Rear brakes on Nissan Primera P12 They are a complex design that integrates a hand brake and an automatic gap adjustment mechanism. Over time, the O-rings lose their elasticity, and the guide pins begin to jam, which leads to overheating of the discs and rapid wear of the pads. Many owners are faced with the need to replace the entire assembly, but a competent overhaul can restore the functionality of the part for a small amount.
The procedure requires care, as incorrect removal of the piston can damage the threads or body. If you plan to carry out the work yourself, you will need a special tool for compressing the piston, a set of wrenches and a high-quality repair kit. In this article we will go through each step, from wheel removal to final system check.
Preparing tools and work area
Before starting any work on the brake system, it is necessary to ensure the safety of the vehicle. Raise the rear of the car with a jack and be sure to place it on a secure stand. Without this, the risk of the car falling is extremely high, especially when applying force to the caliper. Remove the wheel and clean the area around the caliper of dirt and rust.
You will need a standard set of wrenches, but for efficient work it is better to have 12, 14 and 17 millimeter sockets on hand. Pay special attention to the condition of the guides, which require lubricants with a high temperature limit. Do not use regular lithium grease, as it is quickly washed out and loses its properties.
- 🔧 Socket set and ratchet with extension
- 🛠 A special key for turning the piston (or a universal puller)
- 🧴Brake flush fluid and silicone grease
- 🧽 Clean rags and a brush with metal bristles
⚠️ Attention: Brake fluid is hygroscopic and absorbs moisture from the air. Reassembly work must be carried out quickly to prevent moisture from entering the system through open hoses.
Dismantling and initial inspection of the unit
Start by unscrewing the caliper guide pins. On Nissan Primera P12 they often stick due to lack of lubrication, so penetrating lubricant WD-40 or equivalent may be required. Do not use excessive force to avoid stripping the threads in the aluminum bracket body. After unscrewing, carefully remove the caliper, hanging it on a wire so as not to damage the brake hose.
Remove the brake pads and carefully inspect their condition. If the linings are worn unevenly, this is a direct sign that the guides or piston are jammed. Also check the brake disc for deep grooves and runout. If there are serious defects, it is better to replace the disc, since the new pad will not get used to the old surface.
- Whistle when braking
- The car pulls to the side
- The disk is heating up
- Caliper jammed
Disassembling and removing the piston
The most critical stage is removing the piston. On the rear calipers Nissan Primera P12 The piston is not simply pushed out, it is threaded and must be screwed inward when compressed. If you try to push it out with a jack, you are guaranteed to ruin the mechanism. You need to simultaneously rotate the piston and apply force to press it in.
Use a special tool or a piece of an old block to secure the piston and turn it counterclockwise (looking at the end). The inner part of the piston has special grooves. If the threads are very dirty, the process may be difficult. In this case, take your time and clean the threads with a soft brush as you go.
- 🔩 Secure the caliper in a vice (via soft spacers) for convenience
- 🔄 Rotate the piston counterclockwise when pressing the tool
- 💧 Monitor the level of brake fluid in the reservoir so as not to overload the system
☑️ Piston condition monitoring
⚠️ Attention: It is strictly forbidden to use screwdrivers or pry bars to press out the piston, as this can lead to deformation of the inner surface of the cylinder and the impossibility of further repair.
After removing the piston, be sure to remove the old seal from the housing groove. This is done carefully so as not to damage the metal. Inspect the inner surface of the cylinder for scoring. Even minor scratches can cause new seals to wear out quickly. If the surface is shiny and smooth, you can continue. If there are deep risks, housing replacement is inevitable.
Cleaning the guide pins
The guide fingers should move freely by hand. If there is resistance, they need to be cleaned of old grease and rust, and then lubricated with special silicone paste. Never use graphite lubricant or lithol, they destroy rubber boots.
Cleaning and replacing sealing elements
The quality of the assembly directly depends on the cleanliness of the parts. Wash all metal parts thoroughly in brake cleaner. Pay special attention to the groove for the piston boot and the channel for lubrication of the guides. Any particle of dirt can become an abrasive and quickly destroy new rubber.
Install the new seal into the housing groove. It should stand up straight, without distortion. Before installing the piston, lubricate its surface and grooves with clean brake fluid or special lubricant. This will ensure ease of movement and prevent scuffing when you first press the pedal.
Don't forget about the guide boots. If it is torn, moisture and dirt have already penetrated the mechanism. Replace the boot with a new one, lubricating it from the inside with a thin layer of guide grease. A correctly installed boot should fit snugly against the body and piston, preventing dust from entering.
Before installing a new guide pin boot, apply a little grease inside the pin itself so that it slides without friction, but does not squeeze out the grease as it moves.
Assembly and adjustment of the mechanism
Assembly is carried out in reverse order. Insert the piston into the cylinder, turning it all the way until it reaches the working position. Install the guide pins into the bracket, making sure that the boots are not twisted. Tighten the guides to the recommended torque, usually about 25-30 Nm, but it is better to check the service book.
Install the brake pads and press them against the disc. Make sure they don't wobble or jam in the guides. Carefully slide the caliper onto the disc without pinching the hose. Secure it with bolts. Make sure that the piston does not stick out too much, otherwise it will not fit into the bracket.
| element | Material/Type | Recommended Lubricant |
|---|---|---|
| Guide pins | Steel | Silicone high temperature |
| Piston | Aluminium/Steel | Brake fluid (initial) |
| Piston boot | Rubber | Special lubricant for rubber |
| Brake pads (contacts) | Metal | Copper grease (contact points only) |
Proper lubrication of the guide pins and piston is 90% of the success in eliminating jamming and overheating of the brakes.
Bleeding the system and checking its functionality
After assembly, it is necessary to bleed the brake system to remove air. Open the bleeder valve on the rear caliper and have an assistant press the brake pedal several times. When the pedal becomes hard, close the fitting. Repeat the procedure until clear, bubble-free liquid comes out of the tube.
Before leaving, be sure to check the operation of the handbrake. On Nissan Primera P12 The pad spreading mechanism should operate smoothly. Lift the rear wheels and try to turn them by hand with the handbrake pulled on - they should lock. After lowering the wheel, check if the disc gets hot after 10-15 minutes of driving.
If you feel the pedal feel soft or hear any unusual noises, return to the test. There may be air left in the system or the piston may not be installed correctly. Don't ignore even minor symptoms, as they can lead to brake failure in a critical situation.
Checking the hand brake
If the handbrake does not hold, the piston extension mechanism may need adjustment or the pads may be worn out. In some cases, a complete replacement of the mechanism is required if the piston rod has worn out.
Typical repair mistakes
One common mistake is using the wrong lubricant. Many craftsmen use graphite lubricant or lithol, which leads to swelling of the rubber seals and subsequent jamming. Use only specialized compounds intended for brake systems.
Another common problem is damage to the boot during installation. If you tear the boot, dirt will quickly get inside and the repair will have to be done again. Be extremely careful when putting on rubber elements. It's better to spend an extra hour than to buy a new caliper.
- ❌ Using WD-40 as a guide lubricant
- ❌ Piston compression without rotation (for rear calipers)
- ❌ Ignoring the condition of the brake fluid
FAQ: Answers to frequently asked questions
Is it possible to rebuild the caliper without a special tool?
Theoretically, you could use an old piece of block and a vise, but this is risky. A special tool allows you to evenly compress the piston and avoid distortions, which is critical for a mechanism with adjustment.
How often should the grease in the calipers be changed?
It is recommended to carry out preventive cleaning and replacement of lubricant every 60-80 thousand kilometers, or every time the caliper is removed to replace the pads.
What to do if the piston does not screw back in?
Check if you have mixed up the direction of rotation. This is usually counterclockwise. Also make sure that the grooves on the piston are clean and undamaged.
Do I need to change brake pads when rebuilding the caliper?
Yes, if their residual thickness is less than 3 mm. Old pads may have uneven wear that will ruin the new mechanism.
How long does it take to rebuild one caliper?
An experienced technician needs about 40-60 minutes per caliper. For a beginner, this may take 1.5-2 hours including cleaning and inspection.