TEST 4: Using A Chemical Block Tester (Combustion Leak Tester)

Using A Chemical Block Tester (Combustion Leak Tester). Block Tester To Check For A Blown Head Gasket

In some cases, one of the head gaskets gets blown but the engine still starts and runs but it starts to overheat immediately.

Also, the 3 prior tests don't seem to confirm that it's a head gasket problem. In these cases, only a block test with a block tester will confirm a blown head gasket.

In a nutshell, this is how a block test with a block tester works:

  1. A blue liquid chemical, which is blue in color, is placed in the tester (see photo above).
  2. 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).
  3. 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.
  4. 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.
  5. 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.

Where can you get the chemical and block tester? At your local auto parts store or here:

Frequently Asked Questions

1.)  How can I tell if a cylinder head is cracked?

The cylinder head has to be removed and visually inspected. If the crack is wide enough, you'll be able to easily see it.

Sometimes a visual inspection proves inconclusive. In this case only a machine shop's cylinder head pressure test can verify if the cylinder head is cracked.

2.)  Do I need to resurface the cylinder heads?

YES, the cylinder heads should be resurfaced by a machine shop! You should never reinstall your 5.2L V8 Jeep Grand Cherokee's cylinder head without first having an automotive machine shop resurface them. Especially if your 5.2L V8 engine overheated.

Now, of course, if you (or the machine shop) have checked the cylinder heads with a straight-edge and they are not warped then, and only then are the cylinder heads not resurfaced.

More 5.2L Jeep Grand Cherokee Tutorials

You can find a complete list of 5.2L Jeep Grand Cherokee tutorials in this index:

  1. Jeep 5.2L Index Of Articles.

Here's a small sample of the tutorials you'll find in the index:

  1. How To Do An Engine Compression Test (1993-1998 5.2L Jeep Grand Cherokee).
  2. How To Test The Camshaft Position Sensor (1993-1997 5.2L Grand Cherokee).
  3. How To Test The MAP Sensor (1993-1996 5.2L Grand Cherokee).
  4. Ignition System Wiring Diagram (1996-1998 5.2L Jeep Grand Cherokee).
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Jeep Vehicles:

  • Grand Cherokee 5.2L V8
    • 1993,
      1994,
      1995,
      1996,
      1997,
      1998