EGR cooler failure: symptoms and what to do
EGR cooler failure usually shows up as coolant disappearing with no puddle under the car, white smoke with a sweet smell and, in time, overheating. Coolant is leaking inside the cooler into the exhaust gas that's fed back into the engine. It needs dealing with promptly, as it can cause serious engine damage.
What the EGR cooler does
Many diesels pass recirculated exhaust gas through a small heat exchanger before it reaches the intake. Engine coolant flows around tubes inside it, taking heat out of the gas so it does a better job of lowering combustion temperatures.
Because the cooler sits between very hot exhaust gas and the cooling system, it goes through big temperature swings every time the engine warms up and cools down. That's where most failures start.
Signs of a bad EGR cooler
- The coolant level keeps dropping, with no visible leak
- White smoke from the exhaust, often with a sweet smell, especially on a cold start
- The engine running hotter than usual or overheating
- Steam or a coolant smell from the engine bay
- Rough running or a misfire after the car has been parked overnight
- Black smoke or EGR flow codes such as P0401 if the cooler is blocked with soot
- An EGR cooler performance code such as P2457
Leaking or blocked?
Coolers fail in more than one way, and each brings different risks.
| Fault | What you notice | The risk |
|---|---|---|
| Internal leak | Coolant loss, white smoke, sweet smell | Coolant collecting in a cylinder can lock the engine and bend a con rod |
| External leak | Coolant on the cooler or under the car, a smell of coolant | Overheating if the level drops too far |
| Blocked with soot | EGR flow codes, black smoke, sluggish performance | More soot reaching the intake and the DPF |
Why EGR coolers fail
Heat cycling
Repeated heating and cooling makes the metal expand and contract, and over time the thin tubes crack.
Old or wrong coolant
Coolant that's past its best or not to spec loses its corrosion protection, and the cooler's internals start to corrode.
Soot build-up
Soot and oil vapour line the tubes, which reduces cooling and can lead to hot spots.
Overheating
A low coolant level or a failed water pump lets the cooler run too hot, which speeds up cracking.
How a leaking EGR cooler is confirmed
Coolant loss with white smoke can also point to a head gasket, so it's worth confirming before paying for parts.
We carry out the codes and live data check on site as part of our mobile diagnostics (£100 + VAT).
Track the coolant level
Note how much goes over a week, and check for external leaks with the engine cold.
Read the codes and live data
Coolant temperature, EGR readings and misfire counts help narrow it down.
Pressure-test the cooling system
A garage can isolate the cooler and check whether it holds pressure.
Test for combustion gases in the coolant
Exhaust gas in the coolant points more towards a head gasket than the cooler.
Getting it repaired
A leaking cooler has to be replaced by a garage, and on some engines it comes as one unit with the EGR valve. We don't replace EGR coolers, but our diagnosis tells your garage which part has failed.
Some manufacturers have issued recalls over EGR cooler faults, so check yours on the GOV.UK vehicle recall checker before paying for a repair.
Can I keep using a car with a leaking EGR cooler?
It's not worth the risk. Coolant getting into the cylinders can lock the engine, and running low on coolant can overheat it. Keep an eye on the level and get it checked as soon as you can.
Is it the EGR cooler or the head gasket?
Both can cause coolant loss and white smoke. A cooling system pressure test with the cooler isolated, and a test for exhaust gas in the coolant, usually tell them apart.
Will an EGR delete fix a leaking EGR cooler?
No. A software delete changes how the ECU runs the EGR valve, but coolant still flows through the cooler, so a cracked one carries on leaking. The cooler itself has to be replaced.
What causes an EGR cooler to leak coolant?
Cracking from repeated heating and cooling is the most common cause, followed by internal corrosion from old coolant. Overheating speeds both up. Our EGR valve problems and symptoms guide covers the faults that often appear alongside it.
Find out if it's your EGR cooler
Losing coolant with no sign of where it's going? Book a diagnostic check and we'll come to you, read the codes and live data and tell you what to ask your garage to fix. It costs £100 + VAT.
Want to ask something first? Email sales@sgrautomotive.co.uk or read about white smoke from the exhaust.
Eccles, Manchester M30 0SF