Radiator losing water (no leaking) but overflow keeps gaining water

I have 2007 Nissan navara d40 2.5ltr turbo diesel. I have noticed that after driving and the car has cooled down that the water in the overflow has increased. When I open the radiator cap you can hear air/pressure noise and the radiator takes about 3/4 to 1ltr water to top back up. Also when I run the car with cap off and rev it up it bubbles a bit and pushes some water out of radiator. I can't see any leaks and it's not running hotter than normal. Someone said that was normal due to an air block or something and because the two tanks are at different height

My car has 255000 miles

Experienced mechanics share their insights in answering this question :
Based on the information you provided, It sounds like you may have a blown head gasket. What happens is that the high pressure in the combustion chamber squeezes its way through a break in the head gasket into the coolant passages. The result is pressure build up within the cooling system that could push coolant out into the overflow tank. Be sure to check your oil to see if coolant has contaminated it. If so, it will look milky.

I suggest getting help from a certified technician, such as one from YourMechanic, who can diagnose the possible leak and perform a quick test to determine if combustion gasses are getting into the coolant. Best of luck.

How to Identify and Fix Common car Problems ?

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If you`re seeing an overflow, it could be due to a radiator cap, thermostat, water pump, or radiator malfunction.
One common cause of the coolant reservoir being full but the radiator low on coolant is a blown head gasket. Combustion gasses from one of the cylinders leaks into the cooling system, and forces coolant from the engine into the reservoir. Once the reservoir fills up, the rest goes overboard through the overflow outlet.
If the coolant level is dropping and there is no external leak evident, then the coolant is probably leaking internally, into the engine. If the car has recently overheated then this could have caused the head gasket to fail. If it has, it could be leaking coolant into the combustion chambers.
When there`s a leak in the cooling system, the pressure of the liquid drops and so does the boiling point of the coolant/antifreeze. Cooling systems are pressurised to raise the boiling point of the fluid, with the pressure cap and the overflow helping to raise the temperature at which the coolant/antifreeze boils.
Common causes of a car radiator pushing out water can include a malfunctioning pressure cap, a blown head gasket, or an internal coolant leak. If the problem is not immediately obvious, then it`s best to have your vehicle inspected by a qualified mechanic as soon as possible.
The most common cause of radiator leaks is leaky hoses, but you can have leaks in the radiator itself, too, which can be a bigger problem. The coolant continually running from your radiator to your hot, running engine and back again creates a lot of pressure.
It may be a broken hose and/or a hole in the radiator. Solution: Check your hoses to see if any coolant is coming out. Replace the hose(s) if you notice coolant coming out of them. If you notice coolant leaking out of your thermostat that can be an easy fix.
Coolant Leaks

Oftentimes when the thermostat fails, it remains in its closed position. As the engine overheats, coolant will overflow out of the thermostat housing. This means that coolant leaking out of your engine could be a sign that your thermostat has gone bad.

Loose or damaged spindle

This can often be the source of water leaking from a radiator. This is often sorted out by simply tightening the gland nut, which may have come loose over time. If water is still leaking out then wrapping some PTFE tape around the spindle is another common fix for this problem.

If possible, turn off the valves to the radiator. You can do this by screwing them down (clockwise direction). This may slow or stop the leaking water, until a qualified plumber or gas engineer can repair the leak.
If your engine has overheated (due to a stuck thermostat, low coolant or for some other reason), it`s possible for superheated coolant to swell the hose. Swollen hoses should be replaced as soon as possible. This applies to radiator hoses, as well as other hoses under the hood.
In general, it`s because something`s wrong within the cooling system and heat isn`t able to escape the engine compartment. The source of the issue could include a cooling system leak, faulty radiator fan, broken water pump, or clogged coolant hose.
One way to check for proper coolant circulation is to check the upper and lower radiator hoses. The upper radiator hose should be hot, around 190–200 °F. (The safest and most accurate way to get this temperature reading is with an infrared thermometer.)
Use your radiator key to turn the valve at the top of the radiator. Attach the key to the square groove in the centre of the valve as shown in the diagram and turn it slowly anticlockwise. You should hear a hissing sound. This is the trapped air escaping.
The cooling system is one where air bubbles can be a significant concern. They can lead to hot spots in the engine, which can cause it to overheat and lead to all sorts of internal engine damage that will be costly to repair.
Faulty Thermostat

Then stay near to the car as the engine heats the coolant to start it. When a thermostat malfunctions, it fails to open and close at the proper times. As a result of the unregulated airflow, it generates a bubble effect in the coolant reservoir or radiator.

If your car is overheating, but it has coolant, these are some possible reasons: Bad water pump. The water pump keeps the coolant circulating through the engine, so if it stops working your coolant won`t circulate and can reach boiling temperatures. Clogged radiator.
If you are regularly topping off your coolant, you have a coolant leak somewhere in the system. It can be difficult to identify where the leak is coming from. Often it is best to have a professional diagnose a coolant leak, but there are a few things you can check before bringing your car into a shop.
The first thing you need to do is locate the source of the coolant leak. It might not be coming from the radiator. The best way to confirm the source of the leak is to wash the radiator and hoses with water, and then start the engine and look for new signs of coolant.
There`s a leak in the radiator, heater core or one of the hoses. The radiator cap is stuck open. Hot coolant leaving the system evaporates quickly. The water pump or water pump seal is leaking.
A failing thermostat would absolutely cause the system to overheat and build pressure. If you are already seeing signs of leaking near or from the thermostat housing there is a good chance this is where the problem lies.
Simply draining the radiator may get rid of most of the old antifreeze but could leave some coolant and contaminants behind, which would then mix with and pollute your new antifreeze and cause overheating.
If there is a reservoir, you should always add coolant to the reservoir unless the level is extremely low. An overflow or recovery tank will catch excess coolant and send it back to the radiator. It may be worth doing a coolant flush if the car has been in storage for a while.
There`s a leak in the radiator, heater core or one of the hoses. The radiator cap is stuck open. Hot coolant leaving the system evaporates quickly. The water pump or water pump seal is leaking.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

Radiator losing water (no leaking) but overflow keeps gaining water
ANSWER : Based on the information you provided, It sounds like you may have a blown head gasket. What happens is that the high pressure in the combustion chamber squeezes its way through a break in the head gasket into the coolant passages. The result is pressure build up within the cooling system that could push coolant out into the overflow tank. Be sure to check your oil to see if coolant has contaminated it. If so, it will look milky.

I suggest getting help from a certified technician, such as one from YourMechanic, who can diagnose the possible leak and perform a quick test to determine if combustion gasses are getting into the coolant. Best of luck.

I have a leak in the coolant system that I have narrowed to I believe is the water inlet tube off of the lower radiator hose.
ANSWER : First off, I would say it would be best to pressure test the cooling system to verify where the coolant is coming from. With the complexity of repairs to the cooling system on this vehicle, it may be worth the time spent to pressure test the system before tackling the replacement. Now then, as far as replacing the o-ring seal on the water pump inlet tube, it should really only require the removal of the bypass hose, lower radiator hose, and the two (or three, depending on manufacturing changes) mounting bolts that hold the inlet tube to the block. I personally would go ahead and replace the tube while I was there, instead of just the o-ring. Granted, this doesn’t mention what it will take to get down to the inlet pipe, but this is all it should take once you have access to it. If this is something that you feel you could use a hand with, consult with a certified mechanic, like those available at YourMechanic.com.

saw some radiator fluid leak, some clear water. overheated. Water pump? thermostat? Radiator full
ANSWER : Hello, thank you for writing in. Air conditioning systems do condensate and drip water. This is totally normal, and likely unrelated to the cooling system problems. If the coolant is full, and it was not the source of the leak, then the coolant is not being circulated, or it is not being cooled by the radiator fast enough. With the water pump and the thermostat being two of the top components to inspect, you will want to also consider the cooling fans and the radiator need be. Clogs can cause a lack of circulation, but so can bad pressure regulation. Leaks in the system or a bad radiator cap can cause pressure differences. Only further testing will tell. For more help with testing, contact our service department to schedule an appointment.

I have a 2002 Buick rendezvous my radiator has a leak when I open hood there was water spitting out from under the water pump is t
ANSWER : If your radiator and water pump are both leaking, my best recommendation would be to enlist the assistance of a qualfied professional to have them replaced. Allowing these parts to leak for an extended period of time can cause the engine to overheat. If the engine overheats, this can cause damage to the head gasket, cylinder heads, or engine block. Some of this damage may be perminant. In order to avoid serious engine damage, I would recommend having these issues resolved as soon as possible. Once these parts have been replaced, have the cooling system pressure tested to ensure that no more leaks exist.

I think there is a leak and water is dripping? Can you fix water or oil leaks? Thanks.
ANSWER : Hi There,
Yes, we can fix coolant and oil leaks. Generally, if you are noticing a water leak, this would be coming from the radiator, water pump or any of the radiator hoses around the motor that may be going to or from the radiator. Generally, when a water pump is going bad, you may hear a bit of a whining sound combined with the pump leaking. The most common place for the water pump to leak from is the pulley shaft seal which is in the front of the pump where the shaft comes out of the pump housing. When the pump is leaking, it will typically cause the engine to overheat as well. I would recommend having an expert from YourMechanic come to your location to diagnose and replace your water pump.

Leaking top radiator hose? Leaking top radiator hose how to replace a leaking top radiator
ANSWER : If you have not done a job like this before you might want to consider watching a professional from YourMechanic do it for you, especially as the labor time is less than 1.5 hours so it’s pretty economical. The first order of business, of course, is to make sure that the upper hose is actually leaking and you don’t have a different issue such as a crack is the radiator itself where the hose attaches. Also, if that hose is leaking due to a break in aged rubber, the other "old" hoses should be inspected as well. A radiator hose replacement entails removing any plastic shields that prevent access to the hose(s). Then, you have to drain the coolant to a level below the lowest point that you will be working at. The hose clamps are removed and then you have to carefully "debond" the hose from the point it is attached to the tank. Over time, the rubber will bond really tightly to the radiator and you have to break the seal with damaging or severely scratching the radiator "nipple" (the part the hose slides over). Then you slip the new hose on (with clamps already loosely applied), apply the clamps and you are ready to refill. When refilling, you have to open the cooling system bleeder screws (if equipped) to ensure that air does not get trapped. Trapped air could cause the car to overheat as trapped air can block coolant flow.

Car ran hot losing power, pulled over put water in radiator car wouldn’t start, replaced radiator, still won’t start
ANSWER : When you overheated the engine you most likely blew a head gasket and now have low compression in one or more cylinders. Replacing the radiator after overheating the engine that lost power will not fix the fact that the overheating warped the cylinder heads and coolant leaks past the cylinder head gaskets. If you need help with this, a technician from certified mechanic from YourMechanic can come to your car’s location to diagnose your car’s starting problem and conduct any needed repairs.

I have a 00 deville I just changed the water pump housing and water pump the thermostat and radiator the upper and lower radiator 2000 Cadillac De Ville
ANSWER : Hi there – I suspect your radiator is clogged or otherwise corroded so that it is not shedding heat as efficiently as it should. Idling with the heater on was getting rid of heat without loading the radiator. When you’re driving, the engine is generating more heat than both the heater and radiator can get rid of. Checking the difference between hot coolant going to the radiator (top hose), and going back into the engine (bottom hose) may show that there is very little temperature difference. This means the radiator is not doing it’s job, and need to be professionally cleaned or replaced. Good diagnostic effort on your part to avoid the obvious "it’s another Northstar head gasket" diagnosis! For confirmation, I would recommend an overheating inspection by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, diagnose this problem, give you an accurate assessment of damage and cost estimate for repairs.