Coolant in transmission pan? '98 S90

Post by **bmdubya1198** » 17 Jul 2019, 12:46

I finally decided to tear into my '98 S90 that I bought back in March with a "bad transmission", and it seems I found the problem. I'm pretty sure this is coolant contamination from a possibly failed radiator.

The issue is that the transmission moans pretty loudly and apparently slips out of gear after a little while driving. I haven't experienced the latter yet, and the transmission shifts smoothly otherwise. When I drained the fluid, it was dark but not milky. The only residue I noticed was in the pan, as pictured. No metal shavings to be found and the fluid smells normal, not burnt.

Or maybe it's fine and just due for an ATF change... but I have a feeling that milkiness isn't normal.

Do you think the transmission may be okay if I change the radiator and trans fluid and filter? I was happy to find fairly clean fluid, and I'm hoping the transmission may be salvageable.

lummert · Post by **lummert** » 18 Jul 2019, 14:28

Only way that I'm aware of for coolant to get into the transmission is the ATF cooler in the radiator. After engine shutdown the coolant pressure would cause the coolant to leak into the transmission cooler.

Post by **MoVolvos** » 18 Jul 2019, 16:20

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The cheapest way to figure this out is to bypass the radiator with a Transmission Cooler and do a complete flush. I've gone through the winter on this set up with the 03 Odyssey with 235K plus miles in the RTP area.

If the van last another year I will partially block the cooler so it can reach operating temperature quicker and remain so. Have not seen temperatures over 160 this summer. It's a big cooler but the price is unbeatable. Have another from this seller waiting to be installed on the 03 S80 T6 when I pull the bumper and open, clean and reseal the headlights. Will take care of the alarm battery at the same time but I digress, sorry.

You can always replace the radiator later but if it is leaking into the Transmission Cooler portion in quantity you'll need to plug both ends.

US $28.50 - HAYDEN TRANSAVER OIL COOLER 1405 (Transmission Cooler) (OC-1405)
https://www.ebay.com/itm/HAYDEN-TRANSAV ... 7502!US!-1

Get a case of this and you'll flush the entire 12 bottles through it or when it becomes clear. Went up a dollar probably because I keep going to the page.

HAVOLINE 226536481-12pk Full Synthetic Multi-Vehicle ATF-1 Quart (Pack of 12), 384. Fluid_Ounces
Price $53.44 & FREE Shipping
https://www.amazon.com/HAVOLINE-2265364 ... 214&sr=8-3

Sorry if this is obvious to you.

Post by **bmdubya1198** » 18 Jul 2019, 16:28

That's what I suspect is happening. I'm just kind of surprised I don't see any ATF in the coolant. I went ahead and filled the transmission today, and no more moaning! I test drove it around the neighborhood and got the engine up to temp and the car drive surprisingly well. It shifts smoothly and doesn't jerk or stick in gears.
I'm just relieved the transmission seems to be greatly improved after a simple drain & fill and filter change.

I'll probably get an aftermarket trans cooler anyway just for preventive measures if that was only metal paste, but like I said, I wouldn't be surprised if it was coolant. That's what my plan was anyway, no sense in replacing the whole radiator if it still works... this car was $100, it's not going to be a show car!

Thanks guys!

Post by **MoVolvos** » 18 Jul 2019, 16:57

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Glad it's running well, especially when the vehicle was only for a Benjamin. The fluid looked dirty but not bad except for the milky portion so it should improve with a drain n fill. If it is indeed coolant however you should do a complete fluid replacement so nothing gets embedded.

I've never thought about or looked into line pressure specs in an automatic. It could be less than the coolant pressure so it never get into the radiator. Regardless you should confirm via a pressure test to see if the radiator is OK or not. Don't want to go too long with contaminated transmission fluid.

EDIT: You still could use the radiator if it is leaking by using the Transmission Cooler to bypass and as mentioned plugging that portion off. Coolant will eventually fill up in there but no big deal.

Post by **bmdubya1198** » 18 Jul 2019, 17:10

Agreed, I just thought of that after I posted that haha. I think it should be okay with a fluid flush.

I've seen tons of cases on other cars that the coolant reservoir gets all nasty and milky with transmission fluid, so I wouldn't be surprised if that happened on this car. However I think the cooling system pressure is probably higher, which would explain why it's getting into the transmission easier than the cooling system.