My 1994 honda civic is bubbling in the reserved bottle and when its cool and i open the radiator there is no water or coolant in the bottle or radiator whats wrong with it

Change thermostat first! Then change temperature sender!

The most common overlook thing is you got a air pocket, so before you go spend your money turn Heather on full blast, open the radiator cap, car running look for air bubbles, takes patience cause you got to wait for the thermostat to open up, you must refill the coolant really really slow snail pace, some car have a bleeding valve others have two chamber on the overflow bottle,good luck, if that doesn't work change the thermostat first and if that doesn't work I'm afraid you may need to replace water pump. . water pump

The thermostat, a weak point on most internal combustion engines, controls the flow of coolant to the radiator and this is fed into the top tank of the radiator.

The bottom hose is normally at the inlet to the coolant pump.

Vehicles with AC will have two radiators, and even some, a third for transmission or oil cooling but the largest of them will be the one handling engine cooling.

Locate the topmost hose of the radiator and simply follow it back toward the engine and it is normally connected to a dome-like fitting, under which you will find the thermostat.

If you are experiencing overheating though, it may not be a failed thermostat; this can be caused by a radiator blocked with debris, an internally collapsed hose and worst case, a failing head-gasket. The latter can fail in several places and overheating is often caused by the failure of it between coolant channels and one or more of the cylinders. This allows passage of hot combustion gases directly into the coolant flow.

Check the following: the overflow bottle for traces of oil contamination and possible odor of exhaust fumes, the oil dipstick for a milky deposit and when the engine is running, the overflow bottle for bubbles.

The cooling system is overpressurized and is lifting the radiator cap off of its seat at about 14 psi. This will push coolant into the overflow bottle. the most likely reason the system is overpressurized is that combustion gases are leaking past a blown cylinder head gasket into the cooling system. To verify this, you can use a Lisle 75500 combustion gas leak detector kit. it is inexpensive and will show if combustion gases are leaking into the coolant.

you mean your coolant? right,,, check to see if your fans turn on...(not inside your car fan the on in front of the car) and check your Coolant level...

When the car is completely cool,check the electric fan(s) for smooth rotation.

Clean/check/change the thermo sensor,contact and wire.

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Excavate air pocket in coolant system / check for head gasket leak

This test will kill two birds with one stone.

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MAKE SURE THE COOLANT SYSTEM and ENGINE IS COLD!

RAN THIS TEST IN A WELL VENTILATED AREA ONLY!

You will spill some coolant during this air pocket purge test.......BE KIND TO THE ENVIRONMENT and ANIMAL please clean up after the test!

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Put the front end on a pair of ramp or park your car on a VERY STEEP HILL (radiator facing top of the hill) .

Top of the coolant reserve tank

Let it ran for 10-15 minutes.

Monitor for air pockets escaping from coolant reserve tank.

Small amount of bubbles is OK at 1-5 minute mark

After the thermostat open up (after 195 F warm up) at
5-12 minute mark or after high idle you should see less bubbles.

If you do not see any in rush of bubbles then your thermostat may be partially stuck or rusted badly inside the thermostat hosing.

Give the thermostat host few gentle taps.

If you see larger bubbles surfacing after 15 minutes then should do a hydrocarbon (HC) dye test to test for potential head gasket leak.

Let engine cold down and top off coolant reserve tank.

Start monitor for coolant lost

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A coolant flush is require every 2 years or 24,000 miles.

I recommend the thermostat that has a relief pop-let to reduce the change of burst radiator and coolant hoses.

Make sure you get a new thermostat gasket,black RTV and fresh coolant for the job.

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THE MOST COMON PROBLEM IS A FAULTY RADIATOR CAP BUT IF CAP IS OK YOU HAVE A BLOWN HEAD GASKET

Open the radiator cap when the engine is cool and check for any foaming or bubbles when the engine is running. Also check the oil dipstick for a creamy residue which indicates water has mixed with the oil. Either of these point to a blown head gasket which causes overheating even when the cooling system is good.

Look at the oil on the dipstick. If its milky you have a head gasket issue. Also if you can make it to a smog machine they can sniff the coolant fumes to see if gas is in the coolant. Head Gasket again. Any repair shop has a chemical that can test for gas in the coolant also.

The theory here is if your losing water and none is leaking on the ground its got to be going into the cylinder and getting pushed out the exhaust pipe.

Now if its just overheating you may have a stuck thermostat or clogged radiator or a coolang fan that dlesnt turn on when commanded by the computer.Also if its just overheating and the water lost is going on the ground somewhere then you may not have a head gasket issue.

I just did a head gasket on a Honda because as the engine was warming up the overfill bottle would fill up and overflow. The combustion pressure was leaking into the coolant and pushing the coolant out.

heater core maybe going bad