# Coolant disappears -- but no visible leak?!?



## pibboater (Nov 20, 2012)

About two weeks ago I noticed my 2000 Maxima was not putting out much heat from the vents. I googled it, and found the first thing to check is the coolant level. The coolant level was almost empty, just barely visible in the reservoir, so I topped it up to the MAX line (while cold), and then the heater was back to blowing hot. About two days later I opened the hood to check the coolant level, and was surprised to see that the reservoir had nearly emptied again. I decided to try refilling the coolant one more time before having it looked at, so I filled it to MAX again and then started it and let it run with the heater blowing for about 30 minutes. I couldn't see any leaking anywhere, at least anywhere that was easily visible from above and below, and the floor boards weren't wet.

I took it into the local mechanic today and he pressure tested and could not find any leaks, then he refilled it and checked again and couldn't find any leaks, or any sign of previous leaks. I'll be picking the car up and keeping an eye on it, but I expect that in the next day or two the coolant will be gone again.

Does anyone have any ideas of what I or the mechanic should look into next? Thanks!


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## rogoman (Dec 16, 2004)

You may have a blown head gasket. Do a compression test on all cylinders. While performing the compression test, remove the coolant fill cap and make sure the coolant is filled to the neck of the fill tube; this way you may see small bubbles which would be an indicator of a possible blown head gasket.


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## pibboater (Nov 20, 2012)

Thanks for the quick reply rogoman! I will mention the compression test to the mechanic when I pick it up tomorrow morning. If it is a blown head gasket.. that sounds expensive. Any idea of a ballpark cost to have a shop repair that?

Also, forgot to mention a couple other things -- the mechanic said he did not see any exhaust smoke, and did not see any coolant in the oil.


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## chuckster57 (Oct 2, 2012)

There is also a test for combustion gases in the coolant. Kit from Auto Zone is like $15.00. Instructions included, and if the head gasket is bad, repair costs will depend on where you go (dealer or independent shop), labor rates, and possible machine work.


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## pibboater (Nov 20, 2012)

Thank you for the suggestion chuckster57! I'll pick up that combustion test as soon as I can.


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## Outkast (Jan 29, 2006)

IACV gasket, coolant leaks past the bad seal onto the electric motor causing the computer to short out. Do a leakdown test on the cylinders and if they are good pull the throttle body off and replace the IACV gasket even if it hasn't blown. There isn't a 99-01 maxima that comes in with high mileage that I don't try to sell that gasket to as a precaution.


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## smj999smj (Jan 1, 2006)

For price estimates, try this site:

RepairPrice Estimator - Get an Estimate for a Service or Repair on Your Car


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## faisalmakki (Nov 26, 2012)

Replace the radiator cap. 

I did experience a similar problem. No leaks with coolent disappearing. 

Also check the water pump when you start the car. check when your car has been driven for a while. Check you car a couple of time during the drive. 

The pressure test will not work with radiator cap.


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## pibboater (Nov 20, 2012)

@faisalmakki, thank you for the suggestion. A new cap is an inexpensive enough thing to try, so I'll pick one up on my way home. How do you go about checking the water pump -- is it visible under the hood, and you just look for dripping, or something else?

@Outkast, thank you for the suggestion -- I'll mention the IACV gasket when I take it back in.

@smj999smj, that's a neat site, and great for answering my question about a ballpark figure for the repair! Man a head gasket replacement would be expensive.. But since it doesn't run rough, the oil was clean, and there's no smoke, I'm really hoping that's not it. I still need to do the combustion in the coolant test too.


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## Outkast (Jan 29, 2006)

The water pump weep hole is hidden but if you see coolant residue in the A/C compressor then you have a leaking waterpump.


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