why is my car filling up the reservoir tank?

Asked by Mar 23, 2015 at 04:10 PM about the 1997 Subaru Legacy 4 Dr Outback AWD Wagon

Question type: Maintenance & Repair

It used to over heat only in the mornings after having driven it for about ten minutes and I would take off the radiator cap and fill up the radiator and the reservoir tank would be filled up completely, after that it would be fine for the rest of the day until the nest morning.
It seems that it overfills the reservoir tank and looses coolant though there.

4 Answers


Bad thermostat,or water pump.

Ok thank you. I thought it could be that but read that it could be a blown head casket it that likely? It did over fill the reservoir once after having it driven for about more than an hour but I just did the same thing of removing the radiator gap and refilling it and it was fine the rest of the trip


The blown head gasket is still a possibility, cylinder pressure could be pushing coolant up into the reservoir


You need a new radiator cap, and hose going to the overflow. The valve is stuck, and won't reverse pressure, or there is a clog in the hose that dislodges one way but sticks going the other way. by removing the radiator cap, the pressure was able to equalize which is why it was fine for the rest of the trip. I recommend flushing the coolant system afterwards to clear any debris that might be in there.

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