TEST 2: Coolant Shooting Out From Open Radiator
This test will check to see if engine compression pressure are escaping into the engine's cooling system.
What we'll do is open the radiator and then have a helper crank the engine to see if the coolant (inside the radiator) will be shot out.
If the coolant shoots out (while the engine is cranking), then you've confirmed that the head gasket is blown on your 1.5L Toyota Tercel.
IMPORTANT: Perform this test with a completely cold engine! If your Toyota Tercel's engine has been running for any length of time, let it cool down completely before removing the radiator's cap.
Let's get started:
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.
Crank the engine with the help of helper, while you stand at a safe distance from the open radiator.
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 shot out from the radiator as you cranked the engine. This test result tells you the head gasket is blown on your 1.5L Toyota Tercel. The normal test result is for the coolant to remain undisturbed as the engine is cranked.
CASE 2: The coolant DID NOT bubble out NOR shoot out from the radiator. With this test result you can conclude that the head gasket is not letting the combustion pressures leak into the cooling system.
Your next step is a compression test. Go to: TEST 3: Engine Compression Test.
TEST 3: Engine Compression Test
An engine compression test is probably one of the most neglected diagnostic tests for a blown head gasket.
The cool thing about the 1.5L Tercel engine, is that the spark plugs are very accessible. Thus, a compression test is usually a piece of cake to do.
The purpose of the test is to see if there are 2 side by side cylinders with 0 PSI compression.
Why? Because this test result would confirm that the head gasket has burned at the narrowest junction between the cylinders.
The end result of type of head gasket failure is that the compression of one cylinder will escape into the other and vice-versa and thus causing a 0 PSI compression reading in both cylinders.
These are the test steps:
Remove all four spark plugs.
NOTE: If your specific Tercel has a distributor type ignition system, disconnect the distributor from its electrical connector. This will disable the ignition system and prevent spark from being created during the test.
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.
Have a helper crank the engine as you keep your eyeballs on the compression tester.
Once the needle 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 illustration above to help you identify the cylinder).
Repeat the above steps in the remaining 3 cylinders.
Let's take a look at what your test results mean:
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.
If you still suspect a blown head gasket. 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.