Mysterious pink fluid in reservoir


What could cause an odd pink suvbstance to appear in the coolant reservoir of my Toyaota 4Runner? I have had this occur twice in the past month, and everyone is stumped!


This could be evidence of oil contamination of your coolant, and if that is the case, it would likely be the result of a blown head gasket. I would suggest having a competent mechanic (note: Not Jiffy Lube or a chain operation such as Sears or Midas!) check the coolant for the presence of exhaust gases in order to confirm whether your head gasket is leaking. If you ignore it, major engine damage could result in short order.


What color is it normally? What happened last time? Was any action taken? Did it change back to the regular color? What is the regular color? Could it be a rust color? Are you sure what fluid that is? (coolant, wiper fluid, transmission fluid, Power steering fluid etc.?


When I had this problem with my wifes 95 Corolla, it was transmission fluid.

Since the car only had 50k miles on it & the radiator was still good, I simply capped off the leaking trans cooler in the radiator & installed a 30 buck external trans cooler

Also gave the trans a good flush to get the coolant out.

So if yours has a slugomatic a leaking trans cooler is one possibility.


Thanks for your follow-up questions. The normal color is green. Both times this occurred my engine was overheating, so I shut it off, and looked under the hood. I noticed there was no coolant left, but there was a pink substance in the radiator and reservoir. This even caused warping of the rubber in the radiator cap from whatever the chemical reaction was. The first time, I brought it into my mechanic he said he had never seen anything like it, and perhaps when I had my last oil change and service, someone put the wrong fluid in the wrong place. He could not determine what the fluid was. It is definately not a rust color. I had everything completely flushed, and a new radiator cap was put on, and brand new green coolant. The truck drove fine for about a month, and then the same thing happened this weekend.


I just fixed a forerunner with the same problem. The trans cooler in the radiator ruptured allowing trans fluid to mix with the coolant and coolant to mix with the trans fluid. I would recommend getting it to a shop ASAP as the antifreeze in your trans will destroy it.
~Michael (dartman69)