Can a defective EGR valve cause coolant loss?
Water and exhaust don’t mix - right? That’s correct - in theory, but if your EGR valve unit is defective - they can (and that’s bad)
QUESTION
Hi John - Im seeking your advice after a friend's new Ford SUV was diagnosed for coolant loss by the ford dealer.
Can a leaking EGR valve cause coolant loss?
If how and where?
Thanks,
Brad
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ANSWER
EGR stands for ‘exhaust gas recirculation’ system, which pumps exhaust gas back into the inlet side of the engine, at times, in measured doses, to improve fuel economy and reduce toxic emissions. Essentially it reduces oxides of nitrogen, which cause acid rain and are harmful to human health. There’s also a benefit to volumetric efficiency in some engines - pumping losses are reduced with EGR. (Engines aren’t pumps.)
Wikipedia has an excellent entry on exhaust gas recirculation.
The reduction of NOx is especially helpful in lean burn conditions, where there’s typically too much oxygen for the available fuel in the cylinder, and it gets energised by the combustion process and combines with atmospheric nitrogen. (Air is roughly 80 per cent nitrogen gas.) Diluting the air with comparatively inert exhaust gas helps prevent this from occurring. Typically it’s done at low loads, and diesels do more EGR than petrols, typically.
My understanding is that this kind of EGR failure happens quite a bit with Ford Everest - it has to be something about the comparatively poor way the system is integrated into the engine. (Like, a flaw in the R&D - most probably attributable to a beancounter who didn’t let the engineers do their jobs properly.)
Short version: The EGR system is water cooled - it’s capturing hot, highly energetic exhaust gas from between the exhaust port and the turbocharger, and sending it back to the inlet side, and the heat is a gross disadvantage to engine operation.
Therefore, water from the engine’s cooling system is pumped through the EGR inlet to capture some of this heat before it gets to the EGR valve. That heat is rejected to passing air in the vehicle’s radiator, with a great deal of other waste heat from the engine.
If the EGR cooling system develops a leak, water can escape into the EGR system and pass through the engine, accounting for gradual coolant loss.
If that happens, the whole EGR body - which is typically one big stainless steel component - needs to be changed out.
Also bear in mind that a leaking EGR installation is good news - comparatively. Apart from obvious causes like defective hoses, most other engine cooling system leaks are very expensive to fix and require significant disassembly, such as a blown head gasket or defective turbocharger, or (even more expensive) a cracked cylinder head.
Unfortunately, coolant loss of this nature can cause catastrophic engine failure - often with few warning symptoms (or none).
