Where is the radiator cap on my 1994 6 cylinder E320?

Sounds like a leaking head gasket. The head gasket can allow coolant to leak into the cylinders, and compression to leak into the cooling system.

Should have a clear plastic tank on one side of the engine compartment with a cap. A hose runs from the top of the radiator to the tank.
The tank for the windshield washer has a snap on cap, the radiator reserve tank has a twist on cap.

(I don't know much about cars so bear with me).

I've had problems of overheating previously where my car's thermostat would hit 140. I think I've fixed the issue, I've replaced the thermostat but it was still doing that and 2 hoses blew and needed to be replaced. I've had to consistently fill my radiator with 50/50 antifreeze on a daily basis to ensure it won't overheat, so far that seems to be keeping the peace.

But now as of 5 days ago, I'm experiencing these new issues of stalling. Upon taking my civic into my mechanic, his meter showed that there was a misfire in the 2nd cylinder a month prior and now all 4 are misfiring. He thought it was the head gasket at first. I had just recently replaced the spark plugs with NGK Platinums, new spark plug wires and a new distributor cap.

I've received many possible culprits to my problem consisting of possibly the Throttle Position Sensor, Fuel Filter/Injection, Distributor or a radiator cap. I'm financially strapped at the moment and only could afford the radiator cap which didn't solve anything, however my radiator is running on 80% water at the moment. I'm really at a loss and I feel like I've done what I could and I'm at my wits end. Please help my poor little Civic cheat death for a little longer.

FILL COOLANT SYSTEM UP BY POURING COOLANT IN THE EXPANSION TANK UNTIL COOLANT LEVEL STOP DROPPING IN THE EXPANSION.WHEN YOU POUR COOLANT IN EXPANSION TANK AIR BLEED OFF THROUGH THE SMALL COOLANT LINES GOING TO EXPANSION TANK.WITH PRESSURE CAP OFF RADIATOR COOLANT LEVEL IN EXPANSION IS AT FULL COLD MARK.WHAT YOU TO DO CRANK ENGINE UP LET IDLE WARM UP UNTIL COOLANT DROPS IN EXPANSION TANK KEEP ADDING COOLANT UNTIL STOP DROPPING STAY AT FULL COLD MARK.WHEN COOLANT LEVEL START RISING IN EXPANSION TANK.PUT PRESSURE CAP BACK ON RADIATOR.WHILE ENGINE IDLING WATCH TEMPERATURE GAUGE.IF START CLIMBING TURN OFF ENGINE LET IT SIT FOR LITTLE WHILE TAKE A LARGE RAG OPEN RADIATOR PRESSURE CAP A LITTLE AT A TIME TO KEEP FROM GETTING SCALDING TO RELEASE AIR IN COOLANT SYSTEM.WHEN PRESSURE IS RELEASED OPEN PRESSURE CAP ADD MORE COOLANT IN THE EXPANSION TANK.CRANK ENGINE AGAIN LET IDLE WHEN TEMPERATURE GAUGE START CLIMBING. TURN OFF ENGINE WAIT FOR WHILE BEFORE OPEN RADIATOR PRESSURE CAP.WHEN YOUR THERMOSTAT OPENS WHEN TOP RADIATOR HOSE IS HOT AND ENGINE COOLANT TEMPERATURE GAUGE STOP CLIMBING AND COOLANT LEVEL STOP DROPPING IN THE EXPANSION TANK.ALL AIR IS EXPELLED FROM COOLANT SYSTEM TO KEEP ENGINE FROM OVERHEATING.

you need drain fuel tank.fuel tank probably need to be removed and cleaned out to remove all sediment in bottom of fuel tank.remove each sparks and label them.squirt some clean engine oil down the spark holes into cylinder bores to help lubricate cylinder walls and help seal the piston rings to build up compression.replace fuel filter.best to change spark plugs and wires.check all brake hoses they more likely old cracked. i would change brake fluid bleed out all the old brake fluid out of the brake system.also change power steering fluid and change transmission fluid and filter also change engine oil and oil filter.replace the antifreeze and all the coolant hoses and radiator hose.replace thermostat and radiator pressure cap.replace battery and add new full tank of gas.you should be ready go. check ignition timing also.

Javier, have you checked the coolant overflow tank for holes, cracks, or loose hose? When the engine in your car heats up, the coolant expands. The coolant overflow tank (located near the radiator) takes up any coolant that is forced out of the radiator. If the tank is damaged or not connected to the radiator correctly, the coolant will not siphon back into the cooling system when the engine cools off.

Overheating is not always caused by a bad water pump or bad engine firing timing.

The most common causes are:

• faulty radiator cap: steam/water will be escaping from the caps when engine is hot or oveflow tank overflows or empty!
  
• crack cylinder head gasket: check when engine is cold thru radiator cap hole for milky oil in water radiator or large bubbles in radiator water after starting engine. Also check if water steam comes out of exhaust.
  
• cylinder head itself: same symtoms as for gasket above.

Hope it helps you find your problems.

Should be a drain **** at the bottom of the radiator that unscrews out. It looks like a wing nut has been welded to a bolt on the end of it. Another way to do this is just pull off the bottom hose.

Thats a common thing, Just replace the radiator and the radiator cap.

Good morning;
does this critter have a radiator fill w/cap? I've run accross som large Sotrd trucks that don't.
Well, anyway, it soesn't make sense you would need to fill the radiator via the resenoir. That is only good for short pressure relief and cook down vacuum recovery of coolant. 60/40 is the mix ratio. If it hs a resevoir it should have a radiator cap.The air in system will purge itself as it starts to circulatte cioolant. turn heater off till your system is full, then on when engine reaches operating temp. then if needed top iff coolant. Leave radiator cap off while waiting for coolant to start circulating. When thermostat opens out comes the air. Then put coolant mix in reservoir to fill line. check for leaks and all hose clamps are tight and you should be set, Good luck - Ned