Blown Head Gasket Diagnosis, Symptoms and Preventive Measures

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Are you have a head gasket problem? Find out What Causes Head Gaskets to Blow, how to fix blown head gasket and if you can you drive with a blown head gasket. We will also look at why does a blown head gasket ruin an engine and how long can you drive your car with a blown head gasket?

The head gasket of a car plays a very much essential part in the smooth functioning of a car’s engine, and if your car head gasket is blown, it can cause very serious damage to the car and even lead to major repairs.

What does it mean to Blow a Head Gasket?

A head gasket is a mechanical seal that is sandwiched in between the surfaces of the engine block and the heads of the cylinder. The main purpose of the head gasket is to help contain the combustion process so that you can have a functional engine since it is part of the combustion chamber. Secondly, the head gasket provides a physical extension of fluid passages from head to block.

Being this close to the combustion process, the head gasket has to be strong. Most contemporary gaskets are produced from steel, composite materials with copper used in high-performance applications. The head gasket sets are quite affordable in spite of the importance of this part. Removing the cylinder head can be very laborious, hence the high cost of replacing a head gasket.

What Causes Head Gaskets to Blow?

Usually, the head gasket forms a kind of seal between the engine block and the cylinder head.  The head gasket has to seal both exceptionally hot, high-pressure combustion gases and engine coolant which can extremely vary in temperature.  It is normal for head gaskets to develop leaks over time as a result of the wide range of temperatures and a relatively large surface area. Head gaskets can blow irrespective of the model of your vehicle or the type of head gasket that is being used.

The head gasket seals the coolant passage from the atmosphere and the combustion chamber, meaning you can’t see much of the head gasket on a vehicle with an installed engine. The symptoms of blown head gaskets can be difficult to diagnose since much of the gasket can’t be seen without taking the engine to pieces.  A mere visual inspection will not prove a leakage in the head gasket, so it is essential to know other symptoms so you can perfectly identify the problem with a head gasket.

Symptoms of a Blown Head Gasket

  • External leakage of coolant from below the exhaust manifold
  • The emission of white smoke from the exhaust pipe
  • Engine overheating
  • Bubbles in the radiator or bubbles in the coolant overflow tank
  • Low cooling system
  • White milky oil
  • Fouled spark plugs

Now let’s look at the symptoms one after the other.

External Head Gasket Leak

External leakage of head gasket could cause coolant to come from below the intake or exhaust manifold. This may only occur when the engine is warmed up totally. You may be able to identify the leak as a head gasket lead if there are no other cooling passages or hoses near the head gasket. But it may require you to add a UV dye to the coolant then observe if there are other cooling passages nearby. You can carefully locate the head gaskets with a UV light to spot the leak.

White Smoke From Exhaust

In most cases, head gasket leaks are internal to the engine permitting coolant to run into the combustion chamber on every intake stroke.  When this happens, the coolant burns with the combustion process and appears as white smoke being emitted from the exhaust. White smoke can excessively surge from the exhaust when this happens.

Overheating Engine

It is normal for your engine to overheat after longer drives if you have a blown head gasket.  This is as a result of the lack of coolant as your engine consumes it. Overheating engine can cause lots of issues, with the major problem being the expansion of metal components past what they were designed for, which can cause cracks and distortion. It can cause irreversible damage to the seals and gaskets.

Bubbles in the Radiator

A leak from an internal head gasket allows exhaust gases into the coolant, apart from allowing coolant into the combustion chamber. This can lead to the formation of bubbles in the radiator or coolant reservoir. The coolant may appear to be boiling even when it’s cold. Bubbles occur when the exhaust gases force their way into the cooling system during the combustion process. 

Low Cooling System Integrity

A leak in your head gasket, pressurizing your cooling system and inspecting for pressure loss can prove you have a blown head gasket. Still, this isn’t quite a convincing test because there could be other leaks you don’t know about.

White or Milky Oil

The leakage of coolant leaks into your combustion chamber, it cause it to trickle past your piston rings into your oil.  Oil and water can mix over time, causing the oil to turn a milky white in appearance.  You can check for this on your dipstick and around the oil cap of your engine. The mixture of water in your oil will reduce the effectiveness of the oil in lubricating your car. Lack of proper lubrication will allow wearing on your cylinder walls and on the crank and camshaft bearings.

Fouled Spark Plug

The burning of coolant in your combustion chamber will leave tiny white deposits on your spark plug typically around the ground strap and electrode.  A fouled spark plug may not be a conclusive symptom of blown head gasket because other problems can cause these white deposits. 

How to Prevent a Head Gasket Failure

Head gasket failure can be prevented in a number of ways:

  • Keep pressures of the combustion chamber as low as possible. For vehicles that are turbocharged or supercharged, ensure your boost level is set to the factory setting. 
  • Ensure your engine doesn’t have any pre-ignition from carbon build-up. 
  • Maintain a low engine RPMs to reduce stress and heat on your head gasket and avoid running your engine at high RPM. 
  • For cars with a manual transmission, avoid downshifting to slow the car and rev-match to reduce head gasket pressure.
  • If you are rebuilding an engine, reduce the risk of a blown head gasket in the future by using head studs that are properly lubricated and torqued in the proper arrangement to the correct torque setting. 

What is the Cost of Repairing a Blown Head Gasket

The cost of fixing a blown head gasket can vary significantly from vehicle to vehicle.  Cost factors include:

  • Head or block damage
  • Number of cylinder banks
  • Overhead cam VS pushrod engines
  • other components replaced

It is mostly the labour cost that makes the head gasket repair to be expensive. So, the cost can change depending on how complex the job. A “V” style engine has 2 heads, so the cost of repair will be high because the gasket on both heads will need to be replaced. Also, an engine with overhead cams adds the intricacy of removing the timing belt or chain, thereby making the job more complicated. For a pushrod engine, repair may not be too costly since you only need to remove the rockers and pushrods.  Machine work can add lots of expenses to a head gasket job so knowing how much damage has been done to the head or block is vital in calculating the cost of fixing your head gasket. 

Also, you should note that other parts may need to be replaced when repairing a head gasket like other seals, gaskets, bets, or water pump.

Avoid driving with a blown head gasket as this can cause damage to the engine.

Does a blown head gasket ruin an engine?

Yes. A blown head gasket can damage an engine. Ignoring a blown head gasket symptoms can lead to problems such as a coolant leak. This could lead to damage to the catalytic converter. It can cause leakage into the engine oil, erosion of lubrication, which can damage the engine.

So can a car still run with a blown head gasket that is the next area we are looking at?

Can you drive with a blown head gasket?

No. It isn’t advisable to drive with a blown head gasket as it can foul spark plugs and cause your engine to run inefficiently due to the deposits left by burning coolant. Leaking coolant and combustion gases can lead to high-temperature gradients causing erosion of the leak area and possible cracking. Hot gases and cold coolant moving through the gasket hole can erode the metal head or even engine block. This can make the cost of repair to be quite expensive.

How long can you drive your car with a blown head gasket?

It depends if there’s coolant in the oil or if the oil has a milky appearance. A grey smoke coming out from the exhaust pipe when it starts may mean the coolant is leaking into the cylinders. The coolant burns up in the cylinder and may lead to longer-term destruction to the rings and other parts. However, if the damage hasn’t been for too long, you can get Bar’s Leak Head Gasket Repair and pour it into the coolant reservoir. Ensure to follow the instructions. This should get you a year or more of usage depending on how far gone the gasket is. You can equally get a gasket kit, which is usually not costly. It’s hard to remove, but not impossible, or you may have to take the head to a machine shop if it’s damaged.

How to Start a Car with a Blown Head Gasket?

Watch this video to see a few actions to take if you are trying to start your car with a blown head gasket.


Head gasket failure can be prevented by avoiding overheating of your engine. Check the radiator and coolant overflow tanks whenever you check your oil level. Add coolant as required, and immediately check for any mysterious fluid loss. Check hoses of the radiator for splits or frays, and replace it at the first sign of damage.

Also, check for leakage of fluid under your vehicle and any strange smoke. Note that symptoms of a blown head gasket will vary from vehicle to vehicle by the engine and the specific way the gasket failed. Note that the gasket may still fail in spite of your best efforts, you don’t expect it to last for eternity due to its construction and the environment.

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