Ford Fiesta Engine Coolant Guide

Your Ford Fiesta engine generates a lot of heat while you're driving it. As all of the engine parts, such as the flywheel, pistons, valves and cams move, they create friction, which in turn generates heat. 

Some of these parts are lubricated with oil, which does help to dissipate some of that heat, but in order to dissipate it to the level where the engine can run safely without destroying itself, you need engine coolant.

In this article we’re going to go through everything you need to know about your Ford Fiesta’s engine coolant, including which coolant you need to buy and for which engine, how often you need to change your coolant, what you need to do if you think your engine is running too hot, and more.

What does engine coolant do?

As we’ve mentioned, engine coolant does what the name might suggest - it cools your engine. It’s not just as simple as that, however. Engine coolant is actually designed to regulate the temperature of your engine during extreme temperatures - hot and cold. This is why coolant is sometimes called antifreeze.

Engine coolant is usually mixed with water (although you can buy pre-mixed coolants) and this liquid is pumped through your car’s engine in order to regulate and create an optimal temperature during hot or cold. In short, it stops your car engine from overheating as well as freezing.

Coolant often comes in different colours, and while this used to be an indicator of the chemical makeup of the coolant, it no longer is - nowadays manufacturers have no need to make a certain type of coolant a certain colour, so it’s difficult for you to know exactly what coolant is in your vehicle by the colour alone. 

Be very careful with this, because some people still think the coolant colour dictates the type of coolant; for example, you likely have pink coolant in your Ford Fiesta - some people will just buy the first pink coolant bottle they see without looking at the chemical makeup. This can cause problems.

A guide to the correct coolant for your Ford Fiesta

Coolant generally comes in one of three different types - IAT (inorganic additive technology), OAT (organic additive technology) and HOAT (hybrid organic acid technology). IAT was generally used in older vehicles - so it won’t be applicable for your modern Ford Fiesta. OAT is generally pink, blue or orange. HOAT is a hybrid of both. 

Generally, modern Ford Fiestas will use a pink OAT coolant. Any OAT coolant will be fine - you do not need to purchase the coolant from Ford directly, and most motor factors or motor stores such as Halfords will always have this particular type of coolant in stock.

Checking and adding coolant to your car

To check your coolant, you need to open the bonnet. Your Ford Fiesta has a coolant expansion tank, which is an oblong shaped box on the left hand side of the engine. This expansion tank (sometimes called a header tank) will contain a varying level of coolant depending on the temperature of the engine. It will have a MIN and MAX line. 

In general, if the level is anywhere below the MAX line and even just a little bit below the MIN line, you do not need to top up your coolant. 

If the tank is dry, your coolant needs topping up. If your Fiesta has done over 100,000 miles, I would suggest draining and refilling the coolant as it is likely to need replacing. 

In order to add coolant, I would suggest that you leave the car until the engine is cold. The reason for this (and most coolant tanks will have a warning to this effect) is because you will get burned - the cooling system is pressurised and you will get a face full of boiling water. Engines take longer than you might think to cool down, so I’d suggest leaving it at least three or four hours after driving before trying to open the tank.

In order to top the tank up, simply use a funnel and pour the coolant in. If the tank is dry, the cooling system may need to be bled up, which we will discuss in the next section.

I’ve filled up my tank, but after driving, the tank is empty?

After filling the tank, you should leave the engine running and if possible take the car for a test drive. This will show you whether you have an air lock or not. Air locks are common when changing coolant and this is where air gets into the cooling system, preventing the header tank from filling up.

If this is your problem, you need to bleed up the system to get rid of any air. There are two ways of doing this on the Ford Fiesta.

Firstly, open the expansion tank and let the car idle for a few minutes until it warms up. Set the heater control inside as hot as it will go. When doing this you may notice the level in the expansion tank (if it isn’t completely dry) drop - this is perfectly normal and shouldn’t worry you, it’s as a result of the thermostat opening when the engine gets to temperature.

Watch the header tank, and eventually lots of bubbles will come out of the coolant. This is the cooling system bleeding itself up. Do not be tempted to touch anything inside the engine while this is happening - you will likely burn yourself. 

If this doesn’t work, you can try to bleed the system up another way - fill the tank with coolant and have the engine running. There is a thin pipe that clips to the radiator. You should pinch the two clips together, and pour coolant in until it starts to come out of the hole where the pipe is. This is very fiddly and sometimes it can be difficult to get all the air out - so my advice as a mechanic would be to try the first step a few times until your coolant level stays where you filled it and doesn’t drop if you leave the car overnight.

This is a common issue, and as a mechanic I have had to bleed up a car’s cooling system loads of times - particularly after we’ve done a timing belt and water pump change, for example. If you’re struggling, you might want to get a garage just to check your car over. Any mechanic will know how to get rid of an air lock.

Is it OK to mix coolant?

You should never mix different types of coolant, unless you are using a universal coolant which specifically says that it’s OK to mix with other coolant types. Mixing coolant that is not supposed to be mixed can result in an unwanted chemical reaction between the two coolants that can cause the coolant itself to become sludgy and viscous, which won’t be able to flow through your cooling system properly and will cause damage to your engine.

If you’re unsure about which type of coolant to put in your car, consult a local garage - however the Ford Fiesta uses an OAT coolant, so if you’re just topping up your coolant tank, you won’t have any issue using any OAT coolant to do this.

Can I use water instead of coolant?

There are two situations where you might want to use water instead of coolant. One is if you are changing your Fiesta’s water pump, and you just want to ensure that there are no leaks before you build the car back up. There’s no point using good coolant for this because you’ll need to flush it out later. 

The second situation is where you have a coolant leak and you are driving - where you might not have coolant available. In this case it’s OK to fill the header tank with water just to get you to a garage - it is not a permanent fix and as soon as your cooling system is repaired you should use proper coolant.

Some say that it’s OK to use water in the summer months and switch to antifreeze in the winter months - this is not recommended, as antifreeze is not just to stop the engine freezing up, it’s also to keep the engine cool when it gets hot, which coolant will do a much better job of than water.

Can you mix old and new coolant?

Generally, yes, it’s fine to mix old and new coolant in your Ford Fiesta providing the old coolant isn’t past it - the original coolant will last anywhere between 75k - 100k miles so as long as you’re before that you are fine just to top it up. If your coolant is a rusty brown colour, you might consider draining and refilling the coolant rather than just topping it up.

Check out some more of our articles on the Ford Fiesta!