap attempts to relieve pressure. When the pressure is relieved, the coolant mix suddenly has a lower boiling point at ambient pressure, and thus, boils over.

So (as you figure from my other post) that something in the system is not doing an adequate job of keeping the system temps down...

Coolant Is A Misnomer...
 

The Mercedes-Benz product is correctly labeled "Antifreeze Anticorrosion Agent"...

The term "coolant" was applied to antifreeze by marketing people who wanted to increase sals during the summertime. They expected that using just the term "antifreeze" would make peple think that they didn't need to use it during warmer weather. Although these substances do raise the boiling point of water when added to it, they really do not provide any additional cooling ability.

The previous explanations of the thermal aspects are correct as far as my understanding, so you might try adding some antifreeze to make it a 60/40 mixture, or perhaps JimF. will pick up on this thread and share his knowledge again. As I recall, he runs a higher ratio mixture like you describe.

. . . 80/20. . ?
 

Not sure that you want 80/20. 60/40 might be better from the corrosion standpoint as Mike pointed out- catch22.

Currently have 60/40 and 1-1/2 cans WW. The car does what your car does; on the road it holds about 85C (w/ A/C going).

Going directly into stop-and-go traffic quickly raises the temp to 95C area. But that's where my fans cut in (based on temp) and it stays there maybe maxing at 98C. The fans may also come on sooner if the A/C pressure builds regardless of engine temp.

I don't think there's anything wrong other than the mixture ratio is a little low in AF. Remember 100C is only 212F which is boiling at atmospheric pressure. So with a 140 cap there sb no problem.

JimF,
I though I recalled you saying that you used 20/80, MB antifreeze to water..? And 2 bottles of WW.
I could swear I remember you saying 20/80 and not 40/60...?
I'll remove some of the mixture and add more MB Antifreeze.

. . .started out with 20/80 but
 

changed (to 40/60) when I found that 20/80 would be very problematic even at SoCal temps in the winter (up at 5000+ feet).

Re-read this thread, second page, bottom of page: http://www.peachparts.com/shopforum/showthread.php?threadid=17519&pagenumber=2

Also re-read my web page, #15 toward bottom of page.

Anyway, my main point was that I think you car is operating normally. Don't think that changing the ratio will make it any cooler or hotter but will give better corrosion protection as well as increased boil/freeze points.

[Edited by JimF on 07-25-2001 at 08:16 PM]