I have a Nissan FB13 Supersaloon.

The car started having radiator problems when the radiator was blocked. After repairing the radiator the engine started building pressure and you could see bubbles from the radiator cap within 3 minutes of starting the engine.

I then took the head for repair suspecting that it could have warped. I bought a 3 mm thicker head gasket but still the problem persisted. The head has been skimmed 2 to 3 times. The guys who serviced the head said they did every tests on the head including pressure test and they say the head is 100% perfect.

What could be the problem?

  • Did they measure the block mating face to see if that is true?
    – Solar Mike
    Feb 15, 2018 at 7:24
  • Welcome to Motor Vehicle Maintenance & Repair! Feb 15, 2018 at 13:09

1 Answer 1


There are a limited number of places where combustion gasses can get into the coolant. A cracked head is the obvious one. It is also possible that it is a crack in the block going from the cylinder into the water jacket.

You could use an exhaust gas analyser to sniff the bubbles in the expansion tank to verify that it is exhaust gas coming through.

  • 1
    This does not provide an answer to the question. To critique or request clarification from an author, leave a comment below their post. - From Review Feb 15, 2018 at 17:37
  • @MooseLucifer Are you saying that it couldn’t be a cracked block?
    – HandyHowie
    Feb 15, 2018 at 19:07
  • Definitely could be a cracked block, but unless you expand on what makes you think it's a cracked block, then I think this is better suited as a comment. Feb 15, 2018 at 19:19
  • 1
    @MooseLucifer Updated
    – HandyHowie
    Feb 15, 2018 at 19:34

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