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Common Mistral Boiler Problems & Repair Advice

Rob Wells
By: Rob Wells
Updated: 27th March 2024

Mistral boilers are very reliable

If you do need an engineer or are ever in any doubt at all, you should contact an engineer. With our service, you canrecieve free boiler repair quotes from reliable engineers near you.

Most common Mistral boiler problems

Smelling oil

You shouldn't be able to smell oil coming from your oil fired boiler, so you are then it probably means that oil is leaking somewhere. You should contact an OFTEC qualified engineer if this is the case.

Burner not starting

If your burner isn't running or starting at all then there's probably a block somewhere along the supply lines that's preventing fuel getting into the tank.

Smoke coming from the burner

Seeing smoke coming from your boiler will be very worrying and could happen for a few reasons such as the air supply being restricted, a build up of dust or the tank is topped up with the wrong fuel.

Radiators not heating up

You might find that not all of your radiators are getting hot or that only the bottom section is heating up. This can be down to a number of reasons but the two most common are sludge or air build up in the system and unequal distribution of heat.If only the bottom of your radiator is getting hot, you may need to bleed it. This is fairly straightforward and doesn't require an engineer (unless you don't feel able to carry out the task yourself).

Boiler losing pressure

It's important to keep an eye on your boiler pressure (you can do this by looking at the pressure gauge) because if it's too low then your central heating won't function properly. If the boiler pressure is below 1 your boiler probably has an issue, this can be caused by a water leak in the system, issues with the pressure relief valve, or because the radiators were recently bled.

Need a boiler repair?



Which Mistral boiler problems need a heating engineer?

If you're ever in any doubt about what's wrong with your Mistral boiler, get in touch with an OFTEC engineer as soon as you can but there are some faults you can resolve yourself. Use the table below to help you identify the possible causes of a problem your boiler is experiencing.

Problem Possible cause(s) Do you need a heating engineer?
No heat or hot water Broken diaphragms and airlocks, failure of motorised valves, issues with the thermostat or low water levels Yes
Leaking and dripping Most common cause is a broken internal component but it will depend where the water is leaking from Yes
Banging, whistling or gurgling noises A common cause is air in the system, alternatively it could be that the water pressure is too low or it's kettling Yes
Pilot light goes out Could be a broken thermocouple which is stopping the gas supply Yes
Losing pressure Could be a water leak in the system, the pressure relief valve needs replacing or due to recently bleeding radiators No, unless there’s a leak
No flame established (burner fault) Boiler failing to ignite or a nozzle is locked Yes
Thermostat issues Thermostat may be turned off or not set to the correct settings (time etc.) Consider replacing
Kettling Limescale or sludge building up on your boiler's heat exchanger Yes
Radiators not getting hot Sludge or air build up in the system or an unequal distribution of heat You will need to bleed the radiators which doesn't require an engineer unless you don't feel like carrying out the task yourself.
Smell of oil Oil is leaking somewhere from your boiler Yes

Mistral boiler warranty

Mistral's range of condensing boilers come with 2 years of parts warranty and 5 years on the heat exchanger. Get more familiar with their warranties by reading our complete guide to Mistral warranties.

A Mistral warranty will only remain valid if you hire a Gas Safe engineer to carry out an annual Mistral boiler service. Not only will this keep the warranty intact but also ensure the safe and efficient running of the boiler.

Boiler insurance and ongoing cover

Considering boiler insurance after your boiler warranty has expired is well worth doing. Many offer annual services and safety inspections, they're the ones you want to make a note of. While you could just take out boiler insurance with your energy supplier.

Is it time to replace your Mistral boiler?

If you've had your Mistral boiler for a number of years, then you might want to think about having a new one installed as you could be saving up to £300* a year in a detached home. The table below shows you how much you could be saving depending on your current boiler rating and property.

House Type G (less than 70%) F (70-74%) E (74-78%) D (78-82%)
Semi-detached £195 £140 £125 £110
Detached £300 £210 £165 £135
Detached bungalow £155 £110 £100 £90
Mid-terrace £170 £120 £105 £95
Mid-floor flat £80 £55 £50 £45

How to find the best installer to replace your Mistral boiler

When deciding who you'd like to install your new Mistral boiler, you will have the choice of a national company or local engineer. Both offer very good, yet very different benefits.

If you prefer service with a personal touch then a local engineer could be for you as you'll probably be in communication with the same person from start to finish. They'll also be able to offer pretty competitive rates which is always a bonus.

National companies might cost you a little bit more but you'll have big brand protection and they can provide extra services like ongoing boiler cover.

To make sure you're getting the best possible deal, it's always a good idea to get quotes from 3 engineers rather than just the 1.

Considering boiler insurance after your boiler warranty has expired is well worth doing. Many offer annual services and safety inspections, they're the ones you want to make a note of. While you could just take out boiler insurance with your energy supplier, there's no obligation for you to do so.

With our free service you can receive free quotes from trusted engineers near you, so send us an enquiry today.

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*According to the latest figures from the Energy Saving Trust

Rob Wells

About the author

Rob Wells

Rob is another of our resident home heating experts. He manages our external partnerships, making sure you get the most up to date information.

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