CP5 Low-Pressure Circuit Access Wrench – Semi-Open Offset Design For Gear Pump Bolt Removal

The Bosch CP5 high-pressure pump, widely used in commercial vehicle common rail systems (e.g., DAF MX-13, MAN D26, and Volvo D13), incorporates a low-pressure gear pump mounted on its rear face. The gear pump cover is secured by four M8 bolts, two of which are positioned directly behind the high-pressure outlet fitting and the fuel temperature sensor-leaving a clearance of only 12 mm between the bolt head and the adjacent component. A conventional ring spanner or socket cannot engage these bolts without removing the high-pressure line, a time-consuming operation that risks fuel contamination and requires new sealing washers. This CP5 Low-Pressure Circuit Access Wrench solves the access problem through a semi-open offset design: a 13 mm hexagon cut-out that engages the bolt head from the side, combined with a 15° cranked handle that allows the tool to swing in a plane parallel to the pump body. The wrench's head height is only 6 mm, enabling it to slide between the bolt head and the obstruction, while the open throat (7 mm wide) accommodates the fuel line without requiring disconnection.

Unlike a standard open-end wrench, which has a U-shaped jaw that can slip if not perfectly aligned, this semi-open design incorporates a spring-loaded retaining pin that closes the throat after the bolt head is engaged. The pin is retracted by pressing a knurled button on the back of the head; once the bolt is positioned in the hexagon cut-out, releasing the button allows the pin to snap across the throat, effectively converting the tool into a ring spanner for the duration of the turn. This mechanism provides the side-entry convenience of an open-end wrench with the torque-holding security of a ring spanner, preventing the tool from slipping and rounding the bolt head. The retaining pin is made from hardened 440C stainless steel (58 HRC) with a polished tip, ensuring smooth engagement and a long service life.

The wrench body is forged from SCM440 alloy steel (AISI 4140 equivalent), hardened to 48–52 HRC, with the hexagon cut-out induction-hardened to 58 HRC to resist wear. The surface receives a black oxide coating with a PTFE-impregnated top layer, reducing friction when sliding the tool into tight spaces and providing corrosion resistance against diesel and moisture. The handle is offset by 15° from the head axis, providing a 25 mm clearance from the pump body, and the overall length of 200 mm gives ample leverage for breaking loose bolts with up to 100 N·m of torque. A hexagonal cross-section on the handle (17 mm flats) allows the use of a standard spanner for additional torque if required, though the wrench is designed to handle the CP5 cover bolt torque specification of 25 N·m without assistance.

This wrench is specifically designed for the low-pressure circuit access bolts on the following Bosch CP5 pump variants and their applications:

Bosch CP5 (0 986 435 0xx series) – used on DAF MX-11 and MX-13, MAN D26, Volvo D13, and Iveco Cursor 9/13, with the gear pump cover bolt arrangement described.

Bosch CP5.1 and CP5.2 (updated variants) – the same bolt geometry is retained, though the adjacent components (fuel temperature sensor, high-pressure outlet) may vary in position; the wrench's offset angle accommodates these differences.

Bosch CP3 with similar low-pressure pump configuration – some CP3 pumps use the same M8 bolt pattern and obstruction; the wrench is compatible, though the bolt size may differ (check the specific pump model).

The tool is also used for removing the low-pressure fuel inlet fitting on certain Bosch CP4 pumps (e.g., CP4.2 used in Ford 6.7L Powerstroke), where a similar access restriction exists.

Identify the target bolt – Locate the two obstructed gear pump cover bolts. Ensure the pump is depressurised and the fuel system has been bled.

Retract the retaining pin – Press the knurled button to withdraw the pin, opening the throat of the wrench.

Slide the wrench over the bolt – Position the hexagon cut-out over the bolt head, sliding the tool from the side, parallel to the pump face. The open throat accommodates the adjacent fuel line or sensor without requiring removal.

Release the pin – Allow the retaining pin to snap closed, converting the tool into a closed-ring configuration. The bolt is now captured; the tool cannot slip off during rotation.

Apply torque – Turn the handle to loosen the bolt (counter-clockwise). The handle's offset provides clearance to the pump body. Use a standard spanner on the handle's hex section if additional torque is required.

Remove the bolt – Once loosened, retract the pin again to withdraw the tool from the bolt. Repeat for the remaining obstructed bolts.

Reverse for installation – When installing the cover, use the same procedure, tightening the bolts to 25 N·m (use a torque wrench on the handle's hex section). The retaining pin ensures the wrench remains engaged during torque application.

Q1: Can I use this wrench on the CP5's high-pressure outlet fitting instead of the cover bolts?
No, the high-pressure outlet uses a larger 17 mm or 19 mm bolt, and the wrench's hexagon is specifically 13 mm. Attempting to use this tool on the wrong size will damage the wrench and the fitting.

Q2: Is the retaining pin mechanism strong enough to withstand high torque?
Yes, the pin is designed to handle torque up to 100 N·m without deforming. However, the CP5 cover bolts are only torqued to 25 N·m, so the pin is well within its safety margin.

Q3: What if the bolt head is already rounded or damaged?
The wrench relies on a clean hexagon profile. If the bolt is rounded, the tool may not engage securely – we recommend using a bolt extractor or replacing the bolt before using this wrench.

Q4: Can I use the wrench without engaging the retaining pin (i.e., as an open-end wrench)?
Yes, you can leave the pin retracted and use the tool as a standard open-end wrench, but you will lose the anti-slip feature. We recommend using the pin for all tightening operations and for loosening stubborn bolts.

Q5: Does the wrench fit the gear pump cover bolts on the earlier CP3 pumps?
CP3 pumps often use a 15 mm hex for the gear pump cover, and the bolt spacing may be different. This tool is specifically for the CP5's 13 mm bolts. For CP3, we offer a separate 15 mm version – please check your pump model.

Q6: How do I clean the retaining pin mechanism if it becomes sticky?
The mechanism is exposed to fuel and dirt. Periodically, apply a drop of light oil (e.g., WD-40) to the pin's sliding surface and operate the button several times to work the oil in. If the pin sticks, do not force it – clean the area with brake cleaner and then re-lubricate.

 

To make your purchasing experience smooth and easy, we offer a variety of secure payment options:

We're here to make your order process worry-free - choose the payment method that works best for you!

 

 

Hot Tags: cp5 low-pressure circuit access wrench – semi-open offset design for gear pump bolt removal, China cp5 low-pressure circuit access wrench – semi-open offset design for gear pump bolt removal manufacturers, suppliers, factory