Workshop Manuals Factory service & repair Peugeot

Peugeot common faults and how to fix them

Faults that are well known on Peugeot models we hold manuals for: what the owner notices, what causes it, and the pages in our manuals that cover the repair.

Peugeot 405 coolant leak: thermostat housing and seals (1989–1991)

Symptoms

A slow coolant leak at the thermostat housing, a falling radiator level and, eventually, the coolant level warning light. In extreme cases the engine overheats. On the 16-valve Mi16, coolant reaching the temperature sensor can make the cooling fan run erratically.

Cause

Peugeot bulletin 434 (December 1991) covers all 1989–1991 model year US 405s up to VIN 0518560. The thermostat housing can develop a slight leak. From that VIN the factory fitted a reinforced thermostat housing with a one-piece seal around the thermostat, in place of the two O-ring seals used on earlier cars.

Fix

Fit the new-style thermostat housing and one-piece seal, with the adapter plate listed in the bulletin. Partially drain the cooling system first, and on the J2 (8-valve) engine fit a new thermostat with the housing. Refill and bleed the system using the bleed screw, then check for leaks with the engine warm. The Peugeot 405 thermostat housing bulletin lists the parts for each engine and gearbox.

Repair instructions on this site

Sources: Peugeot service bulletin 434 (December 1991).

Peugeot 405 heater fan stuck on high, and water in the passenger footwell

Symptoms

The heater and air conditioning blower speeds up to maximum and stays there, whatever the fan switch is set to. Water may also appear in the front passenger footwell.

Cause

Peugeot bulletin 350 (July 1989) covers all 405s. Leaves and debris get in through the air intake and blower fan. When the air conditioning is used, condensation from the evaporator carries the debris to the end of the evaporator drain hose and blocks it, so water backs up into the car and reaches the blower motor and its control module.

Fix

The drain hose is on the right of the bulkhead, reached from under the car. Open the flap on its end to let the water out, cut 13 mm off the end, and make sure it points down at about 45 degrees, clear of the heater hose. Fit the cowl weatherstrip to the air intake grille to keep debris out, and let the blower motor and module dry out. The Peugeot 405 heater bulletin gives the full procedure.

Repair instructions on this site

Sources: Peugeot service bulletin 350 (July 1989).

Peugeot 405 won't start after a car wash: water in the Motronic ECU

Symptoms

The engine won't restart after the car has been through an automatic car wash with a heavy rinse cycle, but may start again after several hours.

Cause

Peugeot bulletin 335 (March 1989) covers all US 405s up to VIN 506980. The drain holes on each side of the scuttle (cowl) can be partly or fully blocked by dead leaves and other debris, so a large volume of water can't drain away fast enough. The water level rises and gets into the Motronic engine control unit (ECU), stopping the engine from restarting.

Fix

Remove the cover over the ECU and clear the oval drain hole, pushing back the inner wing lip from the wheel arch side to make sure it drains. Do the same for the drain on the other side, under the washer bottle. The bulletin then seals the ECU with a specific 3M silicone and warns against sealants containing acetic acid, which can damage the ECU. Follow the Peugeot 405 won't start bulletin for the full procedure.

Repair instructions on this site

Sources: Peugeot service bulletin 335 (March 1989).

Peugeot 405 stalling at idle when selecting Drive or Reverse (automatic)

Symptoms

On automatic 405s, the engine intermittently stalls at idle when the selector is moved from Park to Reverse, or from Neutral to Drive or Reverse.

Cause

Peugeot bulletin 312 (November 1988) covers 405 DL and S models with automatic transmission, up to VIN 505290. The original starter relay, a black relay without a resistor, can cause the stall when the selector is moved. Peugeot introduced a white relay with a built-in resistor to prevent it.

Fix

The starter relay is on a bracket on the steering column, under the left of the dashboard; it is the one with wires 45, 45A, 46, 46A and 46B. If it is the black relay, replace it with the white resistor-type relay. If the car already has the white relay, the stall has another cause, so check the idle speed and look for vacuum leaks. The Peugeot 405 stalling bulletin gives the replacement procedure.

Repair instructions on this site

Sources: Peugeot service bulletin 312 (November 1988).

Repair instructions for every Peugeot model: Peugeot workshop manuals