Toyota Sienna AC Service, Part III: Evacuation and Refrigerant Recharge (With Video)

Updated on July 14, 2018
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Hardlymoving writes about do-it-yourself automobile maintenance on various makes and models.

Typical portable HVAC vacuum pump with manifold gauges, hoses, and quick disconnect couplers for high/low fittings
Typical portable HVAC vacuum pump with manifold gauges, hoses, and quick disconnect couplers for high/low fittings

This is Part III of a three-part article on servicing the air conditioning (AC) on a 2004-2010 Toyota Sienna.

Evacuating and Recharging the AC System on a 2004-2010 Sienna

This DIY describes the evacuation and Freon (refrigerant) recharge of the AC system of a 2004 Toyota Sienna with the 3MZFE V6 engine.

Tools Needed

The tools linked to here on Amazon will work for this job.

  1. Evacuation vacuum pump
  2. AC manifold gauge and hoses
  3. Freon 4e-charger dispenser
  4. AC valve core remover/installer
  5. Three 12-oz cans of R134A Freon refrigerant
  6. New valve stem core

Why You Need to Pull a Vacuum on an AC System

If you don't evacuate (pull a vacuum on) an AC System, these can be the consequences.

  • Compressor failure due to moisture (water) making the condenser "blow out."
  • Aluminum corrosion of the condenser and evaporator which will eventually cause a pressure leak. The leakage will require the part(s) to be replaced.
  • Freezing of the expansion valve or orifice tube which will stop the expansion of the Freon gas, hence stopping the cooling.
  • Displacement of the Freon refrigerant gas with other gasses (hydrogen, oxygen, nitrogen and inert gases), reducing cooling efficiency.

When to Replace the Accumulator/Drier

If the A/C System has been "open" (exposed to normal outside air) for a very long time, and the condenser with its built-in accumulator / drier has not been replaced, replace the accumulator / drier itself. An open system will ruin an accumulator / drier. The accumulator contains a moisture absorbing substance called desiccant. Silica gel was first used in early automotive A/C systems but was replaced by molecular sieves, economical desiccants for modern refrigerants. Accumulators also filter out debris that may be passing through the A/C system.

Video of Toyota Sienna A/C Evacuation and Refrigerant Recharge

This 4 minute video will provide you with visual step-by-step help for completing the evacuation and recharge on a Toyota Sienna. The steps are also described lower down in the article.

Step-by-Step Instructions for Toyota Sienna A/C Evacuation and Refrigerant Recharge

I. Replacing the A/C Low Pressure Valve Core Stem

This is optional, but recommended, if you did not replace the valve core stem while replacing the compressor (as described in part II of this series).

Use the valve core remover/installer (see photo a), unscrew the old valve core stem (see photo b) from the low pressure connection port. Screw in the new valve core stem.

(a) Valve core removal and installation tool
(a) Valve core removal and installation tool | Source
(b) AC valve stems
(b) AC valve stems

Connecting the Hoses for Evacuation (Pulling Vacuum)

  1. Attach the blue colored hose to the blue-dialed low-pressure port valve coupler. (see photo (c) below)
  2. Attach the other end of the blue colored hose to the manifold gauge's low side gauge port (underneath the blue dial knob). (See photo d).
  3. Connect the low-pressure port valve coupler to the car's low-pressure port. Connecting is easier if you turn the blue dial valve counterclockwise. Once the coupler is connected, turn the blue dial on the coupler clockwise to apply pressure to the valve and open a connection.
  4. Attach the yellow hose to the center port of the manifold gauge.
  5. Attach the other end of the yellow hose to the vacuum pump.
  6. Pre-vacuum setup check: The blue low-pressure adapter knob is open when turned clockwise, and the blue knob valve on the manifold gauge is open when turned counterclockwise.

(c) AC high- and low-pressure quick-connect couplers
(c) AC high- and low-pressure quick-connect couplers
(d) AC manifold gauge
(d) AC manifold gauge

Starting the Evacuation

1. Turn the vacuum pump on. The needle on the low pressure gauge will swing counterclockwise into the minus zone (which is the green area on the gauge I am using). Let the evacuation go on for approximately 30 minutes to remove or "pull" all moisture.

Note: If after a few minutes the vacuum reading is minus 25 or less, there is, more than likely, a leak or open area in the AC system. A solid leak-free system should be in the minus 28 zone. To know for certain, close off the low pressure side blue dial valve by turning the dial counterclockwise and turn off the vacuum pump. If the system cannot hold vacuum (the needle moves towards zero after around 10 minutes), there's a leak and introducing freon refrigerant will be a waste of time and money. A mild leak may indicate either the high or low pressure valve stem springs are too weak to hold a high amount of vacuum and is not indicative of a leak in the system. In that case, a mild amount of leakage is acceptable. Although leaks are mostly outside the scope of this set of articles, a brief discussion of possible leak solutions is at the end of this article.

2. Complete the evacuation by:

  • Closing the valve on the low-pressure coupler.
  • Closing the valve on the low-pressure manifold gauge.
  • Turning off the vacuum pump.
  • Disconnecting the low-pressure coupler from the low pressure port.

Recommendation: After removing the low-pressure coupler, immediately connect the Freon recharge dispenser fitting. Sometimes the valve stem will allow air to come into the system because the valve spring is too weak.

Recharging the A/C System with Freon Refrigerant

Typical sedans and SUVs will need approximately 25+ oz of Freon refrigerant. Some vehicles will have a label fixed inside the engine compartment indicating the amount of Freon needed for the system. Under-or overcharging the car's AC system with Freon can reduce the efficiency of the system, or disable it by freezing up the expansion valve.

  1. Spin on a new can of Freon onto the Freon recharge dispenser.
  2. Press the trigger on the dispenser to pressurize the dispenser line.
  3. Connect the dispenser's quick connect fitting onto the low pressure port.
  4. Begin dispensing Freon into the system. Rotate the can up and down every few seconds. When the dispenser's pressure needle is around 60 psi, the can should be close to empty and the car may be started with the AC on.
  5. If there's enough Freon in the system, the AC compressor's clutch should engage. Engagement can be seen by the center cap of the compressor's pulley moving with the pulley. If not certain, have someone push on and off the car's AC button and you'll see the cap stopping and then rotating with engagement.
  6. Set the bottom of the dispenser's dial to the approximate outside temperature (if you have a dispenser with a temperature dial). The gauge's needle should be between the red lines. If there's too little Freon, the gauge needle will oscillate. As the proper amount of refrigerant is being reached, the oscillation will stop. The gauge needle should be somewhere between 35 and 40 psi based on outside temperature. The hotter the ambient temperature, the higher the psi.
  7. For the Toyota Sienna in the video, I dispensed approximately 24 to 26 oz of Freon into the system, where the pressure reading was approximately 40 psi and the outside temperature 80 + degrees F.
  8. Disconnect the dispenser's quick connect and screw on the low-pressure valve cap.

(e) A/C recharge hose and gauge
(e) A/C recharge hose and gauge

What to Do if There's a Leak?

Option 1: Purchase a can of Freon with UV dye. Perform a evacuation and recharge. You can then use a UV flashlight and UV glasses to look for the source of the leak. Worst case scenario: The leak is in the evaporator core, which is inside the car, behind the dash and will take a ridiculous amount of time and effort to replace. Evaporator Core leakage can be detected when condensation moisture (water) is vented onto the ground and the UV dye is mixed in.

Option 2: Buy and use a can of A/C Pro Super Seal which will seal up small metal-related leaks. This product has worked for me on minor leaks and saved the customer a lot of money on repair estimates.

Questions & Answers

© 2018 hardlymoving

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