Any engine oil leak is not normal,
when you notice oil underneath your car it means an engine oil leak has developed.
Inside the engine there are two states of oil, pressurized and non-pressurized.
Oil leaks that are not pressurized tend to be less aggressive. Oil that is pressurized
will leak more when the engine is running, while non-pressurized oil leaks tend
to be steadier. Always check the engine oil level before you start, and if your
engine is dirty it is a good idea to clean the engine before so you can locate the
exact source of the leak. Use a good degreaser like 409 or equivalent. Always clean
an engine cold to avoid steam.
Steam is the cause of many electrical problems after an engine has been cleaned.
Try to inspect the engine yourself to get an idea of where the oil is coming from.
This will help you estimate the repair if you are going to have the oil leak repaired.
Oil leak repairs can vary greatly so it's best to get a second opinion if the repair
estimate is extreme. Use a flash light to pin point the source of the leak, then
formulate a plan to repair it. When inspecting for engine an oil leak always start
at the top of the engine and work your way down. We have listed common causes for
oil leaks below.
Car Repair Guide
Step 1 - The
engine oil fill is used
as a port to add oil to the engine. If this cap is left off it will cause engine
oil to be expelled from the port when the engine is running. With the engine off
lift the hood and located the engine oil fill port. Once this port has been located
check the cap and its condition. If the cap is missing replace the oil fill cap
with a new unit. If the oil cap is leaking remove the cap and replace the cap seal.
Clean the area and recheck for the leak after a short operation period. Even though
the engine oil is not under pressure internal engine pressure can force oil out
of this port.
Engine Oil Fill Port
Step 2 - The engine oil filter is used to filter engine oil
of carbon and other by products created by the engine and the combustion process.
This oil filter is in direct connection with the engine's oil pump and is subject
to high oil pressure. One of three things generally occurs when oil leaks from this
area. First and most common is the oil filter is not installed properly. The filter
either is not tight enough or the old oil filter gasket was not removed. When there
are two gaskets or the filter is not tight enough the oil filter cannot seal. These
problems can surface long after the filter replacement. Finally the oil filter itself
is leaking, but this doesn't happen very often.
Step 3 - The
oil drain plug is used
to remove the oil from the engine when a service is performed. The drain plug is
a threaded flanged plug that uses a sealing washer to contact the oil pan. This
seal is what keeps the engine oil from leaking out. If the drain plug is loose or
the sealing washer is missing or worn it can cause an oil leak. This plug is located
at the bottom portion of the engine oil pan. To check your oil drain plug gasket
attach a wrench to oil drain plug and try to turn it counter clockwise. If the plug
is tight but oil is still leaking the washer has failed and must be replaced. If
the drain plug is loose and will not tighten the threads on the drain plug or inside
the oil pan have failed and must be replaced or repaired to fix the problem.
Typical Oil Drain Plug Configuration (FWD front wheel drive)
Step 4 - The valve train inside the engine is covered by valve
covers, these covers are sealed to the cylinder head with a valve cover gasket.
When this gasket ages it can become brittle and crack allowing engine oil to leak
out. Sometimes a valve cover can become loose over time. Fit a socket or wrench
over the valve cover hold down nuts or bolts. Try to rotate the socket or wrench
counter clockwise, it should be snug. If the mounting bolts or nuts are loose tighten
and recheck. If the hold down bolts or nuts are tight and the valve cover is still
leaking the gasket needs to be replaced.
Step 5 - This step is for V12, V10, V8 or V6 engines only, The
intake manifold is mounted to the cylinders heads with a seal between the engine
block and intake manifold. These seals are located at the front and rear of the
intake manifold. Over time theses seals can age causing them to deteriorate and
leak motor oil. Unfortunately there is no easy fix for this condition, the intake
manifold must be removed and the seals replaced to repair this problem.
Step 6 - An engine is designed with a number of shaft seals
depending on the type of engine it is. A
timing belt style of engine has
more shaft seals than a non-timing belt engine such as cam and balance shafts. All
engines have front and rear crankshaft seals. These seals are designed to ride against
a turning shaft without allowing oil to pass through the seal. Engine heat can cause
these seals to become brittle; as a result the rubber lip contained in the seal
will fail allowing oil to exit the engine. Depending on the location of the seal,
replacement procedures can vary from removing the transmission to disassembly of
the engine front
Step 7 - Timing chain style engines
have timing chain covers that are sealed to the
engine block using a gasket. With
time this gasket can become weak allowing engine oil to leak. If after inspection
this is the case with your engine, the only remedy is to disassemble and remove
the timing chain cover to replace the gasket.
Step 8 - Some engines are designed with an engine oil adapter
that seals to the block with a gasket or "O" ring seal. This adapter is what the
oil filter screws onto. Heat can cause the seal or gasket to fail, once a failure
has occurred replacement of the seal or gasket is required.
Step 9 - Most engines are equipped with a distributor drive
port where the distributor
or sealing plug is mounted. If the "O" ring seal fails it will allow engine oil
to leak out under pressure. If this is your engines oil leak the "O" ring seal must
be replaced to repair the problem.
Step 10 - The engine oil pan is used to collect the engine oil
into a centralized area so the engine oil pump can re-circulate it back into the
engine. This pan is bolted to the bottom of the engine and uses a gasket to seal
it to the engine block. If the oil pan gasket fails it can allow oil to leak from
the engine. To repair this problem the oil pan must be removed and the gasket replaced.
Step 11 - Overhead cam designed engines have oil ports in the
engine block that connect to the cylinder head. Oil is pumped under pressure into
the cylinder head to lubricate the camshaft and other valve train components. If
the head gasket on these engines fail it can cause this pressurized oil to leak
out from between the engine block and cylinder head. If this is the case with your
engine the head gasket must be replaced to repair the problem.
Note: Some engines are equipped with an external engine oil cooler that can leak.
This engine oil cooler should be inspected when checking for an oil leak.
If further assistance is needed, our certified car repair technicians are ready
to answer your car questions.
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