99 Chrysler 300M. As there is no visible radiator cap, when I drain the cooling system does it refill through the reservoir?

Jacquelin! The thermostat n a 3.5 Chrysler 300M is on the block right next to, and toward the front of the engine by the oil filter. Yes, that sems a bit strange, but then I'm not a bit surprised about this engine any more. As the big radiator hose leaves the radiator finding its' way toward the block, it terminates at a traditional "goose neck" at the block behind the power steering pump- only accessible by removing the oil filter and using an extension and a u joint BUT FIRST: lower the anti freeze in the system by draining some fluid. But anyway- THAT'S where it is. Have fun, fix it up and GO!

If you look AT&T en using on the engine where the upper hose is attached you should see a bleeder valve. Open that valve. Keep it open until you see coolant come out. Then start the vehicle and periodically open it throughout the warm up process to purge any additional air out of the system.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

The only thing I can think of that would cause this is if the antifreeze is old or weak or diluted down with too much water. Try the following: DRAIN & REFILL Fig. 1: Remove and drain the reservoir recovery tank
Fig. 2: Location of the radiator draincock
Fig. 3: Use your hand to unscrew the plastic draincock
Fig. 4: To refill the recovery tank, twist the cap . . .
Fig. 5: . . . then pull up to remove it from the tank
Fig. 6: Adding coolant to the reservoir bottle
Fig. 7: Always check the condition of the radiator cap gasket and seal. Place a light coating of coolant on the seal and gasket when installing
CAUTION
When draining the coolant, keep in mind that small animals and domestic pets are attracted by ethylene glycol antifreeze and may attempt to drink any that is left in an uncovered container or from puddles on the ground. This can be fatal if ingested in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused until it becomes contaminated or several years old. To avoid injuries from scalding fluid and steam, DO NOT remove the radiator cap while the engine is running or if the engine or radiator is still hot.

1. Before draining the cooling system, place the heater's temperature selector to the full WARM position while the engine is running.
2. Turn the engine off before it gets hot and the system builds pressure.
3. Make sure the engine is still cool and the vehicle is parked on a level surface.
4. Remove and drain the reservoir recovery tank.
5. Place a fluid catch pan under the radiator. Turn the radiator draincock counterclockwise to open, then allow the coolant to drain.
6. Remove the radiator cap by performing the following:
   1. Slowly rotate the cap counterclockwise to the detent.
   2. If any residual pressure is present, WAIT until the hissing stops.
   3. After the hissing noise has ceased, press down on the cap and continue rotating it counterclockwise to remove it.
7. Allow the coolant to drain completely from the vehicle.
8. Close the radiator draincock. NOTE: When filling the cooling system, be careful not to spill any coolant on the drive belts or alternator. To refill:
   
9. Make sure the heater temperature is placed in the full hot position.
10. Open the bleed screw on the thermostat housing.
11. Install the reservoir recovery tank and using a 50/50 mixture of the recommended antifreeze and clean water, fill the cooling system reservoir tank to the FULL mark. WARNING
    If any coolant is spilled on a painted surface, wipe it up immediately.
    
12. Begin filling the radiator with the 50/50 mixture of coolant. Watch for air being released from the open the bleed screw on the thermostat housing. Once coolant mixture begins to steadily flow through the bleeder, close the bleeder.
13. Continue to fill the radiator until the radiator is full.
14. Start the engine and allow the engine to run until the cooling fans operate two times, making sure to top off the system as the fluid level drops.
15. After the cooling fan has run for the second time, top off the system as necessary, then install the radiator cap.
16. Allow the engine to run and inspect the cooling system for leaks.

Hello sounds like you have overheated your engine or cooling system hose or radiator is leaking let your engine completely cool down open radiator cap and refill you engine coolant close it up and restart and watch for your leaking point this could be a rad cap.radiator hose or the radiator tank and at this point you can access the problem and feel if you can attempt to repair or not.Or you can let the car completely cool down top up cool;ant in radiator and take the car into a garage.

If there is other leak other than the one you have found, air may have entered the system. To ensure that it does not get in and that your are filling up the correct amount of water squeeze the radiator hose on top after each fill to squeeze out the air. You can also let the engine run while pouring water one at a time.

that small hole is a vent since the filler hole is capped

its a pitcock facing the cab bottom of the radiator, plastic flat. once you find the pitcock just put a bucket underneath and turn it.then refill. if you want to flush(run fluid thru to clean it out) the radiator id suggest taking it in. you dont have to flush it every time you change the coolant out.

hi, you can add two ways, one is threw the the over flow tank and the other is threw the radiator cap. i would flush the radiator soon. you may have sludge build up that is interfering with the flow of coolant.

I Suspect that you have AIR in your COOLING SYSTEM Fallow Procedures BELOW to Insure there is NO AIR IN COOLING SYSTEM


Draining and Filling Cooling System

Draining Procedure

Important: Do NOT add any engine coolant supplement sealant pellets to the cooling system. Drain and refill the engine cooling system every 5 years or 240,000 km, (150,000 mi) , whichever occurs first.

1. Park the vehicle on a level surface.
2. Remove and clean the coolant recovery reservoir.

Caution: Refer to Radiator Cap Removal Caution in Service Precautions.

1. Remove the radiator cap when the engine is cool:

3.1. Slowly rotate the cap counterclockwise to the detention tab. Do not press down while rotating pressure cap. 3.2. Wait until any residual pressure, indicated by a hissing sound, is relieved. 3.3. After all hissing stops, press down on the radiator cap and rotate the cap counterclockwise in order to remove the cap.
Important: Recover and store used coolant in a used coolant holding tank and submit the used coolant for recycling on a regular basis. Do NOT pour used coolant down the drain. Ethylene glycol antifreeze is very toxic. Disposing of ethylene glycol into the sewer system or ground water is both illegal and ecologically unsound.

1. Place a drain pan under the radiator drain valve in order to collect all of the used coolant.
2. Open the radiator drain valve located at the bottom of the radiator tank. If only partial cooling system draining is required, drain enough coolant to perform the procedure.
3. Open the air bleed valve on the thermostat housing 2 full turns
   1. Open the air bleed valve above coolant pump 2 full turns.
   2. Place a drain pan under the engine block drains in order to collect the used coolant.Important: Allow the coolant to drain completely.
      
      
      1. Remove both of the engine block drains.
      • The front left engine block drain is located between the starter motor and the engine oil filter.
      • The rear right engine block drain is located near the crankshaft position sensor.
      Filling Procedure
      Reinstall the engine block drains
      
   3. Close the radiator drain valve,
      1. Install the coolant recovery reservoir. Notice: When adding coolant, it is important that you use GM Goodwrench DEX-COOL or HAVOLINE DEX-COOL coolant. If Coolant other than DEX-COOL or HAVOLINE DEX-COOL is added to the system the engine coolant will require change sooner; at 50,000 km (30,000 mi) or 24 months.
      2. Slowly add a 50/50 mixture of GM Goodwrench DEX-COOL or HAVOLINE DEX-COOL and clean, drinkable water to the radiator until the coolant level is at the base of the radiator fill neck.
      3. Wait for 2 minutes and reinspect the level of the coolant in the radiator. If necessary, add coolant to the radiator until the coolant level is at the base of the radiator fill neck.
      4. Install the radiator cap.Ensure that the radiator cap arrow points toward the radiator overflow tubeImportant: The air bleed valves are brass. Do NOT over-tighten the air bleed valves.
         
         
         1. Close the air bleed valve above the coolant pump.
            1. Close the air bleed valve on the thermostat housing.
            2. Fill the coolant reservoir with a 50/50 mixture of GM Goodwrench DEX-COOL or HAVOLINE DEX-COOL and clean, drinkable water. Caution: Refer to Radiator Cap Removal Caution in Service Precautions. Important: If the coolant temperature indicator turns ON, turn the engine OFF immediately and allow the engine to cool. Do NOT remove the radiator cap.
            3. Start the engine and allow the engine cooling fan to cycle on and off 3 times. If the low coolant indicator does not turn OFF and the coolant level is above the Full Cold mark on the coolant recovery reservoir, refer to Engine Coolant Temperature Gage Inaccurate or Inoperative.
            4. Turn off the ignition.
            5. Allow the engine to cool.
            6. Ensure that the engine coolant concentration is sufficient.

there is no ap on the radiator itself the coolant system cap is on the overflow bottle