Transmission Cooler - Bypass Rad, or install in series

Engineerdiyer · May 17, 2012

Hi folks,

Wondering if anyone has installed the transmission cooler upgrade and bypassed the radiator. I read some instructional posts here and they run the cooler in series with the rad. I'm thinking I'd hate to have this new (15,000 miles) transmission fail when/if the rad fails and puts antifreeze in my AT, so I'm thinking of a bypass.

thanks!

0dyfamily · May 17, 2012

I've replaced Honda radiators, and the radiator in-tank ATF heat exchanger (sometimes it's a heater, most times it's a cooler) is pretty robust; it's made of a fairly thick gauged brass, as far as I've been able to tell.. I've pulled apart two radiators and actually have pics of one from our 1998 Accord somewhere on this forum.

OF

Engineerdiyer · May 17, 2012

Thanks OF, that makes me feel less urgent about it. Just thinking that as long as I'm doing the cooler, may as well make it as bulletproof as possible.

EDiyer

0dyfamily · May 17, 2012

Sir, just glad to help. One item that one of our members (Odytech?) found was in his case, the radiator in-tank ATF cooler was clogged. He had no flow out of it, but normal flow of ATF out of the transmission. This is rare, but I think two members have had it happen.

I found the thread with pics of the in-tank ATF cooler, and a pic of ATF coolers by generations: Link to Thread

OF

buildit · May 17, 2012

Leaking ATF cooler is often connections, not the middle of the cooler

Do not know what year you have. MDX is similar to Odyssey. Leak of ATF and coolant has wrecked transmissions. The problem is not the strength of the cooler but corrosion of the connections. For an older radiator, adding an ATF cooler that bypasses the radiator trans cooler can avoid leak of ATF and coolant if the old connections corrode and leak. But in Harrisburg, PA, downside of bypassing radiator trans cooler is ATF too cold in winter. Or replace the radiator and add ATF cooler in series.

See this analysis of and MDX leak.
Failure of transmission cooler inside of radiator (w/ pics) - Acura MDX Forum : Acura MDX SUV Forums

• The failure/leakage was internal to the radiator. All external hoses and fittings were still attached when the radiator was removed.
• The inlet and outlet fitings for the transmission cooler (TC) were easily broken off with a little pressure . The radiator and the TC line fittings are shown below:

Conjecture on what went wrong with the connection:
• Corrosion around the threads weakened the connection.
• The corrosion could have come from two places.
• Water (and salt, being in the rust belt) can get between the steel washers and the tank and eventually enter the threaded area. There are no O-rings on the outside.
• Coolant might have slipped past the internal large O-rings and also entered the threaded area.
• The internals to the transmission cooler looked good, The end of the cooler fitting had no corrosion and a tight small O-ring.
• The threaded connection eventually starts leaking internal to the radiator.
• Due to the higher fluid pressure, the ATF is mainly forced into the coolant.

Engineerdiyer · May 18, 2012

Thanks OF & Buildit for the detailed info! That's great to be tuned into! After seeing the pic's, it looked exactly what I was writing about. Not going to chance it on a 2004, w/155,000mi. I'm going to bypass the rad. As for the low temps, I didn't think w/sythetic ATF low temps were a concern. I don't have a specific reference here, but I thought it was a concern w/the older AT fluids. After I'm done, I'll post the results!

buildit · May 18, 2012

Size of ATF cooler if bypassing radiator ATF cooler

Have been thinking of bypassing the radiator. But have not been able to find info to find the right size aftermarket ATF cooler when bypassing. The info I have found seems to assume using the radiator ATF cooler and aftermarket ATF cooler in series. I want to change to bypassing. Would the same size cooler work well enough when connected as bypass.

Currently have a Tru cool 4454 rated at 18000 gvw according to various stores selling the 4454.

Since you might be bypassing the trans cooler in the radiator, have you figured what size to get? Thanks.

Engineerdiyer · May 21, 2012

First off sorry for the delay on the reply post! I was working on another vehicle all weekend and didn't go near my computer!

The short answer to your question is, no the same sized cooler will not work for a bypass installation. However, looking at Hayden spec's your 4454 is upsized at least one and maybe 2 (considering the Ody with a GVW of less than 11,500 lbs). If you are planning on towing, I would go one size bigger yet, if I were you.

From what I've found a good way to size the cooler is on HP of the engine. However, I"ve only found high performance (read really expensive) coolers with sizing information shown that way. (Most give Gross Vehicle Weight ranges assuming the cooler is in series w/the Rad.)

A second way to size it is on BTU rating. I've found some coolers that show that info. I haven't researched the BTU rating of the Ody Rad. So I don't know if that info is available or not. I'm going to look into that some more. If I find it, then I'll pick a cooler that exceeds either the rated cooling of the existing part of the rad that provides ATF cooling, or a cooler that well exceeds the btu demands of the tranny. (I want to exceed that demand because I will be installing a screen on the front that will slightly limit air flow.)

And finally, size based on GVW. I've found that Hayden recommends up sizing the cooler 1 or 2 sizes if it is not in series w/the Rad. Further, Hayden has a 'self regulating' cooler that helps the warm up the ATF quicker if you're in a colder climate. So, at this point I'm planning on going w/a a biggy sized Hayden self regulating stacked plate cooler such as #4490. This is up sized at least 2 sizes considering I do not have a tow hitch and will not be putting one on. Also, I'm toying w/the idea of installing 2 temp sensors (inlet and outlet) to monitor performance. In the interest of Science and my transmission health, I think I it would be good to do that....

To be fair to Hayden, they don't recommend bypassing. But I'm thinking it's more of a liability thing, because if you are under some type of vehicle warranty it will probably be voided by bypassing the Rad. And, I'm sure no cooler mfg wants to be responsible for something going wrong in that situation. I have no warranty on my vehicle.

I'm planning on continuing to post as I make more progress. I hope to have it done in time for the really hot summer days!

buildit · May 23, 2012

Thanks. The Tru cool 4454 I have installed is rated:
GVW Rating - 18,000 lbs.
BTU Rating - 13,000 btu.
11/32" Hose Barb

Will search more how to know how many btu's a cooler needs to cool a transmission.

Have been busy also. Rear Odyssey wheel stud broken. Needed to remove wheel hub, pound out stud with hammer. New one hammered in and fully installed by using a wheel nut with a hole through both sides to draw the stud in.
Did not find a "how to guide" so here are relevant pages of the service manual on removing the hub.

Transmission Cooler - Bypass Rad, or install in series

Engineerdiyer

0dyfamily

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0dyfamily

buildit

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