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.