Simple: Run A/c or Defrost coolant disappears from overflow tank (no more than a 1/4 cup). Doesnt happen any other time. No symptoms of leaks, just loss from tank.

 

Causes?

 

History:New water pump, thermostat, rad, rad cap, hoses all done at subbie shop within last 10k.

 

I almost want to think air in the system but Im not sure, because afaik when there is air in the system it usually runs hotter than normal, which in my case it isnt doing. The needle stays pegged right in the mid. Again there is NO visible leaks, no oil in coolant or coolant in oil....just a small loss from the overflow tank.

 

Ideas....where to start?

Ideas....where to start?

 

Lets start with:

 

Car type

Engine type

Odometer reading

Question: Are you saying that you lose 1/4 cup of coolant from the overflow tank EACH TIME that you use the AC? And that it doesn't return to the tank later?

 

If that is the case, then you are actually losing coolant somewhere.

 

However, if the level of coolant returns to normal later, then this is nothing to be concerned about.

 

Please clarify.

Our Forest did something similar for a bit, coolent just went MIA.

Put some stop leak in it a few times and it went away.

DO NOT, DO NOT just put in some stop leak. It cause more problems than it ever fixed. Find the cause of the loss of coolant and fix it. There has to be a loss somewhere and it can be found. Smell the coolant and see if it smells like exhaust, if it does you have a bad headgasket and it only effecting things when the A/C is on, It will get worse as time goes by if it is a HG. Fixing it now will prevent heat from destroying a bearing and resulting in engine replacement. You can also have the coolant tested for hydrocarbons and that will give a definitive answer as to the HG.

 

Good luck

been working fine for over a year.........

 

Was no sign of a leak anywhere, coolent just went MIA at random times.

Doesn't anymore.

Type= 02 Impreza RS

2.5 (obvious)

 

Problem was that I would lose 1/4 from overflow after each A/c use and it wouldnt return. Changed out radiator cap and I dont seem to be having the problem now. Hopefully that was it.