ATF consequences of changing my radiator

[aaron]

I have a radiator on order from BMA, and a service manual on the way from Amazon.

It appears that the transmission is cooled with the same radiator as the coolant, so those lines will have to come off too.

My question is: How should I treat the replacement of ATF fluid?

I assume a chunk will leak out, and I may as well just drain the pan and replace all I can if I'll have to deal with it anyway. I have a '90 with 128k miles. Shifting seems fine. Some mentioned that a trans fluid flush can be hard on an auto. Do you think I'm safe draining the pan and filling it back up again? About 50% is replaced with that method, right? Or should I spill as little as possible and leave the transmission be?

Should I get trans. fluid from the dealer? Or is a brand from autozone acceptable?

I guess the consensus here is that BMW coolant is the way to go. PO put *something* green in there (gasp). Should I really drive 50 miles to the nearest dealer to get the real stuff?

Thanks!

Aaron

[Kalevera]

I'm assuming you have a 535 here; no other E34 has an integrated trans cooler and radiator.

You won't lose much ATF by disconnecting the lines from the fittings; the cooler is quite small. It'll also be a good chance to see how the fluid is doing and if it merits considering a fluid change (if the car's had regular 15k fluid/filter changes on the trans, and you're getting to the next 15k mark, it'd be a good idea to change it while you're in there; edit -- if it's brown or burned, you might want to just keep it in there).

Install the new radiator and run the car/bleed the cooling system. Get it up to operating temperature by driving the car around and then check the trans fluid level with the car running. The 4hp is an easy trans to service; the more difficult one is the 5hp-30 and variants with the so called "lifetime" (aka 70k) fluid, which requires a specific operating temp to correctly fill.

Use cool blue. Any dexron III / mercon compatible is fine for the trans, or get redline D4 if you're a big spender :)

best, whit

[uscharalph]

When I changed my radiator, there was such a small amount of ATF lost that the dip stick reading was fine. BMA has BMW Cool Blue Coolant for $19.00 / gallon.

[uscharalph]

I'm assuming you have a 535 here; no other E34 has an integrated trans cooler and radiator.

You won't lose much ATF by disconnecting the lines from the fittings; the cooler is quite small. It'll also be a good chance to see how the fluid is doing and if it merits considering a fluid change (if the car's had regular 15k fluid/filter changes on the trans, and you're getting to the next 15k mark, it'd be a good idea to change it while you're in there).

Install the new radiator and run the car/bleed the cooling system. Get it up to operating temperature by driving the car around and then check the trans fluid level with the car running. The 4hp is an easy trans to service; the more difficult one is the 5hp-30 and variants with the so called "lifetime" (aka 70k) fluid, which requires a specific operating temp to correctly fill.

Use cool blue. Any dexron III / mercon compatible is fine for the trans, or get redline D4 if you're a big spender :)

best, whit
Actually my 1989 E34 525i (M20) automatic has the integrated trans cooler and radiator.

[Kalevera]

Ah, yes...of course. I forgot about that little factoid :D


best, whit