Five-Layer Silicone Construction
The MMHOSE-GM-17U is constructed from five layers of high-grade silicone with embedded heat-resistant fibers. This reinforced design improves resistance to temperature, pressure, cracking and age-related hardening.
Key features include:
- Five-layer reinforced silicone
- Heat-resistant embedded fibers
- Maximum temperature rating of 330°F
- Molded factory-style routing
- Black finish
- Two worm-gear clamps
- Mishimoto Lifetime Warranty
Hose Dimensions
The hose uses different diameters at its two ends to match the intended radiator and thermostat-housing connections.
| Specification | Measurement |
|---|---|
| Inside diameter | 1.18–1.54 inches |
| Outside diameter | 1.57–1.93 inches |
| Maximum temperature | 330°F |
| Material | Reinforced silicone |
| Color | Black |
Measure modified or aftermarket connections before ordering. Radiator manufacturers occasionally relocate or resize the upper inlet, because apparently keeping a 40-year-old truck simple was unacceptable.
What’s Included?
The package includes:
- One black silicone upper radiator hose
- Two worm-gear hose clamps
This listing is for the upper hose only. It does not include the lower radiator hose, heater hoses, bypass hose or overflow hose.
When Should the Upper Radiator Hose Be Replaced?
Replace the hose if you notice:
- Cracking near either connection
- Swollen or unusually soft areas
- Coolant stains around the clamps
- Abrasion from a fan shroud or accessory
- A hardened hose that no longer flexes
- Steam or coolant spray
- Persistent coolant odor
- Falling coolant level
- Engine overheating
Use our coolant-leak diagnostic guide if the source is difficult to identify. Small pressure-dependent leaks may leave dried residue without producing an obvious puddle.
Installation Notes
Never remove the radiator cap from a hot engine. Wait until the cooling system is completely cold.
A typical installation involves:
- Confirm the radiator and engine configuration.
- Drain enough coolant to lower the level beneath the upper hose.
- Remove the old clamps and hose.
- Clean the radiator inlet and thermostat-housing neck.
- Inspect both connections for rust, cracks or distortion.
- Compare the new and original hose shapes.
- Install the hose without twisting or stretching it.
- Position each clamp behind the raised connection bead.
- Refill with the correct coolant mixture.
- Bleed trapped air from the system.
- Bring the engine to operating temperature.
- Inspect both connections for leakage.
- Recheck the coolant level after the engine cools.
Don’t overtighten the clamps. Excessive force can damage an aluminum radiator neck, distort the hose or cut into the silicone.
If the coolant is old or contaminated, follow our cooling-system flushing guide during installation.
Inspect the Entire Squarebody Cooling System
A new upper hose cannot repair a clogged radiator, weak pressure cap, failing water pump or incorrect fan setup. Inspect the complete system while the coolant level is lowered:
- Lower radiator hose and anti-collapse spring
- Radiator core and tanks
- Fan shroud
- Mechanical fan and clutch
- Thermostat
- Water pump
- Heater hoses
- Overflow hose and reservoir
- Drive belts
- Radiator cap
Our complete car cooling-system guide explains how these components work together.
For an overheating truck, also review:
- Why a vehicle overheats while driving
- Seven signs of a failing radiator
- Bad thermostat versus bad water pump
- How to deal with overheating
- Can radiator stop-leak cause damage?
- When should you stop driving?
Frequently Asked Questions
What vehicles does MMHOSE-GM-17U fit?
It fits select 1978–1986 Chevrolet and GMC C/K trucks using the 305ci 5.0L or 350ci 5.7L V8 and the matching original-style radiator arrangement.
Does it fit a Chevrolet C10?
Application catalogs list compatible 1978–1986 Chevrolet C10 configurations with the 305 or 350 V8. Verify the radiator inlet, thermostat housing and hose dimensions.
Does it fit a GMC C1500 or K1500?
Yes, on listed 1978–1986 configurations equipped with a compatible 5.0L or 5.7L V8 cooling system.
Does it fit a 454 big-block?
No. The listed application is limited to the Chevrolet 305 and 350 small-block V8 engines.
Does it fit an LS-swapped C10?
Not automatically. LS swaps use different water-pump outlets and custom radiator arrangements. Select hoses according to the installed cooling system.
Is the lower hose included?
No. MMHOSE-GM-17U is an upper radiator hose. The lower hose is sold separately.
Are clamps included?
Yes. Two worm-gear clamps are supplied.
Will it work with an aluminum radiator?
It may fit a direct-replacement aluminum radiator with factory-style inlet placement and diameter. Measure custom radiators before ordering.
Does a silicone hose lower engine temperature?
Not directly. It creates a durable coolant connection with better heat and pressure tolerance. Actual operating temperature is controlled by the cooling system as a whole.
Product Specifications
| Specification | Details |
|---|---|
| Brand | Mishimoto |
| Part number | MMHOSE-GM-17U |
| Product type | Upper radiator hose |
| Color | Black |
| Material | Five-layer reinforced silicone |
| Inside diameter | 1.18–1.54 inches |
| Outside diameter | 1.57–1.93 inches |
| Maximum temperature | 330°F |
| Clamps | Two included |
| Engine fitment | 305ci 5.0L and 350ci 5.7L V8 |
| Vehicle range | Select 1978–1986 GM C/K trucks |
| Warranty | Mishimoto Lifetime Warranty |
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