Backflush on OM617---Using a Kit (Question)
 

Howdy all,

I'm going to backflush my OM617 in my 81 300D (84 engine/trans) tomorrow. Question: if I use a Prestone Flush Kit (or similar), it appears to me the hose to "cut into" would be the #4 hose in the link below to install the kit, yes?

Coolant Hoses - Mercedes-Benz Forum

My plan to do this is as follows:

1. Drain the system, including from the engine block, as shown in the iFixit below (my car only has expansion tank---no cap on radiator):

https://www.ifixit.com/Guide/How+to+change+Mercedes+W123+coolant/22768

2. Install the backflush kit; put in flushing fluid, fill w/water, run for 20 (until warm). Let cool.

3. Drain backflush garbage. Then run hose thru backflush kit until running clear. Drain.

4. Put 3 gal. distilled water in system; run for 20 (until warm). Let cool.

5. Drain again.

6. Fill system with antifreeze, properly mixed. Fini.

What this article fails to mention is the proper flush of the system. The manufacturer recommends a citric acid flush. The Prestone flush is much to harsh on some of the metals in the system and you may cause leaks in very unwanted places, such as the heater core.

Here is the reference in the FSM (Factory Service Manual)
https://www.startekinfo.com/StarTek/outside/12265/disc_2/program/Engine/615/20-015.pdf

Also, it fails to mention the proper fill procedure. The coolant should be refilled with the car "nose high", such as on ramps. This is to prevent an airlock which would lead to overheating.

There is an excellent DIY section, here on the forum, that will help you with many of these tasks. They are posts written by members here that can help you avoid many of the pitfalls of outside articles.

Much success with this product:
http://www.irontite.com/store/index.php?main_page=product_info&products_id=4&zenid=53e02116248995f1968779c04e44bc89

NAPA has it or gets it the next day. Highly recommed. Open the heater core valve to
flush that component.

Flush it well. No need to run distilled water, unless your water supply is questionable.

Drain it completely, so that your anti freeze ratio is correct.

SD Blue, are you referring to the DIYs in the link below? I had never seen those before until you pointed them out. :D

DIY Links by Parts Category - PeachParts Mercedes ShopForum

And probably you're referring to the link below in my case.

http://www.peachparts.com/shopforum/diy-links-parts-category/142410-cooling-system.html

Appreciate the good tips, including the Irontite! Looks like that does the degreasing/citric flush all in one step.

Not going to get to this stuff it looks like this week; since the heat in my current "setup" of the car is "working" (aux pump and monovalve electrically unplugged), I can get by with cycling the buttons on/off. For now. Weather may not cooperate for me to do this weekend, either.

Husky, did you install your kit at the #4 hose location I mentioned at the top of this thread? Just want to clarify which hose I should install the kit properly to before doing.

This is why you should never install this kit permanently. I've seen several overheating cars caused by this "T" connection bursting open over the years.


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Yes, those are the links I'm referring to. Using these links have helped me to avoid a lot of possible grief. They are full of little nuggets of information. WHunter, who put them together is one of the gurus on this site with many years of MB specific experience.

For such kits - its best not to cut your original hose but to get generic by the foot hose and use that and put the kit/adapter valve in it. Replace with original once flushing is done.

I dont have such a kit - I simply use a barb fitting and hose adapter on my water supply, and then a clear hose to a heater hose nipple (in the bypass circuit) and flush away. Works with every car ive ever flushed. I also made a bucket with a pipe nipple drilled in it and fill it with RO/distilled water if Im in the mood for real fancy work. The bucket is put on a ladder and the water pushes itself through the system.

citric acid flush is the nicest and lowest cost too (ebay has lots of it) or oxalic acid (wood bleach).

For red gooey GM sludge use cascade commercial grade, It gets it all out.

Husky, yep, that is the #4 hose. The pic of that #4 hose is buried deep in the post I mentioned above.

And Zulfiqar, I'd agree with the idea of not cutting into your original hose, but...the #4 hose I'm referring to (the one that goes over the oil filter assy.) is not a "straight line" hose. What I mean is, I'm not sure how you could easily "bend" a temporary one around everything in the engine compartment and make it "work". I'd think it would kink too easily.

Placing the car in "defrost" mode ensures the heat core is open for business and stays open during the entire flush cycle. Unless you have a 240D with manual controls, on those just crank the knobs all the way to the red zone.

Ditto on not putting the flush kit in permanently, I have too heard stories of those flush adapters blowing out.