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Discussion Starter #1
Hi MDXers,

Long time lurker, but I've taken plenty of great advice from this forum so I thought I'd give back a little with my experience with a dedicated transmission cooler with radiator bypass.

So I have a 2007 MDX with 180,000K and it all started last Oct 2018 when I noticed the transmission starting to slip. Pulled over ASAP and noticed the dreaded strawberry milkshake of death pouring out of the coolant reservoir. Got it towed to my mechanic and confirmed the tranny cooling line into the radiator failed just like all those MDX/Pilot/Ridgeline stories. Replaced the radiator, drained and refilled the tranny, and flushed the cooling system . I specifically asked the mechanic what the ATF looked like when he drained it, and he wasn't concerned with it's color or consistency so I was hopeful the tranny was saved by stopping ASAP (within 3km) of noticing the slip.

Fast forward to June 2019 and about 2000km after the the radiator repair. On my first boat towing session of the summer, the tranny started slipping really bad especially when waiting at left turn lanes in the heat. No milkshake of death this time. Just slipping. Towed it to the mechanic and the transmission was toast. Unsurprisingly, coolant from the radiator failure incident destroyed the clutches.

Went ahead with the transmission rebuild but also decided to do the radiator bypass and put in a Hayden's "678 Rapid Cool Transaver Plus Auto Transmission Oil Cooler". So far it’s been great and zero risk now of the same radiator issue happening again.

Now here's the good part. Most people will worry that the bypass 1.) won’t cool the tranny enough during summer and 2.) won’t heat up the tranny enough in the winter. I have scientific data that proves otherwise. With my Scan Gauge tool reading transmission coolant temps, I'm seeing ~200F ATF temp while towing a boat in 30C summer and ~130F ATF temp driving around -8C in the winter. The coldest I’ve seen the tranny fluid temp was 22F when parked overnight and it shifted fine upon start up and warmed up quickly within the first few KM.

Most will argue that 170F is the optimal ATF operating temp and that heat (and coolant in the MDX's case) is the killer of all transmissions. The Hayden oil cooler does a great job cooling in the summer under severe service and the transmission operates perfectly fine in the winter with colder ATF.


Long story short, I like my bypass setup and haven’t experienced any of the potential issues people hypothesize about when it comes to bypassing the radiator.
 

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Thanks for sharing! Can you let me know where you rebuilt your tranny.

Mine is fine and I avoided the coolant getting into it back in 2016, when my fittings failed. But who knows for the future!
 

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Discussion Starter #3
Markville Transmission Centre on Laidlaw Blvd did the rebuild and did a great job.

BTW, I love your MDX Youtube channel and am a subscriber. I wish I knew about the steering wheel upgrade earlier when the parts were more available.
 

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Hi MDXers,

Long time lurker, but I've taken plenty of great advice from this forum so I thought I'd give back a little with my experience with a dedicated transmission cooler with radiator bypass.

So I have a 2007 MDX with 180,000K and it all started last Oct 2018 when I noticed the transmission starting to slip. Pulled over ASAP and noticed the dreaded strawberry milkshake of death pouring out of the coolant reservoir. Got it towed to my mechanic and confirmed the tranny cooling line into the radiator failed just like all those MDX/Pilot/Ridgeline stories. Replaced the radiator, drained and refilled the tranny, and flushed the cooling system . I specifically asked the mechanic what the ATF looked like when he drained it, and he wasn't concerned with it's color or consistency so I was hopeful the tranny was saved by stopping ASAP (within 3km) of noticing the slip.

Fast forward to June 2019 and about 2000km after the the radiator repair. On my first boat towing session of the summer, the tranny started slipping really bad especially when waiting at left turn lanes in the heat. No milkshake of death this time. Just slipping. Towed it to the mechanic and the transmission was toast. Unsurprisingly, coolant from the radiator failure incident destroyed the clutches.

Went ahead with the transmission rebuild but also decided to do the radiator bypass and put in a Hayden's "678 Rapid Cool Transaver Plus Auto Transmission Oil Cooler". So far it’s been great and zero risk now of the same radiator issue happening again.

Now here's the good part. Most people will worry that the bypass 1.) won’t cool the tranny enough during summer and 2.) won’t heat up the tranny enough in the winter. I have scientific data that proves otherwise. With my Scan Gauge tool reading transmission coolant temps, I'm seeing ~200F ATF temp while towing a boat in 30C summer and ~130F ATF temp driving around -8C in the winter. The coldest I’ve seen the tranny fluid temp was 22F when parked overnight and it shifted fine upon start up and warmed up quickly within the first few KM.

Most will argue that 170F is the optimal ATF operating temp and that heat (and coolant in the MDX's case) is the killer of all transmissions. The Hayden oil cooler does a great job cooling in the summer under severe service and the transmission operates perfectly fine in the winter with colder ATF.


Long story short, I like my bypass setup and haven’t experienced any of the potential issues people hypothesize about when it comes to bypassing the radiator.
I didn't wait for my oem radiator to mix with its lower ATF tank.
I installed a 34,000 btu long tru cool and in the (below freezing months) I use an additional coolant bypass valve. The bypass valve 180 degrees bypass ATF bypasses the long tru cooler, until the temp gets up to 180 degrees.

How many BTU is your Hayden 678?
 

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Markville Transmission Centre on Laidlaw Blvd did the rebuild and did a great job.
Great, thanks! It's not far from me, just in case :)

BTW, I love your MDX Youtube channel and am a subscriber. I wish I knew about the steering wheel upgrade earlier when the parts were more available.
Thanks a lot!
 

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Markville Transmission Centre on Laidlaw Blvd did the rebuild and did a great job.

BTW, I love your MDX Youtube channel and am a subscriber. I wish I knew about the steering wheel upgrade earlier when the parts were more available.
How were they able to rebuild the tranny when a rebuild kit does not exist, at least not from Honda? Thanks for sharing your info here.
 

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How were they able to rebuild the tranny when a rebuild kit does not exist, at least not from Honda? Thanks for sharing your info here.
Search for "BYFA Rebuild Kit Acura MDX"
 
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