lbs of pressure in tranny cooler/exchanger

[bork]

I thought I was leaking trans fluid into radiator coolant. I hooked up air compressor to trans connection on radiator & blocked off outlet. & put 2 latex gloves over coolant in/out ports. (empty on floor) Put 50 lbs or air pressure over night & gloves are still collapsed & air pressure still holding. So maybe my drain pan had some old oil in it before I emptied coolant into it? (floating red oil) So I just wanted to be sure, before I reinstall rad cause I just did timing belt. Should I have put more air pressure to it?

>

BTW overflow bottle did looked clean.

[porcupine73]

I would not put more than 50 psi on it, even that might be a bit much.

 

Usually if the radiator to in-tank cooler breaches, you end up with coolant in the ATF, which is definitely the worser of the two mixings. The coolant usually ruins the friction materials in the AT pretty fast rendering it useless.

[MilesFox]

I had an ea82 dual row radiator do this to me, but lucky for me it was a MAT car. I just looped a hose between the cooler ports and was good to go.

[CNY_Dave]

The cooler lines should normally be under very little pressure.

 

Fluid gets pumped through the spin-on filter (if present) then through the cooler, then it just dumps back into the pan.

 

 

Dave

[bork]

Hmmmm, how does coolant get into tranny fluid, if tranny runs at a greater pressure, than coolant?

[WoodsWagon]

The cooler lines should normally be under very little pressure.

 

Fluid gets pumped through the spin-on filter (if present) then through the cooler, then it just dumps back into the pan.

In most transmissions the fluid goes from the pump to the torque converter, out through the cooler, and then back in to lubricate the bearings, then drains to the pan through the bearings.

 

The cooler circuit and tc run at the lubrication circuit pressure, so there's usually around 30psi in the cooler hoses when it's running.

 

You will have pepto-bismol foam in the radiator if the trans fluid is leaking in. The radiator runs at 15psi, so while the engine is running the trans fluid will pump into the radiator. Once you shut if off though, the oil pressure drops off quick while the radiator holds pressure until it cools, so coolant will pump back into the transmission.

[CNY_Dave]

In most transmissions the fluid goes from the pump to the torque converter, out through the cooler, and then back in to lubricate the bearings, then drains to the pan through the bearings.

 

The cooler circuit and tc run at the lubrication circuit pressure, so there's usually around 30psi in the cooler hoses when it's running.

 

You will have pepto-bismol foam in the radiator if the trans fluid is leaking in. The radiator runs at 15psi, so while the engine is running the trans fluid will pump into the radiator. Once you shut if off though, the oil pressure drops off quick while the radiator holds pressure until it cools, so coolant will pump back into the transmission.

 

I could be thinking of a different discussion, but I recall a diagram showing a dedicated pump and circuit just for the trans cooler on subes.

 

Dave

[porcupine73]

Hmmmm, how does coolant get into tranny fluid, if tranny runs at a greater pressure, than coolant?

 

Well there's a few additional things at work here. Let's suppose the engine is off. Now you've got the static liquid head of the coolant in the radiator, and it will be able to leak into the ATF.

 

Also, seemingly strange things happen when you have a small hole with something flowing past. It's like those little taps on the spigots in chemistry labs, where it draws a vacuum in the tap as the water flows past. This sort of thing also happens in compressed air systems. A little pinhole leak actually gets water into the system, because it is drawing in outside air through the pinhole leak. It sounds weird but that's what happens. I forget what this effect is called.