Got a blown head gasket? We are a team of ASE certified mechanics that have
created this guide to help you check to see if your car's engine has a head
gasket that is blown or at least what you are paying for when having the job
What Goes Wrong?
Head gaskets are made up of thin metal plates together with a hard gasket
composite. With constant expanding and contracting due to the engine
heat cycle and the acidity of the coolant the gasket can become weak and fail.
These gaskets must withstand the extreme pressures of the combustion process and hold radiator coolant which enables the transfer of anti freeze from the engine block to the cylinder head.
If the coolant is neglected it will turn acidic which eats away at the gaskets
throughout the engine and especially the metal parts of the head gasket which
seals the cylinder head to the block.When the gasket fails it can do so in five different ways.
Allowing coolant into the engine oil
Allow coolant to leak outside of the engine
Mix combustion gasses into the cooling system (radiator)
Allow combustion to transfer between two cylinders
Allow engine oil to leak outside of the engine
There is one condition motioned here that effects the engine performance
solely which is when the gasket lets go between two cylinders which then makes
the engine run rough and sometimes creates a continuous backfire through to
How Does It Work?
A head gasket seals the main engine block to the cylinder head using head
bolts which are tightened to a specific torque specification. This gasket is
meant to be a complete seal with absolutely no leakage.
How Much Does It
In general checking for a blown head gasket is the same on most cars and the
pricing should not vary much.If you want to check the problem for
yourself the chemical kit costs about $35.00 bucks which you can get from Amazon
or any auto parts store.If you are having the job done at a repair garage the
cost should be:
Between $90.00 dollars and $150.00 dollars US currencyThis should
include: Check for coolant in the oil, check for exhaust gases in the radiator
and check for coolant in the combustion chamber. If the problem includes and
engine misfire then a
compression test will need to be preformed which might cost a bit more.
How Long Do They Last?
A head gasket can let go at anytime but will typically last between 110,000
and 160,000 miles depending on the engine condition, driving habits and engine
Let's Start Testing
The most common problem you will notice when this gasket fails is the engine
overheating. Below is a video to help troubleshoot and determine which problem
if any you may have. Once the video has concluded please read through the article to pick up on additional tips and
information the video may have missed.
I hope you enjoyed that video we are creating a full guide of
automotive repair guides so
please check our 2CarPros
YouTube channel often for new additions.
Begin with the vehicle parked on level ground, engine cold, with the parking brake set.
Step 1: Remove Oil Fill Cap
With the engine cold remove the oil filler
cap to inspect for brown milky goo that has collected on the bottom of the cap.
This is an indication that coolant is leaking into the oil. This leakage could be
generated by a cracked cylinder head, block or a leaking intake manifold (in some
cases) the intake gasket is also prone to this kind of failure. Note: A small amount
of moisture maybe present inside an engine that doesn't get used much which is normal.
Step 2: Check for Coolant in the Combustion Chamber
Head gaskets are designed to control engine coolant in and around the engine block and cylinder head. When the gasket fails
it can cause a leak which can be found by
of the spark plugs (continued below).
Here is a spark plug that has been removed for the test
Once all spark plugs have been removed pressurize the cooling system and
crank the engine over while observing the spark plug holes. If coolant is
present at any one of the holes the head gasket is blown.
Its a good idea to disable the ignition or fuel system fuse before testing to avoid
fire (rare). If the engine is warm it can leave residual pressure in system which can
aid the test without using the pressure tester.
Step 3: Check the Radiator for Bubbles
With the spark plug reinstalled wait until the engine is cool and then remove the radiator cap. If the head gasket has failed and is allowing
combustion gases into the cooling system they can be detected by removing the radiator
cap and observing the liquid while checking for a continuous stream of bubbles
while the engine is running.
Here is a video to help you determine if you can remove the cap safely.
This is what it will look like if the head gasket is leaking combustion gages
inside the radiator and cooling system. This will
make the engine overheat.
Step 4: Performing a Chemical Check
To confirm exhaust gases inside the cooling
system (gasket failure, cracked head or block) use a
chemical tester which you can get from Amazon or the local parts store. Drain a small amount of coolant from the radiator as to not
contaminate the test.
Once the coolant has been drained down slightly insert the test tube and add the test fluid and fill to the full line.
Start the engine. While using the hand pump draw air inside the radiator into the tester.
If the test fluid turns yellow exhaust gases are present and the head gasket is blown. If
the fluid remains blue the system is most likely okay. This test can rarely fail and cause a false positive
because the combustion process is not 100% efficient. Small consistent pockets
of fuel enriched air (not exhaust) exist inside the combustion chamber after
ignition which is not detected by this test.
Step 5: Cylinder Compression Test
A head gasket can fail between cylinders
causing two consistent cylinder misfires and low compression in each misfiring
cylinder. To check for this condition remove
all of the spark plugs while conducting a compression test
to test each cylinder. If two readings are consistently low in neighboring cylinders this is an indication of failure
between these cylinders and the head gasket needs to be replaced.
Here is a video on how to do a compression test.
This is what the gauge will look like if the compression is low
Step 6: External Leakage
Some engines are designed with oil pressure
passing though the engine block and into the cylinder head along with engine
coolant (each in separate ports) via the head gasket. When the gasket fails it can cause an
or coolant leak which is detectable by inspection.
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