I looked at a Ford F-150 truck for sale today with the 5.4L V8 Modular motor. The truck had no running issues.

After raising the hood, I noticed something odd. There is solid material stuck to the inside of the coolant system bottle. I have not seen this before. I have seen extensive mixing of oil and coolant, this usually looks like a brownish sludge.

What causes solid material to accumulate, and in this case stick to the inside of the coolant bottle? Is this indicative of a failure in the cooling system?

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  • You need to look inside the radiator and see what it looks like. If it's a mess of chocolate milk, it very well could be a serious issue. If it just looks like coolant, you would just need to clean your overflow reservoir out (completely) and go from there. – Pᴀᴜʟsᴛᴇʀ2 Sep 5 '17 at 22:55
  • Since the expansion tank is where coolant is added, it's likely that you can't access the interior of the radiator. What does the oil on the dipstick look like? The tank is certainly indicative of a previous failure and oil/coolant mixture, but it may not have been cleaned properly when it was fixed [although that's bad practice and may ring alarm bells]. – Andrew Leach Sep 6 '17 at 9:53

Failure of the cooling system? More like failure of the head gasket. Looks like the exact same material as this post, so it may also be a transmission cooler gasket.

Even if the head gasket was repaired, I have experienced big problems with the cooling system afterwards. It is difficult to remove 100% of the particles pushed into the coolant when the gasket blows, so problems emerge later with the water pump, radiator, heater core, etc. That's probably why the vehicle is for sale!

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