I have attached a collage of the EGR repair. Note the features of the respective EGR coolers differ, specifically the original has 32 gas ports and a large chamber clearly intended to maximize exhaust gas transfer to the engine. The new (Jul 2017) cooler drops the large chamber but retains the
32 gas ports increasing the amount of coolant that can circulate between the ports and likely reducing the volume of exhaust gases that are drawn into the EGR valve chamber. A bypass tube was fabricated from the salvaged port tubes of the original cooler, to be used to reroute coolant from the egr cooler thus it is only exhaust gas that passes through the egr cooler to reach the egr valve. The efficiency of a cooler can reduce by 25% to attain a stable state. The amount of heat transferred from gas @ ~375° to a 32 vane cooler @ ~103°C may be negligible and the increased efficiency of coolant passed to the radiator is believed by some to compensate for this loss in egr cooling. The bypass can also be used temporarily if there is uncertainty regarding the functioning of the egr valve or if a head gasket failure is still a concern.
The collage shows evidence of coolant crystals present in the egr valve ports. Moreover, the accumulated soot with coolant coating the head can
be mistaken for a head gasket failure.
A tapped hole in the exhaust aft of the manifold is an easy solution to draining the exhaust of fluids, a bolt or screw is then seated to plug the hole. Two alu 3mm blanking plates are available for blanking of the egr circuit at the exhaust manifold and egr vacuum hose should the effect
be warranted.
Following the repair and recharging with coolant (bring engine up to temperature to open thermostat, drain and recharge. Run HOT aircon to purge heater core) all symptoms disappeared:- exhaust gas bubbles in expansion tank, white smoke from exhaust, poor idle unblanked and rapid loss of coolant (with no visible leaks). Noticed that cold start is easier, the engine reaches temp sooner, the engine sounds smooth and am anticipating improved mpg.