There is coolant leaking from my 2007 Tacoma's radiator SOMEWHERE because there is leakage dripping from the lower right corner. I saw it when I took the skid plate off to replace the serpentine belt.

How do I test that the leakage is indeed in the radiator and not some hose somewhere with liquid just flowing to the point from where it is dripping? Can I disconnect all the hoses, drain the fluid, and pump it up (like a residential gas pipe) to test for fluid leaks, without actually taking the radiator out before I know it needs replacement?

At this point, my hopes are that the leak is coming either from the radiator or some hose and not blown head gasket. The engine gets overheated and the coolant resi tank boils soon after a fresh coolant/water refill, no froth on the dipstick or white smoke from the tail pipe, which would indicate coolant/oil mix and blown head gaskets.

1 Answer 1


You have at least two options to find the leak. You can buy or rent a coolant system pressure tester. It is a small air pump that pressurizes the system to force coolant out of any weak (leak) points. The advantage to this method over just letting the engine idle is because the engine is cool you can reach your hand around the system without getting burnt. The disadvantage is for very small leaks it can take awhile for a drip to actually form. There are dyes that can be added to the coolant, the engine is then run and a black (ultra violet) light is used to locate the stain that will glow under the special light. This may be more useful for slow leaks as the dye stain will remain for several days. The minus side is depending on where the leak is the fan can blow the dye around and stain many places. I would check with your local parts store and see if they rent or loan pressure testers. I can think of very few cases where I couldn't find the leak with one. In some cases if the spark plugs are removed and the system pressured overnight you may find coolant leaking out the spark plug holes indicating a more serious problem than a hose radiator leak.

  • yep. i already ordered a coolant system pressure tester. thanks
    – amphibient
    May 18, 2015 at 21:06
  • what seals the spark plug holes when the spark plugs are taken out ? is there a gasket between the sockets and cylinder heads? if those are leaking, does that mean the cylinder has a leak ?
    – amphibient
    May 18, 2015 at 21:16
  • Coolant is circulated between the engine bock and the cylinder head. The head gasket seals the block and head interface. While doing the pressure test if the head gasket has failed the coolant can be forced into the cylinder. The spark plugs are removed so you can observe the coolant in the cylinder.
    – mikes
    May 19, 2015 at 1:59
  • If you have a leak into the cylinder, you can usually see a difference in the spark plug themselves. When you pull the spark plugs, if one (or more) of them appear very clean while others have a bit of suet on them, this is usually a sign the cylinder has a leak. Coolant (and/or water) has the propensity for leaving the cylinder/combustion chamber/spark plugs sparkly clean. You'll usually notice a large difference in how the spark plug looks. May 19, 2015 at 10:59

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