Coolant flush - best coolant for 300SDL - PeachParts Mercedes-Benz Forum

cmac2012 · #1 09-30-2018, 07:52 PM

I am really liking this car, this motor, I should stay on top of the game on maintenance. I'm thinking I should look into this.

Diseasel300 · #2 09-30-2018, 07:54 PM

If the coolant is just old and needs drained/refilled, go back with 50/50 Zerex G-05. It's the original spec coolant used and is a good coolant. Don't forget to drain the block to get the most old stuff out.

cmac2012 · #3 09-30-2018, 08:55 PM

Thanks. I thought to just do a search but also wondered if there were any new developments on that score that might not be common knowledge. I read somewhere recently where the wrong coolant can be a problem with these heads.

vwnate1 · #4 10-01-2018, 10:08 AM

After 30 years it prolly needs a good proper flushing, this takes time if not much effort .

Mercedes says to use citric acid powder mixed with water, look it up, I've done it to amazing results and never had any problems .

Zulfiqar · #5 10-01-2018, 12:26 PM

Quote:

Originally Posted by vwnate1

After 30 years it prolly needs a good proper flushing, this takes time if not much effort .

Mercedes says to use citric acid powder mixed with water, look it up, I've done it to amazing results and never had any problems .

I use this on all makes and models of vehicles, it cleans the best and is easy on everything.

Diseasel300 · #6 10-01-2018, 05:37 PM

Quote:

Originally Posted by Zulfiqar

I use this on all makes and models of vehicles, it cleans the best and is easy on everything.

Be aware that the citric acid can be a little rough on aluminum. If the coolant is clean and maintained and there are no signs of overheating, skip the citric acid flush.

The most likely casualty will be the radiator - and they're made of unobtainium for the SDL's. Unless you have deep pockets for one of the all aluminum Wizard radiators, that's a part you want to be nice to.

MTUpower · #7 10-02-2018, 08:50 AM

Drain and fill with distilled water. Run until hot then sit till cool and drain. Repeat. Fill with proper G-05 mix.

vwnate1 · #8 10-02-2018, 09:10 AM

Actually, it doesn't damage alloys at all ~ that's why Mercedes decided to recommend it .

I've used it in horribly clogged Japanese tinfoil aluminum radiators and never a problem yet .

Hondas and Mazdas are famous for "uncleanable" aluminum radiators, not with citric acid mix they're not .

If this opens a leak anywhere, the leak was there already and waiting to do you dirt .

Diseasel300 · #9 10-02-2018, 09:36 AM

Mercedes recommends the citric acid flush to remove SCALE (lime) from the system. Not because it's "gentle" because it isn't. Take some oxidized aluminum pieces and throw in a vat of citric acid diluted to the strength that MB recommends and watch the fizz. The fizz is the acid attacking the aluminum and stripping away the oxide layer (for those familiar with physics, that's removing material). We use it at work to clean up oxidized aluminum for that very reason, it also requires a good neutralization bath (we use baking soda in water) to stop it oxidizing again later. They also suggest to use it only in dirty systems or vehicles with overheating issues.

If the car has clean coolant in it, it's been changed semi-regularly, and has been topped up with distilled water instead of tap water, there will be no scale in the system, or if there is it'll be a small enough amount to not bother with.

vwnate1 · #10 10-03-2018, 07:56 PM

That's fine, you're kidding yourself if you think any 34 year old car doesn't have scale in it's cooling system .

I won't belabor the point because I know what's right and unlike most, I've done it repeatedly and never had any issues, those who own older Japanese cars think I'm a genius because it works so well .

BTW : right on target about needing to neutralize with baking soda .

cmac2012 · #11 10-04-2018, 05:06 AM

Good information to ponder. I haven't drained it yet, I was thinking to wait until after I swap in a new mono valve. I gather a gallon or two needs to be drained to put one of those in.

I just happen to have a about 8 oz. of citric acid - long story. I'll see if I can find any info about the recommended strength of the acid as well as base neutralizer, rather the timing on that.

oldsinner111 · #12 10-04-2018, 06:12 AM

I use the old hot rod trick.Drain coolant cold motor,remove thermostat,and put conection back.Fill with one gallon vinegar with one good squirt of dawn,fill rest with water.Go drive 15 miles on the freeway.Let car cool,and flush good with water,use your anti freeze.I use prop gycol,as its way better,at 100% and no water.Good for 10 years.

Diseasel300 · #13 10-04-2018, 08:54 AM

Replacing the monovalve cartridge will loose maybe a teaspoon of water. The valve body is at a very high point in the cooling system, so barely anything is going to come out if any at all.

Don't drive a 603 with the thermostat out. It isn't an American car and uses a bypass cooling system design. If you like overheating, go for it, otherwise, use a thermostat please.

Maxbumpo · #14 10-04-2018, 10:31 AM

Quote:

Originally Posted by oldsinner111

I use the old hot rod trick.Drain coolant cold motor,remove thermostat,and put conection back.Fill with one gallon vinegar with one good squirt of dawn,fill rest with water.Go drive 15 miles on the freeway.Let car cool,and flush good with water,use your anti freeze.I use prop gycol,as its way better,at 100% and no water.Good for 10 years.

If it's worked for you so far, you've been lucky. There is a risk that an MB coolant system will overheat with no thermostat installed, because it is a bypass system. Removing the thermostat does NOT force full flow of coolant through the radiator. Worse, the OM603 has a bad reputation for cracking the aluminum head when overheated, especially the first versions installed on the OPs car from the factory.

In order to do this properly, the factory manual says to use an old thermostat that is blocked open. I cut a piece of plastic (MB white headlight adjusting knob from a 201) so it fits very securely in an old thermostat, and use that when I flush the engine / radiator.

vwnate1 · #15 10-04-2018, 11:06 AM

Vinegar is not a good thing to use inany cooling system containing Aluminum ! .

Yes, this worked fine on older vehicles produced in the 1920's through maybe the 1960's but you're courting diaster to do this in any modern car .

No thermostat is very bad too as among other things it allows the coolant to circulate so quickly it doesn't pick up the heat, the gauge reads cool as the engine is running seriously overheated with hot spots .

Older Ford flathead V* Hot Rodders used large flat washers in the upper hoses to slow the coolant circulation down so it'd transfer far more heat out of the engine .