cooling

Heater Hoses

for 1970 AMC Rebel Machine 390ci V8 · RWD

Difficulty

Easy

Time

1.2 h

Tools

Steps

✓Fact-checked. Built from OLP's spec database, then independently fact-checked line by line with every correction applied. Master-tech sign-off by Chris Hackleman is queued. Cross-check torque values against the factory manual, and stop if anything looks unsafe. How our data is made.

Replace deteriorated heater hoses on the 1970 AMC Rebel Machine 390ci V8 to restore proper coolant circulation through the heater core.

Warnings

⚠️Engine must be completely cold before starting this procedure. Hot coolant under pressure can cause severe burns.

⚠Ethylene glycol coolant is toxic to animals and humans. Clean up all spills immediately and dispose of used coolant properly.

ℹ️The 1970 AMC 390 V8 heater hoses route from the water pump and intake manifold to the firewall-mounted heater core connections.

Tools required

Flathead screwdriverEssential

Needle-nose pliersEssential

Drain pan (2 gallon minimum)Essential

Utility knife or razor blade

Wire brush

Shop ragsEssential

As an Amazon Associate and Autel/ANCEL partner, OLP earns from qualifying purchases — how we link. This never changes the specs we publish.

Parts

Heater inlet hose (5/8 inch inner diameter) × 1 — Use OEM specification
Heater outlet hose (5/8 inch inner diameter) × 1 — Use OEM specification
Hose clamps (screw type, 5/8-1 inch range) × 4 — Use OEM specification

As an Amazon Associate and Autel/ANCEL partner, OLP earns from qualifying purchases — how we link. This never changes the specs we publish.

Fluids

Engine coolant (ethylene glycol 50/50 mix) — 1 qt

Preparation

Ensure engine is completely cold to the touch
Place drain pan beneath radiator and open petcock or remove lower radiator hose to drain approximately 2 gallons of coolant
Locate heater hose connections at the firewall on passenger side and trace hoses forward to engine connections
Identify inlet hose (connects to water pump or intake manifold) and outlet hose (connects to heater core return)

Procedure

1
Access heater hoses at firewall
From the engine bay, locate both heater hoses where they pass through the firewall on the passenger side. These connect to the heater core valves. Note the orientation and routing of each hose before removal.
2
Remove firewall-side hose clamps
Using flathead screwdriver or needle-nose pliers, loosen the hose clamps at both firewall connections. If clamps are spring-type, squeeze tabs with pliers and slide back along hose. If screw-type clamps are rusted, cut them off with utility knife and replace with new clamps.
3
Disconnect hoses from heater core fittings
Twist each hose gently while pulling to break the seal and remove from heater core pipes at firewall. Expect residual coolant spillage. If hoses are stuck, carefully cut lengthwise with utility knife without damaging the metal pipes underneath, then peel off.
4
Remove engine-side hose clamps
Locate the engine connections for both heater hoses. The inlet typically connects to a fitting on the intake manifold or water pump housing on the passenger side. Loosen and remove clamps at these connection points.
5
Disconnect hoses from engine fittings
Remove both heater hoses from their engine-side connection points. The outlet hose typically connects lower on the engine block or water pump. Note any brackets or clips that route the hoses and remove as necessary.
6
Clean connection points
Use wire brush to clean all four hose connection points (two at firewall, two at engine) removing any old rubber, corrosion, or buildup. Inspect metal pipes for cracks or damage that could cause leaks.
7
Install new inlet hose
Route the new inlet heater hose from the intake manifold or water pump connection to the upper heater core pipe at the firewall, following the original path. Ensure hose does not contact exhaust manifolds or moving components. Push hose fully onto both fittings.
8
Install new outlet hose
Route the new outlet heater hose from the lower engine connection point to the lower heater core pipe at the firewall. Verify proper clearance from exhaust and belts. Push hose fully onto both fittings until it bottoms out.
9
Secure hoses with clamps
Install new hose clamps at all four connection points, positioning each clamp 1/4 to 1/2 inch from the end of each hose. Tighten screw-type clamps firmly but do not overtighten, which can cut into the hose. Clamps should be snug enough to prevent rotation of the hose.
10
Refill cooling system
Close radiator drain petcock or reinstall lower radiator hose. Refill cooling system with 50/50 coolant mix to proper level. Fill radiator to neck and overflow reservoir to cold fill line.
11
Bleed air from system
With radiator cap off, start engine and allow to warm up to operating temperature while monitoring coolant level. Add coolant as level drops during air purging. Run heater on high to circulate coolant through heater core. Squeeze upper radiator hose periodically to help release trapped air.

Reassembly

Reinstall radiator cap once system is fully bled and coolant level is stable
Recheck all hose clamp tightness after engine reaches operating temperature
Top off overflow reservoir to hot fill line if necessary

Verification

With engine at operating temperature, inspect all four hose connections for coolant leaks
Verify heater produces warm air inside vehicle when heater controls are set to heat
Check coolant level in overflow reservoir after engine cools completely, top off to cold line if needed
Recheck for leaks and coolant level after first drive cycle

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