Jim Grant's Tech Tips
Jeep CJ-7, Water Problems
I've got an '84 CJ-7, 258 straight six. There is quite a bit of water-oil
mixture in the valve cover. I've notice just a tiny bit on the dip stick.
But, when I drop the oil there is no water. Also, there is lots of water-oil
accumulation in the air cleaner. And I notice the radiator is short on
water about every two months. I get the feeling I have either a cracked
block or a blown head gasket but the engine is actually running under
temp during normal operation. Okay, HIT ME!!!!! ...Margaret
no need to get physical. I don't believe that you're cooling loss is related
to the watery-oil problem in the valve cover and air cleaner. It's not
uncommon for a vehicle of that age to have small leaks that could account
for the loss. The accumulation of water-oil in the air cleaner is a good
indicator that the Positive Crankcase Ventilation (PCV) system is not
functioning properly. Next, you're going to ask, "Where did the water
come from that's in the engine?"
you seen condensation on a glass of water? Well, the same thing happens
to engines. With temperature change, moisture will condense and collect
inside an engine. But, that's only a small part of the picture. The greatest
source of water in an engine is the combustion process, the burning of
gasoline. How do you get water from gasoline? Gasoline is a hydrocarbon
(HC). When gasoline is mixed with oxygen and heat, a thermal-chemical
reaction occurs, it burns. Am I scaring you yet?
the gasoline (HC) and oxygen (O2) burn, they break apart and re-join becoming
water (H2O) and carbon dioxide (CO2). Of course there are other chemicals
but these two are the main players. The remains of combustion (exhaust)
H2O, CO2 and other chemicals are supposed to exit the tail pipe, but that
doesn't happen. A portion of the combustion gases leak by the pistons
in the engine, into the crankcase.
job of the PCV system is to pull these gases H2O, CO2, and other chemicals
out of the crankcase so as not to contaminate the engine oil. If the PCV
system is not operating properly H2O will collect in the valve cover and
be forced into the air cleaner assembly. Cold weather will make matters