Changing out green coolant/installing new MB/Zerex - should I flush?
 

I am soon going to remove the "green" coolant and put in new MB or Zerex coolant. I am wondering if I should flush the radiator or just simply do the drain. I do not have any overheating problems (highest it has been was just above 80*C). I have read a couple of other topics where people has flushed and "clogged" and ruined the heater core. I DO NOT want to do this, because it is my understanding that it is a terrible replacement. In this case, should I bypass the "flushing" process?

Also- should I drain with the engine coolant being hot/warm/cool/cold? Also-do I just HAVE to drain the engine too, or would draining the radiator be sufficient?

Thanks in advance!

Well, if you want to do a complete job, you are supposed to drain the block. I didn't do this when I went from green to yellow. I got nervous about identifying the location of the drain plugs (apparently easily mistaken for important engine bolts). There was a lot of AF that came out from behind my water pump when removed after I thought I had drained everything via the lower hose. No apparent ill effects, 1.5 years later. But no doubt, draining the block is best, and I don't know about "compatibility" between the two.

Just a comment, I have essentially the same engine, etc - if you've never seen your car go over 80 C, I'll bet that your thermostat doesn't actually work - it's stuck open! This is a lot better than stuck closed, but the engine is not really running at an optimal temperature. I didn't go above 80 in the summer and not above 70 in the winter. I did major work, replaced the thermostat due to age and that I was already in there, and the temps went up to 85-95 C! Many people in these forums have observed this phenomenon with a new thermostat.

Well, if you don't see any contaminants in the coolant, then I would not consider using a chemical to 'flush' the system. You DO need to remove all old coolant, though, and you won't even come close by just draining the radiator. To avoid clogging the radiator, you can remove several hoses and the thermostat, using water to flush out the radiator and block. This will leave H2O in the block, so on reattaching it all, you will need to fill with the prescribed amout of antifreeze for a 50% fill, then top off with water until it stops accepting more.

Steve

Here's the location of the drain plugs on your engine. Once you are under the car, they aren't that difficult to locate, but can be a b***h to get started if they have been in there since new. Be sure to use the right size 1/2" drive socket and some extensions.
I read lots of threads on changing coolant before I decided that draining the radiator and the block was more than adequate to switch out the old green to Zerex.
For some reason though, I was unable to get the final liter of Zerex in the plastic fill tank, until a about month later (summertime) when the level dropped enough to accomodate it. I assumed that there may have been some air in the system, possibly in the heater core, even though I did refill with the heater auto control on max defrost setting.
BTW, the design of the cooling system is interesting, in that it allows air entrapped in the coolant to percolate out through the small vent hose on the radiator top and from the thermostat housing into the upper portion of the plastic resevoir tank, under pressure. It's not your standard overflow tank/setup, since if the cap pressure is exceeded the coolant will spill out the overflow hose onto the ground.

I have never drained coolant from a block. I would take extra precautions (penetrating oil or something similar) before trying to loosen the bolt heads. Maybe even try to slightly tighten the bolts before trying to loosen
.
I would wear gloves to prevent skinned knuckles.

good luck

I agree with the aforementioned posts that recommend that you locate and drain the block. On the diesels, the block holds at least 3 quarts that won't get changed if you simply drain the radiator.

Additonally, the heater core will also hold about a quart of fluid. For a better job, I'd recommend filling the system with water, after draining, then driving it for 15 minutes with the heat on high to circulate the water through the heater core.

Park the vehicle for one hour and drain everything, yet again.

Now you can fill it with the proper mix and be reasonably certain that the concentraton of the green stuff is negligible.

I would recommend doing a citrus cleaning. Use the search feature on this site with the key word: Citrus.

Haasman

<<citric>> also is good to "search". ;)

What is the differance between the "normal" blue coolent and this yellow thing you are talking about? :)

Thanks. No, there are no particles or anything in the coolant reservoir, but I just want rid of the green coolants.

About it going over 80*C - actually it has went over that to about where it is exactly horizontal. This was when I was in stop/go traffic. I read in the owners manual that it could safely go to 120*C, but that seems extreme. I am guessing mine was at about 85-90*C at its highest point.

On the highway or in smooth flowing traffic, it stays below 80*C, sometimes well below at highway speeds. Perhaps the thermostat needs replaced? Hopefully the proper coolant will keep it below 80*C. I want to change it soon, but seems like a messy task.

I still really did not get any information about it possibly clogging my heater core. I may just wait and simply do the complete drain/refill since the coolant in there is clean, but green. :D

Thanks

I was able to drain the heater core by disconecting the hoses from the heater core to the intake manifold and hooking up a shop-vac and sucking the old coolant out. You might also want do the same from the two hoses that go to the windshield washer tank heater.

The same trick might work on the block from the water ports once you take the water pump off. At least you could suck out some, refill with water, suck again. Repeat until the water coming out is no longer green. Buy some 1/2" clear plastic tubing and push it into the water ports to extend the reach.

As others have mentioned, the two plugs are very difficult to remove. They have a 6MM allen head and may strip the head when you try to remove them.

The MB manual describes a flushing technique that requires two tools (a tee fitting and a special thermostat). I checked out the price from the dealer, about $100 for the two of them. Since I had the cylinder heads off I choose to suck it out with a shop-vac. If you think your system could use a cleaning, then a flush would be better. If you don't want to buy the tools can always take it to a shop that has them.

I actually bought this from MB (hard to beleive, it's really industrial grade Vitamin C!), but I became concerned about my ability to actually flush it out entirely after using it. Leaving it in might make things worse than doing nothing at all. Besides, my cooling system seemed to be in reasonably well-maintained shape (even with green stuff in it). OTOH, I had googled a story somewhere on the Internet where someone did this on a 40+ year old car with incredible results, it was like a concrete slurry that came out of his block!

If you do decide to use the citric acid, you must fill the system, run the vehicle, and drain it at least three times. It's vital to get all the acid extracted from the system prior to filling with coolant. There are some members that did this five times until they could not feel any slippery sensation in the flush water.

If you don't want to make the complete effort, it's better to forego the acid treatment.

Also, once warmed up with the heater on, leave the heater on and set to high when draining.

As for the difference between blue and yellow, well I reckon that depends on where you live. Many places outside of the US get the blue colored coolant (Phillipines comes to mind), apparently if it has the MB label it is basically the same stuff, just different color.

I drained my dexcool coolant the other day, and refilled with Zerex 05.
To get to the engine drain plug, work your way around the exhaust manifold with a 13mm (?) socket drive. We've got to get the coolant out of there!
Also, pull out heater hose at the rear of the engine, closest to the firewall.

To refill, open up the bolt atop the engine head while pouring coolant to the reservoir. Watch out until coolant overflows on this bolt, then screw it back on. If you do this, you will not have any air pockets in the system.

I did not make this up it is in the MB procedure manual!

My manual for the 116 engine shows a 'vent screw' (bolt) used up until Aug 1981, after which a vent hose from the thermostat housing leading to a T fitting and then to the expansion tank is used. Not to confuse the OP, but if this is the bolt I don't believe it's on his engine.

Brian is spot on IMHO. Requires a good bit of work to do a proper flush. I like to drive the car for 10-15 minutes b/w each drain.

When mixing your coolant/water use soft drinking water. I've done a fair bit of research and apparently using DI water is not as ideal as you remove the sacrificial ions that help save the cooling system/heads/block etc..

Jonathan

[QUOTE= I've done a fair bit of research and apparently using DI water is not as ideal as you remove the sacrificial ions that help save the cooling system/heads/block etc..

Jonathan[/QUOTE]

Your research is flawed. All the "sacraficial ions" necessary for corrosion protection is in the antifreeze. Distilled water is best to mix since it does not introduce any foreign organic or inorganic material that may reduce the effectiveness of the corrosion inhibitor package.

When changing from an IAT to OAT the cooling system should be thoroughly flushed. Flushing is not as critical when switching from an OAT to a HOAT, but it's still a good idea since any of the residual organics in the OAT may not be compatible with the organics in the HOAT.

The myth that distilled water is "bad" got started 50 years ago when some idiot thought that STRAIGHT distilled water was good - that meas straight without any antifreeze or corrosion inhibitor. Pure distilled water is about the worse coolant you can use as corrosion will be rapid, but it's best when mixed in proper proportion with an antifreeze that has an effective corrosion inhibitor package.

Duke

Agreed, that is what the coolant is for... The articles I came across were discussing the merits of using soft filtered drinking water over mixing w/ DI water. The logic didn't seem terribly flawed @ the time.

My degree was in bio and I never did enjoy organic chem so perhaps I am off kilter..I'll have to see if I can dig up the article, see if they have any sources cited etc..

Jonathan

The trouble with most "journalists" is that they have degrees in journalism and rarely have any background in the subjects they write about, but a little Chemstry 101, which I doubt is required in any journalism curriculums, goes a long way.

It is known that the effectiveness and life of the organic corrosion inhibitors in OATs like Dexcool can be lessened by inorganic salts in the water used to mix with the antifreeze or the inorganic salts left behind by traditional OAT antifreezes, which is why a thorough flushing is called for when switching from IAT to OAT. IATs and HOATS are more tolerant of salts mixed in the water, but for a buck a gallon, why not use "uncontaminated" water.

All antifreeze has about ten percent water in the jug when you buy it (It's a byproduct of the manufacturing process.), so adding distilled water just dilutes the mixture more without adding any "foreign" ions, and most commercial antifreezes are blended to have an optimum initial concentration of the corrosion inhibitors when mixed about 50/50 with water - preferably water that has no "contaminants", even in very low concentration.

Duke

Well, I suppose I will have to go with the Mercedes coolant from the dealer, because ZEREX is NOWHERE to be found around here. I phoned and/or looked at: Autozone, Advance, O'Reilly, Wal-Mart, CarQuest. I do not think we have a local Pepboys since we only have a population of 150,000 in the metro area. :rolleyes:. I say that, because awhile back someone said they were only in high populated areas, which is not a good business move in my opinion. Maybe one in Johnson City - I will have to look. I doubt it though. I think the closest one is in Knoxville, which is 120 miles away.

I phoned the local MB dealer and it is $22.00 per gallon there. I can buy it here for $20 and some change, but then there is shipping, so I may be better off going to the dealer.

When I phoned O'Reilly, he said we do have a new Prestone coolant. I asked him if it said for Mercedes and he said it said safe for ALL cars. The guy there he asked to verify said that his mother used it in her Mercedes, for what that is worth.

Obviously Zerex is going by the wayside- at least around here. Ridiculous.

I think you might have a point here. I had to search far and wide the last time I needed two gallons for the SD. I wonder what the deal is..................:confused:

i have a 420sel and i still CANNOT find the darn coolant drain plugs on the engine block! There are so many bols which confise me so better to leave it all there before i start taking things off. Once I get those off, my job will be a breeze. Can anyone post pics or tell me where they exactly are for my 420sel

Not sure, but I am sure this is a problem I will face when I change mine out. :rolleyes: If you find out, please let me know if they are in the same location on the 3.8L V8.

Now I am confused as to what type of water to use in my cooling system with the anti-freeze. We have a water purification system built into our homes water system, that is supposed to be even better than any bottled water purchased in a market.

Would this water be safe to use in my cooling system, or should I use bottled water instead? If so, what should I use - distilled, drinking or spring water?

Also- since the green coolant has been in my radiator, will any further corrosion be halted if I switch to the MB coolant? Lastly, will one gallon of MB anti-freeze be sufficient for my car? I live in a climate where our temperature rarely drops below 15*. Our "coldest" average low in the dead of winter (which this time of year) is 24*, but last night we only dropped to 47*, and it was 68* today (average is 44* for the date) so as you can see, winters can be rather mild here.

So, if I use one gallon of MB coolant and the rest is water, about what temperature will it be protected to?

Thanks!

Look at the manual page I posted above. The 380SE engine (116.963) is laid out the same as the 420SEL (116.965) as far as these plugs go. Yours could be covered in crud, making them hard to see, as the socket-heads may be filled up with grime too.
86560SEL, I wouldn't be too concerned about the water quality, and there is at least an hours worth of reading on the controversial issue right here on this forum. IMO, use your household filtered water. The shop manual doesn't mention anything about using distilled water only. Others will disagree, but I think this whole distilled thing only is way too anal.
The container will tell you the temperature range of the product, mixed to the specs provided, so you will need to settle on this first. I live in Canada, so can certainly attest that all of them protect in winter up here, MUCH colder than Tennessee

It's important to maintain a 50-70 percent antifreeze concentration - regardless of the lowest anticipated temperature.

Less than 50 percent will not provide sufficient concentration of corrosion inhibitors and aluminum is VERY unforgiving.

I've seen many Cosworth Vega engines (open deck block like the early Merc aluminum V8s) where the top of the bores were beveled from the cooling system side to the inside of the cylinder wall resulting in head gasket failure. It looked like someone went crazy with a die grinder, but it was corrosion due to lack of cooling system maintenance i.e. regular antifreeze changes or running without or with insufficient antifreeze.

The fix was sleeves, which basically means a major bottom end overhaul. When I had my CV's head off for a refresh a few years ago the top corner of the bores on the cooling system side were still almost sharp enough to cut your finger. A borescope inspection of the head cooling passages reveled what looked like fresh aluminum right out of the casting mold That's the result of regular coolant changes

Duke

My manual says my cooling system for my 420sel holds around 13.5 quarts. i am guessing they are getting this number if you drain the Radiator and the engine block of coolant?

Distilled has nothing except water in it... tastes metallic almost, mabey even tasteless.....

Anyways would it be prudent to fill the radiator with distilled water when your going on your warm up drive? I put the green antifreeze in mine:mad: , so I'll do a MB fluid and thermostat change this summer...

Also where are the drains on a 617.910?
Thanks alot
~Nate

Distilled water is the absolute WORST thing to use for a hot flush, and why waste the money.

If you do a hot flush - drain, flush, then fill with water from your garden hose, warm up the engine and drain one or more times - just use potable water, which most domestic water is.

Use distilled water to mix with the antifreeze to target an antifreeze solution no less than 50 percent.

The OEM spec for cooling system capacity is the total amount, and you have to drain both the radiator and block to refill close to this amount, but there will be some trapped in the system, so your can rarely install the entire amount specified.

I divide the system capacity by two to determine the correct amount of antifreeze - example - 6 quarts of antifreeze for a 12 quart system. First install the antifreeze then top off with distilled water. In this case it will probably be a little less than 6 quarts, so you end up with a 55-60 percent antifreeze concentration.

Duke

why is it the worst thing to put in after you drain the radiater and before you go for a ride?

~Nate

When I first got my car it had what looked like Dexcool in it. So I bought some flush from Autozone and used that. Then I ran water in it and drained that a few times. After the water came out nice and clear I refilled with MB coolant and it seemed to work good.

My coolant change is coming up this spring and since I have replaced much of the cooling system since then and I know everything is clean I won't flush. I'll just drain the old coolant and refill with the new stuff. Maybe if I go nuts I'll refill with water first and use that as a flush.

coolant change
 

I just did a few repairs that required me to remove the radiator, and I was about due for a coolant replacement so I was wondering how to correctly do everything. This is an 88 300E.

Is Mercedes coolant premixed 50/50? I didnt quite understand their "instructions" as they were more like precautions.

Also, how do I drain the block?

Does anybody know what my total capacity is, or know how I can find out?

Be careful with used coolant

From: Repair Tips, Short-Cuts

Haasman