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Brakes, suspension & tyres BMW 3-Series 1998 - 2006 Petrol 325i - 2.5

OnDemand step-by-step maintenance & repair BETA

BMW 3-Series 1998 - 2006  | 325i - 2.5 Brakes, suspension & tyres

  • time 20 minutes
  • difficulty 3
Start with the front wheels
With the wheel off the ground, check for wear in the wheel hub bearings by grasping the wheel and trying to rock it. Very slight play is OK, but if the movement is appreciable, you should seek further advice
Now remove the wheel
Check condition of the brake discs. Some light scoring is normal on the area in contact with the brake pads, but if heavy scoring and/or cracks are found on the disc or around the wheel bolt holes, the disc must be renewed. ALWAYS replace both front discs & pads
Now locate the brake pads, there are two, one on each side of the disc. Locate the brake pad's wearing surface, it's the wear material that is pressed against the brake disc to slow the vehicle when the brake pedal is applied
Using a ruler, measure the approximate thickness of the remaining wear material on the brake pad. If it is less than 2.0mm, all front pads need replacement. For how to replace the front pads, click below
- Close + Open

Front brake pads replacement

Warning: Renew both sets of front brake pads at the same time – never renew the pads on only one wheel, as uneven braking may result. Note that the dust created by wear of the pads may contain asbestos, which is a health hazard. Never blow it out with compressed air, and do not inhale any of it. An approved filtering mask should be worn when working on the brakes. DO NOT use petrol or petroleum-based solvents to clean brake parts; use brake cleaner or methylated spirit only.
1 Apply the handbrake, then jack up the front of the vehicle and support it on axle stands. Remove the front roadwheels.
2 Using a screwdriver, carefully unclip the anti-rattle spring from the side of the brake caliper, noting its correct fitted position (see illustrations) .
Lever the spring away from the hub . . .
. . . then lever it out from the caliper
3 Slide the brake pad wear sensor from the brake pad (where fitted) and remove it from the caliper aperture (see illustrations) .
Release the clips (arrowed) . . .
. . . and slide the wear sensor from the brake pad
4 Remove the plastic plugs from the caliper guide bushes to gain access to the guide pins (see illustration) .
Remove the plastic plugs to access the caliper guide pins
5 Slacken and remove the guide pins, noting that a suitable Allen key will be needed. Lift the caliper away from the caliper mounting bracket, and tie it to the suspension strut using a suitable piece of wire (see illustrations) . Do not allow the caliper to hang unsupported on the flexible brake hose.
Slacken . . .
. . . and remove the caliper guide pins
Tie the caliper mounting bracket to the suspension
6 Unclip the inner brake pad from the caliper piston, and withdraw the outer pad from the caliper mounting bracket (see illustrations) .
Unclip the inner pad from the caliper piston . . .
. . . and remove the outer pad from the caliper mounting bracket
7 First measure the thickness of each brake pad’s friction material (see illustration) . If either pad is worn at any point to 2.0 mm thickness or less, all four pads must be renewed. Also, the pads should be renewed if any are fouled with oil or grease; there is no satisfactory way of degreasing friction material, once contaminated. If any of the brake pads are worn unevenly, or are fouled with oil or grease, trace and rectify the cause before reassembly.
Measure the thickness of the friction material
8 If the brake pads are still serviceable, carefully clean them using a clean, fine wire brush or similar, paying particular attention to the sides and back of the metal backing. Clean out the grooves in the friction material (where applicable), and pick out any large embedded particles of dirt or debris. Carefully clean the pad locations in the caliper body/mounting bracket.
9 Prior to fitting the pads, check that the guide pins are a light, sliding fit in the caliper body bushes, with little sign of free play. Brush the dust and dirt from the caliper and piston, but do not inhale it, as it is a health hazard. Inspect the dust seal around the piston for damage, and the piston for evidence of fluid leaks, corrosion or damage.
10 If new brake pads are to be fitted, the caliper piston must be pushed back into the cylinder to make room for them. Either use a piston retraction tool, a G-clamp or use suitable pieces of wood as levers. Clamp off the flexible brake hose leading to the caliper then connect a brake bleeding kit to the caliper bleed nipple. Open the bleed nipple as the piston is retracted; the surplus brake fluid will then be collected in the bleed kit vessel (see illustration) . Close the bleed nipple just before the caliper piston is pushed fully into the caliper. This should ensure no air enters the hydraulic system. Note: The ABS unit contains hydraulic components that are very sensitive to impurities in the brake fluid. Even the smallest particles can cause the system to fail through blockage. The pad retraction method described here prevents any debris in the brake fluid expelled from the caliper from being passed back to the ABS hydraulic unit, as well as preventing any chance of damage to the master cylinder seals.
Using a piston retraction tool, with the hose clamped, and the bleed nipple open
11 Apply a smear of brake anti-squeak compound to the backing plate of each pad, and the pad backing plate contact points on the caliper bracket; do not apply excess grease, nor allow the grease to contact the friction material.
12 Fit the outer pad to the caliper mounting bracket, ensuring that its friction material is against the brake disc (see illustration) .
Fit the outer pad to the caliper bracket
13 Clip the inner pad into the caliper piston, and manoeuvre the caliper assembly into position (see illustration) .
Clip the inner pad into the caliper piston
14 Install the caliper guide pins, and tighten them to 35 Nm (26 Ibf ft). Refit the plugs to the ends of the caliper guide pins.
15 Clip the pad wear sensor back into position in the inner pad, making sure its wiring is correctly routed (see illustrations 3.3a and 3.3b) .
16 Clip the anti-rattle spring into position in the caliper (see illustration) . Depress the brake pedal repeatedly, until the pads are pressed into firm contact with the brake disc, and normal (non-assisted) pedal pressure is restored.
Refit the anti-rattle spring
17 Repeat the above procedure on the remaining front brake.
18 Refit the roadwheels, then lower the vehicle to the ground and tighten the roadwheel bolts to 100 Nm (74 Ibf ft).
TIP! - Virtually all cars have this inspection window in the brake caliper body, you can usually see the brake pad thickness from here
Now quickly check all the brake pipes for condition, check for any leaks, also inspect the rubber gaitors for integrity. Should the front suspension strut need to be replaced, click below
- Close + Open

Front suspension strut replacement

Note: New suspension strut upper mounting nuts, and strut-to-hub carrier bolt will be required on refitting.

Removal

1 Chock the rear wheels, apply the handbrake, then jack up the front of the car and support on axle stands. Remove the appropriate wheel.
2 To prevent the lower arm assembly hanging down whilst the strut is removed, screw a wheel bolt into the hub, then wrap a piece of wire around the bolt and tie it to the car body. This will support the weight of the hub assembly. Alternatively, support the hub assembly with a jack.
3 Unclip the brake hose and wiring harness from its clips on the base of the strut (see illustration) .
Pull the brake hose and wiring harness grommets from the bracket
4 Slacken and remove the retaining nut and washer, then disconnect the anti-roll bar link from the strut. Use an open-ended spanner to counterhold the anti-roll bar link balljoint whilst undoing the nut.
5 On models fitted with a ride height sensor for headlamp range adjustment, undo the nut and remove the link bracket from the lower control arm.
6 Slacken and remove the bolt securing the suspension strut to the hub carrier. Slide the hub carrier down and off from the end of the strut. To ease removal, insert a large screwdriver into the slot on the back of the hub carrier and slightly spread the hub carrier clamp (see illustration) . Take care to spread the carrier clamp only as much as absolutely necessary, as excessive force will cause damage.
Use a large screwdriver to gently spread the clamp
7 From within the engine compartment, unscrew the strut upper mounting nuts, then carefully lower the strut assembly out from underneath the wing. On some models, a centring pin fixed to the strut upper mounting plate aligns with a corresponding hole in the vehicle bodywork (see illustration) . On models where no centring pin is fitted, make alignment marks between the mounting plate and vehicle body. It is essential that the mounting plate is fitted to its original location to preserve the strut camber angle.
Note the centring pin (arrowed) adjacent to the strut upper mounting bolts

Refitting

8 Prior to refitting, clean the threads of the strut-to-hub carrier bolt hole by running a tap of the correct thread size and pitch down it.
9 Manoeuvre the strut assembly into position, aligning the centring pin with its corresponding hole, or previously-made marks, and fit the new upper mounting nuts.
10 Locate the hub carrier correctly with the suspension strut (see illustration) , and insert the new retaining bolt. Tighten the bolt to 81 Nm (60 Ibf ft). Note that the wiring/hose support bracket is also retained by the bolt.
Unsure the locating pin slides into the slot in the clamp
11 Tighten the strut upper mounting nuts to the specified torque.
Strut mounting-to-body nuts: Nm Ibf ft
  Nuts with 18 mm diameter flange 24 18
  Nuts with 21 mm diameter flange 34 25
12 Where applicable, refit the suspension height sensor link bracket to the lower control arm, and tighten the retaining nut securely.
13 Engage the anti-roll bar connecting link with the strut. Make sure the flat on the balljoint shank is correctly located against the lug on the strut, then fit the washer and new retaining nut and tighten to 65 Nm (48 Ibf ft).
14 Clip the hose/wiring back onto the strut, then refit the roadwheel. Lower the car to the ground and tighten the wheel bolts to 100 Nm (74 Ibf ft).
It's a similar procedure with the rear wheels. Check for wheel bearing movement, then remove wheel
Check condition of the rear brake discs
Locate rear brake pads
Measure brake pad wear thickness. If it is less than 2.0mm, all rear pads need replacement. For how to replace the rear pads, click below
- Close + Open

Rear brake pads replacement

Warning: Renew both sets of front brake pads at the same time – never renew the pads on only one wheel, as uneven braking may result. Note that the dust created by wear of the pads may contain asbestos, which is a health hazard. Never blow it out with compressed air, and do not inhale any of it. An approved filtering mask should be worn when working on the brakes. DO NOT use petrol or petroleum-based solvents to clean brake parts; use brake cleaner or methylated spirit only.
1 Apply the handbrake, then jack up the front of the vehicle and support it on axle stands. Remove the front roadwheels.
2 Using a screwdriver, carefully unclip the anti-rattle spring from the side of the brake caliper, noting its correct fitted position (see illustrations) .
Lever the spring away from the hub . . .
. . . then lever it out from the caliper
3 Slide the brake pad wear sensor from the brake pad (where fitted) and remove it from the caliper aperture (see illustrations) .
Unclip the wiring...
. . . and slide the wear sensor from the brake pad
4 Remove the plastic plugs from the caliper guide bushes to gain access to the guide pins (see illustration) .
Remove the plastic plugs to access the caliper guide pins
5 Slacken and remove the guide pins, noting that a suitable Allen key will be needed. Lift the caliper away from the caliper mounting bracket, and tie it to the suspension strut using a suitable piece of wire (see illustrations) . Do not allow the caliper to hang unsupported on the flexible brake hose.
Slacken . . .
. . . and remove the caliper guide pins
Tie the caliper mounting bracket to the suspension
6 Unclip the inner brake pad from the caliper piston, and withdraw the outer pad from the caliper mounting bracket (see illustrations) .
Pull the inner pad from the caliper piston . . .
. . . and remove the outer pad from the caliper mounting bracket
7 First measure the thickness of each brake pad’s friction material (see illustration) . If either pad is worn at any point to 2.0 mm thickness or less, all four pads must be renewed. Also, the pads should be renewed if any are fouled with oil or grease; there is no satisfactory way of degreasing friction material, once contaminated. If any of the brake pads are worn unevenly, or are fouled with oil or grease, trace and rectify the cause before reassembly.
Measure the thickness of the friction material
8 If the brake pads are still serviceable, carefully clean them using a clean, fine wire brush or similar, paying particular attention to the sides and back of the metal backing. Clean out the grooves in the friction material (where applicable), and pick out any large embedded particles of dirt or debris. Carefully clean the pad locations in the caliper body/mounting bracket.
9 Prior to fitting the pads, check that the guide pins are a light, sliding fit in the caliper body bushes, with little sign of free play. Brush the dust and dirt from the caliper and piston, but do not inhale it, as it is a health hazard. Inspect the dust seal around the piston for damage, and the piston for evidence of fluid leaks, corrosion or damage.
10 If new brake pads are to be fitted, the caliper piston must be pushed back into the cylinder to make room for them. Either use a piston retraction tool, a G-clamp or use suitable pieces of wood as levers. Clamp off the flexible brake hose leading to the caliper then connect a brake bleeding kit to the caliper bleed nipple. Open the bleed nipple as the piston is retracted; the surplus brake fluid will then be collected in the bleed kit vessel (see illustrations) . Close the bleed nipple just before the caliper piston is pushed fully into the caliper. This should ensure no air enters the hydraulic system. Note: The ABS unit contains hydraulic components that are very sensitive to impurities in the brake fluid. Even the smallest particles can cause the system to fail through blockage. The pad retraction method described here prevents any debris in the brake fluid expelled from the caliper from being passed back to the ABS hydraulic unit, as well as preventing any chance of damage to the master cylinder seals.
Clamp the hose and attach a tube to the bleed nipple
Use a retraction tool to push back the piston
11 Apply a smear of brake anti-squeak compound to the backing plate of each pad, and the pad backing plate contact points on the caliper bracket; do not apply excess grease, nor allow the grease to contact the friction material.
12 Fit the outer pad to the caliper mounting bracket, ensuring that its friction material is against the brake disc (see illustration) .
Fit the outer pad to the caliper bracket
13 Clip the inner pad into the caliper piston, and manoeuvre the caliper assembly into position (see illustration) .
Clip the inner pad into the caliper piston
14 Install the caliper guide pins, and tighten them to 35 Nm (26 Ibf ft). Refit the plugs to the ends of the caliper guide pins.
15 Clip the pad wear sensor back into position in the outer pad, making sure its wiring is correctly routed (see illustrations 3.3a and 3.3b) .
16 Clip the anti-rattle spring into position in the caliper (see illustration) . Depress the brake pedal repeatedly, until the pads are pressed into firm contact with the brake disc, and normal (non-assisted) pedal pressure is restored.
Refit the anti-rattle spring
17 Repeat the above procedure on the remaining front brake.
18 Refit the roadwheels, then lower the vehicle to the ground and tighten the roadwheel bolts to 100 Nm (74 Ibf ft).
Take a good look around brake system and the suspension arm, check for any leaks. Should the rear shock absorber need to be replaced, click below
- Close + Open

Rear shock absorber replacement

Note: New shock absorber upper mounting nuts and a new mounting gasket will be required on refitting.

Removal

1 Check the front wheels, then jack up the rear of the car and support it on axle stands. To improve access, remove the rear roadwheel.
2 On Saloon and Coupe models, lift up the luggage compartment floor panel and remove the oddments tray/battery cover. On the left-hand side, remove the warning triangle, prise out the plastic rivet, and remove the warning triangle bracket. Prise out the retaining clips securing the luggage compartment side trim cover in position, and remove the trim and insulation panel to gain access to the shock absorber upper mounting (see illustrations) .
Prise out the warning triangle bracket plastic rivet (arrowed)
Lever up the centre pin, then prise out the plastic rivets

Touring models

3 Pull the top of the C-pillar trim towards the centre of the cabin to release the top push-on clip (see illustration) .
Pull the top of the trim to release the clip
4 With the top released, pull up the lower edge of the trim and remove it.
5 Open the tailgate, press the release button, and fold down the flap in the luggage compartment side panel.
6 The D-pillar trim is secured by two bolts in the centre, and two push-on clips at the top edge. Undo the bolts, pull the top of the trim to release the clips, then lift the trim away (see illustration) . Disconnect the luggage compartment light as the trim is removed.
Undo the D-pillar trim bolts (arrowed)
7 Fold the rear seat forward, unclip the top section of the side trim adjacent to the door aperture, then lift the trim upwards and remove it (see illustration) .
Unclip the top section of the side trim
8 Release the two clips at the front edge, and remove the seat belt reel trim cover from the top of the side panel (see illustration) .
Release the two clips (arrowed) and remove the trim cover
9 Undo the bolt securing the lower seat belt mounting.
10 Undo the two retaining bolts, and remove the luggage compartment roller cover mounting from the side panel (see illustration) .
Undo the two bolts (arrowed) and remove the roller cover mounting
11 Lever out the centre pin and prise out the expanding plastic rivet, undo the bolts/nut, then remove the cover from the seat belt reel (see illustration) .
Prise out the expansion rivet, undo the bolts/nuts and remove the cover from the seat belt reel (arrowed)
12 Slacken the retaining bolt and remove the trim from the lower edge of the rear side window (see illustration) .
Undo the bolt (arrowed) and remove the trim
13 Lift the trim flap, undo the bolts and remove the ‘lashing eye’ from the side panel (see illustration) .
Lift the flap and undo the lashing-eye bolts
14 Carefully prise the 12V power socket from the side trim, and disconnect the wiring plugs as the socket is withdrawn.
15 Prise out the centre pin and lever out the plastic expansion rivet from the lower edge of the trim panel.
16 Lever out the mounting at the top, and remove the trim panel, feeding the power socket wiring through the hole as the panel is removed.

All models

17 Position a jack underneath the trailing arm, and raise the jack so that it is supporting the weight of the arm. This will prevent the arm dropping when the shock absorber is unscrewed.
18 Slacken and remove the bolt securing the shock absorber to the trailing arm (see illustration) .
Undo the lower shock absorber bolt
19 From within the luggage compartment, unscrew the upper mounting nuts (see illustration) . Lower the shock absorber out from underneath the car, and recover the gasket which is fitted between the upper mounting and body.
Undo the rear shock absorber upper mounting nuts (arrowed)

Refitting

20 Ensure the upper mounting plate and body contact surfaces are clean and dry, and fit a new gasket to the upper mounting plate.
21 Manoeuvre the shock absorber into position, and fit the new upper mounting nuts.
22 Ensure the lower end of the shock absorber is positioned with the mounting bush spacer thrustwasher facing towards the bolt. Screw in the lower mounting bolt, tightening it by hand only at this stage.
23 Tighten the upper mounting nuts to the specified torque setting then refit the insulation panel, luggage compartment trim panel, rear light access cover and loudspeaker (as applicable).
24 Refit the roadwheel and lower the car to the ground. With the car resting on its wheels, tighten the shock absorber lower mounting bolt and roadwheel bolts to the specified torque.
Roadwheel bolts 100 Nm (74 Ibf ft)
Shock absorber lower mounting bolt 100 Nm (74 Ibf ft)
Shock absorber upper mounting nuts:
  Strength grade 8.8 (see head of bolt) 22 Nm (16 Ibf ft)
  Strength grade 10.9 (see head of bolt) 30 Nm (22 Ibf ft)
Check rubber exhaust mountings
Before refitting the tyres, take a look at the tyre tread, there is a UK legal requirement to have a minimum of 1.6mm remaining tread depth.Also check sidewalls for any kerb damage
Finally, check the condition of the spare wheel / emergency tyre repair system
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