Automotive

Bypass transmission cooler

  • Last Updated:
  • Dec 23rd, 2019 12:41 am
[OP]
Member
Mar 15, 2004
415 posts
16 upvotes

Bypass transmission cooler

Wondering if anyone has done this... One of the transmission cooling hose connected to radiator on 2007 Acura MDX broke. The fix is to replace radiator but was wondering if installing a separate bypass cooler would make sense. would ther me any harm?
14 replies
Sr. Member
Oct 1, 2005
877 posts
25 upvotes
If the transmission cooler is part of the radiator, it means it uses the coolant temperature to regulate the temperature of the transmission fluid.

If you were to put a separate bypass "air" cooler, you may be inhibiting the quick warm up provided by the coolant on cold starts. The air cooler may also cool the fluid beyond the optimal operating temperature.

I'd replace the radiator as that would be the correct thing to do.
[OP]
Member
Mar 15, 2004
415 posts
16 upvotes
blackice168 wrote: If the transmission cooler is part of the radiator, it means it uses the coolant temperature to regulate the temperature of the transmission fluid.

If you were to put a separate bypass "air" cooler, you may be inhibiting the quick warm up provided by the coolant on cold starts. The air cooler may also cool the fluid beyond the optimal operating temperature.

I'd replace the radiator as that would be the correct thing to do.
I didn't think of quick warm up as you described, agree with you thanks!
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Feb 11, 2007
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Tik wrote: Wondering if anyone has done this... One of the transmission cooling hose connected to radiator on 2007 Acura MDX broke. The fix is to replace radiator but was wondering if installing a separate bypass cooler would make sense. would ther me any harm?
Yes, as blackice mentioned, you lose the quicker warm up from the engine coolant, as well as losing the enhanced cooling when it gets hot. Now you probably won't need the extra cooling during the winter, and even in the summer it's probably not an issue, unless you're towing or driving like a maniac.
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Jun 12, 2007
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Tik wrote: Wondering if anyone has done this... One of the transmission cooling hose connected to radiator on 2007 Acura MDX broke. The fix is to replace radiator but was wondering if installing a separate bypass cooler would make sense. would ther me any harm?

If you mean leaving the existing rad and installing a new aftermarket transmission cooler to bypass the one in the rad, I don’t believe this will work.

The threads on hose nipple/ connector for the transmission cooling hose fitting likely failed, allowing trans fluid pressure to pop it off the radiator.

The problem is the hose nipple /fitting is also part of the seal for the rad itself (pulls the transmission cooler tight against the rad tank wall, sealing the rad coolant inside)

Without the hose nipple/ connector, the transmission cooler is now free to move inside the rad tank , away from the seal, allowing radiator coolant to leak out

Replace the rad

Image
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Dec 20, 2005
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Having a similar engine, J35, and having had the same issue happen to me just a year ago...i'd strongly recommend changing out the radiator. Funny enough just this week had to help a friend do the same as theirs also had the tranny cooler line blow out. It's a rather common issue. A TYC rad on amazon/wrenchmonkey is around 150ish with lifetime warranty. Koyorad is around 220 on autopartsway.

PS. I still have a TYC one on hand i need to return to amazon seeing we ordered from both wrenchmonkey and amazon and used whichever came first.

A few things to do however seeing the cooler line can fail and cause 2 different scenarios.
1-You loose tranny fluid but the seal keeping tranny fluid and coolant from mixing doesn't break.
2-You loose tranny fluid but also end up mixing tranny fluid and coolant together...causing a rather risky situation for your transmission.

Either way you SHOULD change out the radiator and drain and fill the tranny with ATFDW1 at least 3-4 times and hope for the best if scenario #2 took place. Coolant would ideally damage the clutchpacks. You'll have some means of info when you drain the atf and pay attention if it looks its normal red color or more of a pinkish/milkshake color.

Getting back to the question at hand...the cooler inside the rad acts 2 ways to stabilize fluid temps. It helps cool but also helps warm up the fluid on those cold winter days.

PS. If youre doing the job yourself in the cold weather we've been having...get a heat gun to warm up the hoses somewhat to make your life easier in maneuvering things on and off. They get pretty damn stiff. In addition go easy on the clips...cold makes then brittle and easy to break.

After replacement try to rust proof those cooler lines coming out of the rad once a year. What i tried the latest time is painting them with bbq paint to seal them off from rust going fwd.
Tik wrote: Wondering if anyone has done this... One of the transmission cooling hose connected to radiator on 2007 Acura MDX broke. The fix is to replace radiator but was wondering if installing a separate bypass cooler would make sense. would ther me any harm?
Last edited by 001Stunna on Dec 20th, 2019 7:43 pm, edited 2 times in total.
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Nice pic @l69norm
What vehicle is that? I know there were a few Hondas that had a similar issue.
@Tik if your tranny fitting is like this, double check the colour of your tranny fluid and coolant. You don't want ether looking like a strawberry milkshake.
aka SMOD Strawberry Milkshake Of Death for the tranny.
Some of the forums speculate it is the rusting of the steel belleville washer that expands pulling the 2+ threads holding the connection together apart. Resulting in an intermingling of fluids.

On edit: Here is a link to a Denso rad deconstruction for the Ridgeline. It looks similar in design to the pic @l69norm posted.
https://www.ridgelineownersclub.com/thr ... or.116753/
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ROYinTO wrote: Nice pic @l69norm
What vehicle is that? I know there were a few Hondas that had a similar issue.
@Tik if your tranny fitting is like this, double check the colour of your tranny fluid and coolant. You don't want ether looking like a strawberry milkshake.
aka SMOD Strawberry Milkshake Of Death for the tranny.
Some of the forums speculate it is the rusting of the steel belleville washer that expands pulling the 2+ threads holding the connection together apart. Resulting in an intermingling of fluids.

On edit: Here is a link to a Denso rad deconstruction for the Ridgeline. It looks similar in design to the pic @l69norm posted.
https://www.ridgelineownersclub.com/thr ... or.116753/
Its from a Honda Pilot - seems to be a common Honda problem
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A new radiator is like $100-200. Just do the job right. The car is probably due for new coolant anyways.
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Mar 4, 2007
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Hi,
https://www.haydenauto.com/media/5479/b ... _flyer.pdf
The rapid warm up thing doesn't happen in the winter because the engine thermostat doesn't open until the engine reaches 190*F. and the transmission cooler lines are in the cold side of the radiator. Depending on how cold it is & how fast you're going, there might not be all that much warm coolant reaching the oil cooler lines in the radiator. If you still want to replace the oem cooler with an aux. cooler, should get a cooler with a built in temperature bypass valve.
https://www.rockauto.com/en/parts/hayde ... ooler,2088
https://www.rockauto.com/en/parts/hayde ... ooler,2088
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Sep 6, 2017
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I find it humerous the hacks people do to their cars and not their homes.
If a part is broken or cannot be used just replace it. You don't see people asking "room radiator leaking water should I bypass?"
[OP]
Member
Mar 15, 2004
415 posts
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001Stunna wrote: Having a similar engine, J35, and having had the same issue happen to me just a year ago...i'd strongly recommend changing out the radiator. Funny enough just this week had to help a friend do the same as theirs also had the tranny cooler line blow out. It's a rather common issue. A TYC rad on amazon/wrenchmonkey is around 150ish with lifetime warranty. Koyorad is around 220 on autopartsway.

PS. I still have a TYC one on hand i need to return to amazon seeing we ordered from both wrenchmonkey and amazon and used whichever came first.

A few things to do however seeing the cooler line can fail and cause 2 different scenarios.
1-You loose tranny fluid but the seal keeping tranny fluid and coolant from mixing doesn't break.
2-You loose tranny fluid but also end up mixing tranny fluid and coolant together...causing a rather risky situation for your transmission.

Either way you SHOULD change out the radiator and drain and fill the tranny with ATFDW1 at least 3-4 times and hope for the best if scenario #2 took place. Coolant would ideally damage the clutchpacks. You'll have some means of info when you drain the atf and pay attention if it looks its normal red color or more of a pinkish/milkshake color.

Getting back to the question at hand...the cooler inside the rad acts 2 ways to stabilize fluid temps. It helps cool but also helps warm up the fluid on those cold winter days.

PS. If youre doing the job yourself in the cold weather we've been having...get a heat gun to warm up the hoses somewhat to make your life easier in maneuvering things on and off. They get pretty damn stiff. In addition go easy on the clips...cold makes then brittle and easy to break.

After replacement try to rust proof those cooler lines coming out of the rad once a year. What i tried the latest time is painting them with bbq paint to seal them off from rust going fwd.
Its been little too cold to inspect anything further than the hoses... i will push it garage today to look ot over. If you haven't returned your radiator let me know.
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cristianosham wrote: I find it humerous the hacks people do to their cars and not their homes.
If a part is broken or cannot be used just replace it. You don't see people asking "room radiator leaking water should I bypass?"
Also no one replaces a broken window with plastic wrap and tape; no one just leave rusty holes in their doors; no one replaces broken door locks with paperclips, glue, and duct tape; and other silly things ppl do with cars :lol:
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cristianosham wrote: I find it humerous the hacks people do to their cars and not their homes.
If a part is broken or cannot be used just replace it. You don't see people asking "room radiator leaking water should I bypass?"
ES_Revenge wrote: Also no one replaces a broken window with plastic wrap and tape; no one just leave rusty holes in their doors; no one replaces broken door locks with paperclips, glue, and duct tape; and other silly things ppl do with cars :lol:
You guys obviously never opened any walls or crawled through some crawl spaces that aren't meant to be used regularly; whether don't by previous renovators or crooked builders shortcuts are done all the time in homes.
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Sr. Member
Sep 13, 2001
627 posts
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Thornhill, ON
Hi Tik,


I have a 2007 MDX with 180K and recently had the same problem and solution you propose.

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. Got it towed to my mechanic and confirmed the tranny cooling line into the radiator rusted out just like all those MDX/Pilot/Ridgeline stories. Replaced the radiator and flushed the cooling system hoping to save the transmission since I only drove the car about 3km when I noticed the slipping started.

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. 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 dedicated Hayden tranny rad. So far it’s been great and zero risk now of the same radiator issue happening again.

Now, most people will tell you that either the bypass won’t cool enough during summer or won’t heat up the tranny in the winter. I have scientific data that proves otherwise. With my scan gauge tool reading transmission coolant temps, I was around 200F towing a boat in 30C summer and around 130F driving around -8C in the winter. The coldest I’ve seen the tranny fluid temp was 22F overnight and it shifted just fine and warmed up quickly.

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

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