Proper procedure for flushing radiator - PeachParts Mercedes-Benz Forum

rino · #1 07-13-2008, 04:41 PM

I need to replace some of the radiator fluid which leaked out (see here), so I thought I might as well do a full flush...

This is the procedure I understand to be correct. Please give me some feedback.
I drive a 1979 240D.

I'll use Zerex G-05 coolant (plan to get 2 gallons) and distilled water for the final filling.

1) Drain the radiator by unscrewing the radiator drain plug underneath it.
2) Close drain plug plus fill the radiator with tap water.
3) Run engine until warm with heater on, then wait 30 minutes.
4) Repeat 1, 2, 3, four more times to rinse system.
5) Finally, replace with a 50/50 mix of Zerex G-05 and DISTILLED water.

My questions are:
1) Is there a block drain on the 240D which I should also plug/unplug during this
procedure?
2) Is there a product I can use to thoroughly cleanse the system (I heard
something about citric acid - but what brand specifically, when and how?) Or
should I use baking soda?
3) How do I properly take care of BURPING (air pockets) - what do I do?

Rino

compress ignite · #2 07-13-2008, 05:48 PM

Procedure is:

H2o flush(es)
De-Oil with H2O and Dawn dish detergent(Yes,in the cooling system)
As many plain H2O flush(es) as you can stand
Citric acid flush as per FSM instructions
As many more H2O flush(es) as you can stand (I'd say minimum of 2)
Refill with Distilled H2O and Zerex G-05 (or MB coolant...same thing)

All previous disclaimers apply.
(That would be EVERY disclaimer EVER printed or implied)

citric acid flushes may bring to light neglected
maintenance items that need to be replaced or repaired.

#3. Fill the engine using the top radiator hose...(with the thermostat removed
IF NECESSARY)...replace all required components...
turn on the heater and monitor the expansion tank as the engine warms up...top up as needed.

rino · #3 07-21-2008, 02:02 PM

Quote:

Originally Posted by compress ignite

Procedure is:

H2o flush(es)
De-Oil with H2O and Dawn dish detergent(Yes,in the cooling system)
As many plain H2O flush(es) as you can stand
Citric acid flush as per FSM instructions
As many more H2O flush(es) as you can stand (I'd say minimum of 2)
Refill with Distilled H2O and Zerex G-05 (or MB coolant...same thing)

My question, which I also asked in the other thread - but no one cared to reply there, is, I already have one gallon of Purple Power (multi-purpose degreaser). Can I use that in place of Dawn dish detergent (it would seem more effective) and if yes, to what water ratio and how many cycles?
Also, about citric acid... In what form do I get it and where? (If there is a mild form of citric acid, that's what I'd like to use... This is not the right moment for me to have issues that need further attention come up...)

Thanks to all...

LUVMBDiesels · #4 07-21-2008, 02:42 PM

I would not use the degreaser. Use either Dawn or Tide these have both been used by many people with good results.

Here is a procedure that I posted last summer:

This is what I did...
To convert from the green stuff to the proper Zerex G05 coolant is a time consuming process, but well worth it.

This is what I did...

First I drained the radiator and block. I pull off the small hose that leads to the expansion tank to drain the radiator. If you don't have an expansion tank, pull off the lower radiator hose. Once the radiator is drained replace the hose. The block drain is located on the right side of the block in front of the starter. It takes a 19mm socket. You must remove this as most of the old coolant is still in the block and will not come out via the radiator.
It helps to put the car up on ramps.

Next I removed the thermostat, but left the rubber ring in place.

Then I flushed the system with hose water by attaching a 1/4 inch galvanized pipe nipple approximately 3 inches long to the engine block drain. I then threaded an elbow and a six inch pipe nipple to the one in the block. I cut off some old garden hose and clamped it to the six inch nipple. This way I can back flush the system.

Once I had this set up, I started the engine and turned on the defroster. With the hose running, I flushed the block until the water coming from the expansion tank was clear.

Next comes the flushing steps to remove any rust and grease in the system.

Put the block drain back in.
Fill the system with water by removing the top radiator hose from the radiator and filling it until there is water at the top of the hose, replace it and fill the rest of the way from the expansion tank.

Next put in a cup of Tide detergent. Start the car and run it with the defroster on for about 1/2 hour. Let it cool down then repeat the water flush steps until the water is no longer soapy.

Replace the thermostat. You can reuse your old one if, when you put it in a pan of boiling water it opens fully. I went with a 75 degree one when I replaced mine. It is normally for a 1970's vintage 450, but it works fine in a OM617 engine.

Next you want to do the citric acid flush. drain the system and fill it with a mixture of two gallons water with 2 pounds of citric acid dissolved in the water. (it helps to use very hot tap water to dissolve the acid powder)

Run the car with this as the coolant for a week.

Repeat the steps to flush with water. You will be amazed at the garbage and rust that comes out when you back flush the system. I flush with water at least three times, letting the car cool down between flushes. (don't want to burn yourself )

When the water is clear and does not feel 'slippery' the acid is gone.

Now you can fill the system with 50% Zerex and 50% distilled water.

If you always use the fill from the hose method, you should not have air bubbles in the system.

To purge out any air in the system during any of these steps, put the car on ramps or at least point it uphill. Remove the expansion or radiator cap. Start her up and get her up to operating temperature. Turn on the defroster. Rev her up to 3000RPM a few times. The air should come out of the system.

I know it is a lot of work to do these steps, but you will thank yourself for it when you see how dirty the acid flush water gets. Remember, if you use the correct coolant, you will not have to do this again

rino · #5 07-21-2008, 09:45 PM

Thank you so much for your detailed explanation! Yes, I am convinced and am going to convert to the proper Zerex G05 coolant.

I have some questions regarding your post:

1) When you say, "Use either Dawn or Tide," do you mean *dishwashing detergent* or *laundry detergent*? (to my knowledge, Dawn makes dish soup, and Tide laundry soup...) And the quantity for either one is JUST a measured half a cup (JUST 4 liquid ounces) into the radiator (I don't have an expansion tank) *AFTER* filling up the cooling system with tap water - correct?

2) The water flush steps AFTER putting the block drain plug back in the first time, and after putting in the detergent, are normal flushes as described in the FSM, right? (I mean, I no longer have to back flush the cooling system with a hose attached to the block drain plug, right?)

3) Where do I get the 2 pounds of citric acid, and what type/brand (if any)? I was at the auto parts store today and they know NOTHING about citric acid...

4) Drive ONE WHOLE WEEK with the citric acid in the cooling system and regular tap water (no coolant in it)? Are you positive about this?

Thank you so much in advance for answering these questions.

300SD81 · #6 07-21-2008, 09:49 PM

ebay has the best prices for citric acid. I just did this and had no idea how long to leave the acid in, I probably did for around 30 minutes, probably should have left it in longer. I'm on my 12th rinse now, and still have yellowish water coming out...

tangofox007 · #7 07-21-2008, 10:10 PM

Quote:

Originally Posted by rino

My question, which I also asked in the other thread - but no one cared to reply there, ...

I got the rather distinct impression that if a respondent did not have a PhD in radiator technology, you didn't care to hear from him.

Quote:

Originally Posted by rino

When you say, "Use either Dawn or Tide," do you mean *dishwashing detergent* or *laundry detergent*? (to my knowledge, Dawn makes dish soup, and Tide laundry soup...)

Are you positive about that? I heard that soup was made by Campbells and Lipton!!!

Quote:

Originally Posted by rino

3) Where do I get the 2 pounds of citric acid, and what type/brand (if any)?

Make sure that the brand of citric acid that you select is compatible with the brand of distilled water that you plan to use. That's absolutely critical.

Quote:

Originally Posted by rino

Drive ONE WHOLE WEEK with the citric acid in the cooling system and regular tap water (no coolant in it)? Are you positive about this?

That's definitely a whole lot longer that what is recommended in the service manual!!!

rino · #8 07-22-2008, 11:45 AM

Quote:

Originally Posted by tangofox007

I got the rather distinct impression that if a respondent did not have a PhD in radiator technology, you didn't care to hear from him.
Are you positive about that? I heard that soup was made by Campbells and Lipton!!!
Make sure that the brand of citric acid that you select is compatible with the brand of distilled water that you plan to use. That's absolutely critical.
That's definitely a whole lot longer that what is recommended in the service manual!!!

Tangofox, for sure that's a lot of waste in bandwidth with absolutely no constructive purpose whatsoever...
Maybe I rubbed you on the wrong side somehow... It's not a matter of having a PhD or anything like that, it's just that sometimes respondents provide answers they themselves are not sure/knowledgeable about, and it does come across. Am I guilty of not paying too much attention to those answers? Certainly so, and I think that anyone with a bit of good sense will do the same...

Thing is, I still have no idea where to find the citric acid locally and all the others details I've kept asking about.
It takes just 25 words or so to write: Buy citric acid here, use this specific detergent, etc. Is it so difficult to do? There are some things that may seem very obvious to some of you guys who have a lot more experience about these things, but you also need to understand the perspective of someone who does not know as much as you do and is trying to do his best with this situation and needs to ask some questions to make sure he understands sufficiently well the matter at hand too, which may seem superfluous and even ridiculous to you.

Best to all,
rino

rino · #9 07-22-2008, 05:20 PM

OK, I've found my answers, unfortunately, I have to say, from sources outside this forum. I am posting them here, for the benefit of other forum members who might come across this thread looking for the same answers as I did.

I'll quickly open and close a personal note. I have to say that I have been a member of this forum for over three years and during this time I had always received prompt and extremely helpful answers to all my questions. This time around (after about a one-year absence) is the first time ever that I have encountered so much reticence and even that overtly antagonistic reply (in very poor taste) from the last poster... Perhaps, this time around, the good ones were busy with other threads and did not notice this one, or maybe are away enjoying their summer vacation somewhere or something. Regardless, I am very much grateful to this forum for all the help I had received in the past and am always willing to contribute in return to it as much as my knowledge/experience allows me to. End of personal note.

So, to the answers. Citric acid can be bought locally from any restaurant supplies store (food or lab grade doesn't matter - any powder citric acid will do the job). I just located one in my area which is selling me a 7-lb. container for about $14 (at their wholesale price!). The amount of dishwashing detergent to be used (in my case, I am using Dawn) is the whole container (16 to 20 liquid ounces). Make sure to never pour the citric acid or the dishwashing detergent in the radiator directly without first mixing them well with plenty of HOT water!

Follows a set of instructions from another forum which I am attaching verbatim, one among several which I have found very helpful and highly informative. Enjoy, and I hope this helps answer some of the questions from first-timers at this procedure such as myself.

How to Flush the Cooling System with Citric Acid

To start with acquire 2.5 lbs of Citric acid. Food or lab grade doesn't matter. This can be acquired at many food suppliers locally, online or ebay.

Now is a good time to locate your block mounted drain plug which will make each step of this far quicker.

1. You will need to drain and flush your cooling system to remove as much anti-freeze as possible before you start. You should flush at least three times with clear water. Running the car to operating temp each time and allowing it to cool enough to comfortably hold the lower radiator hose or the bottom of the radiator between flushes. Make sure your heater is set to run full blast (maximum temp setting) during each and every stage so the heater core is cleaned as well as the radiator, and the engine block.

2. You need a degreaser, preferably non-sudsing one. Shout will work as will some dishwasher detergents (properly dissolved in hot water completely first) or get Some Prestone radiator flush from the parts store. This will degrease however is too wimpy to do much more than that. How much is enough? I would use a 17 - 20 once container. Better to err or the side of too much than too little and not degrease the system enough. This is a critical step as the Citric acid will not do its job with any oil or lubricants from the antifreeze in the system. Since you are taking the time and expense to this then it would be best to do it properly. Mix the degreasing agent of your choice and fill the radiator full of water, and run the car at least 20 minutes after it is up to operating temp. It is easiest to do this with a short drive. Allow to cool down and flush several times until the water no longer feels slippery that you are draining. Three times should be enough.

3. Mix your citric acid (it’s a dry powder) with 1.5 gallons of hot tap water in a clean bucket or other container. When it’s been completely dissolved pour the mixture into your radiator and top off with tap water.

Take a drive....of about 30 to 60 minutes duration (with heater on maximum temp) after it is up to operating temperatures, you need to get a good vigorous circulation so idling in the driveway will not cut it.

I would avoid leaving this in the radiator for several days or even over night so try to do this step when you have the time to complete it, and the first couple following flushes within a few hours at most.

When the engine has cooled down drain it well, and refill with tap water run up to operating temp for a few minutes then drain when its has cooled off. You do really want to drain with the block plug removed as well as the radiator drain or removing the lower hose. Sediment or rust flakes will not exit the system via the radiator and trust me there will be a lot. You want to do this at least 3 times. This is very important. If you wish you could also do the next step and dissolve 1 lb or baking soda (sodium Bicarbonate) into a gallon of hot water and use this on your third flush. This will help neutralize any pockets of acid that may remain. If you do this step you still must flush at least 3 more times thoroughly.

4. Refill your cooling system with a 50/50 mix of antifreeze that is recommended for your vehicle and distilled water.

This is time consuming and will take a weekend to complete....but you will only have to do this once...and it will be a better more thorough flush than any shop will achieve.

NOTE: As far as the fluids being drained, you need only be concerned about the initial draining of coolant. Please capture the initial drain and take it to an appropriate disposal center. All subsequent flushes are almost 100% water, water with a biodegradable degreaser, or water and citric acid and are safe to be drained straight to the ground.

tangofox007 · #10 07-22-2008, 05:24 PM

Quote:

Originally Posted by rino

Tangofox, for sure that's a lot of waste in bandwidth with absolutely no constructive purpose whatsoever...

Totally unlike fussing about whether "Dawn" is detergent or soap!!!

Rino. given your intolerance for inaccurate information, you should be aware that the recommendations that you posted above are not consistent with the cooling system cleaning procedure specified in the MB service manual.

LUVMBDiesels · #11 07-22-2008, 07:22 PM

I used liquid Tide when I did mine.

I did a quick flush with citric acid ~60 minutes and when I saw the amount of gunk that came out did another one. That one I left for a week, driving with just the acid/water mixture. when I flushed it again the water looked like red mud. I did all my flushes with the thermostat out and the wires to the monovale disconnected. I did use my hose setup to back flush each time. I would fill with water from the block drain run the car flush so that water was coming out of the expansion tank for 15 minutes, with the thermostat in the car the constant running of cold hose water would keep the t-stat closed. This is why I removed it.

After 15 minutes I would shut off the hose, disconnect it from the block drain and also pull the lower radiator hose to drain the rad.

Cervan · #12 07-22-2008, 07:30 PM

4 drops of dawn dish soap vs water wetter

larrym · #13 08-11-2008, 10:18 AM

1) Drain the radiator by unscrewing the radiator drain plug underneath it.
2) Close drain plug plus fill the radiator with tap water.
3) Run engine until warm with heater on, then wait 30 minutes.
4) Repeat 1, 2, 3, four more times to rinse system.
5) Finally, replace with a 50/50 mix of Zerex G-05 and DISTILLED water.

Rino
Do these instructions apply to the '80 300SD as well? I need to do it soon and just found your thread here. Also when you begin the draining should the engine be hot or at least warmed up?
Thanks for all the detail.

vstech · #14 08-11-2008, 12:10 PM

Tango... I don't know for certain, but a week with an acid in the system could eat a good portion of the block away... I used a weak citric acid solution to clean up a rusted pipe threader head that got left out in the rain... I left it in a bucket for two days... not much left of the thing after that...

tangofox007 · #15 08-11-2008, 01:13 PM

Quote:

Originally Posted by vstech

Tango... I don't know for certain, but a week with an acid in the system could eat a good portion of the block away... I used a weak citric acid solution to clean up a rusted pipe threader head that got left out in the rain... I left it in a bucket for two days... not much left of the thing after that...

Please note that I did not recommend leaving acid in the system for a week. I was simply quoting someone who did and commenting that the service manual recommends a much shorter period of time.