Should I add an additional Transmission Cooler to my Sienna?

Discussion in 'Tow Vehicles, Hitch & Towing' started by tgore76, Mar 18, 2014.

  1. tgore76

    tgore76 Member

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    Sep 5, 2011
    I have a 2009 Toyota Sienna XLE with the "Towing Prep" Package. I have added Air Lifts, Hitch, wiring/controller, run Mobil 1 Synthetic Oil, and added brakes to my pup). I am within the towing limits when I pull our 2004 Flagstaff 208. I am about to get the Transmission Oil Changed and thought this would be the time to add an aftermarket Transmission Cooler if I want one.

    For those that don't know....this generation of Sienna all have a Trans Cooler internal to the radiator. In fact...the ONLY thing that the towing prep package has that standard van does not, is an oil cooler.

    When I talked to my transmission shop, he said to get the dealership's recommendation. I called two dealers. The local one (that I don't trust much) simply said to go ahead and add it...that the stock cooler is only for "normal driving conditions." The second dealer I called said that the stock one is sufficient for towing a pup...part of the "towing prep" package! The master mechanic said that you can overcool the fluid and adding another cooler may even make the transmission shift.....funky.

    I don't have a transmission oil temp gauge....but since it's internal to the radiator...I kind of go off my engine temp gauge. I pulled the pup across country last summer....through Southern CA, NV, TX...etc. with temps up to 115 and the temp gauge never went above half way. Made me nervous and hence why I'm getting the fluid flushed and considering a secondary cooler.

    Any experience with Sienna's towing (particularly transmission) or thoughts?
     
  2. mickaqua

    mickaqua Member

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    I do not have a Sienna, but a Silhouette minivan with a towing package.

    Mine does just fine with a pup, and I think you have all of the bases covered with the towing package. :)

    If you do a search on "Sienna", you will see many posts all about the Sienna.
    Most are about towing, and they run on the positive side. [:D]
     
  3. rawlus

    rawlus New Member

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    Jul 24, 2011
    theres really no downside to adding an aftermarket stacked plate transmission cooler. it <$100 well spent in my book.
    i dont really care what the dealer says, theyre not towing experts and tend to discourage non-factory parts.
    i would go with a B&M stacked plate design and not look back. you can keep the existing run through the bottom of the radiator if you like as well.
    it is very easy to superheat your transmission fluid on a long steep uphill grade when towing
     
  4. gec66

    gec66 New Member

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    Absolutely add an aftermarket cooler. The existing cooler built into the radiator is not enough for towing situations. A mini van can be an excellent TV as long as you set it up right.
     
  5. tgore76

    tgore76 Member

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    After posting..have spent time on siennachat towing forums...opinions on there are split as well, but lean towards saying the factory one is sufficient. I'm not trying to go cheap, just concerned about over cooling or voiding power train warranty....both concerns suggested in the various forums. (Argument can be made that the van is designed with the factory cooler to self regulate?) if I opt to still add a secondary cooler, would using a low pressure drop cooler as the secondary cooler help prevent over cooling?
     
  6. Haybale

    Haybale I'd rather be camping!!

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    San Diego via MN
    Better to have it than not, a cooler is much cheaper than a failed tranny, especially on the side of the road, ruining your trip!!
     
  7. JungleJim

    JungleJim New Member

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    Never trust what a dealership says.
    Call Toyota directly.
     
  8. mickaqua

    mickaqua Member

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    Remember that the both the engine oil and the coolant temperatures are controlled, somewhat, by the engine thermostat. [:O]
    External factors then enter into the picture... [RTM]

    On Ebay you will see many replacement radiators for Siennas, and they are mostly divided by "without tow" and "with tow". [;)]

    This shows that some difference does exist in "cooling capacity" for the Sienna radiators. [A]

    Just how much benefit is gained with the "towing package" radiator remains to be found out, but it is there.
    That is, if you indeed have the "towing package" radiator. :)

    If you are going to do hilly terrain, it would not hurt to add an additional trans oil cooler. [;)]
    And/or, watch your engine temp, as a little increase for a short time is no big deal, but anything more might be. [RTM]
     
  9. tenttrailer

    tenttrailer Art & Joyce - Columbus, O

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    yes, cheap insurance for your transmission. Also plan on changing you transmission more frequent then your maintenance schedule if your towing. I do it every fall after camping season.
     
  10. joet

    joet Well-Known Member

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    Elkins WV area
    The only way to determine if the internal cooler is sufficient is to find a temp gauge, and see what your temps are running when towing. You want temps under 200 deg. to achieve long a trans life.
    With the internal cooler, you won't see much temp difference from engine temp.
    A quality stacked plated cooler by its design will keep the fluid from over cooling. Thicker, cooler fluid will bypass.
     
  11. Tonimus

    Tonimus Member

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    Jul 11, 2012
    Something to keep in mind about trans-coolers internal to the radiator, they serve two purposes. One, to keep the fluid from getting too hot, the other, to keep it from getting too cool. An external trans cooler will help vent some of the heat that the fluid carries, but if your engine runs about 200*, your trans fluid isn't going to get any cooler than that without help. Run your trans cooler in line AFTER the radiator on the way back to the transmission.
     
  12. Haybale

    Haybale I'd rather be camping!!

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    San Diego via MN
    Fluid, changing your trans fluid more often....lol
     
  13. JungleJim

    JungleJim New Member

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    Feb 25, 2008
    Call Toyota. That's what I did.

    I called twice. Each time I ran a scenario by them....towing at full capacity, with a fully loaded vehicle, going uphill in hot weather. Each time, they transferred me to a technician. They told me that even under those conditions, Toyota recommends against adding an additional transmission cooler.

    Also, the OEM Toyota ATF is really good stuff. It has a much higher rating than "normal" and will do it's job at much higher temperatures.

    I'm not against additional coolers. But every additional thing you add, is additional equipment that can break down ( and in this case, leak.). A lot of axillary coolers are not located where you can visually check them.
     
  14. rawlus

    rawlus New Member

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    Jul 24, 2011
    I've yet to see evidence that proactively preparing for high demand situations like towing is somehow detrimental.

    What I would ask Toyota is, if the transmission fails as a result of towing with only OEM equipment, are they prepared to stand behind their product and replace the tranny for you or are you on your own?

    There comes a point where the factory or the technician doesn't matter because they don't have skin in the game... I wish people realized this more often. Factories and technicians rarely recommend additional parts because they are avoiding liability, they don't discuss I what they don't make or control.... It's not because they don't think it will work, it's because that's what they are inducted to say. Do not elaborate. We can't have factory techs recommending B&M trans coolers for towing duty because that opens up liability for why Toyota isn't providing them with the vehicle in the first place.

    It is a universal fact that temp control is important to transmission longevity and performance. If you intend to work the transmission harder, then you should be thinking about that. If you choose to close your eyes and hope for the best because a tech told you you'll be alright, then do so knowing that if something happens that wrecks your tranny, that tech won't be holding your hand and helping you fix it unless you brought your wallet with you.

    Cheers.
     
  15. tenttrailer

    tenttrailer Art & Joyce - Columbus, O

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    What would you expect the factory to say. We have a tow package we sell, and yes it's a good idea to add an additional trans cooler if you have our tow package installed?

    I know with my sienna with the tow package and an extra trans cooler on long steep grades with the camper will be running around 220 degrees. I hate to think what it would be without the extra cooler.

    Just by running hot it does not destroy the transmission until you get in the upper 200's. But it does greatly reduce the life of the transmission fluid. Which if you don't change it in a shorten timely manor will destroy the transmission.

    Check with your dealer what the cost is to replace a transmission?
     
  16. ccptbo

    ccptbo Well-Known Member

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    We encountered same thing as JJ. We were advised against adding a secondary tranny cooler. We have an '06 Sienna with tow package and all the fixin's.
    We've never had any issues at all towing (except for minor rear sag which is getting dealt with this Spring). It's never ran "hot" even in hot weather with A/C running.
    Other then a truck (a whole other discussion), we're quite happy with our van!
     
  17. tgore76

    tgore76 Member

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    Sep 5, 2011
    Replies above and additional research have led me to a few more points for discussion / questions:

    1) IF I add an additional cooler, would using a LPD model such as Tru-Cool (in line AFTER the Factory cooler) be wise to help prevent overcooling in winter? It seems that this is designed for the fluid to bypass when it is not warmed up yet.

    2) Lots of people on here and SiennaChat giving the temperatures for their Transmission fluid....what do I buy/install so that I can monitor the actual temperature of the transmission oil?

    3) Came across concerns revolving around oil line (and oil cooler line) failures at https://sites.google.com/site/toyotav6oillinescandal
    Wonder if anyone has had any experience with this? I haven't had any leaks...but it sounds like it may be wise to pre-emptively change out these lines.
     
  18. tenttrailer

    tenttrailer Art & Joyce - Columbus, O

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    That the best type. We got the B&M SuperCooler that has the same feature to bypass the cooler based on viscosity of the transmission fluid during the colder weather.


    B&M seems to be the cooler that most the people I know use. They are huge into transmissions from make racing transmissions, to having a line of fluid.

    If you do install one have the flow go through the radiator one first then to the additional cooler last. Make sure you follow the directions for what directions to connect the hoses.
     
  19. jherrington93

    jherrington93 Member

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    May 5, 2013
    The ScanGauge II is what most people in the Rav4 forums are using to monitor their trans temps when towing.
    http://www.scangauge.com/products/scangaugeii/

    It plugs into the OBDII connector - the same one your mechanic uses to pull the diagnostic codes. I think there is also another thing out there that uses an app on your smartphone, but I don't recall the name of it.
     
  20. tenttrailer

    tenttrailer Art & Joyce - Columbus, O

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    I use my cell phone app troque to read my trans temp, which I verified with with an expensive autoxray scan tool. It was a free app, I upgraded for $5 and bought a $20 bluetooth odb adaptor. It's nice to have an ODB tool on the road. My TV get a cat check every 500 to 1,000 miles.

    One of my upstream cats will every once in awhile will have the same value as the down stream cat, which indicates it's not working at that time. So I just reset it. The new cat is very expensive and with 185K miles on the van I don't want to sped 1/3 the value of the van to replace it.
     

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