EGR VALVE CLEANING, TESTING & REPAIRS

B1

While many EGR manufacturers do not recommend cleaning valves, because mechanical wear might still be present that could cause damage, many CM readers report that it can be a costeffective solution to try before replacement.

B2

Unlike the dirty valve from Step B1, this EGR valve has been affected badly by oily deposits. We have held the valve open on this unit to show how deposits can accumulate in and around the stem, restricting valve movement (circled).

B3

A variety of products are available, advertised as being suitable for cleaning EGR valves, although intake cleaners can also be used. Never use them to clean MAF sensors, because many types contain lubricating additives.

B4

With aerosol cleaners, spray the solvent into the valve and agitate it with a nylon-headed brush (an old toothbrush is ideal), before rinsing away the deposits. Ensure that the EGR valve is thoroughly dry before refitting it to the engine.

B5

Stubborn deposits can be removed by immersing the valve assembly in a vat of intake cleaning solution. Ensure that neither the vacuum ports (plug them before cleaning) nor the electrics become damp.

B6

Some EGRS are not easy to clean. This one, for example, has a curved internal tract. Instead of a brush, consider using a small, flexible sink drain cleaner.

B7

If your EGR valve is contaminated, be aware that other parts of the circuit might also be affected, such as pipes or the cooler. The EGR cooler’s bypass valve on this Volkswagen T5 unit can be checked by applying vacuum to verify that it moves.

B8

This one did not budge, meaning that either the vacuum unit is faulty, or the valve has seized. On this unit, the vacuum aspect and its operating rod can be unclipped from the main assembly.

B9

The bypass valve on this assembly had obviously seized, because handpressure would not budge it. Being a simple flap design, it is likely that carbon deposit build-up has jammed it solid.

B10

Fortunately, this EGR cooler can be dismounted by removing the bolts that hold it to the valve assembly. Note that a metal gasket may be fitted, which must not be damaged, while separating the parts.

B11

The EGR cooler’s condition explains the poor cooled exhaust gas flow, because the chamber that feeds the EGR valve is almost totally blocked. This may require extensive soaking in intake cleaner to clear it fully (see Step B5)

B12

Referencing Step B9, the cooling bypass flap’s movement in the left chamber was restricted due to the excessive carbon deposits entering via the EGR cooler. The combination of these issues was the cause, rather than a failed EGR valve.

B13

It took only several sprays of EGR cleaner while manipulating the flap manually to free it. More extensive cleaning would need to follow, before allowing the unit to dry and refitting the cooler and vacuum unit.

B14

Coolant flow on an EGR unit can be checked by flushing the unit through with a garden hose and verifying an unimpeded flow. The presence of brown water indicates sludge and it may worth using a cooling system flush afterwards.

B15

Consider also that the inlet manifold and throttle bodies may suffer from deposit build-up. Should you be unsure, remove and inspect a fitting (such as an air temperature sensor, if possible) from the manifold and check how much deposits have built

B16

Should the inlet manifold be contaminated badly, remove and clean it. It might be easier and more economical to ask a garage, or engineering works, to clean it for you in their parts washer. Be wary of damaging delicate parts, such as swirl flaps.

B17

You can clean the inlet by spraying intake cleaning fluid into the manifold with the engine running. Follow the instructions carefully and avoid the risk of ‘pooling’. EGR cleaning ability depends on the chemicals surviving the combustion process and…

B18

…whether the EGR valve opens during the procedure. You can buy various other professional and DIY decarbonising solutions that are applied indirectly by being sprayed into an intake hose. (Photo courtesy of Revive).

B19

Some professionals inject intake cleaner solvents through an EGR cooler temperature sensor aperture, or by removing a pipe that connects the exhaust manifold to the EGR valve with the engine running. (Photo courtesy of Terraclean).

The latest in EGR development sees the original high-pressure system, where exhaust gases are taken from the exhaust manifold and introduced into the intake manifold, supplemented with another low-pressure circuit that introduces filtered and cooled exhaust gases, supplied downstream of the catalyser/particulate filter, and introduces them upsteam of the turbocharger. Pictured is a layout from Mercedesbenz’s OM651 engine.

Pure electrical ECUS have a potentiometer, but employ two ways of operating the valve. We have split two EGR valves in half to show this. On the left is an EGR valve operated by an ‘in-out’ solenoid; on the right is a motor-activated EGR valve with its associated gears. All types can be checked for an open circuit with a multimeter and the gears can be checked visually for damage, caused by a seized mechanical valve.

Cooler catalyst EGR cooler EGR coolers add extra complications because they are plumbed into the cooling system. Some EGR valves/coolers are fitted with catalysts that help to oxidise soot particulates, thus reducing deposit build-up. Ensure that any replacement part matches the original’s specifications.

The gas channels within the EGR coolers can block with soot. This single-chamber part is shown being cleaned with an EGR solvent. The internal water channels can become restricted should the cooling system be neglected.