What Size Silicone Heater Hose Do You Need?
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Table Of Contents
Heater hose size refers to the inside diameter, not the outside. Before ordering, check the hose size your vehicle requires and the connections at both ends.
Mammoth's silicone heater hose comes in five inside diameters: 3/8, 1/2, 5/8, 3/4 and 1 inch. It is sold by the foot, so a quantity of 10 means 10 feet of hose.
Start with the size your vehicle needs
Check the vehicle's service information or the size marking on the original hose first. Don't choose a size just because it is common on another truck.
If you need to measure, let the engine and cooling system cool completely before working on a hose. Follow the vehicle's instructions for draining coolant and removing the hose safely.
For a plain slip-on connection, measure across the outside of the fitting where the hose sits, behind any raised bead. Use calipers if you have them. Compare that measurement with the specified hose size rather than measuring the outside of the old hose, which includes the wall thickness.
Check both ends. If the fittings differ in size, the hose has molded bends, or it uses quick-connect ends, don't assume straight bulk hose is a direct replacement. Confirm the correct replacement before ordering. If your measurement falls between sizes, recheck it instead of forcing a fit.
Mammoth silicone heater hose sizes
These are the inside diameters and metric equivalents listed on Mammoth's product pages:
All five sizes are listed in black, blue and red. Size alone does not establish vehicle fitment. Check the application and connection style too.
How much hose should you order?
Measure the length needed along the original hose route, including the sections that fit over the connections. Allow enough length to trim the ends without leaving the installed hose stretched or kinked.
Mammoth sells this hose in one-foot units:
- Quantity 1 = 1 foot
- Quantity 5 = 5 feet
- Quantity 10 = 10 feet
Round your required length up to the next whole foot. The product listing says up to 250 continuous feet are available in one roll. If your project depends on receiving one uninterrupted length, confirm that requirement before ordering.
Choose clamps separately from hose size
Hose size is the inside diameter. Clamp size is based on the outside diameter of the hose at the installed connection. Those are different measurements.
Use the clamp type specified for the hose and application, and make sure its stated range includes the installed hose's outside diameter. Follow the clamp manufacturer's tightening instructions rather than guessing at a torque setting.
Our hose clamp size guide explains the measurement.
What is this heater hose intended for?
Mammoth lists its reinforced silicone heater hose as suitable for hot coolant and heater applications. This guide covers that use. It does not establish suitability for fuel, oil, transmission fluid or other fluids.
Before you buy, check the size, connection style, routing and application requirements. Then select your hose diameter, color and quantity on the silicone heater hose page.
Frequently asked questions
Is 16 mm the same as 5/8 inch?
Mammoth labels its 5/8 inch hose as 16 mm. Use the hose size specified for your application; the metric labels in this guide follow Mammoth's listings.
Can I measure the outside of my old hose?
Not to identify its inside diameter. The outside measurement includes the hose wall. Check the marked size, vehicle information and fitting instead.
Does quantity 10 mean ten separate one-foot pieces?
Quantity 10 orders 10 feet. If you need it in one piece, confirm that requirement before ordering.
Will any 5/8 inch heater hose fit my truck?
Diameter is only part of the fit. Check both connections, the route and the vehicle's requirements before replacing a molded hose or an assembly with straight bulk hose.
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