T4 auto trans: which trans cooler pipe is which?

[dlb]

does anyone know which transmission oil cooler pipe is the inlet and which is the outlet on the auto trans? there's an upper and a lower pipe. my guess is the lower is the outlet. i'm adding an auxiliary trans oil cooler (like a mini rad for trans oil) in my friend's terc and need to know the direction of flow so i can avoid air locks in the system.

thanks in advance.

[marlinh]

I don't remember which one is which. I did a flush on one and I am not sure. You could disconnect one hose from the rad and start the car for a few seconds and see the direction of flow. That will remove any doubt.

[Mark]

I just sent you a PM, but I'll include it here as well:
I'm actually not sure, but on this parts layout:http://www.toyotapartsoverstock.com/sho ... evel=18408 it seems to show that the line going into the top of the trans is the INLET to the COOLER and the line going into the lower part of the trans near the pan is the OUTLET from the COOLER.
I'm still not sure of the value of a trans cooler on our cars. The trans itself is aluminum which acts as a massive heat sink with excellent heat transfer properties. It seems to me that the airflow over the bottom of the trans while driving has a much greater cooling effect than the tiny stock trans cooler which is surrounded by hot water and the cooler lines pass right next to the hot exhaust manifold. It almost seems more like a oil heater to me. The automatics also have an oil temperature switch in the transmission that lights up in the dash if the oil is too hot.

[marlinh]

I think that light is an engine 'hot' light. There is an extra sensor in the outlet at the head.

[Mark]

It's wired to the switch that's near the pan in the trans. The sensing element is submerged in the trans fluid. The wiring diagram shows it and the water temp switch on the same circuit (in parallel) if either one is closed the oil/water temp light lights up. The standard doesn't have it. it's supposed to close between 125-132 degrees Celsius according to the manual.

[marlinh]

Oh cool, didn't know that.

[dlb]

marlinh, i wound up doing what you suggested before i had heard back from anyone here. i put an oil catch can under the disconnected hose but oh boy, the ATF didn't dribble out. instead it shot right over the can and all over the ground. fantastic. it was only long enough for me to check where it was coming from though so not a huge mess. turns out the top pipe is the outlet.

i put an aux cooler in my friend's terc because she was going to take it to burning man, and it's hot as all hell in that desert so i thought it was a good precaution. there are no mechanic shops around for many miles so every precaution should be made to avoid break downs out there. i had the cooler kicking around after i got from the wrecker a while back so the only cost was the hose, which you were correct about: 5/16". anyway, turns out my friend is not taking the car there now but it still may make the voyage in future years so it still might serve her well.

i also didn't think the orientation of the cooler made any difference until a guy on the all trac forum mentioned this about his car:

"And while it did have a transmission cooler installed it was installed incorrectly and really not doing much. Anytime a cooler is installed the inlet/outlet ports should face either side ways or up. This is so the air can bleed out of the cooler. The shop that installed the cooler on my cat for the past owner installed it port facing down so the air was stuck in the top half of the cooler reducing its effects greatly. Also its possible that at time it could hydro look the flow and stop cooling completely. "

and

"Sideways is perfered with the inlet being the bottom and the outlet being the top. The reason for this is so air will bleed out of the cooler instead of getting stuck. If you have the port facing down then the air pocket would be trapped in the top portion and in effect reduce how much fluid would flow through the cooler. The same thing could happen with the port facing up in that yes the air would bleed out but the fluid would take the shortest distance and only skim acrossed the top half of the cooler. Then flow when sideways if fluid comes in the bottom port, to get out it will have no choice but to fill up tell it reaches the top and flows back out."

regarding the 'temp' light, the manual says it is for both the engine and trans. the directions say that if the temp light comes on, pull over and put it in park, then look at the engine temp gauge. if the engine temp is good, let the car idle until the temp light goes out and then continue driving. if the engine temp is too high, you're in a bad way.

[marlinh]

I should have warned you, it does shoot out pretty good. I usually get someone to crank the engine over for me so I can watch the show.

[Mark]

Ah. So the direction of flow would matter for a cooler where the inlet and outlet are at different levels, but not for the stock cooler which is just a straight pipe.

[Petros]

I did a fluid change on an auto T4wd last month, I put the left hose in a large jug (as you face it from the front), and yes it comes out pretty fast. I pump a gallon of ATF out in only about 30-40 seconds of idling. Fortunately no spills, I clamped everything in place since I expected it.

Changing the AFT fluid before a trip like that is also a good idea, as well as putting in some valve body cleaner, and some low friction adative (it will lower the trans operating temp). On an old ATF, anything will help make it last longer.

I have seen the temp light come on, I think it is only for the trans, because the temp gauge was just a little above half way, but I was climbing up a long grade in the very hot California central valley, making the trans hot. After going down hill a ways and the temp gauge dropped below half way the light went off. It was a bit low on coolant.

I have never seen this light before so I assumed it was for the trans oil temp, most auto trans cars have some means of indicated the trans fluid is running hot, and it is not always obvious what it is. On our Ford one ton van they little "OD" light (for overdrive) blinks when it get hot, no matter what gear you are in. I had to look that one up, I was wondering what idiot at Ford thought making the overdrive indicator light also double as a temperature overheat light, with the potential to cause a $3500 repair if you do not know what it is trying to tell you.

[irowiki]

I like planning ahead. Petros recommended getting an extra oil cooler for the transmission since it is hotter down in new mexico. Plus it'll be going over mountain passes in the summertime, so I'd like to be covered.

As usual, I searched and found this thread. This forum is amazing for this stuff! However I have a few more questions.

Is this the sort of thing I should be buying?

http://www.partsgeek.com/tsqjxn9-toyota ... ooler.html


So, dlb, where does the little mini radiator part actually go? Any other tips? I'm assuming this one replaces the stock one inside the radiator. Can those lines be reused or is it best to run new ones?

Petros, so you stick the outlet from the radiator into a bucket and idle the car and pump the fluid out, this doesn't harm the transmission? I'm assuming afterwards you just pour new fluid in and tada?

[dlb]

yes irowiki, that is a suitable auxiliary trans cooler. on the auto trans t4 i worked on, i removed the plastic air dam from behind the radiator and mounted the cooler there. i used metal strips with holes in it and nuts and bolts to mount the cooler solidly but also used a few zip ties for added support. i don't see that car often but if i do see it soon, i can take a pic of what i did.

because the cooler in the bottom of the radiator does supply a certain amount of cooling (especially at idle when the rad fan kicks on—the aux cooler only cools when the car is moving and causing wind current to pass over the aux cooler's fins), i routed from the trans, to the aux cooler, to the rad cooler, and back to the trans.

[marlinh]

When I've done a flush like Petros, I pour fluid down the dipstick tube as the car is running to prevent cavitation in the transmission. Once you're done, I wait til the fluid coming out of the hose looks red, reconnect everything and then top up the transmission.

[irowiki]

I'm having a hard time picturing it, so when I get the car I'll take a picture of that area and perhaps you can draw a circle around the area


It makes me wonder if that setup could possibly heat up the AT fluid after the aux cooled it if the engine was running hot? I'm glad someone here has done it so when I do it, I'm not as lost


marlin: Ah! That makes a lot of sense, thanks!

[Petros]

That is a good way to go, but where I think DLB was talking about mounting it is where the A/C condenser is, so it would have to go in front of the A/C condener is located. There is not really room in front of the radiator because of the fan. It possible if you can find a longish low cooler (like 4" tall and 24" long) that in can go under the radiator, under the bumper in front of the holes in the rubber part of the bumper skirt. That way it will not be adding heat to the air in front of either the radiator or the a/c condenser. However, because of the risk of stones I would put a heavy wire mesh in front of the oil cooler. That would be the "Hot" set-up, a real performance installation.

The procedure Marlinh outlines is exactly the way I have done it. Much easier than dropping the plan (which does not get all of the fluid out of the trans anyway). there is not really a filter to change in the auto trans, it is just a screen, so there is no reason to drop the pan and change it with every fluid change.