How To Test For A Blown Head Gasket (2000-2006 1.8L Nissan Sentra)

If your 1.8L Nissan Sentra has overheated and now won't start, or starts and runs but overheats (and you've already confirmed that the fan, thermostat and water pump are working), chances are you have a blown head gasket on your hands.

There are 4 very simple tests you can perform on your Nissan Sentra to determine if the head gasket is blown. In this tutorial, I'll show you how to do them step by step.

You can find this tutorial in Spanish here: Cómo Probar Un Empaque De Cabeza Quemado (2000-2006 1.8L Nissan Sentra) (at: autotecnico-online.com).

APPLIES TO: This tutorial applies to the following vehicles:

• 1.8L Nissan Sentra: 2000, 2001, 2002, 2003, 2004, 2005, 2006.

Symptoms Of A Blown Head Gasket

The most common cause of a blown head gasket is excessive engine overheating due to one of the following conditions/problems:

• The radiator fan stopped working.
• Engine lost all coolant (due to a leak somewhere in the cooling system).
• Engine coolant thermostat failed and got stuck closed.

There are cases where the head gasket will leak engine oil but the engine will not overheat. We won't get into this type of condition as the focus of this tutorial is on a blown head gasket as a result of severe overheating.

The most common symptoms of a blown head gasket are:

1. Your Nissan Sentra is overheating for no apparent reason.
2. White smoke comes out of the exhaust pipe and it smells like antifreeze being cooked.
3. The car won't start.
   • You have already verified that it isn't an ignition system problem as all of the ignition coils are sparking.
   • You know it's not a lack of fuel because you verified that the fuel pump is delivering fuel to the injectors.
4. The engine oil is viscous and light brown to whitish in color.

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 coolant mixes with engine oil, the engine oil takes on the color of 'coffee with too much creamer'.

In most cases, this is probably the only test you may need to perform to check for a blown head gasket and you'll not need to perform the other three tests.

However, if this test does not positively confirm a blown head gasket, be sure to continue with the other head gasket tests.

OK, I'll stop talking and we'll get this show on the road, this is what you need to do:

1. 1

   Open your Nissan's hood.

2. 2

   Pull out the engine oil dipstick.

3. 3

   Check the viscosity and color of the oil sticking to the oil dipstick.

4. 4

   You'll see one of two things:
   
   1.) The engine oil is a creamy tan/off-white color.
   
   2.) The engine oil is 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 creamer and your Nissan Sentra starts and overheats or does not start. 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 burned or damaged the head gasket.
2. Once the head gasket burns and the cylinder head warps, the head gasket cannot prevent the engine oil, coolant, and compression/exhaust gases from mixing.
3. This causes the coolant to enter the engine oil pan. When these two mix, the result is a motor oil that is off-white/brown in color.

CASE 2: The color of the engine oil is normal. So far so good, but more testing is needed to make sure the head gasket isn't blown (especially if your Nissan Sentra is overheating or won't start).

The next test is to see if the engine's compression/combustion gases escape through the radiator. Go to: TEST 2: Coolant Shooting Out From Open Radiator.

Here's why: About 90% of the time, a blown head gasket will result in the engine's coolant mixing with the oil in the crankcase, but not always. Therefore, another test or tests are required to either confirm or disprove that the head gasket is blown.