How To Install Silicone Fibreglass Heat Sleeve
Posted by Matthew Marks on 17th Aug 2025
Pop the bonnet after a spirited drive and you'll quickly feel just how intense the heat inside your engine bay can get. Hoses, fuel lines, and wiring are exposed to that heat every time you drive, and over time, it can shorten their life or even cause failures.
One of the simplest ways to protect these vulnerable parts is by fitting a silicone-coated fibreglass heat sleeve. This heat sleeve is rated up to 1200°C intermittent, which makes it perfect for lines close to an exhaust manifold or turbocharger housing.
In this guide, I'll walk you through the installation process step by step and share tips from my own experience fitting sleeves on our turbo AWD Civic.
We'll also cover how to choose the right size, the best way to finish and secure the ends, and some troubleshooting advice. Think of this as your one-stop reference for installing heat sleeves the right way.
We have just filmed a quick and easy installation video on our YouTube Channel, which I'll add below (make sure to subscribe), but if you would rather a bit more depth, then keep reading!
Why Bother With a Silicone Heat Sleeve?
A silicone heat sleeve isn't just about looks. The fibreglass core is designed to handle extreme heat, while the silicone coating adds a clean finish and, more importantly, a strong, flame-retardant outer coating.
Together, they form a flexible barrier that shields your hoses, wiring and other parts from the high temperatures coming from exhaust manifolds, turbos, and other hot components.
When I fitted one to my oil feed line that runs uncomfortably close to the turbo, the difference was immediate.
Temperatures on the line dropped, even to the touch, enough that I no longer worried about the line melting. In anything modified and running more boost than standard, as I'm sure you probably already know, the temperature skyrockets from any of the parts in the engine bay.
Just as importantly, the silicone sleeve looked much neater than before, and stayed in place through repeated heat cycles.
Choosing the Right Size
Getting the right size is crucial, and it's where many people go wrong.
The sleeve needs to slide on smoothly but still grip tightly once installed. The best method is to measure the outside diameter of your hose at its thickest point and then choose a sleeve that is about 2-5mm larger.
The extra clearance makes installation easier, especially if you need to guide it over fittings or bends, without leaving the sleeve baggy once it's in place.
For example, an AN06 nylon braided hose is typically around 14 mm in outside diameter, so a sleeve in the 15mm range will fit perfectly (which is the exact size we used in our installation video below!)
A standard AN06 rubber push lock fuel hose has an OD of about 16mm, so a 20mm silicone heat sleeve is a safe choice. If you're trying to sleeve a hose that already has bulky banjo bolts or AN fittings assembled, then size for the biggest part and secure the ends properly afterwards.
If removing fittings isn't possible, or the silicone sleeve will be too large, then, depending on how close it is to a direct heat source, a Velcro heat sleeve may be a better option.
1. Preparing for Installation
Tools / Parts Needed:
- Sharp Scissors
- Tape Measure
- Vernier Gauge
- Silicone Heat Sleeve
Optional:
- Masking Tape
- Microfibre Cloth
- Heat Shrink
- Heat Gun
- Stainless Steel Cable Ties
Before you start, lay out your tools and make sure the hose you're sleeving is completely clean and dry. A quick wipe with a microfibre cloth works perfectly to make sure you have no oils or residue of anything on the hose or wiring.
If the sleeve catches on the hose as you slide it on, wrapping the hose end with a bit of masking tape creates a smoother surface to guide it into place (as seen in our video). This will stop the end of the hose from fraying out and catching on the fibres of the heat sleeve.
I always recommend cutting the sleeve slightly shorter than the hose itself—about 20mm. This gives you some leeway when positioning and ensures both ends are fully covered. Cutting can be done with sharp scissors, nice and easy!
2. Fitting the Sleeve
Slide the silicone heat sleeve carefully over the hose or wiring, making sure it sits evenly in the middle with a small gap at either end. It doesn't need to be forced—if you've chosen the correct size, it should move with a firm but manageable grip.
Take your time here; rushing often leads to snags, especially on braided hoses. Providing you have measured correctly, though, it should slide over nicely.
Once it's seated, adjust the sleeve so it looks uniform, with no twists or bunches. At this point, the protection is in place, but to keep it secure for the long term, you'll want to finish the ends properly.
3. Securing the Ends
This is the step that separates a rough job from a professional-looking install.
There are several ways to finish the ends, and the best choice depends on your preference and the environment in which the hose will be used.
- Stainless steel zip ties are the simplest option. They're strong, completely heatproof, and won't loosen with vibration. Just tighten them snugly and trim the tails flush.
- Heat-shrink end collars give the most OEM-style look. These are separate pieces that slide over the sleeve ends and shrink tight when heat is applied. You can easily cut this to size to get the look you want.
Whichever method you choose, make sure the finish is secure. The ends are where sleeves most often fray or slip, so taking the time to get them right pays off.
4. Inspecting and Maintaining
With the sleeve in place, step back and inspect your work. The sleeve should look smooth and consistent, and the ends should be tight with no gaps. After the first heat cycle, check again to ensure nothing has shifted.
Maintenance is simple but essential.
At each oil change or once a month if you're driving hard, give your sleeved lines a quick visual inspection. Look for damage by loosening the cable ties or by sliding the sleeve back slightly to check the hose or wiring underneath.
It's a simple habit that helps spot issues before they become expensive failures. Even with the highest temperature sleeve available, you can still have deterioration due to voltage issues/ quality of wiring or the hose used underneath the sleeve itself.
Extra Tips
Over time, we've picked up a few tricks that make installation easier and cleaner. If you're running multiple small lines or hoses together, bundling them and sliding a larger sleeve over them creates a much tidier look.
If the sleeve has to pass through a bulkhead or a sharp edge, adding a rubber grommet or edge trim prevents wear. This is an important one to note, as we actually had a customer install a fuel line through a bulkhead without a rubber grommet, and over time, it rubbed through and leaked fuel everywhere.
Always try to protect the lines as much as possible. Even if he had a silicone heat sleeve on the line, he would have saved the line, but it's always best to add as many safety features as you can.
Common Issues and Troubleshooting
Sometimes things don't go to plan, so here are answers to the most frequent issues:
- If the sleeve snags badly on the braid, use masking tape or a chamfered cut edge to guide it through.
- If it won't pass a bulky fitting, either size up or consider a Velcro heat sleeve.
- If the silicone coating scuffs during routing, don't panic—it's usually cosmetic unless the fibreglass is exposed.
- If petrol or other fuel drips onto the sleeve, wipe it immediately. The coating resists brief exposure but isn't designed for long-term fuel immersion.
Personal Takeaways
The first time I tried fitting a heat sleeve, I worried it would be fiddly and frustrating.
In reality, with the proper prep, it was much simpler than expected. The silicone coating made it easy to handle compared to raw fibreglass (no mega itching hands), and once the ends were secured, the result looked clean and stayed put.
The most important thing I have learnt is that carefully measuring and making sure the heat shrink is on correctly makes all the difference between a sleeve that performs well and one that doesn't.
Conclusion
Installing a silicone-coated fibreglass heat sleeve is one of those upgrades that gets you big results.
It protects your hoses and wiring from high engine bay temperatures, extends their life, and tidies up your engine bay in the process. The process is incredibly straightforward, and once you've done one, you will understand why everyone uses silicone heat sleeves.
If you want to protect your hoses, fuel lines, or wiring from engine bay heat, a silicone heat sleeve is one of the best products. Explore our full range of heat sleeves and give your build the protection it needs.