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Discussion Starter · #1 ·
2001 MDX Touring, 250K miles. Almost completing a 1200 mile round trip, we experienced for the second time a trans temp overheat warning light, small amount of smoke, no slippage or drivability issues since I caught it fast. We did not want to risk a total breakdown at 3AM, so we had it towed home Jerri-Dan style.

I spent better part of 2 days looking for evidence of leaks or mixing of fluids. No contamination of either transmission or radiator found, no evidence of major leaks other than small amounts of trans fluid on the trans case. Trans dipstick was not down at all. Since a Honda dealership could not find reasons for the first occurrence two years ago and I can't find any this time, I just cleaned it up and test drove it. It runs absolutely fine, no slippage, no hunting of gears. After the first failure, I did do the three-time drain and replace of trans fluid but no other repair.

The BIG QUESTION: Is it wise to keep driving it and hope these are just fluke happenings, or, as my wise wife says, "I don't trust it anymore. It is going to let us down big time on the next long trip".

I hate to let it go since it drives so well, uses no oil, I have most of the little annoyances fixed, and it is a great luxury vehicle after years of driving beaters. Used car evaluations on the internet put its value at about $1600-$2400, so I hate to spend big bucks on a new transmission and radiator only to have some other major component fail. And since we only buy used cars, how much do I have to spend to buy reliability on another used SUV? All opinions or actual case histories welcomed.
 

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If it isn´t slipping then what is the problem?
Transmission Over is not uncommon granted is not common on MDX without towing or doing hill climb off road but getting a Transmission Over Heat is not the end of the world and its not a sign of a transmission failure. I have gotten my trans heated up quite a few times on my 2G MDX while doing off road.

If the level is correct and the transmission is working as is I would just call it a problem with the transmission temp sensor.
You would need to install an aftermarket ATF temp sensor inline with the radiator ATF Warmer lines to be sure the ATF temp is not actually over heating.

The correct procedure as your owner manuals states is:
1.- Stop driving and get to the side of the road.
2.- Let your transmission cool down in park or neutral (DO NOT SHUT OFF THE ENGINE).
3.- Wait till the AT Temp light goes away and get on your way.

Are you using the correct Honda DW-1 ATF? Last time my 2G TL-S smoked its trans was because I used Amsoil Syn ATF which foamed up and got puked out of the transmission, Honda trans are very picky with ATF.
 

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Discussion Starter · #3 ·
skirmich,, thanks for the advice. My concern about the overheat is that the first time it happened the trans somehow lost three and a half quarts of ATF. That pretty much makes it undependable for more than a couple of miles to get to a shop. The Honda shop that worked on it could find no reason or even how the fluid got out. I would like to know how the fluid gets out but the Honda shop just said it could come out the dipstick or some "breather" which they did not define well They just replenished the ATF and pressure cleaned the areas that were soaked with ATF and said we were good to go. And yes, the ATF used is correct. I know that shop put the right fluid in and as I mentioned in the first post I did a 3 times drain and replenish with fluid bought at a Honda dealer after we got home following the first incident.

Also, the 1st Gen MDX transmission is the one with all the black marks of reliability, with its recalls and known failures. I hope that by 2nd Gen it was fixed for all of you owners. I am second owner of this one and have talked to the first owner and have his maintenance log. The transmission never let him down like it did us after we put a lot more miles on it. For a little more confidence building I am going to take the MDX to my local Honda dealer (don't have an Acura dealer nearby) and let them do a diagnosis opinion.
 

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Discussion Starter · #4 ·
kirmich,, thanks for the advice. My concern about the overheat is that the first time it happened the trans somehow lost three and a half quarts of ATF. That pretty much makes it undependable for more than a couple of miles to get to a shop. The Honda shop that worked on it could find no reason or even how the fluid got out. I would like to know how the fluid gets out but the Honda shop just said it could come out the dipstick or some "breather" which they did not define well They just replenished the ATF and pressure cleaned the areas that were soaked with ATF and said we were good to go. And yes, the ATF used is correct. I know that shop put the right fluid in and as I mentioned in the first post I did a 3 times drain and replenish with fluid bought at a Honda dealer after we got home following the first incident.

Also, the 1st Gen MDX transmission is the one with all the black marks of reliability, with its recalls and known failures. I hope that by 2nd Gen it was fixed for all of you owners. I am second owner of this one and have talked to the first owner and have his maintenance log. The transmission never let him down like it did us after we put a lot more miles on it. For a little more confidence building I am going to take the MDX to my local Honda dealer (don't have an Acura dealer nearby) and let them do a diagnosis opinion.
 

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Yeah that is what happened to my TL-S (I got a 2G TL-S with also the same dreaded transmission issues as the early 1st Gen MDX) when I used Amsoil ATF. The 2G MDX uses a beefed up transmission specifically made to handle the load capacity and weight of the MDX, The 1st gen MDX trans was a derivative of Honda Sedans V6 Transmissions so its far weaker than the 2G MDX transmission.

ATF literally foams up and the Foam goes out from the transmission casing breather tube (You can find this breather tube directly beneath the Engine Air Hose, its on top of the transmission housing using a very small rubber tube that does not connect to anything. In the 2G MDX they added a small filter box for it. Once outside the foam goes back into liquid form and that is where you lose ATF. This is not normal but it has nothing to do with the transmission issues which are lack of lubrication to the 3rd gear clutch pack.

Something is definitely off if the trans is foaming up the DW-1.. I got 2 dead trans in my TL-S from normal transmission failure and none of them puked the ATF, The only one that did was the Amsoil filled one. I am now running an AV6 Swap so no more dead trans for this guy, Sadly the MDX offers no viable alternative swap.
 

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Discussion Starter · #7 ·
What the dealer found about the overheating transmission

Well, guys and gals,

I took the 2001 MDX with the overheating trans to my local Honda dealer. Happily,they are reasonable in that they only charge $52 for a diagnosis. They found a P0070 trouble code and their solution is a $274 parts and labor "transmission pressure switch" which they sort of half-heartedly say might have caused the overheating. Otherwise, they only found miscellaneous oil leaks, which I did not ask them to do. (Remedy for oil leak: replace oil pump seal, possibly oil pump for either $896, or $1177. Does this vehicle have an external oil pump? Why would an oil pump, which in my experience is usually enclosed in the oil pan, have a seal needing replacement? Just a side question, I won't have the work done, the amount lost must be tiny as the car does not consume oil between changes.)

Would like to hear if any of you with a 1st gen MDX have had same experience with overheating and fluid loss and what your remedy was.

An interesting sideline: a used car dealer told me of a local shop which will install and guarantee a rebuilt transmission for this car for $1400. He has done a lot of business with them and is very satisfied. Seems like that is a lot cheaper than trying to find a replacement used car.
 

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After my trans rebuild at 188K mi, I installed these from Amazon

Pro-comp 9" Inch Electric Automotive Radiator Transmission/oil Cooler Fan 12 Volt

and

B&M 70274 SuperCooler Black Aluminum Fluid Cooler

along with

Hayden Automotive 106 Transmission Oil Cooler Hose
and
Derale 13008 5/16"- to 1/2" Hoses Stainless Steel Hose Clamps


Now, my trans fluid bypasses the in-radiator cooler and instead goes only through this fan-cooled oil cooler. When I'm climbing a slow, twisty, steep grade like the Sierra Nevadas near Whitney, it goes in at around 190F and comes out about 125F, according to my laser-temperature gun. Previously, it was going into my radiator and towing cooler at 230F and exiting at 180F - doesn't seem the Acura tow package system is very good at all at cooling.
 

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^ That is because the OEM Setup in a 1G MDX is a Warmer not a Cooler.
The 2G MDX was the one that installed an ATF Cooler inline with the Warmer.

The idea of the Warmer is to make the ATF keep a nominal temperature not too cold and not too hot... It wasn`t designed to dissipate higher temps from high load, hill climb or towing.
 

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^ That is because the OEM Setup in a 1G MDX is a Warmer not a Cooler.
The 2G MDX was the one that installed an ATF Cooler inline with the Warmer.

The idea of the Warmer is to make the ATF keep a nominal temperature not too cold and not too hot... It wasn`t designed to dissipate higher temps from high load, hill climb or towing.
No - its intended to do both, and does neither very well.

And - its burning up my transmission - I live in Los Angeles.

If you live in areas with cold winters, I would just route the exit hose coming from the after market cooler into the radiator "warmer" to bring it back up to temp. Also the fan is relayed into the radiator fan circuit and only blows when the radiator fan is also blowing. Its not blowing constantly, only in parallel to the radiator temp. This is the ideal set up according to forums dedicated to transmission and engine oil cooling, there's a whole subculture going on there.

By the way, some light reading on this issue will confirm the idea that warming the fluid is way less important than cooling the fluid. Hot fluid kills your transmission, whereas warming it helps with drivability during the first 10 minutes. Even in sub-freezing temps, trans fluid gets hot quickly.
 

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^ That is because the OEM Setup in a 1G MDX is a Warmer not a Cooler.
The 2G MDX was the one that installed an ATF Cooler inline with the Warmer.

The idea of the Warmer is to make the ATF keep a nominal temperature not too cold and not too hot... It wasn`t designed to dissipate higher temps from high load, hill climb or towing.
Also, I have the Acura tow package add-on cooler - its just a u-shaped tube and only partially finned. Fluid goes in at 230F and comes out at 205F, going uphill. What good is that? Whatever cause/effect/intent you want to apply, its a poor engineering design. Just like the 01/02 transmissions and several model years of the TL.

"It's a great car, just don't go up, or over any mountains, and don't tow anything."
 

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I live in San Diego and have a 2G TL-S with the dreaded 5 speed glass transmission.. Tell me about transmission cooling?.

Again the warmer is not designed to dissipate higher loads.. The warmer is primarily designed to keep a nominal ATF Temp under normal driving conditions ex: No load just driving around I obviously have by passed this in my TLS and now by passed in my 2G MDX for our 120*F Summers.

You will get trans hot from a hill climb because there is no air flow to the cooler radiator.. I explained a trick in my 2G MDX Off Road guide here: https://acurazine.com/forums/1g-2g-mdx-discussion-2001-2013-166/depth-off-road-review-mdx-954458/ on how to avoid this scenario easily for free.
 
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