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Transmission fluid and radiator fluid mixing in 1993 Volvo 960

I’m trying to help my dad out with his 1993 Volvo 960 (approx 130,000, mostly around-town miles) that appears to have a cracked radiator, and the result seems to be coolant mixing with the transmission fluid.

The car recently had a transmission replaced by a local mechanic shop. For a car with an in-line 6 cylinder motor, this vehicle couldn’t get out of its own way – particularly when it was cold. They said the transmission was shot and replaced it for like $900 or something with a used one.

After the replacement, the car seemed to be running in top form: even better than it had run in years. Fast forward a couple of months, and it developed an overheating issue. The car can barely drive a mile without overheating.

My dad took it to a shop very close nearby (different than the guy who changed the transmission) because the car couldn’t make it much further without the temperature getting too high.

This second shop diagnosed the car has having a cracked radiator. They quoted him something like $1,100 for the work – money he doesn’t have. They were going to replace the radiator, the fan, and the hoses which were now squishy and soft after having the mix of radiator/trans fluids coursing through them. So he drove the car home, probably less than 1/2 a mile.

Now, I’m not sure if the first replaced transmission was a result of the cracked radiator or not. The first ship never mentioned it, and they are a pretty reliable bunch. They’ve worked on my dad’s 1973 VW Super Beetle, very much to his satisfaction. I also had examined the transmission fluid a week or two after the replacement, and it was completely normal. (He leaked some very clean fluid in my driveway, and I told him to take it back to them, and they fixed the leak for free).

So, I can change the radiator, fan and hoses myself. But I figure the transmission lines, the transmission itself and the cooling lines all need to be flushed out. There does appear to be the strawberry milkshake-like goop in both the radiator (which I drained), the coolant overflow reservoir, and from what I can see, on the transmission dipstick.

Any advice on the order of operations here? I was thinking I could replace the radiator and fan and leave them disconnected and then tow the car back to the shop to have them flush out the transmission and lines, and then the radiator flushed as well?

I wish I could do the flushing of the transmission myself, but I guess I don’t really have the equipment. I’m not typically hesitant to work on just about anything on a car (I’ve done head gaskets, replaced clutches, suspension components, lots of brake work, etc.), but this is the first time I’ve encountered this kind of fluid contamination.

I’d just like to see if there’s a way I can help salvage this car (which is a really cool vehicle, but which isn’t worth that much) without breaking my old man’s piggy bank.


If the coolant has been in the transmission long enough that the trans fluid looks like a strawberry milkshake you should also price out another transmission, as the odds of this one lasting very long are pretty slim.

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If it was me, and I was broke, I would replace the radiator as cheaply as possible (maybe used), replace the coolant, replace the tranny fluid and filter, and hope for the best.Thats a 25 year old car we are talking about.

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Yeah, it was dark when I looked at the transmission fluid the first time. But it looked milky. And I suppose another transmission ought to be another $900 with the same shop.

I guess that’s the general idea. Part of the question is whether flushing the transmission lines, etc. is worth it. I suppose it will only help, not make anything worse.

The sooner you replace the radiator, the less likely the transmission is to fail. Maybe you can get the radiator recored.

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I was just on the phone with a mechanic (whose shop this Volvo can get to using gravity only) and he indicated he doesn’t use a pressure system to flush out transmissions anymore. He said he runs the engine while pouring in new fluid. He said he does that two or three times, then replaces the filter. And then would do about the same job on the cooling system.

Anyone have an idea whether this procedure is going to potentially further damage the transmission? If the car is just idling in park? I can do this kind of flush myself.

It has been my experience that even a few ounces of water will cause the clutch friction plates to disintegrate from steam regardless how determined an effort is made to flush the system. I was warned that it wasn’t worth the effort by an old transmission expert but felt it was worth a try on 2 occasions and both failed miserably. On a Ford pickup that was caught in a flash flood I dropped the transmission pan before the engine was ever started but the transmission failed as the owner drove home from the shop.

I hope you have better luck @jaimetoes. Please keep us posted.

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Radiator for $100:

Picture 1

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I think you’re probably looking at another transmission, but you could get lucky I guess. If I had that problem I wouldn’t start or run the car another second. First I’d install an inexpensive radiator as a diy’er project. I can’t speak to the Volvo, but when I did that job on my Corolla, it took like 40 minutes and was very easy to do. The replacement radiator cost $90. Been working fine now for 5-6 years, no issues at all.

In your case even after replacing the radiator I wouldn’t start the car untile the transmission pan had been dropped and cleaned out, and the fluid had been thoroughly flushed out. This might take multiple passes, ask your transmission shop for advice on how best to minimize the effects of water in the trans fluid until you can get it all out. Ask if they can drain the torque converter separately, for example. That’s possible on my Ford C4, but not on all transmissions. Only doing the full experiment will tell you if it finally pays off or you have to get another transmission installed.

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If the only problem with the current radiator is the transmission cooler then bypass that cooler with a cheap external cooler. And if you don’t have cold winters to deal with you can run year round using just the external cooler… Transmissions run too cool using only the external cooler when operated in cold weather.