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Hello everyone, I have just been reunited with my 1991 FSB with a 300 CI, automatic transmission. I owned this rig a few years ago and made the huge mistake of selling it. I just bought it back and may have water in my oil. It is leaking water from what appears to be the thermostat housing. The guy who just owned it replaced the thermostat and may or may not have seated the housing properly. The oil is chocolate color and thick. Its still brown and not milky, but doesn't look right to me. The bronco has a brand new radiator now so that leads me to believe that the bronco may have over heated. The previous owner has not been driving the bronco much in the last few months. Has anyone here had this problem with their oil or the thermostat housing? Any input would be greatly appreciated. Thank you in advance.
 

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never had a problem with thermostat housing, but who knows how it was taken care of when you didn't have it. and since the radiator and thermostat were replaced it seems like a good sign that it was overheated and could possibly need a head gasket, check the oil filler cap after running and see if theres like creamy deposits around it. check the coolant level see if its going somewhere or pressure test it. or do an oil change and see if the new oil you put in turns to sort of a chocolate milk
 

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Leaking thermostat would not allow water to contaminate oil. Most likely overheated and blew out the head gasket. I would change the oil and run it to see if it gets milky again. Also see if your oil level increases, due to additional fluid. Be mindful, that oil and water in the crankcase can damage bearings, so don't drive it any more than you have too.
 

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Roller rockers are gay
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a 300 bottom end is damn near indestructible.

change the oil, top off all the fluids and drive it to see how it acts. you will know quickly if it has a badly blown headgasket or not.

btw, a bad head gasket is the ONLY way you can get coolant into the crankcase in a 300, as the intake manifold is a ''dry'' intake. there's no coolant flowing through it.
 

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The other thing that can be done as a check is to get a hydrocarbon sniffer and check to see if you're getting exhaust gasses in the coolant - Sounds like yours is more obvious though. Another question to ask yourself is, do you keep running low on coolant at the same time? That coolant has to go somewhere - you should be low.

Good luck!
 

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Roller rockers are gay
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The other thing that can be done as a check is to get a hydrocarbon sniffer and check to see if you're getting exhaust gasses in the coolant - Sounds like yours is more obvious though. Another question to ask yourself is, do you keep running low on coolant at the same time? That coolant has to go somewhere - you should be low.

Good luck!
this is another great way to diagnose a head gasket. and it can't be wrong.

however the typical DIY guy doesn't have that equipment.

OP, when in doubt about a head gasket, do a compression test. if the gasket is bad 99% of the time it will be blatantly obvious by the compression readings.

a compression test is CAKE on a 300, lots of room and everthing has easy access.

300 ftw......V-engines...right here....:goodfinge
 
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