9 Symptoms and Signs of a Blown Head Gasket – Some Subtle


Below we’ll highlight all the possible symptoms of a blown head gasket. Some of them are quite subtle and won’t be obvious.

As a general rule, the nine bad head gasket signs are:

  • Loss of Engine Power
  • White Smoke From Tailpipe
  • Boiling Coolant
  • Coolant Loss Without Leaks
  • Rough Idle
  • Cylinder Misfire
  • Engine Overheating
  • Creamy On Dipstick
  • White Residue Filler Cap

Luckily, many signs taken in isolation will not have a blown head gasket as the cause.

However, the more symptoms you have together will increase the chances of your car’s head gasket being blown.

1. Engine Suffers a Loss Of Power

A sudden  – rather than a gradual – loss of power is a good indicator that your head gasket has failed. The suddenness is caused by a rapid lack of compression within the engine occurring, especially if your car has shown signs of overheating. 

Worn rocker cover gasket

Is the temperature gauge on the dash in the red? You need to stop immediately. 

Other reasons that your car may have lost power are 

  • Clogged air filter
  • Clogged oil filter
  • Dirty spark plugs
  • Bad fuel injectors.

The above are easy fixes.

If the only symptom your car is experiencing – out of the nine we discuss – is a loss of sudden power, one of the above is likely the cause rather than your head gasket.

2. White Smoke Coming out from the Tailpipe

If your head gasket has blown, coolant will have leaked into the engine’s combustion chamber and been burned along with the fuel. This process causes white hue color to come from the exhaust.

The coolant burning causes a sweet smell and is noticeable even through the car’s AC.

Is the smoke thick? If so, this indicates a head gasket fault, I’m afraid.

white smoke exhaust blown head gasket

However, if there is no sweet smell or the smoke isn’t thick, there could be other reasons for the white smoke.

  • Is it just condensation? Moisture can settle in your car’s exhaust system – especially during the autumn or winter – and then be burned off through your tailpipe when the engine heats up. If the white smoke disappears after a few minutes of your car engine warming, it’s probably just condensation and nothing to worry about.
  • Bad fuel injectors 
  • The car’s ECU (Computer) has a fault, and it’s affecting your car engine’s timing.

Why Does My Car Smoke At High RPMs? Blue, Black or White [GUIDE]

3. Boiling Coolant  in the Reservoir or Radiator

This can be a good indication that your head gasket has blown. The coolant system is supposed to be a sealed liquid –water and coolant– circuit that’s now receiving pressurized air that should be contained solely within the head gasket. 

The escaped air can cause pockets within the cooling system and cause blockages. If the coolant can’t be circulated because of these blockages, the temperature will increase and cause bubbling. This is the water and coolant reaching and exceeding their boiling point.

Has your car been serviced recently? If so, the mechanic may have mistakenly let air into the system after he drained away your old coolant. 

4. Coolant Loss with No Leaks

If your head gasket is slowly getting worse, then it’s possible you haven’t noticed the other signs we discuss here. Not likely, though.

If the loss is gradual, it’s far more likely to be a leak you haven’t discovered yet than a head gasket issue. 

Check again if you’ve completed a visual check of your coolant hoses. Get a dry cloth and run it over the joints. Quite often, the underside of a hose will be damp. As your car warms up and the water pump fires into life, the amount of coolant leaking from that joint will increase.

Tighten the connection with a new hose clamp or get a new hose if it looks split or corroded.

If you don’t see any hose leaks, then it’s time to inspect the radiator cap. The radiator cap is also a pressure release valve. Its job is to 

  • Keep the coolant inside the radiator.
  • Allow pressure to be released if the cap detects too much of a pressure buildup.

Sometimes, the seals on the caps get corroded and don’t keep a tight seal on older cars.

When this happens, water and vapor can escape even when the pressure isn’t that high, and you notice a gradual decrease in the fluid level. 

When the car is cool, remove the radiator cap, check out the seals, and see if the spring inside is working and not getting stuck. If it is, it may be stuck open and leaking coolant. 

Radiator caps aren’t expensive. Average prices are $15 to $60 depending on the car brand and whether you buy aftermarket parts.

5. Creamy Build-Up Under the Oil Filler Cap

When the engine is cool, remove the oil filler cap and inspect it inside. Do you see a butterscotch/creamy goo? If so, that’s pretty maybe a bad sign.

It could indicate that the head gasket had blown and coolant was getting into the head. 

However, there is another cause for this. 

If you only drive short distances, you’re not giving natural condensation in the crankcase a chance to burn off, and as the vapor rises in the engine, it’ll show at the highest point of the engine, which is the filler cap. 

This is a normal situation and not one to be concerned about. If you are worried, consider changing the PCV valve, especially if your car is more than seven years old.

The PCV valve controls the emissions leaving your vehicle and directs them back to your engine to be burned again. If faulty, it can also affect the amount of water vapor being sent back to the engine.

6. Creamy Oil on the Dipstick

This is a more reliable indication of a head gasket problem. A creamy, oily mixture around the filler cap can indicate water vapor from condensation. However, creamy oil is more likely to indicate excess coolant getting into the engine and mixing with the oil. A sure sign the head gasket has blown.

7. Engine Overheating

Sometimes the head gasket being blown can make the engine overheat.

Other times, overheating by another cause can make the engine swell as the metal expands, resulting in the head gasket blowing. 

overheating engine caused by blown head gasket

In any case, as soon as you notice the needle going into the red, you need to stop the car and get it investigated.

Other reasons that could cause overheating are examined in detail here:

Often read next by other visitors: Complete Guide To Overheating – Reasons and Fixes

They include, 

If your car has few other indicators in this article, such as white billowing smoke or loss of sudden power, likely, your vehicle isn’t overheating due to a blown head gasket.

8. Rough Idle

Compression can escape from one cylinder to others within the engine when a head gasket is severely damaged.

This causes a rough idle because the affected cylinder needs all its compression to push down the cylinder.

Without this, it’ll sound rough and feel less smooth.

This, coupled with other symptoms highlighted above, will show how likely the rough idle is caused by the head gasket.

Don’t worry too much if you have no other symptoms, as there are many reasons why your car is rough, including 

  • Clogged Air Filters
  • Dirty Spark Plugs 
  • A Vacuum Leak
  • Defective Air Flow Ratio Sensor 

If you have no other head gasket symptoms check out our article Reasons Car Is Rough At Idle

You’ll be able to do many fixes yourself, and the parts are mostly inexpensive.

9. Cylinder Misfire

This can occur at idle and driving speed, so we’ve put it in its section here.

Although you should notice your car idling, it can be difficult for an inexperienced driver to know for sure.

However, there is no mistaking a car misfiring at speed. You’ll get either a loud bang from the exhaust that can sound like a gun being fired or a jerk forward as the car loses power before regaining it again a short time after. 

Many other factors can cause a misfire, and a blown head gasket isn’t likely to be the reason – unless you can say yes to the other symptoms above.

Other more likely and cheaper causes are 

  • Dirty Spark Plugs
  • A Cracked Distributor Cap
  • Catalytic Converter Blocked

We have a complete list of causes and fixes right here: Why A Car Feels Sluggish When Accelerating

A misfire – whatever the cause – won’t go away by itself. There is an underlying fault that needs to be tracked down and fixed.

Is it Safe to Drive a Car with a Blown Head Gasket?

You can drive with a blown head gasket, but you will cause further damage to your car’s engine. 

Continued driving can crack the engine block, completely blow the seals of the gasket cover and cause problems with other components such as the water pump. It’s advisable to stop driving.

How Much Does it Cost to Repair a Head Gasket?

A head gasket repair can cost between $600 and $2,500, with the average price being around $1,000. The parts are inexpensive; however, labor costs are high and make up a large percentage of the final bill.

For many drivers of older cars, it makes better financial sense to scrap the car and buy a new one instead. 

What’s the Best Temporary Fix for a Blown Head Gasket?

There are many sealants available that’ll provide respite for a few weeks. For most people, that’s all they need to do as it gives them time to arrange a repair or buy a new car.

The instructions follow the same script of getting the engine up to a specific temperature and pouring the bottle’s contents into the radiator.

The problem is that unless you’re sure what part of the block is affected, it’s difficult to know if they are a good idea or not. 

Some people report that it can get sucked into the compression chamber and cause further damage and a complete engine rebuild.

It may be better to get the advice of a mechanic before risking.

In Conclusion

The more symptoms you can say yes to below, the more likely your head gasket has blown.

Loss of power, white smoke from the exhaust, boiling coolant or coolant leaks, rough idle, engine overheating, and creamy oil on the dipstick.

It’s always a good idea to look for other causes first, as many symptoms have far more straightforward and cheaper fixes.

A temporary repair will only be that … quick, but at least it’ll give you the chance to organize a repair or buy a replacement vehicle.

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