RangeRider49er

I am looking for the location of the engine block drain plug on the 2008 RDX. I don't have any manuals and can't seem to find it. Does anybody have info on draining the engine coolant and replacing all coolant?

dcmodels

There is no block drain plug. Here are the main points, and unless someone else responds sooner, I will try to post a more detailed response later.

1. all of the coolant cannot be drained, because there is no block drain plug, which is probably why the replacement coolant is rated for 5 years, while the original fill is rated for 10 years (or until the MID requests a change with A5 or B5 display)

2. to drain as much coolant as possible, start the engine. Then set the temperature control to the highest setting (Hi displayed). This opens the heater hose valve, allowing coolant inside the heater core to drain. Shut off the engine. Probably it is only required to turn the ignition key to RUN position, but starting the engine is more sure method.

3. I found it more convenient to remove the lower cover (Splash Guard) between the front bumper and the front frame cradle, to gain ready access to the radiator drain plug. This is not required, but if you want to do so, look here and scroll about half way down:

https://acurazine.com/forums/1g-rdx-diy-faq-161/diy-%96-add-power-steering-replaceable-inline-magnetic-filter-828859/

4. My fingers were not strong enough to remove the radiator drain plug from above (or from below either). I had to use pliers. But remember that the plug is plastic - it will break. For pictures and more information concerning this drain plug, look here, post #5:

https://acurazine.com/forums/1g-rdx-diy-faq-161/diy-%96-how-safety-wire-drain-plug-860310/

5. In theory, the radiator drain plug does not have to be completely removed, as the water can drain from the hole in the drain plug housing - see pictures in the link above. And the water can 'sort-of' drain through the hole in the Splash Guard.

6. The cooling system holds, after an engine overhaul 2.22 US gallons, including 23 ounces in the reserve tank.

But you can only drain and refill with 1.85 gallons = 1 gallon + 3 quarts + 12.8 ounces. That assumes that the FSM is accurate in giving the exact fill quantity, which most often is only 'close'.

7. I found it difficult to completely refill the system, since there is no bleed screw or bolt on the top of th engine.

8. After draining, fill the radiator. At this point I was still about 2 quarts low. Jack up the front of the car about 3-4 inches. That will help release air and allow more coolant to be added.

9. Replace the cap loosely. Start the engine and run until it warms up (the radiator fan comes on twice). Well, the fan won't unless it is 90 degrees, so just check the dash panel for temp gauge. Remove the cap and add more coolant. At this point, I was still about 1-quart low.

10. Depending upon the ambient temp, and how long the engine runs, the thermostat may or may-not open.

11. It may be necessary to install the radiator cap tightly, to get the thermostat to open. IF you do this, you must wait until the radiator cools before you remove the cap, unless you like 3-degree burns. Also, do NOT allow the engine to run very long as it may overheat because of trapped air inside the engine block.

I did not do the above. I left the cap installed loosely, and ran the engine, and kept removing the cap and checking. Remove the cap carefully, as the level will rise and drop and possibly overflow, making it difficult to avoid spilling, and thus impossible to keep track of how much coolant you have added. I did this in the driveway, not inside my garage. It is impossible not to spill some coolant either during draining, or refilling.

It was obvious when the thermostat opened, because the coolant level dropped immediately. If I remember, it took about 15-20 minutes.

I added the final quart. Then tightened the cap, let the engine warm up, then waited an hour or so to recheck the level, and added a bit more. DO NOT drive the car until you are certain that the system is completely full of coolant. Otherwise, again, the engine can get 'hot-spots' from trapped air - very bad.

And recheck the level after the first time you drive the car. If the reserve tank has been filled to the upper line, then probably any small amount of air in the system will be purged, and replaced with coolant from the reserve tank.

13. LOWER THE JACK. Yes, up to this point, I left the car slightly jacked up in front. I found this necessary.

14. I hope that it is clear from the above, that it is necessary to carefully measure just how much coolant you removed, and how much you are replacing. Otherwise, you cannot be certain that you have completely drained the system. And more importantly, you cannot be certain that you have completely refilled the system.

15. A last note: if the car is driven in temps under -31degrees F. then before refilling with coolant, add 1.6liters of Honda Extreme Cold coolant p/n OL999-9020.

Good luck.

RangeRider49er

wow. Thanks for the detailed response. I had no idea it was this hard. I understand the reason to get all the air out of the system. Too bad there is no block drain. I thought all engines had one. This procedure makes me consider going to a shop for this.

dcmodels

OK, so no block drain leaves about 1-quart of coolant inside the block. But that has no effect on a drain-and-fill. Even systems WITH a block drain do not allow a complete coolant drain of the system. There is always some amount of coolant left inside either the block or hoses.

For the RDX, it does mean that you cannot (back) flush the coolant system with plain water, because Honda coolant is only available in a 50% mix with water, but not available in a concentrated form. So that after a water flush you cannot just add the correct amount of concentrated coolant, and then top off with distilled water, to get the required 50% water-coolant mix.

Because I cannot flush the RDX coolant system, I drain-and-fill every two years. Hopefully that will prevent any build-up of deposits.


Well, give it some thought - it is not difficult just tedious, getting out the air. Just put the car on level ground and jack-up the front slightly, or position the FRONT of the car at the higher end of a slightly sloped drive-way, and let the engine run. After 15 minutes or so all of the air will 'burp' out, the thermostat will open, and you can complete the coolant fill.

This is really no different than most cars, my 98 Chevy 4x4 V6 included. The difficult cars, and there are many, are those with the engine positioned HIGHER than the radiator cap, so that a bleed bolt on the top of the engine is required (to open) to get all of the air out.

I do strongly suggest that you use a quart measuring container to keep track of how much coolant you have added. And remember to include the coolant reserve tank, in tracking the coolant amount.
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NOTE: it could be a lot worse. My 98 Chevy V6 does have block drain plugs, but they are not accessible because of the 4x4 front drive axles. And the radiator has no drain plug. And the bottom radiator hose is not located at the bottom of the radiator, but about the middle.

So I have never been able to completely drain the system enough to flush and replace coolant myself. I must let the dealer do it for me, with a flush machine.
---eof

RangeRider49er

Okay thanks for the detailed response. The 2-year coolant replacement interval sounds good. I have heard some say that the coolant flush is no longer recommended by Acura but I called one dealer and they still do coolant flushes. They were also recommending replacing the timing belt at 110k miles which I don't understand as long as the belt is in good condition.

RangeRider49er

dcmodels:

Is it possible/practical to unhook one of the heater hoses to allow trapped air to escape during the refill process?

dcmodels

I am uncertain why you would ask this? Have you located the heater hoses?

Anyway, the problem with the RDX (and any car) is that the air must escape from the highest point of the coolant system. For some cars, this is the top of the engine, which is higher than the radiator cap - so there is a bleed bolt on the top of the engine.

With the RDX, the highest point of the coolant system is the radiator cap - so that is where the air must escape from. And what is keeping the air from escaping? It is the thermostat, which is located in the bottom radiator hose.

1. by positioning the front of the car slightly higher than the rear, you ensure that the radiator cap is the highest point of the coolant system. I found 2-4 inches sufficient. And if the car is leaning to one side, air can be trapped at the top of one side of the radiator, although this amount should be small.

2. the engine must be run until it is hot enough to open the thermostat, so that any air trapped inside the hoses or engine block can escape. This is required with any engine, not just the RDX.


WHO says Acura does not recommend a coolant flush? True, I did not find anything in my FSM (factory service manual) other than instructions for a drain-and-fill. I would assume that most Honda/ Acura dealers would have an aftermarket flush machine, since doing a drain-and-filll is labor intensive (takes longer). I have not checked with my own dealer.

Plus, as I have indicated, a drain-and-fill leaves some coolant behind. A flush machine would (in theory) replace ALL of the coolant. I guess it depends upon how the machine works, and how well it can flush out all of the many hoses in the RDX. Just the cooling hoses to the turbo make the system much more complex than my simple Chevy V6 engine coolant system.

Keep in mind that most aftermarket coolant flush machines allow flushing with a cleaning chemical, before refilling with coolant. When I have my Chevy coolant flushed, I simply ask that the cleaning chemical not be used, because I am concerned that the chemical may affect (damage) the water pump seals.

This is another reason why I drain the RDX coolant every two years. And have my Chevy system flushed every two years (without chemical) - to prevent the buildup of corrosion and sludge, which would then require a chemical flush.

I suppose I would be inclined to discuss with my dealer, how often they recommend a coolant flush, and how well it cleans the system.


The RDX has a timing CHAIN, not a belt. I am unaware of any suggested replacement interval. I would be interested in your Dealer's reasoning for that replacement interval, assuming that the dealer really means a CHAIN replacement and not a BELT replacement.

I am aware that some cars have the timing chain tensioner fail, particularly if the oil is not changed regularly. I am not aware of any particular problems with either Honda or Acura cars with the timing chain - although many Hondas have a BELT. That is why I would be interested in what your dealer has to say in this regard.

Just as a comment on talking with my dealer, whether Acura or Chevy or other, I find that the tech WRITER is not always the most knowledgeable. When I have a technical question, I try to talk with the service MANAGER, or sometimes will ask to speak with an actual mechanic or the SHOP FOREMAN.

Since I always use the exact same tech writer every single time I visit the dealer, they get to know me. And I try to be as polite as possible, and just ask for help - so usually I am able to talk with someone to answer my questions. I also try not to ask too many or too dumb questions. That just means that I try to do a bit of research before my dealer visit, so that I have some understanding of the issues that I am going to ask about.
---eof

RangeRider49er

dcmodels:

Thanks. I need to get a shop manual for this car. You are right, I don't know where the heater hoses are located. I did a spark plug replacement once and can't remember seeing where the heater hoses are located. https://acurazine.com/forums/showthr...1&ref=esp-link
I didn't realize that the thermostat was located in the lower radiator hose! Wow. Every car I have had previously had the thermostat in the upper hose on top of the block. Even my tractor and generator have them on top as well. That explains a lot in the refill process. That should allow most if not all of the trapped air to escape from the engine block and heater too I would suppose. I will try the process you have described soon.

BTW, how hard is it to unsnap the plastic cover at the bottom of the radiator to gain better access to the radiator drain plug? I am somewhat afraid I will break them by pulling too hard. I see the directions on your previous post for removing the snaps from the splash guard. Thanks for all your insight on this procedure. It is definitely doable by the average Joe!

RangeRider49er

BTW, if the thermostat is on the bottom, it seems that the coolant in the engine block wouldn't drain out via the radiator drain plug. Won't that leave old coolant inside the block and heater?

RangeRider49er

It seems that the flush at a dealer without the chemicals may be the best option to replace the most coolant possible. I can get it done for $110 locally so I am now considering that option rather than the labor intensive and less effective home option. It seems that if the thermostat could be opened (remove and replace thermostat in two steps with drain followed by refill) would result in more coolant being replaced?

RangeRider49er

I decided to let the local shop do the coolant job with drain and refill. They used 1.5 gals of Zerex (Silicate and Borate free) for Asian cars and supposedly safe for Honda & Acura cars. I hope so. I plan on doing it myself next time using the method above by dcmodels. Thanks dc! Here is a link to the coolant product: http://www.valvoline.com/products/br...antifreeze/105 You can get it on Amazon.com for about $13/gal

RangeRider49er

The next day after the shop drained and refilled my coolant I added another quart as the air worked its way out of the system. I will check it again for the next couple of days after driving. Total coolant change so far is 1 3/4 gals.

phineasboggs

I made a separate post on this, but what can I do after I put WINDSHIELD FLUID in coolant tank? I don't want to drive to a shop. Can AAA do this for me?

wifesRDXtech

Did coolant replace today , unable to leave cap off while car was raised coolant started shooting out. Did what dc mentioned tight cap run it till fans run 2 times then cooled off , topped off. So far so good will drive around today and check level again tonight. thanks DC MODELS.

Mr Marco

Holy fucking shit.

Save your car and stay out from under that hood.