Cabby Info - Cooling System

Updated: 13-Oct-2025

For coolant/water temperature gauge information, please go to the Gauges page.

Coolant / Antifreeze

Original coolant

Status: The original coolant has been discontinued by VW/Audi. However, if you wish to continue using G11/G48 coolant, the following are available:

You can still flush the system and use a newer coolant. See replacement section below.

Topping off coolant

Which OEM coolants can mix with which? The table below is based on VW technical service bulletin 19-17-01.

Replacement Coolant

You can use any ethylene glycol- or glycerol-based coolant/antifreeze so long as it is phosphate- and phosphorous-free and is mixed with distilled water, if not pre-mixed. There are numerous aftermarket brands that mix with any coolant, and most coolants are now phosphate-free (if using an off- or store-brand, check the label to verify). If wanting to stick with OEM coolant, refer to the table below for information.

System Capacity

4.6 liters / 1.2 gallons

Cooling System Refill

This is how I do it (expansion tank cars):

  1. Turn the heater temperature lever to "hot". (A/C-equipped cars: turn the lower lever to "vent".) Keep the blower fan off.
  2. Remove the expansion tank cap and temporarily set it aside in a safe place.
  3. Pour in coolant until it reaches and stays at the "full" mark.
  4. If desired, use a cooling system pressure tester to push coolant into the system and/or to check for leaks (do not pump more than 15 psi into the system!).
  5. Turn the engine on and let it idle (if you used a pressure tester, remove it first!).
  6. Keep an eye on the expansion tank. Once coolant begins flowing in from the radiator, squeeze the upper radiator hose a few times.
  7. Reinstall the expansion tank cap and keep an eye on the water temperature gauge as you wait for the cooling fan to turn on. If all is well, the fan will turn on and the gauge will read normal. If it does, turn off the engine, let it cool down, recheck the coolant level, and top off if need be. Done.

Other folks have you fill the system via the upper radiator hose; this is totally unecessary (not to mention a PITA) and puts undo wear on the hose. However, if you prefer this method, feel free to use it.

If your car is having an air bubble issue, a common trick is to drill a small hole into the thermostat, which allows for internal air bleed-off. I, personally, have never had a need for this in nearly 30 years of ownership, but others have encountered air issues leading them to automatically drill the hole on every new thermostat they install. Use the method that works best for you and your car.

Not keeping up with timely coolant flushes can lead to internal cooling system corrosion. Flush the coolant every 30,000 miles or every 2 years, whichever comes first, if using G11; if you have switched to a G12 variant or G13, the flush interval is increased to 4 years.

Coolant Expansion Tank & Pressure Cap

Expansion Tanks

Original tanks were transluscent plastic, which eventually turned yellow/brown. New aftermarket replacements can be transluscent or white. Beware: many have a poor fit in the bracket and/or are made from inferior plastic.

Expansion tank, without level sensor:

Expansion tank, with level sensor:

From 1979-1983, Rabbit Convertibles did not have a coolant expansion tank; they had the old style system wherein the coolant was added directly to the radiator via the radiator cap. From mid-1983 to 1993, Rabbit Convertibles and Cabriolets came with expansion tanks; some 1982 models may have the bracket for the expansion tank but VW continued to use the old cooling system on most, if not all, 1982 and most 1983s.

If you would like add an expansion tank to your system you will need the following parts: newer style radiator, hose from radiator to expansion tank, expansion tank, hose from expansion tank to coolant return pipe and a coolant return pipe.

Expansion Tank and Radiator Pressure Cap

All cars:

Help Icons No AttributionCoolant Boils Out of the Expansion Tank (coolant temp is normal, fan turns on, no leaks detected):

Faulty reservoir cap, faulty reservoir, faulty thermostat, faulty after-run thermo switch and/or relay (1988+), blocked radiator, faulty cooling fan thermo switch.

Radiator

1979-1983 ~ without expansion tank

1979-1993

1980-1983

1984-1993

1990-1993

If you desire to rid your car of as much plastic as possible, all-aluminum replacement radiators can be found on eBay.

North America retailer: Radiator Express

Radiator Baffles

The purpose of the baffles (aka cards, ducts) is to direct airflow through the radiator with little air escaping around the radiator; this enables the cooling system to work more efficiently. The baffles were originally made out of cardboard-like material which, over time, disintegrates.

You can purchase new baffles (plastic versions) by using the part numbers listed below to do an Internet search. You can also easily make new, long-lasting ones yourself out of sheet metal or Coroplast (yard sign board material) from your local home improvement center. Simply tap on the links below to download the templates (only the AutoCAD download contains genuine, full-size templates that can be printed at your local Kinko's, etc.; the others contain measurement templates for use as guides in making the baffles).

Top Baffle/Duct

Right Baffle/Duct

Left Baffle/Duct

All three above, with A/C

All three above, with A/C

Thank you to Thomas for creating and sharing these files!

Radiator Cooling Fan

Cooling fan component guide: Fan Guide Download

Cooling fan speed

The radiator cooling fan operates under the following conditions:

Help Icons No Attribution Radiator Cooling Fan Won't Turn On

Check the fan motor and thermo switch by completing the following steps:

Help Icons No Attribution Radiator Cooling Fan Won't Shut Off

Replace the radiator fan switch.

1988-1993 Cabriolets: The after-run relay mounted on the driver's side fender may be faulty, and/or the after-run thermo-switch (back side of the cylinder head) may be stuck closed (permanently grounded).

(Cabriolets equipped with after-run systems (1988+) may have the cooling fan run up to 15 minutes after the engine is turned off.)

Thermostat & Radiator Cooling Fan Thermoswitch

Thermostats & fan switches go hand-in-hand. When replacing one, you should replace the other and both should match temperature-wise (see below). Always, always, always test a new thermostat in a pot of boiling water to ensure that it works before installing it in the car.

Some parts stores incorrectly list the cooling fan thermo switches as being with A/C and without A/C. This is incorrect. From 1980 through 1987, Cabriolets use one-speed fans and use the black 2-pin 95-84° switch; 1988-1993 Cabriolets use two-speed fans and use the white 3-pin 95-84/102-91° switch; A/C is irrelevant. See the electrical page for further info.

Thermostat Part Numbers

If wanting to change to the lower-temp thermostat, you must change the thermoswitch to a lower temperature version (or vice versa). The low-temp thermostat is 80°C; the matching thermoswitch is 85-80°C.

Cooling Fan Thermoswitch Part Numbers

Cooling Fan After-run Thermoswitch Part Numbers

Overheating & Overpressurizing

It is important to keep an eye on the coolant/water temperature gauge in the instrument cluster. If the gauge is reading higher than normal, this is your early warning sign that the engine is running hotter than normal and is having a cooling issue.

Should you see the engine begin running hotter than normal:

  1. Turn OFF the A/C, if on, to reduce engine strain.
  2. Turn ON the heater to "max" in an effort to dissipate heat through the heater core (if need be, turn on the HVAC fan to maximize the dissipation).

If the temperature continues to rise: Pull over in a safe spot and shut off the engine; wait for the engine to cool significantly, or call for a tow. Correct the cooling issue ASAP!

Signs of overheating (usually a combination of two or more of the following symptoms):

Common causes of overheating:

Common causes of overpressurizing:

Coolant Hoses

Hose from radiator to expansion tank:

Other hose information coming soon.

Oil Cooler

Only Cabriolets with JH engines in North America have oil coolers; "why?" remains to be answered. In Europe, only the EG, JH, 2H, DX and KT engines came with oil coolers.

If your Cabriolet is without an oil cooler, you can install the OEM cooler (additional coolant hoses will be needed), or an aftermarket cooler that utilizes air, rather than coolant, to dissipate heat from the oil.

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