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I read the very detailed DIY guide of delirium from the following thread and prepared accordingly. However, many things went sideways in the end. So it is kind of fun to document it and let the others be prepared for what could happen in 2nd Gen MDX coolant flush.

https://www.mdxers.org/forums/74-second-generation-mdx-2007-2013/55914-diy-guide-step-step-how-change-coolant-acura-mdx-w-pictures.html

Step 1: Go to your local Honda dealer to get 2 gallons Type 2 coolant. I did some search online and the answer is unanimous that Honda and Acura sell the same stuff in different bottles. My local Honda dealer charges $22 for each gallon and $28 for the local Acura dealer. The best deal would be to find a Honda dealer that accepts Costco's 15% off coupon.

Step 2: Park the car on your driveway with the wheels turned to max left (driver side). We are also supposed to turn the AC to max hot. But I forgot this part.

Step 3: Use a fluid transfer pump to pump out the coolant in the reservoir. Since the reservoir is pretty deep inside the engine bay with a narrow opening. The usual tools like turkey baster, shampoo bottle pump, syringe etc do not work well. But you can go to any auto parts store, even Harbor Freight, to get a common fluid pump, like this

https://www.harborfreight.com/multi-use-transfer-pump-63144.html

They are all about the same and cost only $5.6 in HF with the ubiquitous 20% off coupon.

Step 4: Drain the radiator from the petcock. It was easy to locate the petcock. It is in the middle of the car, slightly to the passenger side. It was easily seen with a mirror. There are actually two openings on the splash guard for it. So you cannot miss it. However, The petcock on my car was stuck super tight. I tried all my tools and none of them worked. I must have spent 50 minutes trying without success. Before I finally gave up, I put on a glove and gave it the last attempt. Somehow miracle happened. The gist of the story is that to make sure you can finish this very easily, you'd better have nearby a good buddy with very strong fingers. After the coolant started to drain, it will drain from many places. So having more than 2 or 3 buckets ready is important. At the end, I removed the petcock completely and quite some additional coolant drained out. So it is a good idea.

Step 5: Open the engine block drain plug. This step is not comfortable at all. One has to reach for that plug from in between tie rod and sway bar. It was awkward. The best way is actually reaching for that plug w/o looking at it. Just by touch so your head won't be in the way. I first broke loose the plug with a long flex head 3/8 ratchet with 12mm socket, then turned it with my fingers. This plug is strange, once broken loose, it is very loose and does not offer any resistance for ratcheting wrench to work. After that, the most messy part came. I have many tubes and I thought one of them must work. But they are either too wide or too narrow. None of them worked. So I had to use more buckets to catch the coolant. Most of the mess are made here because it again drained from many different places. I also completely removed the drain plug at the end and some additional coolant drain out. However, overall, the amount of coolant from the engine block is tiny compared to that from radiator. It was kinda disappointing to suffer so much and get 'paid' so little.

Step 6: Reinstall the petcock, drain plug and replenish the reservoir to the max line. According to past experience, if radiator is short of coolant, it will somehow suck coolant from the reservoir.

Step 7: Add new coolant. For this step, a Lisle No Spill funnel is recommended. I actually have a new set of Lisle funnel in my garage never used. However, it was getting dark and I was in a hurry, so I just put a small 20 cents funnel on the radiator neck to see whether it would work. It turned out that the super cheap funnel worked really well. (I shall attach a picture later.) I turned on the car and let it idle. I also remembered this time to turn the AC to max hot. I initially poured about 1 gallon coolant into the radiator and the radiator stopped accepting new coolant. However, after about 5-8 minutes, suddenly the radiator started swallowing coolant rapidly. So the thermostat must opened at that time. I checked coolant temperature on the dash, it was about 80% to operating temperature. I poured another 2.5 quarts into the radiator before the radiator refused to accept any additional coolant. So I do not think it is necessary to deliberately rev the engine in any specific pattern.

Then I ask my wife to drive it and go shopping. After she came back, the coolant in the reservoir is in the middle of min and max. I replenished it to max. In total, I used 1.75 gallon of coolant. The spec is 1.88. I am wondering whether this is because I failed to get the coolant from heater core? Can anyone confirm? There is only 0.13 gallon of coolant in heater core?

BTW, the coolant bottle is poorly designed. I had to shine a very strong flashlight behind the bottle and shake it slightly to see the level of remaining coolant.

Overall, this job is one of my least favorite because of the engine block drain. The manual says 10 years/120 miles for the 1st coolant change and 5 years/60k miles afterwards. (It should be maintenance code 5. But I have never seen it.) I did it in roughly 3 1/3 years to be safe. However, given only a very small amount was actually drained from the block, it should be safe to ignore the engine block part if I do 3 times in 10 years. Anyway, this is just my guestimate.
 

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Picture of my very handy 20 cents no spill funnel. I usually use it to replenish windshield washer fluid. The key is to try to keep it 1/3 full so that air bubbles won’t splash coolant out side of the funnel.

Any funnel with a short spout of appropriate size should work. The radiator neck and the funnel seal together very well. No coolant will spill.


Sent from my iPhone using Tapatalk
 

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Discussion Starter #4
The radiator sucked a bit more from reservoir overnight. So I added about 0.2 qt to fill the reservoir back to max. So in total, I have added 1.8 gallon now. Very close to the 1.88 spec. I also did some research on heater core issue. First here is a video showing how much coolant is in the heater core.


Look at 5.20. Seems about half quart there. However, I am not sure that it is feasible to replace the coolant stuck in heater core with fresh new coolant. Here are RockAuto heater cores for MDX

https://www.rockauto.com/en/catalog/acura,2007,mdx,3.7l+v6,1434516,heat+&+air+conditioning,heater+core,6864

We can see that both inlet and outlet are on top of the heater core. There is no way to drain the hc unless one perform the operation as in the ETCG video. So messing with AC during coolant change seems to be unnecessary as well.

Now I finally realized that to do a super thorough coolant flush, one has to drain coolant from 4 places. Radiator, reservoir, engine block and heater core. For most people, especially lazy guys, just do it from radiator and reservoir should be enough. To compensate for the lack of thoroughness, add one more change in 10 years.
 

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Lazy guys would drain the coolant from the radiator tap, refill and be done.

The engine coolant has two main active ingredients: ethylene glycol that is responsible for altering the boiling and freezing points of water, and an anticorrosive to protect the metal that is exposed to the fluid path ( especially the aluminum engine block ). The ethylene glycol will be fine long after we are dust. The anticorrosive is what needs to be replenished. Any remaining spent ( oxidized ) anticorrosive will do no harm; you just need to add fresh stuff to maintain protection.

If some components of the fluid circuit are plugged up, that's a whole different issue.

Not a bad idea to inspect hoses while you're at it, and consider replacing them proactively. Cheap insurance.
 

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I hope you remembered to set the heater to max heat? its in your link steps but not in yours.
I find draining the block on the MDX way to easy compared to my TL.. There is just tons of room to work in the X compared to the TL.
 

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I hope you remembered to set the heater to max heat? its in your link steps but not in yours.
I find draining the block on the MDX way to easy compared to my TL.. There is just tons of room to work in the X compared to the TL.
I hope you have time to read the update. I actually am questioning the need to play with max heat etc. Please let me know if I am wrong. Thanks.
 

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There is fluid on both heater blocks but AFAIK the only that could possibly drain is the main core not the rear seat core in the center console.
In the grand escenario is probably not that much fluid but at least you are draining the most of it by doing so.
 

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There is fluid on both heater blocks but AFAIK the only that could possibly drain is the main core not the rear seat core in the center console.
In the grand escenario is probably not that much fluid but at least you are draining the most of it by doing so.
Why turning AC setting to max warm can help draining the coolant in heater core after I shut down the engine? I guess this is the part I don't understand. Thanks.
 

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When you leave the heat on max cold the valve that allows fluid to be pushed to the core opens, When its closed it creates a vacuum when you are draining the block thus the A/F cannot leave the heater core by gravity so easily. The procedure is not new and it has been noted on basically all Honda Service Manuals that I can recall.
 
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why couldnt you do several radiator drain and refills they same way a trans is done???
This is a feasible option. As the OP mentioned and has been discussed in other threads, you get very little coolant from the drain block. I've done this about 3 times and never measured the volume from the drain block, but dare I say it is like 10% of the volume you get from the radiator.

While I agree draining the engine block is annoying, I've always been able to do it without making too much of a mess. I basically break the drain plug bolt, then loosen it so coolant start to flow at a slow rate, then quickly wedge the hose up onto it. I end up spilling about a 1/4 or 1/2 cup of coolant doing that, but get the rest through the hose. Because I only loosen it slightly, it takes about 20 min. to drain, but during this time I switch over to other tasks to prep for the coolant refill so I'm not just standing there picking my nose.

If you just did radiator drain and fills every few years I think that would be more than enough... you would be getting the majority of coolant swapped out. For my other vehicle, it has 2 block drains that are inaccessible so I only can do radiator drain and fills. I just do them a bit more often. Per your comment, same concept at the transmission drain and fills.
 

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Discussion Starter #13
When you leave the heat on max cold the valve that allows fluid to be pushed to the core opens, When its closed it creates a vacuum when you are draining the block thus the A/F cannot leave the heater core by gravity so easily. The procedure is not new and it has been noted on basically all Honda Service Manuals that I can recall.
Do you have a typo? max cold or max hot?

If you look at the rockauto parts, both inlet and outlet are on the top of the heater core. there is no way for the coolant in heater core to get out. BTW, where is the valve? Do you mean if one turns to max hot before draining coolant, the valve will stay open all the time? Even if that is the case, it won't let old coolant drain. The only benefit is that it will allow new coolant to mix with old coolant in the heater core. Maybe in super hot places, this will make sure the coolant in heater core is refreshed at the same time?
 

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Yeah a typo.. Max Heat.

As I said previously the amount of A/F inside the heater core is very minuscule already but never the less leaving the A/C at max heat is the correct procedure when draining the A/F.
 

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Well, I give up. Maybe there is a good reason why leaving it to max hot will get more coolant out, but I just cannot understand it.

It could be for another reason. Suppose a car operates in Africa and the driver never uses hot air. So leaving unchanged, sooner or later, the coolant in heater core goes bad and the heater core is damaged. Setting it to max hot will make sure in the burping process after draining, the old coolant has a chance to be mixed with fresh coolant. That is the only way for this to make sense. For anyone who uses hot air in winter, this step is not needed. But Honda has to write a single manual for all the people around the world driving the car.
 

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Picture of my very handy 20 cents no spill funnel. I usually use it to replenish windshield washer fluid. The key is to try to keep it 1/3 full so that air bubbles won’t splash coolant out side of the funnel.

Any funnel with a short spout of appropriate size should work. The radiator neck and the funnel seal together very well. No coolant will spill.


Sent from my iPhone using Tapatalk


While I was walking around in harbor freight, a set of funnel caught my attention. One of them should work as a no spill funnel. However the most interesting one is the smallest one inside. I think it might fit into the ATF tube.




Sent from my iPhone using Tapatalk
 

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Discussion Starter #17
Tonight after returning home, I checked my wife's MDX. The radiator sucked additional coolant and the line is close to 'min'. So I added it again to 'max'. By now, I have used about 1.88 gallon of coolant. (I recently replaced timing belt on a Toyota and the same thing happened. So I am not surprised at all.) So I guess the whole procedure is all about done. The key takeaway from my experience are
1. No need to play with AC settings. It does not matter at all.
2. No need to follow elaborate procedures to bleed the air afterwards.
3. A small cheap funnel can be used in place of a fancy Lisle funnel. Just keep the fluid low.
4. Remember to replenish the coolant to max in the reservoir and keep an eye on it in the following days.
5. I probably drained a little bit more coolant from the block than I initially estimated. So draining the block might be a good idea.
 
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