Ok im going to try to keep it simple.
My coolant is BLACK.I did a compresson test and the high was 195 and the low was 169.I then drianed the oil to see what it looked like. It looked like normal oil.I took some of the coolant and put it in a glass to see if it would seperate and it didnt.It got lighter but it looks like dirt and crap on the bottom. When I bought the motor it had a bunch of rust in it so I stuck a garden hose in it to flush it out.Today I reflushed the whole motor and put new coolant and oil in it and the coolant is turning black again.Theres no bubbles in the coolant when the car is running and runs like a champ. Aynbody have any ideas because im stumped.Im almost 100% sure its not oil.By the way I did pull the radiator out today and flushed it real good.Any ideas?

 

sounds like combustion gas, oil would be milky white

 

Yea thats what I was thinking....milkshake type deal.Where would combustion gas get into it?

 

head gaskets

 

Damn....wouldnt that shwo up though on a compresson test?

 

does it stink like engine combustion?

 

No not really.But when you look at the coolant it look like there fuel or something in it.You know when gas get into water it has that rainbow effect.

 

are you running just water or an antifreeze mix? i would tink it would be hard to see that in the green...

 

john...do a leakdown test...that should give you an indication of the problem...never heard of the coolant going black!!!!!!!!!!!!!!!!!

 

Im running 50/50...I going to do a leak down test today. I too have never herd or seen of black coolant.I had one thread on mustang forums and a guy said maybe my bottom radiator hose is coming apart on the inside by the T. He said it did it on his lighting.Im going to take a look at that today too.It runs strong as hell and doesnt smoke.