Radiator flush after flush... the rusty water never stops - PeachParts Mercedes-Benz Forum

Shortsguy1 · #1 11-01-2014, 12:38 PM

My 220D w115 has an overheating problem at high load, so I decided to try a citric acid flush. You all previously warned me of the risks, so I feel I went into it reasonably well informed.

I did the following:
1) remove thermostat
2) remove old coolant by opening radiator and block drain, close again.
3) refill with degreaser (shout and water), drive until hot, let cool, drain. Rinse out degreaser from system.
4) refill with 10% citric acid solution (MBs formula), drive until hot, let cool, drain. For this one step, I kept the heater system closed to avoid damaging the heater core. Other rinsing steps had the heater flow open.
5) refill with hose water, drive until hot, let cool, drain.
6) repeat step 5 at least 5 times...... I also removed the hoses several times and flushed with a hose through every available opening

After all this, the water coming out of the system was still rusty colored. So it occurred to me that perhaps the rust was coming from the heater system, which never saw the citric acid. So I decided to flush the entire system again, but this time using Prestone Radiator Flush. I used the same methodology as above, but with the heater system open the entire time. I used Prestone's instructions for a "heavy" treatment which means I kept the stuff in the car for 3 days of moderate driving.

After doing step 5 several more times, I decided to try distilled water for another flush. The results of that flush are in the attached photo. You can see the water is still pretty murky. So I guess my question is, when can I stop this madness? When is it "good enough"? I honestly didn't expect to be at this for a week with probably 15 total flushes of the entire system. Am I just shooting myself in the foot if I do my final fill now (40% Zerex G-05/60% distilled)? Initial tests with pure water indicate that the car is actually running cooler now(yea!), but I just don't understand why the water coming out of the system is still so rusty colored. What would you do at this point? Thanks for your help.

(as an aside, if at all possible, please don't advise me to use Evans. I have read about it carefully and prefer a water/G-05 mixture in my car)

vstech · #2 11-01-2014, 04:18 PM

Have you been pulling the block drain for each rinse?

Shortsguy1 · #3 11-01-2014, 04:45 PM

Yes, with a caveat. My car is old enough that it has a small stopcock for the block drain. So a quick twist of the valve, and the block drain is open. But the actual opening is relatively small (compared to what I imagine most of you have) so it is not like water gushes out of this hole. It just flows out as a small stream after you open it. It takes a long time for the system to empty through that little hole. If I come back to the car 30 minutes later, it will still be flowing, but at a trickle compared to when it started.

The FSM says my car has a coolant capacity of 11 liters. I can add about 10 liters of water before it is full, so there is still a liter hiding somewhere in there.

NJ300sdl · #4 11-01-2014, 05:16 PM

Good enough is good enough. Time for antifreeze.

vstech · #5 11-01-2014, 05:35 PM

Is the valve stock? I imagine it may have been added by a PO...

leathermang · #6 11-01-2014, 08:18 PM

Here is the physics of the situation...
In cars the age of ours.... `the movement of water pushed by the water pump slows down near the back of the engine... building up rust and stuff... perhaps calcium precipitated out of hard water.
In the old days this was addressed when engines were rebuilt by taking everything off the block and VATTING the block in hot caustic fluid...
But our engines last so long in the first place... and then even when redone often get the main friction items replaced without the VATTING step..
So to really get the rust look out... you would need to take the freeze plugs out...and use some mechanical method to aggravate that sediment formed at the bottom of your coolant cavity... probably at the back end of the engine.. at the same time you flush...
Depending on how often in the life of a car the system gets flushed... it can be enough to affect the ability of the radiator, fan, water pump to keep the engine cooled properly.. but that is an extreme case... but I have seen that in V8's......

Mxfrank · #7 11-01-2014, 09:53 PM

First of all, don't flush with distilled water. Aside from extra expense, it's more corrosive than most tap water. What I would do is go to the parts store and see if they have a radiator flush attachment which replaces the cap. Attach the hose. and just let it run through the system until the water comes up clear. All that gunk is mobilized, now is the time to get rid of it.

leathermang · #8 11-01-2014, 09:56 PM

Quote:

Originally Posted by Mxfrank

..... don't flush with distilled water......, it's more corrosive than most tap water.....

Where in the world did you get THAT idea ?

dkr · #9 11-01-2014, 10:04 PM

I would hook up a Gano coolant filter to your upper radiator hose and call it a day.

Dkr.

Shortsguy1 · #10 11-01-2014, 10:18 PM

Thanks everyone for all your advice and suggestions. A few followups:

The stopcock is a MB part. I suspect that only the earliest w115s got them. They were more typical of the prior generation of cars (w110s I vaguely recall). Or perhaps the original owner moved one over from one of those cars.

I was only using distilled water for what I hoped to be my last flushes. I wanted to do one entire purge with distilled, so that my final fill was adding to what was hopefully mostly distilled water hiding in the block/heater.

I think I will probably just finish the job and move onto the next battle.

Regarding anticorrosion, what is the lowest percentage antifreeze I could get away with if I was willing to do annual coolant changes? I want to maximize the heat removal but not contribute further to the internal rusting of my engine. The lowest temperature ever recorded on San Luis Obispo is 12F (-11C), which corresponds to a 25% antifreeze mixture. That is well below Zerex's lowest recommendation for G-05 (40%).

My car used to reach 250F in 70F weather heading up a local freeway hill (I would pull over at 250F). After all the flushing efforts, with pure DI in the system, it "only" reached 230F which is way better. If I kept the heater on the other day, I was able to keep it at 212F going up the same hill. So the the citric acid and flushing has definitely made an improvement, which I am excited about. But if I go 50/50 coolant/water, the 230F I witnessed could end up being much higher, particularly if it was a warm day.

TheDon · #11 11-01-2014, 10:20 PM

Quote:

Originally Posted by leathermang

Where in the world did you get THAT idea ?

Seriously.....there's nothing in distiller water, it has a neutral PH, and it's clean??

Shortsguy1 · #12 11-01-2014, 10:22 PM

I was unfamiliar with the Gano filter until I just looked it up. Thanks for mentioning it. It sounds like a smart design.

leathermang · #13 11-01-2014, 10:33 PM

I think the FSM specifies about fifty fifty on the water to antifreeze...

HOWEVER.... you do not want to try to use the cold temperature you are trying to protect against...

as the more important consideration is the ANTI CORROSIVE property of the correct mix..

If you violate that... particularly with respect to not changing out the coolant as required by the FSM..

THEN you risk electrolytic action EATING THROUGH YOUR HEATER CORE...

your safety or lack of it... with regards to that situation can be checked by using an ohm meter...

mannys9130 · #14 11-01-2014, 10:50 PM

Mxfrank IS correct.

Distilled/RO water is very pure. Like, VERY pure. It tends to pull minerals out more readily than tap water (already loaded with minerals). Water is a very good polar solvent. It's not corrosive like Sodium Hydroxide, but it is corrosive in the literal sense of the word.

To the OP, I'd personally keep flushing. Back flush the heater core by itself as well. I think that's where most of that junk is coming from.

vstech · #15 11-01-2014, 11:17 PM

Quote:

Originally Posted by mannys9130

Mxfrank IS correct.

Distilled/RO water is very pure. Like, VERY pure. It tends to pull minerals out more readily than tap water (already loaded with minerals). Water is a very good polar solvent. It's not corrosive like Sodium Hydroxide, but it is corrosive in the literal sense of the word.

To the OP, I'd personally keep flushing. Back flush the heater core by itself as well. I think that's where most of that junk is coming from.

So, because water is the best solvent on earth, as in it readily dissolves things and suspends minerals within itself you are calling it corrosive? Which means it converts metals to salts...
Mmmkay...

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