How much does it cost to repair a car immersion heater?

Car immersion heaters, often found in diesel engines, are essential for ensuring reliable cold starts and smooth engine operation. 

When these components fail, it can cause hard starting, rough idling, or pesky engine warning lights. You should get these looked at as soon as possible!

In this article, we’ll break down immersion heater repair costs to help you plan and avoid more expensive engine issues in 2026 and further down the line.

How much does it cost to repair a car immersion heater?

The cost of repairing a car immersion heater in the UK ranges from £60 to £350. These depend on the vehicle make, the type of heater, and the extent of the repair required. 

On average, minor repairs such as replacing a single glow plug or element can be relatively inexpensive, while full heater replacements or electrical maintenance may cost more.

Here’s a breakdown of typical immersion heater repair costs for cars in 2026:

For most repairs, you can use car repair finance to spread the cost into manageable repayments, helping you get your vehicle back on the road without a large upfront expense.

Immersion heater repair vs replacement

Deciding whether to repair or replace your immersion heater depends on the severity of the fault. Here are the main determining factors:

• Minor wear or single-element failure: Usually repairable by replacing the affected glow plug or heating element.
• Multiple failures or age-related wear: Full replacement is often more cost-effective in the long run, reducing the risk of further engine problems and improving reliability.

Modern heaters are also more efficient, so replacement can sometimes improve cold-weather performance and fuel efficiency.

Key factors affecting immersion heater repair costs

As shown in the table above, several elements influence how much you’ll pay for repairs. Alongside the type of repair needed, you should keep the following factors in mind:

• Vehicle make and model: Some diesel engines use more complex heater systems, increasing labour and parts costs.
• Parts quality: OEM parts are more expensive but offer greater reliability than aftermarket options.
• Labour rates: Workshop charges differ across regions and depend on mechanic expertise. London and the South East tend to be more expensive.
• Extent of damage: Electrical faults or related engine issues can raise costs.

How long does an immersion heater repair take?

Repair times can vary based on the vehicle and the type of heater that needs fixing. Your chosen garage will provide an accurate timeline.

However, typical averages are:

• Single element replacement: 30 minutes to 1 hour
• Full immersion heater replacement: 1 to 2 hours
• Electrical wiring or multiple-element repairs: 1 to 3 hours

Signs your car immersion heater needs repairing

Early detection of immersion heater issues can prevent costly engine damage. Five main signs can signal this issue.

Look out for:

• Hard starting, particularly in cold weather
• Rough idling or engine misfires
• Engine warning lights or fault codes
• Reduced diesel engine performance
• Unusual smells or smoke on start-up

If you notice any of these, it’s time to call the garage. Prompt repair ensures your car remains reliable, especially during colder months when diesel engines rely heavily on immersion heaters for smooth starts.

DIY vs professional repairs for immersion heater issues

While replacing a single glow plug might seem simple, there are risks if you go through the DIY route.

Diesel immersion heaters are high-current devices, so DIY repairs can be dangerous and may also void your warranty or affect insurance coverage. 

Having a professional mechanic perform the repair ensures proper installation and reduces the risk of further engine damage, making it the safest option for most drivers.

How to reduce your car immersion heater repair costs

Regular maintenance is important to keep your diesel engine running smoothly and avoid costly immersion heater repairs.

Here’s how to manage costs:

• Schedule routine diesel engine checks before winter to keep everything working properly.
• Fix minor heater issues promptly to avoid more costly problems.
• Use certified garages or Bumper’s trusted network for reliable repairs.
• Inspect block heaters and glow plugs to prepare your diesel engine for winter.

When to consider full immersion heater replacement

If your heater has multiple failed elements, persistent electrical faults, or is over 8 to 10 years old, full replacement may be the most cost-effective solution.

Modern units also provide better durability and improved start-up reliability. But you should always consult a professional mechanic before making a final decision about your vehicle.

Can you drive with a faulty car immersion heater?

Driving with a faulty immersion heater is possible, but cold starts may be difficult and general engine performance may suffer.

Repeated use could cause further damage and more expensive repairs, so it’s best to avoid driving where possible. Prompt repair is recommended for safety.

Will a broken immersion heater fail an MOT?

A broken immersion heater alone is unlikely to cause an MOT failure unless it affects emissions, engine starting, or other critical components.

However, it should still be repaired to ensure reliability and on-road performance.

Last thoughts

Knowing the general immersion heater repair costs and recognising early warning signs is essential for diesel engine reliability. 

Minor element replacements can be relatively inexpensive, while full heater replacements or electrical repairs may require a larger budget. If you’re unsure, contact a trusted garage for a professional assessment.

Split the cost with Bumper 

Fix your car’s immersion heater today. Consider a car repair loan to split the repair or replacement cost into interest-free repayments.

Apply online for up to £5,000 and choose from 1,000s of trusted repairers.