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Discussion Starter · #1 ·
Normally, I'm not the type that's too anal on PM unless it's something that can cause catostraphic damage or leave you stranded.

In this case, the radiator in the MDX should be a PM IMO as there are both transmission fluid and coolant running through the same unit. For warmer climate peeps, you can elect to go the external tranny cooler mod that has been outlined by Skirmich. For peeps living in snow states, it's gonna be a personal toss up on whether you want to maintain the factory setup. I'd rather not get into a debate about that in this thread though.

I would say if you're after the 8-9 yr period, you are pushing it depending on where you live.

If you wait til after the fact, you'll have to flush out both systems(tranny and coolant) which will cause you more headaches in labor and material costs down the line. You can do it as a PM which will set you back ~$300 for OEM Radiator or ~$160 for a Denso unit which also makes OEM radiators for various cars. I'm not sure about the other popular alternative which is Spectra as they seem to have a few different lines for the same car. I'd rather just stick to a Japanese OEM manufacturer personally.

It could cost you potentially more in towing fees if you get stranded from this or if you decide to keep driving it to the nearest shop, you're at their mercy. If you drive it home and it's far, you could be looking at a transmission repair or replacement cost.

So bottom line is if you're driving or don't notice the intermix and continue driving it, you could potentially damage your transmission.

I'd say this is a pretty good case to PM the radiator IMO.

In my case, I lucked out as it slowly started leaking(from passenger front corner) in my driveway. When I went to move it and let it run, the internal line must've ruptured and whole bunch of fluid spilled over out of the coolant reservoir tank.

It's pretty easy to diagnose this vs. say blown head gasket, cracked cylinder head by the color which should be strawberry milkshake like since tranny fluid is normally a reddish color.



 
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Thanks. I was thinking about this for a while myself. Which year is your MDX and the mileage? I got an 07 with 85k miles. So it has been almost 11 years. My old Toyota needed a new radiator at 13 years. So the radiator on MDX is likely near its end of life anyway. Replacing the radiator is likely to be more cost effective than adding a bypass external cooler. Will get it done around October this year when I have more free time.
 

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Discussion Starter · #3 ·
Thanks. I was thinking about this for a while myself. Which year is your MDX and the mileage? I got an 07 with 85k miles. So it has been almost 11 years. My old Toyota needed a new radiator at 13 years. So the radiator on MDX is likely near its end of life anyway. Replacing the radiator is likely to be more cost effective than adding a bypass external cooler. Will get it done around October this year when I have more free time.
Mine is an '07 with 110k but it's been a midwest car all it's life which would probably accelerate the corrosion factor. Ideally it would be great to replace the radiator when you plan on flushing the coolant and/or replacing tranny fluid.

Unfortunately for me, I just replaced the tranny fluid with the good stuff(OEM Acura SH-AWD) fluid last year and have to do it again. Argh...
 

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Yeah, I hear you. It is a royal pain and quite expensive to properly replace both coolant and ATF. I am curious how you flushed them? I can see coolant is easier. Just need to drain coolant from both radiator and engine block. Flush with distilled water once. Then repeat with OEM coolant. Does it sound right?

But replacing ATF is hard. Did you do the drain and refill three times, or you did it via the ATF/radiator hose? Either way, are you sure that you can get the system clean of coolant? If this happens to me, I might have to ask the dealer to flush the ATF.
 

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Yikes!
I personally think the best mod for you it's in the freezing states would be to by pass the ATF Warmer completely... The warmer in the freezing states isn't even a warmer at all since it's getting super freezing air directly to the radiator is more of a Cooler depending on the outside weather. if the air temp is too cold you might be freezing the radiator in hwy speeds.

Remember that the main source of heat for the trans is the Torque Converter.. By pass the radiator warmer and just Idle the car a little longer until the Torque Converter is hot enough. If you want to help the trans get to temp start he car in Second Gear (Which is there is snow you probably do anyway). This will help the ATF get to temp and without the ATF Warmer cooling your ATF it will keep that temp for longer. IMHO there is no need for the warmer in the freezing states, It literally can't do anything once the car is moving because the radiator will get frozen unless it's covered.
 

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I think that warmer is useful. Suppose you are driving on hwy at 70mph for a whole day. The torque converter is locked up. All the torque/energy goes straight from engine to transmission. So torque converter, and ATF, does not generate heat at all. Now with cold wind blowing on your ATF external cooler constantly, the ATF would be too cold. When it is time to use it, it might hurt transmission. I do not think Honda engineers are that dumb. I have thought about it several times, and replacing radiator seems to be the more conservative and money-saving way to keep our car running for another 10 years /100k miles.

Like I said, a factor radiator is very likely to give up anyway by 13/14 years. Replacing radiator solves the problem for a long while and keeps the OEM design.
 

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ATF does not have a temp thermostat in its OE design it constantly flows through the system.

Antifreeze does have a Thermostat in the engine and in the freezing states it does not cycle as often thus the anti-freeze in the radiator gets super cold while waiting for the AF in the engine to heat up this is WORSE in the highway since the engine is idling too low in the overdriven gears it does not heat up much if at all.. This is where the ATF "Warmer" sits at in the freezing states, inside the super cold anti-freeze.. It wont be until it hits city driving and constant on and off the throttle where the Warmer will do some warming for the ATF.

This is the reason why radiator covers exist, even ones made by OEM:
 

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what radiators are you guys replacing the OEM with? On my other cars back then, I'll use a Fluidyne or Koyo all aluminum in replacement of the stock radiator with plastic end caps. Are there any aftermarket aluminum units for the MDX?
 

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All aftermarket units for the MDX are aluminum.. OEM like in all Acuras and Hondas is made by Denso.
 

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thanks shirmich - do you have any recommendation where to buy from?

I just did a quick google search but only see radiators with the plastic end caps, nothing that's fully made of all aluminum.
 

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We call aluminum the main core of the unit, Both end caps are plastic this does not mean the unit is less reliable just means its not serviceable like the old units that could be opened, purged and soldered back together.

For a full aluminum upgrade you will have to use a Racing Radiator.
 

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I am a believer in maintenance replacement of radiators in road salt areas. When my '05 radiator failed, my darling bride ignored the engine noise, the loss of power, the check engine light, and the temp. gauge.

I got to spend a 3 day weekend replacing the motor. I told her that was her anniversary present for the next 5 years.


 

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That poor engine... God Speed honorable J35!
 

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I came here from the ROC (Ridgeline Owners Club). I sold a 2006 Ridge with 625K (Km) with orig engine & Tranny.
Over there are a few preventative maintenance issues that MUST be dealt with to keep the ridge healthy. One is the spark plugs that pop out of the block on some and the other is this same radiator issue that's discussed here. Most members there replaced theirs with Spectra or CSF Brand rads. I chose Spectra. I had thought by now this issue would have been fixed. Damn, now I gotta do it again. Oh well!


Thanks for bringing this up Alpine.
I had forgotten about this issue.
 

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Discussion Starter · #15 ·
You're welcome Babys.

Like I said I don't want to get in a debate. The factory one lasted me 10 years in Michigan winters and I don't doubt my Denso replacement will not go at least 7.

In this case, you can pick up a Spectra unit for around $110 or buy a Denso unit for around $160. I personally think it's worth the extra $50 to go with an OEM supplier.

The Denso part number is: 221-3237

If you google it, you should find all the various suppliers and pricing info.
 

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Discussion Starter · #16 ·
But replacing ATF is hard. Did you do the drain and refill three times, or you did it via the ATF/radiator hose? Either way, are you sure that you can get the system clean of coolant? If this happens to me, I might have to ask the dealer to flush the ATF.
I did the atf hose method and really I think this is the only way to get most/all out especially since you're going to have fluid buildup in the torque converter too.

I plan on even doing a second atf change after driving it around awhile and examining the clarity of the fluid, if it is still cloudy in any way.
 

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if you still have the failed radiator, it would be very interesting if you can cut it open and take a look to see where and how exactly it failed. It may or may not be related to a lot of issues, and we have to take a look up close to really understand. Now you have one actually failed so this should be a very good opportunity ...
 

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Discussion Starter · #18 ·
if you still have the failed radiator, it would be very interesting if you can cut it open and take a look to see where and how exactly it failed. It may or may not be related to a lot of issues, and we have to take a look up close to really understand. Now you have one actually failed so this should be a very good opportunity ...
I sure will!!!
 

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Discussion Starter · #19 ·
Ok, have flushed both fluids and replaced the radiator. However didn't have a chance to disect the old one yet(maybe this weekend).

I've fabbed a good radiator flush mechanism from 1" PVC pipe, 1" PVC mail threaded coupler and a PVC ball valve made for outdoor garden hoses.

For transmission flush, you'll want to get 3/8" - 1/2" clear PVC tubing and plastic 3/8" couplers.

Also flushed the entire contents of the transmission via transmission hose. It took 14 quarts(~$9/qt) to fully flush out any remaining coolant from the transmission system. Ouch!

It was one of the more pain in the arse radiator replacements I've done on a car lately. Anyways, it's done.





You can see the mix separating into it's virgin states after it sits awhile.


I was hoping due to the higher nature of the transmission line that the tranny fluid would've been pushed to the coolant but not the other way. Running a clear tube confirmed that was not the case and I could see the cross contamination. I eventually cut this tube in half and drained the existing fluid to a drain pan.


Bought the good stuff in bulk of course...


My homemade coolant flush system...


Power coolant flush system in action... I had it emptying into a big rubbermaid bin to catch the coolant/trans fluid mix.



Lastly...WTF?!?!?!?

I guess the aftermarket Denso radiators have been farmed out to China. The OEM ones are made in USA. Not sure if you order a brand new OEM one whether they will still have the USA designation or not. Because of this, I would be ok with having used the Spectra brand instead which has been around for awhile and has lifetime warranty and is made in the USA. I can speculate that since this is a relatively big outfit, they may have been contracted at one point by one or more OEM's to manufacture radiators for them. Once again, just a speculation on my part.
 

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Hey Alpine003,

I'm currently having a slow coolant leak from the radiator and the dealer quote me over $900 for the parts and labor. Currently I'm just topping the coolant until i got some time to replace it. Do you think I can get away with just replacing the radiator and filling it back with coolant without having to deal with the transmission fluid?
Since you have replaced the radiator and flush the transmission fluid, I wondering how difficult was it?
 
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