Engine Overheating

An overheating engine can spell disaster for your vehicle and for your wallet too, so recognizing the symptoms early can help you to resolve the problem before further damage occurs and could possibly save you from being hit with a nasty repair bill.

However, while many overheating issues can lead to a serious issue such as a blown head gasket, some are quite minor and can be resolved without the need for major work or costly repairs.

Here we have attempted to list and explain a few of the most common causes to help you to diagnose and choose the best cause of action for your issue.

Before we begin, how can we know if our engine is overheating in the first place?

  • One of the most obvious signs will be the temperature gauge on your dashboard rising into the red or significantly above the normal range, or the displaying of a warning light.
  • Although it is normal for the hood to become hot to the touch, an extremely hot hood is a sure sign that the vehicle is overheating. As a very rough guide, if you can’t comfortably hold your hand on there for around 10 seconds then you have a good indication that there is excessive heat being produced from the engine.
  • If there is steam coming from the hood, then there is almost certainly overheating occurring. This will generally be caused by the boiling of coolant which is turning to steam and escaping from the cooling chambers.
  • If your car ‘smells hot’ then there is a good chance that something is not functioning as it should. This could be the result of the engine overheating and starting to heat up the various parts, seals, fluids and oils within the engine which start to give off an odour that is often described as smelling ‘hot’.
  • Any unusual noises coming from your engine are not something to ignore and should be checked out. Ticking or thumping noises can be signs of overheating and can point to several possible causes. We would always recommend getting these issues fixed immediately to avoid further serious damage such as a blown head gasket. Issues resulting in disruption in flow of coolant, often as the result of a faulty thermostat, may cause the coolant to become super-heated and may result in knocking sounds as hot and cold coolant attempt to mix. When oil heats up it loses the ability to properly lubricate the engine and ticking noises may be heard as the unlubricated parts move against each other.
  • A reduction in engine performance may result from overheating and should be checked out as soon as possible, particularly if it happens in the presence of any of the other above signs.

If you see any of these signs of engine overheating then we would recommend stopping the vehicle immediately, but of course in a sensible way and safe location and following the steps listed at the end of this article.


Your engine is designed to function at an optimal temperature, it’s ‘standard operating temperature’. Generally, this is a range somewhere between 90 to 105 degrees C (195 to 220 degrees F). Any prolonged increase above this temperature is likely to have catastrophic results for your vehicle because certain engine components can simply not withstand high temperatures for long periods of time.

Therefore, it is important not to ignore any signs of overheating. What may start as a faulty thermostat or leaking hose, which can be easily replaced, may end in a blown head gasket and a potential repair bill in the $1000’s. The good news is that there is often time the remedy the situation before permanent damage occurs. Examine your symptoms and if necessary, seek the services of a professional mechanic, it may be that your problem is an easy and cheap fix.


Detonation (Engine Knock or pinging)

Put simply this is the spontaneous combustion of fuel within the cylinders and although there are several factors that can cause this, overheating is certainly one culprit. The engine will rattle, knock or ping and you will likely notice a loss of power. Left unchecked this may cause damage to the seals, rings, pistons or rod bearings causing further damage to your engine.

Head Gasket Failure

Also known as a ‘blown head gasket’, this is a serious failure of a crucial component within your engine for which you will traditionally most likely be handed a large repair bill. Thermal stresses can lead to distortions in the cylinder head, cause pistons to expand and seize and the gasket to crack or ‘blow’. This can lead to compression loss, the mixing of coolant and water, coolant leaks and further overheating. Ultimately, a blown head gasket is a serious issue that if left untreated will see your vehicle off the road.

Traditionally the only option was the replacement of the head gasket. Although the intrinsic cost of the head gasket part itself is extremely cheap, the work involved is very labour-intensive and this inevitably leads to high repair bills. This option is of course the recommended approach and if the vehicle of the owner can afford the job, we would always advise having the work carried out by a professional. However, if either the job is unaffordable or if the vehicle is not of high enough value to justify the repair then pour-in sealants such as Steel Seal are a fantastic alternative for a fraction of the cost.

Scuffed Pistons

As with any metal component, the parts of an engine will expand when heated. This expansion is taken into account when designing an engine, however temperatures exceeding the normal operating range may expand parts beyond their tolerances. This often affects the pistons in particular where expanded pistons begin to make contact with the walls of the cylinder causing scuffing and worn patches. Over time this may lead to piston failure and possibly other serious damage to the engine.

What Steps Should You Take if You Suspect Overheating?

If the hood is very hot or there is steam billowing out, we would recommend leaving it to cool for a few minutes and taking care when opening the hood. The same applies when removing the radiator cap or the cap from the expansion vessel to inspect for low coolant. If there is pressure built up from the heated and expanded coolant there is a danger of this being blown out of the system and causing burns, so always wait until the engine has cooled and remove with caution.

Check for any obvious signs of damage and wear such as coolant leaks and check your coolant levels. If the levels are low refill with coolant and monitor vehicle temperature and levels over the next journey or next several journeys.  If coolant is dirty flush the system and replace the old coolant with fresh coolant. Make sure when examining for a coolant leak that all parts are checked including hoses, water pump, thermostat, radiator and fan.

Of course, if you are not confident in doing these checks or you think the symptoms are very bad you can always take the vehicle to a qualified mechanic for a professional diagnosis. They will hopefully tell you that the issue is simply fixed, however if they tell you that you have a blown head gasket then you can of course consider Steel Seal as an alternative to the likely costly repair.

There are also general maintenance checks that should be carried as standard. These include things such as checking and replacing old and dirty oil. Oil should always be replaced regularly in line with manufacturers guidelines.

Finally, if a visual check fails to identify the source of the problem then a combustion or pressure test can be carried out. These tests are designed to diagnose if you have a leak in the system and are losing pressure, or will show the presence of combustion gases in your cooling system, often the signs of a blown head gasket.

Checklist for Diagnosis of Overheating

Below we have compiled a short checklist of the most common causes and points to consider when attempting to diagnose overheating.

Blocked Radiator

Any blockage within the radiator will restrict the flow of coolant and as a result you may potentially see a rise in engine temperatures and subsequent overheating. This blockage could be the result of all sorts of debris such as general dirt, bugs or dirty coolant. Be sure to visually check the front of the radiator to make sure that it is not blocked or clogged in any way as well as the state of coolant. You can also get an idea whether the radiator may be clogged by feeling the top and bottom radiator hoses, if the temperatures are not around the same temperature the radiator may be clogged. As always, be careful when touching any potentially hot parts of the engine.

Low Coolant

A common cause for engine overheating, and the simplest to remedy is a low coolant level. This may not necessarily indicate a coolant leak, but if coolant is topped up make sure to keep an eye on levels over the coming days and weeks and if levels continue to drop then further investigation is necessary.

Cooling System Leak

Another common cause of overheating is a leak in the cooling system. Any leak in the system will reduce the coolant level and pressure within the system resulting in a reduced capacity for coolant flow. If the coolant cannot circulate to do its job, then overheating will inevitably occur.

There are many points at which a leak is likely including hoses, radiator, water pump or head gasket. If the leak is external you may be able to identify the damages area through a visual inspection or even see a puddle of coolant form underneath your vehicle. An internal leak will not cause a puddle to form and will not noticeable via a visual inspection and may suggest a blown head gasket. If you notice the need to top up coolant without visible signs of a leak it would be advisable to have a mechanic diagnose your problem, carry out a block test to test for combustion gases.

Read more about this issue in our article on Coolant Loss.

Faulty Thermostat

The job of the thermostat is to regulate coolant flow and in turn the temperature of the engine. At a given temperature the thermostat will open and allow coolant to flow reducing engine temperature when required. As such, any fault or damage to the thermostat may lead to overheating and any subsequent problems.

Radiator Pressure Cap

If you suspect that the cap of the radiator or surge tank is the source of the leak it may be worth replacing this, as this can be replaced at little cost.

Faulty Radiator Fan

As you would expect, the function of the fan is to provide cooling to the engine and therefore to maintain the correct engine temperature by removing excess heat from the coolant. The fan may cease to work for several reasons, mostly down to wear but also due to an electrical fault such as a sensor, but if it fails to come on when it should you will need to replace this component, or in the case of a sensor fault this will need to be replaced. If you are checking for a fault in the fan by running the engine it is of course important not to let the car overheat while doing so.

Faulty Water Pump

Like many problems that can occur within the cooling system, if coolant cannot circulate correctly then overheating and engine damage is inevitable. A faulty water pump is a common cause of overheating and may be caused by damage to the pump or simply by becoming old and worn out.

Low Oil Level or Dirty Oil

Although you may think of the main role of your oil being to lubricate the engine, it’s role in cooling is also an important one. Oil can act both directly as a cooling agent, but also reduces friction and heat through the correct lubrication of moving parts.

Be sure to check your oil levels regularly and top up when needed. Changing your oil at regular intervals is also essential as old or dirty oil will become less effective at both lubrication and the dissipation of heat.

Faulty Coolant Sensor

Modern vehicles make use of multiple sensors to regulate the correct working of parts and to notify you when there may be a fault, and a faulty coolant sensor may indicate that overheating is taking place. In this case there may be no further issue at all and the sensor simply requires replacing.

Other Causes

Above we have listed the main reasons that you may experience engine overheating, however there are a few other causes that such as stuck valves, sticking brakes or simply overworking your engine.

What is the Solution?

Firstly, if you do suspect overheating in your vehicle, don’t ignore the signs. Catching the problem early may be the difference between replacing a cheap part like a hose or a critical and expensive repair like a blown head gasket. Follow the steps above and if in doubt, seek the assistance of a professional mechanic. Once diagnosed the problem should be rectified as soon as possible and the problem part fixed or replaced.

Overheating and Steel Seal

If a blown head gasket or cracked block is suspected as the culprit for the overheating, then Steel Seal could be the solution. Certainly, if the price of the work is not an issue or if you feel that the vehicle is of sufficient value to have a replacement then this is your best option. However, when the repair is simply not an option due to cost, or if the cost of the repair is near to or even more than the cost of the vehicle itself, then a bottle of Steel Seal is a fantastic alternative.

Remember however, that an overheating engine is certainly a sign that your vehicle may have a blown head gasket, however it is important to remember that head gasket failure is often a symptom, not the cause of overheating. The original source of cooling system failure, if still present, must therefore be repaired before attempting to repair your vehicle with Steel Seal.

This is why we recommend before going ahead and attempting to repair your vehicle with a sealant like Steel Seal, it is well worth ruling out a few other potential causes. After all, we want you to have the best possible success using Steel Seal, and if the head gasket or block is not the cause then Steel Seal is simply not going to help.

If you feel that your overheating problem may be the result of a blown head gasket then there is no sealer that is more effective than Steel Seal. If you require any more help with this issue, please feel free to call our tech team on 855-771-1972.