Red milky stuff in radiator??

Asked by Jan 30, 2015 at 05:45 AM about the 2006 Holden Calais

Question type: Maintenance & Repair

V6 ve Calais v, six months ago my car
randomly overheated to the point it shut
down. After some research and mechanical
advice I replaces the radiator, the oil is
clean so it can't be the head gasket, and the
red stuff in my radiator suggests
transmission fluid yeah? But my upper
radiator hose keeps splitting and very
randomly my car will get hot (above the half
way red mark.  The oil consumption is
normal, obvobviously radiator fluids aren't
when the hose splits. Noone can give me
an idea of what this is other than the
head....but there are no symptoms for that.

7 Answers


Yes, if it is red, it's probably transmission fluid. The cooler is usually part of the radiator and sometime the two fluids mix. Since you replace the radiator did you check the level and condition of the trans fluid? Do you remember if you removed and attached the small transmission cooler lines on the side of the radiator? Not sure why your car is still overheating

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Best Answer Mark helpful

Thanks, Yeah Changed the radiator but not the cooler lines. Didn't bother checking the trans fluid either :/ the issue I'm really concerned about is the random over heating and the blown upper radiator hose, it's the third one to blow since the first over heating. Could is be a thermostat issue?


I'd be concerned also with the trans fluid and that might be overfilled and has mixed with coolant, which isn't good for the bands. Flush it is has any signs of mixing or overfilled. Yes, first inspect the thermostat, it might be stuck closed, is your coolant level correct and all air bleed out of the system? Your building up pressure.

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It sounds like that you still may have some remnants of the transmission fluids in your system. The shop will tell you they flushed system, but did they really? If there is allot of the old fluid left in the system it can build up around the water pump, the thermostat and coat the inside of the engine as well as other parts on the cooling system. If you installed a new radiator then I would assume that there are no leaks into the cooling system from the transmission. You say your oil consumption in normal, what is normal? A quart a month if that’s the case then maybe a blown head gasket? Here is a you tube to check for a blown head gasket. I would first change my thermostat, with the system now open, clean the system at least TWO TIMES. This method we be the easiest and cheapest way to go in determining what is in the cooling system, Good Luck


Engine coolant will ruin a transmission. This has been a big problem on some Nissan vehicles where the transmission cooler is inside the radiator. A leak develops between the transmission and the cooling system. This needs IMMEDIATE ATTENTION.

Thanks heaps guys! We did flush the system more than once and it's not the head gasket. definitely going to check out the trans levels and the thermostat.

The new radiator has Cracked under pressure and trans fluid is leaking from the cooler, have had someone take a look and said the thermo needs to be replaced because it's not opening up hence the pressure. Thanks heaps for all the advice :)

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