What cooling fluid for my 3.5? - PeachParts Mercedes-Benz Forum

GGR · #1 06-17-2009, 09:32 AM

Hi all,

I'm servicing my 3.5 W111 Coupe for a coast to coast round trip. As I will drive through hot climates, I think it would be a good idea to change the cooling fluid (especially because currently I have a mixture of all kinds in there including rain water from the ditch when I had to make an emergency repair on the side of the road + green fluid bought at the first service station I passed by). I read posts about MBs requiring specific blue MB cooling fluid etc. Should I pay MB price, or can I get one meeting specs at autozone or the like? If yes, what are the specs I should be looking for?

Thanks

alabbasi · #2 06-17-2009, 09:55 AM

I use Zerex in the gold bottle which is MB approved chemistry and is a lot cheaper then MB fluid. Although i've heard many people say that it doesn't matter on the older engines.

Mr.Kenny · #3 06-17-2009, 10:22 AM

Run a greater water ratio than coolant; 60/40 or 70/30 for more effective cooling.
Water will get rid of the heat faster than the thicker antifreeze.
(Race cars use straight water.)

Tony H · #4 06-17-2009, 10:42 AM

I also have often wondered what coolant is appropriate for a 38 year old Benz. It is often said that MB coolant is formulated for our cars but does that apply to a car that's 38 years old? I doubt our cars cooling systems and engines have anything in common with today's. Instead of what brand the question is what is the correct formulation to protect our older engines?

twinockchef · #5 06-17-2009, 11:07 AM

I use the Mercedes coolant because of its properties in preventing corrosion in the head. I had to replace the head on my car because of sever damage. More importantly I will change the coolant (I think) every two years.

meltedpanda · #6 06-18-2009, 10:25 AM

use the Zerex gold ( approved for MB's) - follow instructions , make sure you do a good flush prior, get the old crap out

230/8 · #7 06-18-2009, 10:53 AM

An older MB with all metal cooling system parts can safely use the usual Prestone fluid; it was all that was available back then. I have used it in all my older MBs with no problems and none of the corrosion issues others refer to. Change it regularly and do a good flush with a mild system cleaner. If you have visible corrosion you can use a mixture of citric acid and water to remove the corrosion byproducts and scale, but you should thoroughly flush the system to remove the cleanser. Prestone and other "green" fluids are a little higher pH so they end to neutralize the acid flushing compounds if traces remain. If you use a flush kit like Prestone sells, which attaches your garden hose to the cooling system via an adapter to the heater hose, do not turn on the garden hose fully...your house pressure can reach 60-75 psi and this might damage the heater core or some other weak spot in your system.

The Zerex G05 fluids are essential for newer MBs that have plastic parts in the system, like the top of the radiator. Regular green stuff can make plastic parts brittle and cause them to break.

GGR · #8 06-18-2009, 12:50 PM

Thanks, thats very useful. Do I find that mild system cleaner at Autozone? What about vinegar?

230/8 · #9 06-18-2009, 01:00 PM

You can get cooling system flushing agents at Autozone...they are usually a mild compound that removes light rust and scale and oily residues. This should do the job for you. MB refers to using citric acid and mixing the powdered chemical with water, as I recall it is about 1kg for the system and then flushing with large quantities of water. Don't know about vinegar...use it in the coffee pots all the time to de-scale, can't say I've ever thought about it for radiators.

I think using something like Prestone flush will do it for you. If you see heavy scaling inside that is blocking the tubes, take the radiator to a shop and let them flush it out with their machine. It's much easier than polluting your driveway and then letting the crud run off to the storm drain at the corner...it probably ends up in a creek so that wouldn't be good.

sokoloff · #10 06-19-2009, 11:32 AM

The manual procedure calls for you to deoil before descaling even if there is no evidence of oil in the system. So before you use the citric acid, you need to deoil. Using something like liquid Tide or liquid dishwashing soap will do the trick. Then use the citric acid.