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  • Transmission Oil getting Hot

    So, there's a bit of backstory to this (isn't there always).

    While driving on the weekend up some local trails with some mates, we came to a water crossing. I probably should have walked it, but my mate in his 80 series went through it first and it looked fine (we've got similar heights with lift and tyres etc.) I went through after him but must have picked a slightly different line as the first 10-15 meters were probably at the level of the side steps and then the bonnet briefly nosedived and went under (assuming there was a little hole in the river bed right at one side). Water came into the car through the passenger footwell (which turns out was due to the grommet on the AC overflow being flogged out) but not a hell of a lot- Probably less than a litre.

    I should point out that I was in the water for a total of maybe 10-15 seconds maximum, creek crossing was probably less than 20 meters wide. My main concern is that I don't have raised breathers on anything.


    Fastfoward to today, I was climbing up some pretty windy and hilly terrain at low to medium speeds (40-60kph) when my AT temp light comes on (never has before doing similar terrain). I have the Torque Pro android app installed on my phone and so I checked the temps on everything just to have a look.
    During normal driving my AT temp is sitting on about 105 degrees (which seems hot?) And my engine temp is on about 90 degrees (less worried about that) as the gauge hasn't moved from the normal position of about halfish way.

    EDIT: I should say that after the light came on I let the car sit for a few minutes and then the light turned off and didn't come back on- However I was careful after that to put it in Select Mode to make it stop hunting gears as much.


    So, I've got a few theories about this that I'd like to float (would be really happy to hear of others though)

    1) Water has turned the dust in my radiator (I live and drive on a lot of dirt roads) into mud and is causing cooling issues
    2) Water has made its way through the breather of the gearbox and has borked the oil and is causing issues (really hope not).
    3) Water has got into the electrics of the temp sensor and borked it.

    Any ideas or suggestions are appreciated, tomorrow morning I plan to drop the drain plug out of the AT and have a gander at the colour of the oil, I had it changed about 10K ago so hopefully it's still nice. I plan on fitting breathers to gearbox/ diffs etc. before I attempt such a crossing again.

  • #2
    I think the surge of water would've washed any dust build up out of between the radiator fins, so I think that is an unlikely cause, unless the creek bed was full of muddy stringy sediment which has now clogged the bottom portion of the radiator. Maybe locate the breather hole for the transmission and poke a length of wire into it repeatedly. As an outside option some debris may have found itself into and blocked the breather hole. Id imagine this hole would shed a bit of convexed heat and pressure build up, kind of like the hole in a saucepan lid to vent some steam, so if it's blocked and the tranny is being worked hard, I definitely think it could tip your transmission temp over the edge a little.

    Not sure about Diesel engine temps. I think they run a bit hotter than petrols. My petrol engine runs at about 84 deg at operating temp. But like you touched on, unless the radiator got hot and sent coolant temps soaring it's not of any concern.
    98 GXL 3.4L V6: TJM 2" lift, Airtec snorkel, TJM T15 steel bull bar, T-Max winch, 32in MT's, 4 x breathers & some other stuff, ODO = 381,000km.

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    • #3
      Cheers mate, will try that. I dropped some oil out of the pan this morning and it's nice and sticky and bright red, so I'm pretty happy with that. Will check breathers and rad this morning.

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      • #4
        I had my A/T light come on while backing my boat up into my yard. Decided to fit an additional cooler, and got the A/T serviced, even though Toyota says it doesnt need servicing. Well it has a filter (dont they block up) and the oil can degrade with heat (yep it had at 175,000km), and dont they wear and need adjustment? Anyway even though I know the A/T service guy has a vested interest in servicing it, he did say the oil was burnt, and recommended a service every 50,000, and if done you can expect about 500,000 out of the A/T. I have always added a separate A/T cooler on my cars, and always had them serviced even if not recommended by the OEM. Given a new A/T is about $7000, servicing is cheap insurance.

        I also found that the lower part of my radiator had blocked over time with rubbish, although the top was clean. My son checked his too and his was same and A/C wasnt working. We managed to clean all the radiators with a hose and made up a special cleaning hose so as to clean without removal. It manages to block between the A/C cooler, intercooler and radiator. You have to remove the top plastic cover to see the problem.

        From now on I will service the A/T maybe every 50-75k and clean my radiators more often.

        On a similar note, does the A/T and transfer case have breathers? I have ARB diff breathers fitted but thinking I should also have A/T and transfer case.
        Last edited by peter69_56; 06-02-2018, 10:13 PM.

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        • #5
          I always install flyscreen in front of the radiator on all my cars. The screen gets clogged but easy to clean and never had any overheating or radiator issues.
          [B]Steve[/B]

          2010 Silver GXL Prado 150, D4D Auto, with a few non standard bits

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          • #6
            Originally posted by peter69_56 View Post
            On a similar note, does the A/T and transfer case have breathers? I have ARB diff breathers fitted but thinking I should also have A/T and transfer case.
            yes they do , as well as the actuators on the transfer case and front diff. , so you need 6 breathers in total.

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            • #7
              One would have thought that ARB would have said something to me when I asked for diff breathers. Wel I have a new 4WD guy now so will go see him.

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              • #8
                Originally posted by peter69_56 View Post
                One would have thought that ARB would have said something to me when I asked for diff breathers. Wel I have a new 4WD guy now so will go see him.
                I'd be interested to hear what you find out Peter. I have the ARB breather extenders on the front and rear diffs only. When I inquired about the transfer case etc I was told that the breathers for these are already quite high and should not be an issue. Cheers

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                • #9
                  I believe the breathers are on top on the bellhousing for the transmission- Which isn't really high enough if you're going to the effort of putting a snorkle on to go through deep water. I'd suggest that they're up high enough to keep them clear when fording water at the Prados maximum wading depth (600mm?). Superior Engineering make an interesting one way valve product for those breathers but they're pretty expensive (50 bucks each).

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                  • #10
                    There are quite a few threads on how to do the transfer case and the auto transmission. Fiddly but doable to raise them up to just under the bonnet..

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                    • #11
                      Originally posted by Atherton View Post
                      I believe the breathers are on top on the bellhousing for the transmission- Which isn't really high enough if you're going to the effort of putting a snorkle on to go through deep water. I'd suggest that they're up high enough to keep them clear when fording water at the Prados maximum wading depth (600mm?). .
                      yes thats correct . the fittings on the actuators cannot be removed so the best way is to extend them up a bit higher. this kit is perfect for the job and includes all parts required. https://www.ebay.com.au/itm/HKB6WB-3...53.m2749.l2649
                      i'll be fitting it up today

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                      • #12
                        So as a continuation of this saga- I've found out the culprit, as someone previously mentioned the void between the intercooler and the rad is a great place for a boatload of grass seed. After spending the better part of a few hours with a compressor and a long nosed air gun and then a hose I managed to clean a lot of crap out of it. I'm still seeing tempretures of 90-96 degrees though during normal driving on a coolish day- Reading the toyota service manual it says that temps should range between 70-80 during normal use. I guess I'm asking if others can give me feedback on what sort of temps they get from their A/T's. Speaking to my local mechanic today and he suggested fitting an aftermarket cooler (which I'd previously considered) however I'm probably going to end up removing the radiator from my car first and giving it a proper cleaning down as it's so hard to clean throughly while still in the car with all that plastic crap getting in the way- if that doesn't remediate the problem then a cooler will be on the shopping list.

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                        • #13
                          Next job...

                          https://www.pradopoint.com.au/forum/...diff-breathers

                          Dont reuse the old caps and dont use non return valves. Cheapest filter heads are fuel filters.
                          My 150 build - http://www.pradopoint.com/showthread.php?27423-A-Random-approach-to-a-Bluestorm-150-GXL-D4D-automatic

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                          • #14
                            Yeah, for sure- That'll be happening as soon as I go into town next and purchase some rubber tubing and joiner barbs. I've heard that those fiter heads are the way to go.

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                            • #15
                              " I'm still seeing tempretures of 90-96 degrees though during normal driving on a coolish day- Reading the toyota service manual it says that temps should range between 70-80 during normal use. I guess I'm asking if others can give me feedback on what sort of temps they get from their A/T's. "

                              What are these temps, transmission oil or engine coolant? 70 to 80 can't be engine coolant temp, that's just too low, thermostat is around 80 to 82.
                              90 to 95 for transmission oil is also high as it's basically reading the same temp of your return coolant from the radiator.
                              My old 90 runs 60 transmission oil temp but it has gone way higher when pulling hard and out of convertor lock. That really cooks the oil fast.
                              From memory the diesel 150's didn't score a factory transmission cooler but the V6's did.
                              They all need one. Get the 30-plate model with slim line fan. Works well when plodding along where the engine fan isn't up to max efficiency.

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