TEST 2: Coolant Shooting Out From Open Radiator

How To Test For A Blown Head Gasket (1995-2000 1.8L Mazda Protegé)

This is the second test that doesn't require any tools to perform. OK, now that you've checked and verified that the engine oil is not the color of ‘coffee with too much creamer’, you are going to crank the engine with the starter motor and with the radiator open. The idea behind this test is to see if the engine combustion gases (from inside the cylinders) are being pushed out from the now opened radiator.

The normal test result of this test is for the coolant or water inside the radiator to remain undisturbed as you or your helper are cranking the engine (with the starter motor). If the head gasket is blown, then what usually happens is that the coolant will shoot out (violently) from the opened radiator (as you crank the engine).

IMPORTANT: If your 1.8L Mazda Protegé 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.

Here are the test steps:

  1. 1

    Remove the radiator's cap. Check to see if there is coolant in the radiator. If the radiator is empty then add some water or coolant to bring it up to the radiator's neck level.

  2. 2

    Now, have a helper crank the engine, while you stand at a safe distance from the open radiator.

  3. 3

    You'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 bad news and it's a clear indication that your Mazda Protegé's 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. Your next step is to go to: TEST 3: Engine Compression Test.

TEST 3: Engine Compression Test

How To Test For A Blown Head Gasket (1995-2000 1.8L Mazda Protegé)

Although it's extremely rare to have a head gasket burn exactly between two cylinders, it does happen. In this type of head gasket problem, you're not going to see the oil mixed with coolant and you are not going to see the coolant being pushed out of the radiator.

With this type of head gasket failure, your Mazda's engine won't start. This ‘no start’ condition is caused by the two resulting dead cylinders.

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)..

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.

These are the test steps:

  1. 1

    Remove the spark plug wires. Before you do, I recommend that you mark them with the cylinder number they belong to (just to make it easier to put them back in place when you get done with the compression test)

  2. 2

    Remove all four spark plug wires and then remove all of the spark plugs.

  3. 3

    Thread 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.

  4. 4

    Have 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 1.8L Mazda Protegé's head gasket is burned at a location between 2 cylinders then 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 1.8L Mazda Protegé and I got the following cylinder compression readings:

  1. Cylinder #1 = 170 PSI
  2. Cylinder #2 = 0 PSI
  3. Cylinder #3 = 0 PSI
  4. Cylinder #4 = 169 PSI

As you can see from the above compression readings, cylinders #2 and #2 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 #3 and #4. 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: 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.