cooling and trans fluid mixing - 1999 S70 Turbo

Justinthorpe · Post by **Justinthorpe** » 27 Dec 2017, 05:18

Hi
Just been given a 1999 S70 with what was described as a stuffed trans.
Seems the trans cooler has been leaking and mixing with cooling system.
The vehicle was driven approx 10 kms and parked up. When I received the vehicle it would drive forward and back.
Whats the chance the transmission could of survived this (after flushing out both systems and replacing the radiator??
Engine is a B5204T4 with 4 speed auto.
Cheers

Post by **abscate** » 27 Dec 2017, 05:20

10km? Definitely worth a repair of cooler/radiator, flush, and try ! You will tell your karmic balance by your success

Post by **RickHaleParker** » 27 Dec 2017, 05:42

10 Km ... even a Yugo is tougher then that ... fix it. Get right on it, do not let it sit with water in the transmission. I would do frequent drain and fills, along with filter replacements until the fluid is clear. Then consider a power flush. Trying to Power flush to much crap at once can plug the channels and render the transmission inoperative.

You could do a DIY flush using the transmission cooling lines. First do a drain and fill with filter replacement . Disconnect the transmission cooling lines and connect them to a large reservoir of ATF and a large filter. Let the transmission pump circulate fluids throughout the external filter, next the reservoir of ATF, then back to the transmission. You can keep changing that ATF in the reservoir and the external filter until it clears up. After the fluid clear up, you can try solvents to loosen up any stubborn crap in the transmission.

Post by **scot850** » 27 Dec 2017, 09:48

What external filter are you talking about? I thought the trans pressure was higher than the coolant pressure so the oil flows to the coolant not the other way around for the most part unless there has been a major melt down of the radiator cooler.

I'd certainly do the drain and fill for the trans and then a flush using the coolant line at the radiator doing the 2 liters of drain and fill at a time until the fluid appears clean (having replaced the radiator first). I'd run the car for a few miles and then look at the trans fluid again for signs of coolant still there and re-flush as necessary.

The harder part is if the trans fluid is in the coolant system getting that clean. Flushing with water only will not clean the coolant system. You will need to find something that can clean the oil out if someone can recommend a product.

Finally I would never recommend a power flush on these old transmissions, in fact I'd never recommend a power flush.

Neil.

Post by **RickHaleParker** » 27 Dec 2017, 10:54

What external filter are you talking about?
I was describing a roll your own flush kit.

the oil flows to the coolant not the other way around
I give him some credit. Why would he ask about the transmission if he has not detected coolant in the transmission.

Flushing with water only will not clean the coolant system.
laundry detergent then back flush with water.

Post by **scot850** » 27 Dec 2017, 12:34

Thanks for the clarification.

Neil.

Justinthorpe · Post by **Justinthorpe** » 27 Dec 2017, 19:50

Hi
Thanks or the advice. Pretty much what I thought. The car had been sitting for around 5-6 weeks before I picked it up.
Will get new radiator in the new year and an external trans filter and flush new trans fluid through until runs clean.
Thanks for the tip around cleaning/flushing the cooling system.
Will also overhaul the PVC system while car is immobile.
Many thanks

Post by **cn90** » 27 Dec 2017, 19:59

- Mixing coolant and fluid is possible, only under specific condition: bad radiator design, sealant (plumbing paste or teflon) between trans fitting and cooler deteriorates, allowing coolant (under pressure when car is hot) to enter the AT system.
I posted some photos in forum where under specific situation, coolant enters the AT system.

- Anyway, as mentioned by others, do a flush, drive around, flush again (info on how to flush a 1999-later models is in forum).

Justinthorpe · Post by **Justinthorpe** » 28 Dec 2017, 18:55

I have pressure tested the radiator and trans cooler and definitely an internal leak between the two.
I will get a new radiator, any merit in using a separate trans cooler? rather then using the std unit in the radiator

Post by **scot850** » 28 Dec 2017, 23:45

If you can then it will prevent this re-occuring and may also give better cooling to the trans as well.

Neil.