Car intake manifold

How to detect the intake manifold failure

The intake manifold inspection is quite complicated. First, check its tightness. For this, start the engine and close the air flow meter inlet with your hand. If there are no faults in the intake line, the engine will stop. If there are cracks or burnouts in the manifold, the engine will continue working, and a hiss will come from damaged areas.

Examination can also be carried out on a shutdown engine. For this, close the connecting pipe inlet opening, apply a soap solution to the suspected faulty areas and blow the intake line with compressed air. The solution foaming indicates that the system is unsealed. At a service station the intake manifold is checked for leakage with the help of a smoke machine.

Also check the operable condition of the intake manifold runner control valve. For this, connect the multimeter to its terminals and measure the resistance. If there is no resistance, the integrity of the solenoid valve winding is impaired. Then you have to start the engine, raise the speed to 3500-4000 rpm and see if the runner valve situated on the left side of the intake manifold is working.

You can check by hand whether the swirl flaps are stuck: their actuator rods are located outside the housing. You can check whether they activate at the right time with the help of a vacuum pump. For this, connect it to the corresponding pipes and see at what underpressure the rod starts moving, and then compare the received data with those stated in the technical documents.

You may identify that the intake manifold has to be inspected by the following signs:

• abnormal sounds during the power unit operation;
• increased fuel and oil consumption;
• engine power loss;
• impossibility to switch on increased rpms.

Causes of intake manifold failures

Quite often the part incorrect performance is caused by contamination. The delayed air filter replacement, disintegrity of the intake system lead to the dust accumulation on the manifold moving parts, eventually causing them to stick.

The formation of carbon deposits on flaps and valves’ surfaces is equally dangerous for them. Its causes are often the exhaust and crankcase ventilation systems faults. The oil that has gotten into the manifold turns into a deposit under the impact of high temperature, which leads to the motion failure of the flaps and to a decrease in the channels throughput capacity.

Sometimes the cause for the part non-operability lies in the catalytic converter clogging. If its throughput capacity is violated, the volume of exhaust gas re-entering the manifold through the EGR valve raises dramatically, resulting in the part housing burnout or deformation. In cold seasons, it can crack due to excessive exhaust gas amount and temperature drop.

Another cause of unit cracking or deformation is, in many cases, installation mistakes, for instance, a violation of the tightening order and torque of the bolts, recommended by the manufacturer.

Repair of the intake manifold

Repair procedure usually comprises cleaning the part from dirt and carbon deposits and replacement of damaged components, such as a valve or its actuator, flaps, vacuum tubes. The housing tightness can be restored by welding. The unit repair is quite complex and time consuming, so it is best left to specialists.

Replacement of the intake manifold

To replace the intake manifold, you have to:

1. Shut down the engine and let it cool down.
2. Disconnect the negative terminal from the battery.
3. Dismantle the plastic engine cover by loosening the clips.
4. Dismantle the air filter and then the connecting pipe.
5. Disconnect all hoses from the assembly housing one by one. Depending on the vehicle design, they can be the hoses of crankcase ventilation, brake booster, and hydraulic power steering, evaporative emission control system; fuel supply and coolant supply hoses, as well as air supply pipe from the turbocharger.
6. Disconnect all wires and sensors coming to the engine.
7. Dismantle the intake manifold bracket after raising the vehicle with a car lift.
8. Unscrew the bolts fastening the unit and disengage it from the cylinder head, first lowering the vehicle.
9. Dismantle the intake manifold and mount a new one in its place, doing the steps in the reverse order.
10. After mounting the part, add the fluid to the cooling system and bleed it.

Depending on the vehicle brand and model, the replacement procedures may vary. You can find more detailed instructions in the car technical documents.