I had a very classic (or so I thought) case of blown head gasket in my car:

  • Leaking a ton of coolant
  • Bubbles in the coolant, when engine running
  • Coolant seems to be brownish
  • Failed CO2 Test on the coolant
  • Trouble starting the car from time to time

I spoke to several mechanics, watched a bunch of youtube videos, read a ton of Q&As on this site and posted some questions myself and was absolutely sure that what I had was a blown head gasket.

I than send my car to be repaired in my home country and was surprised to find out, that they didn't think the head gasket is blown, but another part. They fixed that part, didn't touch the head gasket at all and now the coolant leakage is completely fixed (car has been driven for 300km since).

The part they fixed, is some sort of heater, between the motor and the exhaust, which is supposed to heat up the fumes? I didn't understand it and didn't find it on google.

So what could it have been if not a head gasket problem? I thought that C02 test is an absolute certain 100% indicator of head gasket problems?

Where else can fumes enter the coolant, except through the head gasket?

What part did they probably talk about?

I am torn between these guys being absolute geniuses or not knowing at all what they are doing. Maybe the gasket still needs repair? Or I almost changed the head gasket for no reason at all, while not even fixing the problem?

The part in question:

enter image description here

The car in question is a Nissan dci 2.0 2010 Qashqai (Similar to Nissan Rogue in the US).

1 Answer 1


It makes sense.

The picture shows an exhaust cooler, part of the Exhaust Gas Recirculation system which helps control emissions. In a diesel engine EGR takes exhaust and puts it back into the intake manifold to adjust the amount of oxygen in combustion, making it cleaner. Exhaust gas is very hot, and it needs to be cooled before if can be re-used, this is done by running it through the cooler, which uses the engine coolant. A leak in the cooler will cause coolant loss along with the rest of the symptoms you were experiencing.

  • Does the intercooler look like what I just added to my question? Sep 13, 2018 at 14:16
  • That's an exhaust gas cooler, part of the emissions reduction system. I've changed my answer accordingly.
    – GdD
    Sep 13, 2018 at 14:31
  • Hmm so there are many places where coolant and exhaust smoke can mix? Why is the standard answer to "what does a co2 test indicate" always seem to be unequivocal "head gasket"? Or maybe my car is just special? Sep 13, 2018 at 14:43
  • It depends on the car, engines with turbos and advanced emission systems have more that can go wrong @user1721135. Generally it is the head gasket even then, so you've gotten off with a much cheaper fix.
    – GdD
    Sep 13, 2018 at 14:48

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