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.
Here are the contents of this tutorial at a quick glance:
- Symptoms of a Blown Head Gasket.
- HEAD GASKET TEST 1: Engine Oil the Color of ‘Coffee With Too Much Creamer’.
- HEAD GASKET TEST 2: Coolant Shooting Out From Open Radiator.
- HEAD GASKET TEST 3: Engine Compression Test.
- HEAD GASKET TEST 4: Using a Chemical Block Tester (Combustion Leak Tester).
- More 1.8L Nissan Tutorials.
You can find this tutorial in Spanish here: Cómo Probar un Empaque de Cabeza Quemado (1.8L Nissan Sentra) (en: autotecnico-online.com).
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:
Open your Nissan's Hood and check the condition of the engine oil by pulling out the engine oil dipstick.
You'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.