Peugeot 405 Manual

Air cleaner air temperature control system - information and component renewal
Fuel/exhaust systems - carburettor models / Air cleaner air temperature control system - information and component renewal


General information
TU engine
1 The system is controlled by a heat-sensitive vacuum switch, mounted in the end of the air cleaner housing-to-carburettor duct. When the engine is started from cold, the switch is open, allowing inlet manifold depression to act on the air temperature control valve diaphragm in the inlet duct. This vacuum causes the diaphragm to rise, drawing a flap valve across the cold-air inlet, thus allowing only (warmed) air from the exhaust manifold to enter the air cleaner.

2 As the temperature of the exhaust-warmed air in the air cleaner-to-carburettor duct rises, the wax capsule in the vacuum switch deforms and closes the switch, cutting off the vacuum supply to the air temperature control valve assembly. As the vacuum supply is cut, the flap is gradually lowered across the hot-air inlet until, when the engine is fully warmed-up to normal operating temperature, only cold air from the front of the car is entering the air cleaner.

3 To check the system, allow the engine to cool down completely, then slacken the retaining clip and disconnect the inlet duct from the front of the control valve assembly; the flap valve in the duct should be securely seated across the hot-air inlet. Start the engine; the flap should immediately rise to close off the cold-air inlet, and should then lower steadily as the engine warms up, until it is eventually seated across the hot-air inlet again.

4 To check the vacuum switch, disconnect the vacuum pipe from the control valve when the engine is running, and place a finger over the pipe end. When the engine is cold, full inlet manifold vacuum should be present in the pipe, and when the engine is at normal operating temperature, there should be no vacuum in the pipe.

5 To check the air temperature control valve assembly, slacken the retaining clip and disconnect the inlet duct from the front of the valve assembly; the flap valve should be securely seated across the hot-air inlet.

Disconnect the vacuum pipe, and suck hard at the control valve stub; the flap should rise to shut off the cold-air inlet.

6 If either component is faulty, it must be renewed.

XU engine
7 Cold air is drawn into the system from the inlet duct fitted to the front panel.

8 Hot air is drawn from the collector plate over the exhaust manifold. These two ducts join together at the air inlet mixer housing which contains a control flap operated by a wax thermostat (see illustrations).

3.8a Hot-air collector plate on exhaust manifold (XU engine)
3.8a Hot-air collector plate on exhaust manifold (XU engine)

3.8b Wax thermostat on the air inlet mixer housing (XU engine)
3.8b Wax thermostat on the air inlet mixer housing (XU engine)

9 When the engine is cold the thermostat contracts and the control flap closes off the cold air duct and opens the hot air duct. As the air being collected from the exhaust manifold becomes warmer, so the thermostat progressively closes off the warm air duct and opens the cold air duct.

10 If the thermostat should fail, renew the mixer housing.

11 All the ducts are held by worm drive clips.

12 Additional breather pipes are connected to the air filter housing on certain models.

Vacuum switch
(TU engine) - renewal
13 Remove the air cleaner housing-tocarburettor duct, as described in paragraphs 1 and 2 of Section 2.

14 Bend up the tangs on the switch retaining clip, then remove the clip, along with its seal, and withdraw the switch from inside the duct (see illustrations). Examine the seal for damage or deterioration, and renew if necessary.

3.14a Remove the retaining clip . . .
3.14a Remove the retaining clip . . .

3.14b . . . and seal . . .
3.14b . . . and seal . . .

3.14c . . . then withdraw the vacuum switch from inside the duct
3.14c . . . then withdraw the vacuum switch from inside the duct

15 On refitting, ensure that the switch and duct mating surfaces are clean and dry, and position the switch inside the duct.

16 Fit the seal over the switch unions, and refit the retaining clip. Ensure that the switch is pressed firmly against the duct, and secure it in position by bending down the retaining clip tangs. Refit the duct as described in Section 2.

Air temperature control valve (TU engine) - renewal
17 Disconnect the vacuum pipe from the air temperature control valve, then slacken the retaining clips securing the inlet ducts to the valve (see illustration).

3.17 Air temperature control valve assembly (TU engine)
3.17 Air temperature control valve assembly (TU engine)

18 Disconnect both inlet ducts and the hotair inlet hose from the control valve assembly, and remove it from the vehicle.

19 Refitting is the reverse of the removal procedure, noting that the air temperature control valve assembly can only be renewed as a complete unit.


© 2018 www.peugeot405.ru. All Rights Reserved.