Urban Benz Legend? (Case of the Corrosive Coolant) - PeachParts Mercedes-Benz Forum

merci · #1 12-29-2004, 10:12 AM

Hi,

I was told by local MB mechs in my country (the Philippines) that using 50/50 MB coolant/water mix corrodes the water (coolant) channels in the head - making them larger and thus requiring a trip to the welding shop where it will be "resized" back to normal. For this reason, the local mechs are saying that it's better to use water than coolant.

Is this true? Has anyone actually needed a water channel repair in the head/block due to corrosion? They're quite positive it is not the well-known headgasket problem.

I'm guessing that the local mechs use regular tap water (very hard water here) when creating the 50/50 mix. I for one am leaning towards using distilled water and Redline's Water Wetter (ph8.6) only.

Any thoughts on this possible "urban benz legend"?

Thanks

Duke2.6 · #2 12-29-2004, 12:29 PM

Total BS. Use the MB recommends for your car.

Duke

Mike Richards · #3 12-29-2004, 01:40 PM

This is worse than BS.

One reason for using coolant is to prevent corrosion. Pure water, irregardless of whether it's hard or soft will corrode much faster than a 50/50 mix of coolant and water.

The MB techs that told you this were either yanking your chain or are in the wrong line of work.

Find another shop

Kestas · #4 12-29-2004, 01:48 PM

Ford has paid me good money to examine head cooling passages from cars that had peculiar conditions during warranty. A few of the heads investigated were abused by people who drained the factory coolant and used straight water, typically truck owners in Texas who want to increase thermal transfer without realizing the downside of such action. The nucleant boiling from using straight water cavitated (pounded holes) the inside water passages until it reached the outside of the head, resulting in a leak and total loss of coolant.

A 50-50 mix (and proper 15 psi pressure) will raise the boiling point to where you don't get this phenomenon. Whoever told you the story got it backwards. The heads for repair he mentioned were the result of using straight water, not the reason for using straight water.

Rebel62 · #5 12-29-2004, 01:56 PM

Quote:

typically truck owners in Texas

Truck owners in Texas? Not following the rules? Would that really happen???

d2bernhard · #6 12-29-2004, 04:20 PM

not to mention water is not as effective a lubricant for the water pump as coolant.

braverichard · #7 12-29-2004, 07:35 PM

Why would anyone run their car on water alone? That sucka would overheat!! While performing a coolant flush on my 500SEL, I put water in the system and within a few minutes the car would start to overheat -- had to use the heater to keep the temperature down. Then when I opened up the coolant reservoir, the water burst out with high pressure.

To each their own...

Duke2.6 · #8 12-29-2004, 07:57 PM

Straight water will not cause an engine to overheat. In fact, it can make overheating cars run cooler because water has greater thermal capacity than glycol. Most race cars run straight water, or just a little bit of glycol or an anti-corrosion/water pump lubricant like "Water Wetter" (which is useless when used with normal antifreeze concentration). Corrosion is rarely an issue with race cars since the engines are torn down so frequently. They don't sit around with water in the coolant passages.

Your car probably overheated because there was a big void in the system. Most systems require slow, careful fillilng and then some time to self bleed. If they are filled to fast, air can be trapped, which can cause overheating.

Duke

braverichard · #9 12-29-2004, 08:07 PM

Duke2.6,

I can understand your theories as they seem logical (proven with real examples you gave). However, why is it that once I re-filled my system with a 50/50 mixture of water/antifreeze it stopped overheating and started running at 80 C - 90 C? I thought the system was overheating because the boiling point of water is 100C and so once that temperature was reached, the water started boiling.

milhan · #10 12-29-2004, 08:48 PM

If you put straight water in without antifreeze, it will boil over, and it will freeze if it sits in temps below freezing. coolant has a higher boiling point and a lower freezing point. Im not sure about the race car thing, but it sounds a little fishy. Its true you will get better heat transfer with straight water, but your cars engine gets hotter than 212 degrees Faherenheit which is the boiling point of water at atmospheric pressure at sea level. In the mountains the boiling point changes because the air pressure is differant.

Duke2.6 · #11 12-29-2004, 09:33 PM

Quote:

Originally Posted by braverichard

Duke2.6,

I can understand your theories as they seem logical (proven with real examples you gave). However, why is it that once I re-filled my system with a 50/50 mixture of water/antifreeze it stopped overheating and started running at 80 C - 90 C? I thought the system was overheating because the boiling point of water is 100C and so once that temperature was reached, the water started boiling.

Could be a combination of things - air pockets in the system or the pressure cap not installed. A 50/50 mix of glycol and water will boil at about 265F with a 15 psi cap. Straight water with a 15 psi cap will be lower - I think about 235.

The NASCAR guys use straight water with Water Wetter or a similar additive. The added thermal capacity of straight water helps cool those 750 HP engines. They like to run them hot because it makes for lower piston and ring friction. About 210 is ideal, and they pull tape of the grille if it gets up to 230, and I think they run 20+ psi caps, so the boiling point is probably 240-250.

Duke

pete911 · #12 12-29-2004, 09:40 PM

Some race series mandate straight water without coolant. This is to prevent anti-freeze from getting on the track if an engine blows, or a car crashes. Anti-freeze is slicker than oil when on the track, its almost like being on ice.

#13 12-29-2004, 10:04 PM

Sounds like your local MB mechanics are looking for work, work on your MB, and work on your wallet!

here's the bill!

BB

wbain5280 · #14 12-30-2004, 06:04 AM

Quote:

Originally Posted by milhan

If you put straight water in without antifreeze, it will boil over, and it will freeze if it sits in temps below freezing. coolant has a higher boiling point and a lower freezing point. Im not sure about the race car thing, but it sounds a little fishy. Its true you will get better heat transfer with straight water, but your cars engine gets hotter than 212 degrees Faherenheit which is the boiling point of water at atmospheric pressure at sea level. In the mountains the boiling point changes because the air pressure is differant.

The cooling system is pressurized thus raising the boiling point. Anti-freeze also extends the boiling point. The MB M103 has a bolt on the top of the head to vent the cooling system. Very nice feature.

psfred · #15 12-30-2004, 08:09 AM

All MB engines these days are a combination of steel (or cast iron) and aluminum, and without coolant anticorrosive additives, will suffer horribly from electrolytic corrosion. The higher the dissolved mineral content, the faster this corrosion will occur, and it can be so bad the head gaskets won't hold.

This is why MB recommends changing the coolant every three years -- the additives are sacrificed to prevent corrosion, and eventually can no longer protect the aluminum.

Plain water, no glycol, will also cause boilovers because a 50/50 mix will have a boiling point, under pressure, of at least 240 or 260 degrees F instead of 220F. This can make a huge difference, as boiling coolant does NOT transfer heat anywhere near as well as liquid coolant.

Use the proper coolant, change every two or three years, everything will be fine.

Note that MB coolant (aka Xerex G-05) is NOT the same as the green stuff or DexCool types, and those should not be used -- they can cause both excessive corrosion and the deposition of crud in the rad.

Peter