[jtyson8602]

Okay weird stuff yesterday after flushing my 91s cooling system. I just did the heater core replacement which was a living hell I might say. But when I drained all the coolant there was that neat rainbow look to it in the drain pan and of course it was oil. I dont know how. I made sure to check the oil and figured it to be all milky but it is fine. Right away my guess is head gasket. I guess it could be a cracked/warped head too though right? or who knows what? Any ideas? I already have another block im putting together for this one so Im not too stressed about it but it would be nice to know what everyone thinks.

[stangfreak]

Originally Posted by jtyson8602 But when I drained all the coolant there was that neat rainbow look to it in the drain pan and of course it was oil. I dont know how.

not to ask stupid questions but was the drain pan clean? could it have had some oil residue in it?

[grnstang]

was the bottom of your overflow tank peanut buttery looking? cause mine was

[95StangMX]

Originally Posted by stangfreak not to ask stupid questions but was the drain pan clean? could it have had some oil residue in it?

I was gonna ask this same question. I have reused a drainpan before and thought this same thing. It doesnt take much to leave the rainbow effect.

[stangfreak]

Originally Posted by 95StangMX I was gonna ask this same question. I have reused a drainpan before and thought this same thing. It doesnt take much to leave the rainbow effect.

same here. i guess the only stupid question is the one that isn't asked

[95opal]

Originally Posted by jtyson8602 Okay weird stuff yesterday after flushing my 91s cooling system. I just did the heater core replacement which was a living hell I might say. But when I drained all the coolant there was that neat rainbow look to it in the drain pan and of course it was oil. I dont know how. I made sure to check the oil and figured it to be all milky but it is fine. Right away my guess is head gasket. I guess it could be a cracked/warped head too though right? or who knows what? Any ideas? I already have another block im putting together for this one so Im not too stressed about it but it would be nice to know what everyone thinks.

Intake gasket leak.

[1FastFox]

I agree it does sound like an intake gasket...

[jtyson8602]

Originally Posted by stangfreak same here. i guess the only stupid question is the one that isn't asked

it was brand new never used.

and no the overflow wasnt creamy or anything

wouldn't an intake gasket still cause water in the oil? I mean why would one transfer to the other but not both ways?

[e3sean]

uausally its water in the oil cause the water is under more pressure.

[stangfreak]

when i blew an intake gasket my oil turned into a milkshake

[e3sean]

exactly. i have never seen oil in the water unless the pressure side after the pump cracked into the water

[jtyson8602]

I have blown head and intake gaskets both resulting in a creamy milkshake like oil. I understand thats typical. Thats why I said this is really odd. How would I get oil in the water but not water in the oil. it doesn't make sense to me

[itschristorres8]

Originally Posted by e3sean uausally its water in the oil cause the water is under more pressure.

Oil pressure is much higher then coolant
your coolant pressure is as high as your radiator cap states. which is about 16lbs
vs oil that its usually never that low. and about 35-80+psi

an intake gasket leak would only lead to water in the oil which would be milky when first coming out
if you let it sit. the water will be at the bottom but still mixed.

plus no oil runs through your intake so its impossible for oil to get in your coolant through a leak there
most likely a head gasket. thats the only thing that i can imagine would cause oil in your coolant.

which when you turn your car off your coolant pressure stays present while you have 0 oil pressure so water can still get in your oil that way

[ryans88gt]

Maybe the oil was already in the coolant when added. Typically if I drain the coolant and it doesn't need to be changed, I will recycle it. If there was any oil residue in the drain pan it goes in the coolant too. Another possibility, is ATF if you have an automatic. Coolant hoses that route through the radiator for cooling have been known to corrode.

[jtyson8602]

Originally Posted by ryans88gt Another possibility, is ATF if you have an automatic. Coolant hoses that route through the radiator for cooling have been known to corrode.

Ahh maybe that has something to do with it. About 6 months ago I did the swap from aod to the t5. But I haven't flushed the cooling system since then so there could still be residual from the trans before. I guess Ill just have to keep an eye on it