HEAD GASKET TEST 4: Using A Chemical Block Tester (Combustion Leak Tester)
Every now and then a blown head gasket is tough to diagnose. If in your case, the 3 prior tests cannot confirm (or disprove) a blown head gasket, then you need to perform a combustion leak test with a block tester.
This test is accurate and the only reason I don't include it at the beginning of the tutorial is that the first 3 tests correctly identify a blown head gasket 95% of the time (not to mention you don't have to buy a block tester). In that other hard to diagnose 5% of the cases a combustion leak test is THE test.
This is how it works:
- A blue liquid chemical, which is blue in color, is placed in the tester (see photo above).
- 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).
- 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.
- If the blue chemical turns yellow (for gasoline engines), combustion gases are entering the radiator. This result confirms a head gasket failure, a cracked block, or a cracked cylinder head issue.
- If the blue chemical doesn't change color, you can conclude that you don't have a head gasket failure, a cracked block, or a cracked cylinder head issue.
You can shop for one here:
More 4.0L Jeep Diagnostic Tutorials
I've written several more tutorials that may be of interest to you. These are specific Jeep 4.0L Cherokee (or Grand Cherokee, Wrangler) that you can find here:
Here's a sample of the Jeep 4.0L articles you'll find:
- How To Test Engine Compression (Jeep 4.0L).
- How To Troubleshoot A Bad Fuel Injector (Jeep 4.0L).
- How To Test The Ignition Coil (1991-1997 4.0L Jeep).
- How To Test The TPS (1993-1995 4.0L Grand Cherokee).
- How To Test The Crankshaft Position Sensor (1994-1996 4.0L Jeep).
If this info saved the day, buy me a beer!
