Citroen C4 1.2 PureTech
Wet Belt Change &
Low Oil Pressure Fix

Strip Down the Top End

Begin by removing all the upper engine components to gain access to the cam cover. This includes the ignition coils, air intake pipe, boost pipe, turbo air pipe, air box (can be moved back without fully removing), fuel lines, injector rail, and all associated wiring looms. Remove the 8mm bolts holding the plastic upper cam cover and set it aside. Take your time routing wiring out of the way — you'll need clear access to remove the cam carrier later.

Raise the Car & Remove Under Tray and Inner Wheel Arch

Put the car on a lift or axle stands. Remove the under tray and pull the inner wheel arch liner out to the side — this gives you visibility of the auxiliary belt, lower crank pulley, oil filter and sump from below. You'll be working both above and below the car throughout this job.

Drain the Oil & Remove the Sump — Inspect the Oil Strainer

Before touching the belt, drain the engine oil — on a neglected engine this will likely come out very black. Remove the oil filter. Then undo all the 8mm sump bolts and carefully prise the sump away from the block using a small screwdriver — be gentle to avoid damaging the mating surfaces or bending the sump.

With the sump off, inspect the oil strainer immediately. On these engines it is very common to find it packed solid with rubber and canvas debris from the disintegrating wet belt. This blockage is the direct cause of the low oil pressure warning. Clean the strainer thoroughly — scrape out all the debris and flush it clean before proceeding.

Remove the Cam Carrier & Expose the Cams

Back up top, remove the servo pump (undo the top two bolts and bottom bolt, move it to the side). Then remove all the 8mm bolts holding the cam carrier down — there are a lot of them including two awkward ones tucked down near the turbo. Take your time and they will all come out. Carefully wiggle the cam carrier free.

Important — before lifting the cam carrier fully away, remove the high pressure fuel pump piston from the cam carrier and keep it safe. Note exactly how it sits so it goes back in the same position.

Install Cam Locking Tool & Flywheel Pin

With the cams exposed, fit the cam locking tool over the square sections of the cam lobes. It locates onto the cylinder head and bolts down in the middle using two of the original cover screws — once in place the cams are completely locked and cannot move. Then from below, insert the flywheel locking pin up into the flywheel to lock the crank position. The engine is now fully timed and locked ready for belt removal.

Remove the Auxiliary Belt & Lower Pulley

From below, use the 13mm multi-spline socket on the auxiliary belt tensioner to release the tension and slip the belt off. Note the orientation if reusing it. With the crank pin now inserted into the flywheel, remove the 13mm bolts from the lower pulley and wiggle it free — note it is also connected to the water pump belt behind it.

Remove the Front Cover, Tensioner & Idler

Remove the 4x 10mm bolts holding the lower front cover — it will have a rubber seal. Pull the cover away carefully. You now have access to the tensioner and idler pulley. Remove the idler first, then the tensioner. Finally undo the 18mm bottom crank bolt, refit two of the 13mm bolts loosely and wiggle the lower pulley half free from the crank gear. Replace the crank oil seal at this point while you have clear access.

Remove the Old Wet Belt

Back up top, crack off the cam gear bolts (they'll be tight) and remove the cam gears — each has a keyway that locates on the cam, so note orientation and keep them separate. With the gears free the belt can now be carefully pulled out through the top. Inspect it — you will likely see cracking all along the edges and fibres breaking away from the sides. This is exactly what has been blocking the oil strainer.

Fit the New Belt & Reassemble the Bottom End

Use a genuine replacement belt only — this is not a job to cut costs on. Feed the new belt down from the top. Refit the cam gears loosely, making sure the keyway locates correctly on each cam. From below, refit the lower inner pulley (the lug locates into the crank — it can only go one way), then refit the lower bolt. Refit the tensioner into its cutouts and the idler pulley. Use a 6mm Allen key on the tensioner and turn it anticlockwise until the white tab aligns with the mark — then lock it down. Tighten the idler, tensioner and bottom crank bolt to the correct torque specs.

Tighten Cam Gear Bolts, Verify Timing & Rebuild Top End

Tighten the cam gear bolts to the correct torque and angle spec. Remove the cam locking tool and flywheel pin. Paint a small timing mark on each cam gear for reference. Rotate the engine by hand four full turns and recheck — the locking tool must fit back perfectly and all marks must line up. Only then is the timing confirmed correct. Refit the front lower cover with a new seal, water pump belt, lower pulley, auxiliary belt and all top end components in reverse order of removal.

Refit Sump, Fill with Oil & First Start

Refit the sump with fresh gasket sealer and all 8mm bolts tightened evenly. Fit a new oil filter. Fill with the correct grade oil — this engine takes approximately 3.5 litres. Before starting, disconnect the spark plugs and crank the engine over to build oil pressure first — especially important after the system has been fully drained. Reconnect the plugs and start the engine. The low oil pressure warning should not appear. Run up to temperature and road test to confirm the fault is fully resolved.