528e 1985 is transmission coolant in the radiator separate from the rest of the coolant in the radiator?

[Notelect]

In my manual swap that's still going on, I removed the coolant lines that would connect to the automatic transmission as now the manual transmission is in.

Looking online at different manual swap guides, including Dave Kans, they just say to remove the lines from the transmission, never anything about caping them off.

When researching on real OEM, I can't find any cap off bolts for the radiator or the lines.

If I want to remove the lines cause there's no need for them, are there any bolts that are made to cap those two pieces on the radiator? Or do I have to make them myself by welding the end shit for bolts to that radiator?

Or am I dumb and the coolant to the transmission is somehow separate from the coolant that goes to the engine??

I swear the latter doesn't make any sense but it is German, so anything is possible. Especially considering what I have had to deal with on this car

[Aldo525]

Those two lines moves ATF oil from the auto gearbox to radiator...no water. So you can put any kind of cap to seal that holes just to prevent dirty enter to that empty space.

[1st 5er]

Oil and water don't mix.
Leaving the lines open is OK, unless you plan to reverse the swap or at some point get a manual only radiator and sell that one. In either case it'd be beneficial to close off the openings, and anything from painters tape on up will do that.

[Notelect]

Oil and water don't mix.
Leaving the lines open is OK, unless you plan to reverse the swap or at some point get a manual only radiator and sell that one. In either case it'd be beneficial to close off the openings, and anything from painters tape on up will do that.

So there's no coolant that cools the transmission? Makes sense, but when I took off the top hose from the radiator green coolant came out. Unless the ATF fluid is green...?


I'll have to inspect the fluid I caught with my bucket again

[Mike W.]

The ATF runs thru a tube in the radiator so engine coolant cools that tube, but the two different fluids aren't directly connected. Look at the diagram and see the purple part? That's the ATF cooler. It's a separate device that is contained in the radiator tank, but doesn't mix with it.

Now some cars have had failures are or prone to the two mixing and that's a big problem, if ATF gets into coolant, it's a big PITA and has to be fixed, if coolant gets into the transmission, that's typically time for a new transmission.

[gadget73]

^^ this. Usually its going to get ATF into the coolant since the trans runs at higher pressure but it can go the other way. One is a mess, the other is a disaster.

but yeah, just pull the lines off and find some plastic caps or something to plug the holes. Might want to blow the cooler out with air to help keep it from dribbling.

[Aldo525]

So there's no coolant that cools the transmission? Makes sense, but when I took off the top hose from the radiator green coolant came out. Unless the ATF fluid is green...?

That means the radiator is broken inside...If it were my radiator, I would change it for a new one for manual gearbox version (without the automatic transmission cooler holes)

[1st 5er]

That means the radiator is broken inside...If it were my radiator, I would change it for a new one for manual gearbox version (without the automatic transmission cooler holes)

Somebody read, quoted, and responded incorrectly.
OP does not indicate a mixture of coolant and transmission fluid, and does NOT subsequently need a new radiator.

[Aldo525]

I'm a little confuse here...maybe my mistake when I "reply with quote" but was Notelect who wrote:

"So there's no coolant that cools the transmission? Makes sense, but when I took off the top hose from the radiator green coolant came out. Unless the ATF fluid is green...?"...Oct12 9:26 PM

That´s why I suggest a new radiator because I believe old one is broken....

[Mike W.]

I'm a little confuse here...maybe my mistake when I "reply with quote" but was Notelect who wrote:

"So there's no coolant that cools the transmission? Makes sense, but when I took off the top hose from the radiator green coolant came out. Unless the ATF fluid is green...?"...Oct12 9:26 PM

That´s why I suggest a new radiator because I believe old one is broken....

Well, he wasn't completely clear, but the way I read it no, he would not need a new radiator. Assuming it was the top radiator hose he took off, and not the top A/T coolant line, he should get green or blue out of there and red out of the A/T lines/holes.

[Notelect]

I inspected the fluid. It's definitely coolant with ATF fluid mixed in. That's probably what killed the automatic transmission before the swap started

I will have to replace the radiator after she's running again, I'll close up those holes though. Probably will have a welder buddy cap off two bolts to place there

I'll have to make sure I'm very thorough with the coolant flush afterwards as there might be atf fluid leftover in the coolant lines....

[Notelect]

The ATF runs thru a tube in the radiator so engine coolant cools that tube, but the two different fluids aren't directly connected. Look at the diagram and see the purple part? That's the ATF cooler. It's a separate device that is contained in the radiator tank, but doesn't mix with it.

Now some cars have had failures are or prone to the two mixing and that's a big problem, if ATF gets into coolant, it's a big PITA and has to be fixed, if coolant gets into the transmission, that's typically time for a new transmission.

Yeah the coolant ATF mix is what I'm guessing killed the automatic transmission 7 years ago, thank you for the diagram and your reply

Atleast I now know what happened that fateful day

[1st 5er]

Now you tell us.

I inspected the fluid. It's definitely coolant with ATF fluid mixed in. That's probably what killed the automatic transmission before the swap started

I will have to replace the radiator after she's running again, I'll close up those holes though. Probably will have a welder buddy cap off two bolts to place there

I'll have to make sure I'm very thorough with the coolant flush afterwards as there might be atf fluid leftover in the coolant lines....

A new radiator will now be a necessity.
Might as well go ahead and order a new one.
I'd source an all aluminum replacement if at all possible.