Coolant reservoir level goind down but no physical leak?

This is issue is happening to my wife's car and it not an LS1 engine. She has a 06 Nissan Altima 4 cylinder. I'm just trying to see if someone else can point me in the right direction.

The car ran always good. Last year the car overheated and the head gasket was blown. We took it for repair and it was fixed on April. Since December I started noticing the coolant reservoir level was going down. We ran the car for two weeks without checking the reservoir and it was empty the next time I checked it. I always check the level in the mornings with the engine cold. I did noticed some coolant on the top of the radiator around the plastic part. The radiator had some cracks on it. I replaced the radiator and topped of the coolant reservoir. I ran the engine for about 30 mins with the radiator cap off and noticed the coolant level dropped(I had the heater on as well). I put the radiator cap back on.

I still noticed the level going down from like max to low in a few days. Again no visual leak. The car is not smoking, doesn't have any milky mixture in the engine oil. The car is running fine and the a/c cools and the heater works.

I put a coolant system pressure tester to see if I can pinpoint the leak. I put 18 lbs of pressure. I did noticed the gauge slowly go down. I checked all around the engine and found nothing. I did noticed a small leak around the radiator hose were it meets the engine by the clamps. I tighten down the clamps and pressurerized the system again and noticed it was down to 1/2 psi every 3 mins or so. So there was a big difference. I checked around the hoses again and didn't felt any more leaks.

The radiator cap was replaced with a new one. The level of the reservoir went down again a little bit when I checked today. I also noticed this started with the recent weather change in FL.

The radiator level itself it never been low. Is there anything else I'm missing here? No coolant smell around the engine area. I don't think is the head gasket again since the car has not overheated. Any other problems that will cause the reservoir level to go down like this? This is driving me nuts as I don't want the car to overheat. Thanks.

Think because you're needing to run the heater more check around the heater core see if carpet is wet?


Pull plugs see how they look? If you're leaking in the cylinder it will show.

I will check the carpet. If we are using the heater wont the reservoir level come back to normal level once the engine is cold? Like overnight? I can look at the plugs as well. I have to wait for my wife to get out of work.

I agree with Scott. Also, how long was the engine run when it overheated? Check around the intake manifold. Could be warped.

Im not sure how it was ran before it overheated since my wife didn't looked at the gauge. The car was repaired in april and it just started to have this issue. You think the intake issue could just started giving this issue? Everything was working fine.

one more place to check...around the water pump weeping hole and does it have coolant cross over tubes like our LSx motors?

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Originally Posted by SMWS6TA

one more place to check...around the water pump weeping hole and does it have coolant cross over tubes like our LSx motors?

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No cross over tubes. I did check around the pump as well and I don't see it. I might add UV dye to the coolant to see if I can pinpoint. This might sound like a stupid question but is it normal for the car to have a coolant reservoir level that goes down only( it doesn't come back up at any time) but has a full radiator? Some people are telling me that I don't need to worry about the reservoir tank as long as the radiator is full even with an empty reservoir.

I have been adding a little bit off coolant to the reservoir every weekend for the past 2 months. I would think at some point the reservoir level should come back up. Could I still have air in the system after 2 months?

so it's just the reservoir that is constant low?



If so I'd pull it and see if you have a hairline crack in the plastic.

Those 2.5L Nissan heads like to crack between the valves. If you have a video scope I would poke around inside the combustion chamber through the spark plug home and take a look between the valves. When the engine heats up the crack will expand so do it when the engine is warm. Did you have the head checked and magnafluxed when you had it apart. Did you use new head bolts ? You can get a remanufactured head with cams for under 500.00 with a warranty so it is not that bad if it is cracked. Good luck.

a shop did the work so who knows what they really did vs what they said they did.

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Originally Posted by 2002ssslp

Those 2.5L Nissan heads like to crack between the valves. If you have a video scope I would poke around inside the combustion chamber through the spark plug home and take a look between the valves. When the engine heats up the crack will expand so do it when the engine is warm. Did you have the head checked and magnafluxed when you had it apart. Did you use new head bolts ? You can get a remanufactured head with cams for under 500.00 with a warranty so it is not that bad if it is cracked. Good luck.

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Kind of along the path of what I was thinking too.