I have a 2001 Chevy Astro Van. Yesterday the radiator starting spewing a thick, black substance out the side of it. It looks like old oil. I had the oil changed 1 1/2 weeks ago. The oil on the dipstick is clean and full. It almost looks like someone poured old, dirty oil into the radiator?

  • This may seem stupid, but what exactly is your question? Commented Mar 28, 2014 at 17:12
  • Is the van overheating? Shifting erratically? Check engine light on? Is the transmission fluid low? As much info as you can gather will help us help you.
    – cinelli
    Commented May 10, 2014 at 1:39
  • 1
    Is your mechanic this guy? Or this? Commented Jun 7, 2014 at 18:38
  • Directly above the leak, do you find two steel tubes connected to the side of the transmission? Pointing rearward, around the engine? Those would be your transmission cooler lines, and that section of the radiator has an integral transmission oil cooler. Also... it only leaks when the van's running true? Because the engine powers the transmission's front pump and cycles transmission oil through the cooler. No engine, no pressure. So... if all that's true, it's radiator time... Commented Aug 5, 2014 at 22:06

3 Answers 3


If you're getting oil into the coolant, odds are there's coolant in your oil too (a much worse symptom). You likely have a piston ring problem or headgasket is blown.


Have you ever changed the coolant? Ot does get old. I havent heard of it turning black though. That is weird.

Try draining your coolant and putting new stuff in. If it turns black, the inly thing I can think of is a cracked water jacket, but then you should be having oil that looks like a frappucino.

I ahve seen purple coolant that turns kinda dark when it gets old. Is it thick like oil, or thin?


one possibility comes to mind.If by chance you have used different brands of coolant to top up this can cause an adverse outcome.Drain flush and replace with one brand only and stick to it.Reccomend premix to avoid water quality issues

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