2005 Volvo s60 Trans fluid in the Coolant

mal81394 · Post by **mal81394** » 27 Oct 2015, 15:46

So this is the story. I keep loosing coolant with no leak and I just kept filling it up. When I went to fill it up on Sunday I noticed brown what I think was transmission fluid in the resovoir container. It had that smell of transmission fluid. So I ordered a new radiator and coolant and transmission fluid thinking there would be a ton of coolant in the transmission and that is where my coolant has been going. Today I drained the transmission from the plug and I got a little over a gallon of fluid out and no evidence of antifreeze or water mixed with the oil. I am confused. First I am only supposed to get 3.5 qts out of that plug right? I did have the car on a hill is that why so much came out or is there antifreeze mixed with the trans fluid and I can't see it? I didn't think trans fluid and water would mix. So, where did all my coolant leak to and why did I get so much trans fluid out? Any help would be great guys I know that was a long post I am just beside myself.

Post by **oragex** » 01 Nov 2015, 19:46

Can't answer were all the coolant has gone, but sure after installing the new radiator, I would flush the transmission as shown in Youtube videos through the return line from the radiator and fill it with fresh 3309 type fluid. Better not take chances as these transmissions are sensitive when it comes with the fluid.

Post by **cn90** » 13 Apr 2024, 12:56

I am trying to roubleshooting a very very slow coolant loss, 1/2 cup every 2-3 months/2K-3K miles etc.

I have a question re P2 radiator design: the 2 sections (coolant vs ATF passages): are they bullet-proof?
In other words, is there a possibility for the 2 passages to fail and connect with each other, causing ATF
---> cooling system vs coolant ---> transmission?

PS: Some BMWs years ago had this issue of ATF and Coolant mixing, courtesy of bad radiator!

Post by **jonesg** » 14 Apr 2024, 10:55

cn90 wrote: 13 Apr 2024, 12:56 I am trying to roubleshooting a very very slow coolant loss, 1/2 cup every 2-3 months/2K-3K miles etc.

I have a question re P2 radiator design: the 2 sections (coolant vs ATF passages): are they bullet-proof?
In other words, is there a possibility for the 2 passages to fail and connect with each other, causing ATF
---> cooling system vs coolant ---> transmission?

PS: Some BMWs years ago had this issue of ATF and Coolant mixing, courtesy of bad radiator!

possible but far more likely to be the coolant bottle, i just changed mine after finding a tiny leak on the seam, i saw tiny bubbles.
can also be the cap or hose clamp unions. .

dikidera · Post by **dikidera** » 14 Apr 2024, 13:20

Not just possible, but highly likely as well.

This is what happened to mine

How it works. During startup, the transmission starts generating pressure before the coolant system has had time to pressurize(34 psi usually) which allows then easy way for atf to get into coolant. When you shutdown the car, there is 34 psi of coolant pressure and 0 psi of transmission atf pressure allowing coolant to empty out into the transmission.

During working of the transmission, it's pressure should still be higher than that of the coolant but still, they fight each other when they are both pressurized. But mostly, it is exactly when you shutdown the car and the leftover coolant pressure starts entering the atf.

Glycol is extremely damaging to the clutch packs. When this issue happened to me I just happened to be running pure water as coolant and perhaps avoided catastrophic failure.