For a while I thought I had a blown head gasket but I ruled that out because there is now way my car would run so well for so long with a blown head gasket. I flushed my radiator and heater core and ran a coolant flush through the system for a few days. The radiator fluid stayed clean for about a week but then went back to being brown, muddy, oily pasty. I saw a few videos that said it is possible for blown head gasket symptoms to be something else such as a leaky oil cooler or possibly the transmission cooler leaking fluid into your radiator. I am starting to believe it is the oil cooler but I am not even sure if my 2000 Ford Ranger has an oil cooler. I have searched for them online but I only see what seems to be oil coolers that look like small radiators but the oil cooler that I saw on the videos for other fords sits behind the oil filter. Does anyone know if Rangers have those types of Oil coolers? What should I check first the radiator cooler or oil cooler?

 

No connection between an oil cooler and radiator

If you have an automatic transmission then there is a transmission cooler IN the radiator so that could be the source of the oil

Blown head gasket covers a bit of ground, if its blown between a cylinder and cooling system then yes engine would not run well and you would see white smoke from exhaust
But a head gasket can fail between a coolant passage and oil passage, rare occurrence but can happen

But you would see coolant in the oil pan, as well as oil in the radiator
So check dipstick for "chocolate milkshake" oil

There are different types of coolant and they can't be mixed
Silicate was 1st type of coolant usually green in color
in the 1990s OAT coolant was starting to be used, red or pink color

These two types can NOT be mixed or you will get what to have, brown sludge

In the 2000's HOAT was starting to be used, yellow or gold color, it can be used with any other type, its a hybrid silicate/OAT blend

The colors are NOT standardized, most coolant makers do stick to these color codes but it is NOT required

If you read the label(fine print, lol) it will have "silicate", or "OAT", or "HOAT"

 

Thanks RonD. However I saw that the oil cooler has a piece that runs behind the oil filter and there are two coolant lines that run into it. I saw in a video that if that part is faulty or has a crack between the oil filter and the coolant area oil may leak into the coolant system. But as you said I do have an automatic transmission so I will start with checking the transmission cooler. I did check the oil dipstick and it does not appear to be milky brown like a milkshake.

 

What engine do you have in your 2000 Ranger?
2.5l
3.0l
4.0l

 

I have the 3.0L flex fuel 6cyl

 

Never seen an oil cooler like that on any 3.0l Ranger, and it wouldn't make sense, to run a "heat exchanger" for engine oil, like they do for automatic transmission fluid
Heat exchangers run two fluids near each other to maintain a constant temperature, the radiator heat exchanger for automatics is there to cool but also heat ATF fluid in colder climates

This may be something a previous owner added on, or a dealer option, engine oil coolers are better off using outside air to cool the oil not coolant at 180degF, same as engine coolant uses outside air to cool it in the radiator

But yes, if you have a heat exchanger then yes it can break inside and fluids can be exchanged/mixed, which is not good