Removal of elements of the exhaust gas recirculation system UAZ-3151, -31512, -31514, -31519

The system consists of a recirculation valve with a diaphragm, a thermo-vacuum switch and two hoses.

Diagram of the exhaust gas recirculation system: 1 — hose from the thermo-vacuum switch to the recirculation valve; 2 — hose from the thermo-vacuum switch to the carburettor; 3 — carburettor; 4 — thermo-vacuum switch; 5 — cylinder head; 6 — exhaust manifold; 7 — intake pipe; 8 — recirculation valve; A — with a cold engine; B — with the engine warmed up to a coolant temperature of 40 °C, at partial loads.

One hose connects the switch to the space above the carburettor throttle; while the engine is running, a vacuum is created in the hose.

The other hose leads to the switch from the recirculation valve.

As the engine warms up, the thermo-vacuum switch valve opens and passes the vacuum to the recirculation valve, opening it.

Part of the exhaust gases is drawn through the bypass port into the intake manifold and burns in the engine cylinders, which reduces the toxicity of the exhaust gases.

Removal of the recirculation valve and thermo-vacuum switch

Drain the coolant from the engine cooling system.

Disconnect the two hoses from the thermo-vacuum switch.

Two hoses disconnected from the thermo-vacuum switch — Disconnecting the hoses from the thermo-vacuum switch

Unscrew the switch from the cylinder head using a 27 mm socket spanner.

Thermo-vacuum switch unscrewed from the cylinder head — Unscrewing the thermo-vacuum switch with a 27 mm spanner

Disconnect the hose from the recirculation valve union and unscrew two nuts with a 13 mm spanner.

Two recirculation valve retaining nuts unscrewed with a 13 mm spanner — Unscrewing the recirculation valve retaining nuts

Remove the recirculation valve from the exhaust manifold.

Recirculation valve removed from the exhaust manifold — Removing the recirculation valve from the exhaust manifold

A sealing gasket is fitted between the valve and the manifold.

Unscrew three bolts with an 8 mm spanner.

Three recirculation valve body bolts unscrewed with an 8 mm spanner — Unscrewing the three valve body bolts

Take the valve out of the body.

Recirculation valve taken out of the body — Taking the valve out of the body

Assembly and installation of the valve and switch are carried out in the reverse order.

Materials used and recommendations

Sealing gasket between the valve and the exhaust manifold — recommended to be replaced each time the valve is removed.
System hoses — check for cracks, delamination and loss of tightness; replace if necessary.
Fasteners (M8 nuts, M6 bolts) — tighten evenly without skewing; recommended torques: valve nuts 15–20 N·m, body bolts 8–10 N·m (verify against the manual for the specific model).
Coolant — drain into a clean container; after assembly, top up and bleed air from the cooling system.
Before installation, check the operation of the thermo-vacuum switch and the recirculation valve (by blowing/vacuum).