Chery QQ6 (S21) / S12LHD. Manual — part 121

Page 9 of 38

3.3 EBD Control Mode

In order to guarantee the operation stability, the EBD function is designed in such manner that front
wheels are stopped ahead of the rear wheels. As the front brakes undertake more works than that of
the rear brakes, it will cause that the rear wheels will be stopped firstly when apply with same braking
pressure. In order to preventing the occurrence of above thing, a device to reduce the braking pressure
applied on the rear wheels under certain pressure is required, of which this function is fulfilled by the
pressure reducing valve (P-Valve). The special pressure reducing valve is not required for the vehicles
equipped with ABS as the procedure supplemented to the ABS will fulfill the control function on the
braking pressure of the rear wheels so as to effect the improvement of vehicle operation stability.

Page 10 of 38

II. Removal and Installation

1.

Spare Part Supply Status

①

Differentiation between Dry Type HECU and Wet Type HECU

The biggest differentiation between the dry type HECU and wet type HECU is that the no air
discharge is conducted in the 2nd circuit (namely the circuit from the normal close valve to the
general pump) of the dry type HECU. Therefore, when the spare part is of wet type HECU, it’s
only necessary to conduct the air discharge and oil refill in accordance with the regular brake
system after the replacement. When the spare part is of dry type HECU, besides that the air
discharge and oil refill are required in accordance with the regular brake system after the
replacement, it’s necessary to conduct the air discharge and oil refill to the 2nd circuit of the HECU.
In addition, for the appearance, the wet type HECU has the bolts for sealing purpose and the dry
type HECU has the protection film. The product label located on the motor is marked with the part
number of the products, through which the dry type HECU and wet type HECU can be
differentiated.
Take the S21 model for instance, the dry type Mando product number is BH601-086-00 and the wet
type Mando product number is BH602-386-00.

Dry Type

Wet Type

②

Notices

If the bolts on the wet type HECU are fallen off (such as during the transportation), besides that the
air discharge and oil refill must be conducted for 1st circuit, maybe it’s necessary to conduct the air
discharge and oil refill to the 2nd circuit.

2． Notices for Removal and Installation

①

Notices for HECU Assembling

During the assembling of brake pipeline:

† Remove the protection film attached onto the HECU

before the operation.

† Confirm the pipeline of general pump and wheel branch

pump before the operation.

(General pump: MCP, MCS Wheel branch pump: FR,
FL, RR, RL)

† Confirm if the brake hose is tightened to 120~160

kgf·cm with special tool or torque wrench.

† Notice to keep away the impurity ingress into the

HECU hole and brake hose during operation.

Page 11 of 38

②

Notices for HECU Bracket Assembling

During the assembling of HECU bracket:

† During the tightening of the bolt (3

pcs), it may cause the incorrect
assembling due to the friction
resistance of the cushion pad. It’s
preferable to use the lubricating oil
with the physical properties that will
not impair the cushion pad.

† Insert the bolts (3 pcs) onto the

cushion pad installed onto the bracket
before install to the HECU, which
will help the operation.

† Confirm if the bolts (3 pcs) are tightened to 80~100 kgf·cm with special tool or torque

wrench.

③

Notices for Installation of HECU and Bracket Assembly

During the installation to vehicle body:

† Attach the components of brake hose and

bracket to the HECU and install to the
vehicle body with the body fixing bolts.

† Confirm if the body fixing bolts are

tightened to 190~260 kgf·cm with special
tool or torque wrench.

† Again confirm if the pipeline installation

of general pump and wheel branch pump
is correct.

(General pump: MCP, MCS; Wheel branch pump: FR,
FL, RR, RL)

† Tighten the brake hose not fully tightened to the specified torque (120 ~ 160

kgf· cm) with special tool or torque wrench.

④

Other Notices

† Find out the trouble cause with diagnosis instrument before repair.
† The package of the spare parts should be unwrapped only before the installation.
† Only use the parts supplied by the original manufacturer.
† Notice the cleanliness during removal and only use the non-fuzz cloth for cleaning.
† Use the detergent not containing the mineral oil to clean the appearance before removal.
† Do not use the compressed air or move the vehicle when the system is opened.
† After the removal of the ABS assembly, plug various hydraulic outlets with plugs as soon as

possible.

† Remove other components interfering the operation.
† Use DOT#3 brake liquid.
† Immerse the seals with brake liquid, instead of engine oil or braking ointment.
† Check all hydraulic connectors for leakage.

Bracket

Bumper block

Installation bolt

Page 12 of 38

3． HECU Replacement

①

When the vehicle is stopped, remove the 25-pin connector and harness wiring of the HECU

located within the engine compartment.

25-Pin Connector Used in MGH-25 ABS

(P/No：AMP 368482-1)

② Screw off in counter clockwise direction the 6 bolts (M10x1.0) connected to the HECU brake
hose with 11mm tool (wrench) (rotate in clockwise direction during refit). The tightening torque for
the brake hose is 120 ~ 160 kgf·cm.

③

Screw off in counter clockwise direction the 3 bolts or nuts connected to the bracket with

12mm tool (wrench) (rotate in clockwise direction during refit). The tightening torque for the fixing
bolts or nuts of the bracket is 190 ~ 260 kgf·cm.

④

After the removal of the product, screw off in counter clockwise direction the 3 embedded

bolts (M6x1.0) attached to the HECU with 5mm tool (hex wrench) (see the figure in next page).