Running rough or sporatic overheating can be obvious clues. A mysterious loss of antifreeze with no apparent "leak" should REALLY be investigated. If you pull your oil dipstick and it looks milky and/or is overfull then that is a sign that you have water in your oil (which most likely came from your cooling system via blown head gasket or cracked head). If it DOES show overfull, let it sit for a while (all the water will separate from the oil and drain to the bottom of your oil pan) and then loosen the oil drain plug until fluid starts dripping out. If the fluid is water then you can pretty much bet on a cracked head or at least blown gasket. If you have access to a pressure tester you can see if your cooling system is losing pressure (with no sign of an obvious leak) or there is also a test that involves some special chemicals that will turn different colors if there are exhaust gasses in your cooling system. I am not sure if there is a way to tell the difference between a cracked head or block and a blown head gasket except to tear it down and look, but that doesn't necessarily mean that there ISN'T a way....I just don't know of one. Hope this helps.
Last edited by Bronco2guy; 01-26-2003 at 10:25 PM.
I just finished a friends Bronco II with this problem. He was losing coolant, but there was no apparent external leak. The first thing I did was rent a radiator pressure tester and test the system which would tell if there was a blown head gasket or crack in the head in the cylinders. IF there is a blown head gasket or crack, there will be bubbles in the coolant when the engine is running, and also when the tester is on the radiator, the pressure in the cooling system will rise.
Another thing to look at is the spark plugs. Crank the engine over with the coil wire grounded, and the remove the plugs. check and see if they wet with coolant.
If you have access to a compression tester, run a compression check on all the cylinders ( described in repair manual) If there is a reading on two adjacent cylinders are 20 pounds or lower than the other cylinders, there is a possibility of a blown head gasket.
If you are experiencing coolant loss and al the other things check out, consider the Intake manifold is leaking coolant into the intake for that cylinder. ( personal experience ) That is what was happening on the above mentioned Bronco. Once a new intake gasket was installed, and the manifold tourqued down, there was no more problems.
What your Bronco do you have? sounds like a fuel leak. If you have a mechanical fuel pump the gas may be leaking thru the internal diafram. If you have fuel injection it could be thru the fuel pressure regulator. ???
How many miles are on the engine and what year is it? Carb or fuel injection? First thing I would do is a compression test on the motor. Might be blowby past the rings, letting the air/fuel mixture into the crankcase. After you do the inital test, write down the readings for each cylinder, then squirt some oil in the cylinder, and do the test again. If there is a differance in the two readings, then you need to rebuild the engine.
A very easy way to confirm the head(s) being cracked is to slowly remove the radiator cap when motor is at normal temp. If there is little or no pressure or even a release of vacuum, then its reallity.
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