So the coolant reservoir tank seems to boil after around 15 minutes of the car running and spills some coolant too. What can be the issue and will it be expensive?

enter image description here

enter image description here

  • Is this the cap you speak about? – Elvira Gaona Jul 15 '18 at 6:17
  • Suggest you add the images to your question as that will make people understand it is your tank and not just an example image. – Solar Mike Jul 15 '18 at 6:20
  • That does not look like the cap for the pressurized cooling system. That may be the cap for the windscreen washer fluid... – Solar Mike Jul 15 '18 at 6:26
  • I take it your Civic is a 2001-2005 model year? Is it an EX, DX, LX, or ? And you stated it boils from the white bottle, yet you've recently changed the metal cap to try and fix the issue? – Pᴀᴜʟsᴛᴇʀ2 Jul 15 '18 at 13:21
  • Yes any idea why? – Elvira Gaona Jul 15 '18 at 13:46

I had this same problem recently on a 02 Honda Civic LX. Boiling coolant, overfilled overflow tank, overheating. The problem was caused by a warped cylinder head that was allowing exhaust gas to leak into the cooling system. I pulled the head, had it shaved. A LOT OF WORK! Have fun! :-)


This sounds like the system may not be pressurizing - there are a couple of things to check:

1) is the cap tight? Or is it broken, as some are designed to allow air to enter if the system goes below atmospheric pressure

2) are there any leaks evident?

Edit the cap may look something like: enter image description here enter image description here

  • I close the cap right after I check it, how do I verify that maybe the cap needs to be changed? – Elvira Gaona Jul 15 '18 at 6:20
  • When you say "close" is it properly tight? Does it have the seal inside? Is the seal in good condition ie no cracks, splits or chunks missing? – Solar Mike Jul 15 '18 at 6:23
  • Yes I meant I close it tight. And was that the cap you were speaking about? I recently changed the other cap – Elvira Gaona Jul 15 '18 at 6:25
  • The one I just addded is the one I just changed – Elvira Gaona Jul 15 '18 at 6:31
  • The one with the white cap is the one that boils. – Elvira Gaona Jul 15 '18 at 6:35

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