I blew a top radiator hose.It has transmission fluid mixed in with the radiator fluid. what would cause this?

Flush cooling system maybe you need to Replace the Thermostat or radiator cap.

Transmission cooler inside the plastic parts of the radiator may be leaking and causing the oil to mix with the coolant. GM also has a problem with their lower intake gaskets leaking, which would allow the oil and coolant to mix. Last possibility is the head gasket is leaking and mixing the oil into the coolant side but not the other way. Check your transmission fluid for mixing evidence. Another thing to do is pressure test your cooling system (Radiator, hoses ect) to see if there is a leak. Another test to try out is compression.

Remove the fan and shroud. Put a large (!) drain pan under the radiator and drain it - if you're lucky it'll have a drain petcock near the lower radiator hose. Unscrew the radiator hose clamps and disconnect the upper & lower radiator hoses. Disconnect the transmission cooler lines if they also go into the radiator (some do, some don't)... you'll want a second, small, drain pan to catch the transmission fluid.

Now unbolt the clamps that hold the radiator to the radiator support plate (across the front of the car). Lift the radiator straight up, being sure not to lose the rubber mount isolator pads. Remove it from the car.

Replacement is pretty much the reverse of disassembly - put the new radiator in place CAREFULLY so you don't damage it, put the mounting clamps back on, reconnect the transmission cooler lines and radiator hoses, check the petcock (if the new radiator has one) to be sure it's closed snugly, reattach the fan and shroud.

Now refill the cooling sytem with all NEW antifreeze/coolant and water mix, about 50/50. DO NOT reuse the old antifreeze. Take close note of exactly what brand and type of antifreeze you used, and never NEVER mix any other brand/type of antifreeze with it, only exactly the same brand/type.

After refilling the cooling system, start the car & check the transmission fluid. Top off if necessary.

On one of the tanks on the radiator you have two hosed that come from your transmission. This tank is your transmission cooler. Inside the plastic on the radiator you have a metal tube through which your transmission fluid pases through. That tube is surrounded by coolant/antifreeze which is used to cool your transmission fluid. A rupture in the tube would case fluids to mix possibly causing damage to the transmission.

Blown water pump seal or the radiator core itself is cracked at the bottom. Check the lower part of the vehicle visually and identify where the liquid is coming out. If it is from the front of the motor it is most likely the water pump. If it is from the base of the radiator the core is damaged. There is a slim chance, if your radiator mix was off and it froze in your area, that one or more of the Engine Freeze plugs popped. This will be the case if the leakage is from the side of the motor, which also brings into play the possibility the Engine core cracked as well causing your problem.

If no external leak and the transmission fluid colour looks white, the problem belongs to the automatic gearbox oil cooler. The oil cooler has broke mixing the gearbox oil and coolant causing this milkshake. It's a small radiator core type oil / water heat exchanger. It is cracked inside and transmission oil is mixed with engine coolant. Because the transmission oil pressure is greater than engine coolant pressure, the transmission fluid level drops. See also the coolant colour inside recovery coolant reservoir inder bonnet! It could be like this:



The automatic gearbox oil cooler type oil / water heat exchanger (oil cooler):


(In the picture above the transmission oil pan was removed for oil filter replacement).

Transmission fluid is sometimes cooled by way of a seperate internal tank within your radiator, the fluid is passed through hoses and steel or aluminum tubes from the transmission to the radiator, as the fluid flows thru the internal tank within the radiator it transfers heat from the fluid into the coolant within the radiator which then exchanges the heat from the coolant thru the radiator fins and into the ambiant air around the radiator.
That being said, if the internal transmission fluid tank or the connections at or within the radiator develop some sort of leak, the two fluids(coolant and transmission fluid) will mix and will show up where it shouldn't be! You may have an internal leak within the radiator, which means the radiator needs to be replaced.
Good Luck!

If it's losing tranny fluid and there are no visible leaks externally, try looking in the radiator and seeing if it looks like chocolate milk in there.More than likely you blew your transmission cooler which is built into the radiator, and that has been mixing with your engine coolant.Get back to me, I hope I could help..Thx,

Well first off, coolant in the transmission will cause transmission failure if left in long enough. Proving why the radiator failed will be another story.

I hate to contradict the prior poster, but I would not see how a blown head gasket could get transmission fluid into the radiator. Motor oil, yes, but transmission fluid, no.

the transmission fluid in your tranny runs out of the transmission and up into the radiator to cool it off.

So if there is transmission fluid in the radiator, I'd look for a leak in the radiator. If it is mixing the two fluids then the leak is probalby internal.

Remember that if the radiator is now 'mixing' water and transmission fluid, there is a possibility that the fluid/water mixture may be going back into the transmission as well