How To Test for a Blown Head Gasket
Blown Head Gasket Testing
Nissan Runs Hot and overheats while driving
The average cost for a Head Gasket(s) Replacement is between $1314 and $1679. Labor costs are estimated between $1270 and $1603 while parts are priced between $44 and $76.Get a personalized estimate based on your location and specific car. Estimate does not include taxes and fees.But first test and confirm that headgasket is faulty.
If your 1.8L Nissan Sentra has severely overheated and doesn't start or it starts and runs but overheats (and you've already confirmed that the fan, thermostat and water pump work)... there's a good chance you've got a blown head gasket on your hands .
There are 4 very simple tests that you can perform on your Nissan Sentra that will let you know if the head gasket has blown. In this tutorial, I'll show you how to perform them in a step-by-step way.
To prevent an expensive, recurring problem, the integrity of the entire Nissan cooling system should be inspected and tested when a head gasket is replaced.
During this repair, the cylinder head(s) may need to be inspected and machined. Additional repairs may be needed after the inspection.
Cylinder head gasket replacement often occurs when the engine has high mileage; several additional parts may be needed during the repair. These may include cooling system components (hoses, water pump, radiator, thermostat, etc.) vacuum lines, timing belt, ignition wires, and more.
Common Symptoms
Nissan head gasket failures are often due to an overheated engine, but can also be caused by high mileage and/or age.
An early sign of a failing head gasket will be a rough running engine when you first start the vehicle, especially if it's been sitting overnight. The rough running will generally last for only a few seconds.
A leaking headgasket will often leak engine coolant into the oil, causing a "chocolate milk" like appearance and the oil level my be higher than normal.
Failed head gaskets can produce a white, sweet-smelling smoke from the tail pipe.
How To Test for a Blown Head Gasket
(Nissan 1.8L)
Symptoms of a Blown Head Gasket
The number one cause of a blown head gasket is severe overheating. This overheating is usually due to the fact that one of the following failed:
- The radiator fan stopped working.
- Engine lost all of the coolant (due to a leak somewhere in the cooling system).
- Thermostat went BAD and got stuck closed.
There are instances the head gasket starts to leak engine oil (due to a manufacturer's defect of the head gasket), but the engine doesn't overheat... we won't get into that type of condition... since the focus of this tutorial is a blown head gasket as the result of severe overheating. Now, the most common symptoms a blown head gasket are:
- Your Nissan Sentra is overheating. You know it's not the fan or thermostat.
- White smoke is coming out of the tail-pipe and it smells like anti-freeze being cooked.
- The car won't start.
- You have already verified it's not an ignition system problem because you have spark coming out at all of the spark plug wires.
- You know it's not a lack of fuel, because you have verified that the fuel pump is delivering fuel to the fuel injectors.
- The engine oil is thick and tan to off-white color.
HEAD GASKET TEST 1:
Engine Oil the Color of ‘Coffee With Too Much Creamer’
This first test is a simple test and checks for one of the most common results of a blown head gasket: coolant mixing with the engine oil. When this happens, the engine oil turns the color of ‘coffee with too much cream’.
In most cases, this is probably the only test you may have to do, to verify a blown head gasket, and not have to do the other two tests. But if this test doesn't conclusively verify a blown head gasket, then by all means proceed to the other two head gasket tests.
OK, I'll stop talking and we'll get this show on the road... this is what you need to do:
- 1Open your Nissan's Hood and check the condition of the engine oil by pulling out the engine oil dipstick.
- 2You're gonna' see one of two things:
1.) The engine oil will be a creamy tan/ off-white color or...
2.) The engine oil will be its usual normal color.
Alright, let's interpret the color of the engine oil:
CASE 1: The color of the oil is a light tan, like coffee with too much cream, and your Nissan Sentra starts and overheats or does not start.. then this result confirms that you Nissan Sentra's head gasket is blown.
If you're wondering why the oil looks like this? Well this is what happened:
1.) Your Nissan Sentra overheated to the point that the cylinder head warped (since it's made out of aluminum). This led to the head gasket to burn.
2.) Once the head gasket burns and the head warps, the head gasket is unable to keep engine oil, coolant, and compression/ exhaust gases from mixing.
3.) This leads to the coolant entering the engine oil pan.. As both of these mix... the result is an engine oil that is an off-white/tan color.
CASE 2: The color of the engine oil is normal, so far so good, but more testing is necessary to make sure the head gasket is not blown (especially if your Nissan Sentra is overheating or not starting), go to HEAD GASKET TEST 2: Coolant Shooting Out From Open Radiator.
Here's the reason why: In about 90% of the times, a blown head gasket will cause the engine's coolant to mix with the oil, but not always. And so another test or tests are needed to either confirm a blown head gasket or exonerate the head gasket as blown. The next test is to see if the engine's compression/ combustion gases are escaping thru' the radiator.
HEAD GASKET TEST 2:
Coolant Shooting Out From Open Radiator
The second test, that you'll perform on your Nissan Sentra, is to see if the engine's compression or combustion gases are entering the cooling system.
When this happens... you'll have coolant shooting out violently from the radiator (with the radiator cap removed of course).
IMPORTANT: If your Nissan Sentra starts and runs and it has been running for an extended amount of time, let the engine cool down for at least an hour, since this test step requires that you remove the radiator cap. Be careful and remember that a radiator cap should never be removed from a hot radiator.
There's a good chance that your 1.8L Nissan Sentra is not starting, in this case... you don't have to worry about a hot engine.
- 1Remove the radiator's cap. Check to see if there is coolant in the radiator. If the radiator is empty... add some water or coolant to bring it up to the radiator's neck level.
- 2Now, have a helper crank the engine, while you stand at a safe distance from the open radiator.
- 3You'll see one of two results:
1.) The water or coolant inside the radiator will shoot up and out of the now open radiator.
2.) The coolant will not be disturbed. In other words, cranking the engine will have no effect on the level of the water or coolant in the radiator.
OK, now that the testing part is done... let's take a look at what your results mean:
CASE 1: The coolant bubbled out or shot out from the radiator: This is a clear indication that the head gasket is blown.
This test result only happens when the head gasket has blown and/or the cylinder head has warped due to the engine overheating. No further testing is required.
CASE 2: The coolant DID NOT bubble out NOR shoot out from the radiator: If cranking the engine had no visible effect on the level of the coolant in the open radiator... then so far so good, since this is the normal result.
If you were to ask 10 persons, what is the most common symptom of a blown head gasket, 9 out 10 would say, without hesitation, engine oil mixing with coolant and engine compression/ combustion gases shooting out of an open radiator neck... and yes they would be right but not in all of the cases. There are times when this doesn't happen and so the next test will help to further verify this, GO TO: HEAD GASKET TEST 3: Engine Compression Test.
HEAD GASKET TEST 3: Engine Compression Test
There are times that when the head gasket gets blown... it just burns between two cylinders.
When this happens... you usually don't see engine oil mixed with coolant and you don't see the coolant being pushed out of radiator (with it open and with the engine cranking). I have seen this enough to know that one more test has to be done.
To explain this a little further: When the head gasket has burned at a point between two cylinders, the resulting gap in the head gasket will let only the compression/ combustion of one cylinder leak into the other and vice-versa, but nothing else (like coolant). If this happens, in a Nissan Sentra, this will cause a No Start Condition.
In this test step I'll show you how to test the engine compression and more importantly, how to interpret the results to see if the head gasket is burned or not.
This is what you'll do:
- 1The Ignition System must be disabled so that spark won't be created and delivered to the spark plug wires.
Distributor type ignition system:You can do this by disconnecting the ignition coil's connector, if the ignition coil is located outside of the distributor on your Nissan. If your Nissan Sentra has the ignition coil inside the distributor, disconnect the distributor's connectors, and this will disable the ignition coil.
COP ignition coil system: Removing all 4 COP ignition coils will disable the ignition system. - 2Remove all four spark plug wires and then remove all of the spark plugs.
- 3Thread in the compression tester by hand, on the first spark plug hole you're gonna' start with.
Do not use any tools to tighten the compression tester. Hand tightening the compression tester is more than enough to get the proper results. - 4Have a helper crank the engine while you keep your eyes on the compression tester. The needle will climb, as the engine cranks, till it reaches the maximum cylinder compression. At the point it stops climbing, have your helper stop cranking the engine.
On a piece of paper, write down the reading and what cylinder it belongs to (you can use the image in the image viewer to help you identify the cylinder). Repeat the above steps in the remaining 3 cylinders.
If your Nissan Sentra's head gasket is burned at a location between 2 cylinders... your compression test readings will give you 2 good compression readings and 2 compression readings that will be 0 PSI. Let me give you a more specific example:
Let's say that I tested my Nissan Sentra and I got the following cylinder compression readings:
- Cylinder #1 = 175 PSI
- Cylinder #2 = 165 PSI
- Cylinder #3 = 0 PSI
- Cylinder #4 = 0 PSI
As you can see from the above compression readings, cylinders #3 and #4 have 0 PSI readings. And this is a clear indication that the head gasket has burned at the point between them both. Now, in your specific case... you may not see those exact same cylinders with 0 PSI readings. It may be #1 and #2 or it may be #2 and #3... the main idea is that whatever cylinders are affected, they will always be side by side.
CASE 1: All cylinder compression readings where normal: These compression gauge readings confirm that the head gasket is OK and not burned at a point between two cylinders.
Your next test doing a block test. For this test go to: HEAD GASKET TEST 4: Using a Chemical Block Tester (Combustion Leak Tester).
CASE 2: Two side by side cylinders had 0 PSI compression: This engine compression reading confirms that the head gasket is burned thru' at the point between those two cylinders. You will need to replace the head gasket.
HEAD GASKET TEST 4: Using a Chemical Block
Tester (Combustion Leak Tester)
Using a block tester, to check for a blown head gasket when the previous 3 tests don't confirm it, will tell you without a shadow of doubt if it's blown or not.
Why didn't I start of with this test? Because TEST 1, TEST 2, and TEST 3 usually pin-point a blown head gasket condition in about 95% of the cases (not to mention you don't have to spend any $$ to do them). It's the remaining hard to diagnose 5% percent where the effort of finding a block tester is worth it.
In a nutshell, this is how a block tester works:
- A blue liquid chemical, which is blue in color, is placed in the tester (see photo above).
- The tester assembly is then placed on the open radiator neck (you may have to drain some of the coolant in the radiator since this tool needs to ‘gulp’ some of the air inside the radiator).
- The rubber bellow is then squeezed to suck in the air up through the two fluid-filled chambers. As the air bubbles up through the fluid, it will cause a chemical reaction.
- If the blue chemical turns yellow (for gasoline engines)... then combustion gases are entering the radiator thus confirming a head gasket, a cracked blocked, or cracked cylinder head issue.
- If the blue chemical doesn't change color, then you can conclude that you don't a head gasket, a cracked blocked, or cracked cylinder head issue.
Also check this for more help.
The best instruction you'll find is from the factory manual. I've attached a link to it below.
This will help.
Thanks.
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