If you suspect that you have a blown head gasket on your hands, then this tutorial will show you the three most common tests done to check for a blown head gasket.
A blown head gasket is the result of one of two things:
- Severe overheating.
- Hot spots on the engine deck or cylinder head surface (created by a leaking cooling system that does not pressurize), that burned the head gasket.
The end result is either a vehicle that starts and runs yet overheats or a vehicle that cranks but does not start. To get into more specific symptoms of a blown head gasket, let's jump into the next subheading.
Contents of this tutorial:
- Symptoms Of A Blown Head Gasket.
- TEST 1: Engine Oil The Color Of 'Coffee With Too Much Creamer'.
- TEST 2: Compression/Exhaust Gases Shooting Out Of The Radiator.
- TEST 3: Compression Test.
- TEST 4: Using A Chemical Block Tester (Combustion Leak Tester).
- Frequently Asked Questions.
- More 4.7L Dodge Tutorials.
Puedes encontrar este tutorial en Español aquí: Cómo Probar El Empaque De Cabeza (4.7L Dodge) (at: autotecnico-online.com).
Symptoms Of A Blown Head Gasket
The most common symptoms a blown head gasket are:
- White smoke coming out of the tail-pipe when the engine is running.
- This smoke has a very sweet smell to it (it's coolant cooking in the exhaust).
- The engine in your 4.7L equipped Dodge or Jeep ‘Cranks but Won't Start’. You have verified that:
- Ignition system is OK (since you have spark coming out at all of the ignition coils).
- Fuel pump is OK (you have verified that the fuel pump is delivering fuel to the fuel injectors).
- All fuel injectors are injecting fuel.
- Engine is overheating. You have checked that:
- The fan clutch is good.
- Thermostat is good.
- There are no coolant leaks.
- The engine oil is thick and tan to off-white color (mixed with coolant).
The most common cause of a blown head gasket is that the engine overheated because: 1) Fan clutch is not working, 2) All of the coolant leaked out of the engine and you kept driving it this way. 3) Thermostat went bad and is stuck closed and the coolant could not circulate.
TEST 1: Engine Oil The Color Of ‘Coffee With Too Much Creamer’
There are three tests in this article, and chances are that you'll probably not have to do all three. Why? Well, because if the first or second test confirms you have a blown head gasket on your 4.7L Jeep or Dodge SUV or pickup, there's no need to do the third (the 3rd test is an engine compression test).
Before you start your troubleshooting, take a look at the entire article. The first two tests should take you less than 5 minutes to do.
OK, on with show, this is what you need to do:
Open the hood on your SUV or pickup
- Once the hood is open, pull out the engine's oil dipstick.
Check the color of the engine oil and its viscosity. What you're looking for is:
- The engine oil (sticking to the dipstick) is a color like ‘coffee with too much milk’.
- Or its color is normal.
OK, let's go into a deeper explanation of what these two results mean:
CASE 1: The engine oil looks like ‘coffee with too much cream’. This tells you that one (or both) of the head gaskets is history. You're gonna' have replace both head gaskets.
CASE 2: The color of the engine oil is normal. This is the correct and expected test result.
The next step is to go to: HEAD GASKET TEST 2: Compression/Exhaust Gases Shooting Out Of The Radiator.
Here's why: This is always the very first test that most automotive mechanics or technicians do to easily diagnose a blown head gasket, even we (or they) know that a blown head gasket doesn't always result in oil mixing with the coolant. Thankfully, there are more easy and simple tests to continue checking for a blown head gasket.