Coolant

Use phosphate-free coolant/anti-freeze that is mixed with distilled water (see mixture table below).  VW's Autobahn brand (part #ZVW 237 105) is recommended, but not required.  You should never mix coolant/anti-freeze brands or types, even to top off the expansion tank or radiator; always flush the system before switching brands or types (ex: blue stuff to red stuff) -- corrosion and leaks will result if brands or types are mixed.

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.

Coolant Expansion Tank

From 1979-1982, 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 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, 1982s.

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.

Radiator Cooling Fan

The radiator cooling fan operates under the following conditions:

• When the coolant reaches a specified temperature.

• The thermo switch in the radiator is normally open; when the coolant reaches the switch's pre-determined temperature (see below), it closes completing the path to ground, which turns the fan on.
• 1988-1993: The two-speed fan runs on low.

• When the A/C compressor engages.

• When any of the A/C settings are switched on and the compressor engages, an electrical signal is sent to the A/C relay, which in turn sends a signal to the fan, switching the radiator cooling fan on.
• 1988-1993: The two-speed fan runs on high.

• After engine shut-off, if the under-hood temperature is above a specified temperature.

• 1980-1987: The single-speed fan will run until the radiator fan thermo switch opens, thereby interrupting the ground path.  The fan usually doesn't run for more than a couple of minutes and definitely not more than 5 minutes.  If the fan runs longer than 5 minutes, there is a problem.
• 1988-1993: The two-speed fan will run on high until the after-run thermo switch cuts its electrical path to the after-run control unit.  The fan usually doesn't run for more than 5 minutes, but is capable of running for up to 15 minutes.  If it runs longer than 15 minutes, there is a problem.

Cabriolets up to 1987 with A/C do not have two-speed cooling fans; these cars have one-speed fans that are two-stage (fan is turned on when the A/C is turned on).  From 1988-1993, Cabriolets were equipped with two-speed fans; those with A/C would then have two-speed, two-stage cooling fans.

Radiator Cooling Fan Won't Turn On

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

Step 1

Disconnect the thermo switch connector.

Step 2

Using a jumper wire, make a connection between terminals (2-speed fans: low speed is red/white wire, high-speed is red/black wire).  Leave this connector disconnected!  By jumping these terminals, you are bypassing the fan switch and supplying 12V directly to the fan motor.

Step 3

Does the fan run?  Yes: The thermo switch is faulty and needs to be replaced.  No: Proceed to step 4.

Step 4

Check for voltage at the thermo switch connector (red wire).  Is there voltage?  Yes: Proceed to step 5.  No: Check fuse #1.  

Step 5

If the thermo switch is good and the fuse is good, the thermostat (in the water pump housing) may be faulty.  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 open.

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.)

Coolant Boils Out of the Reservoir (coolant temp is normal, fan turns on, no leaks detected):

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

Thermostat & Radiator Cooling Fan Thermo Switch

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.

*Notes:

• An 87° thermostat begins opening when the coolant temperature has reached 87°C and is fully open at 102°C.
• If wanting to change to a lower-temp thermostat, you must change the thermo switch to a lower temperature version (or vice versa).  The low-temp thermostat is 80°C; the matching thermo switch is 85-80°C.
• Some parts stores, such as German Auto Parts, incorrectly list the thermo switches as being "with A/C" and "without A/C".  From 1980 through 1987, Cabriolets used one-speed fans and use the black 95-84° switch; 1988-1993 Cabriolets use two-speed fans and use the white 95-84/102-91° switch; A/C is irrelevant.  See the electrical page for further info.

Radiator Baffles

The purpose of the cards is to direct airflow through the radiator with little air escaping around the radiator; this enables the cooling system to work more efficiently. New ones are no longer available.  The cards were originally made out of cardboard which, over time, disintegrates. Rather than sourcing used cardboard radiator baffles, you can easily make new, long-lasting ones yourself out of sheet metal from your local home improvement center.   Simply click 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).  Although not all baffles are listed for all years, they can be adapted to fit your particular car.

PDF

• Top (part #171121293G)
• Left  (part #155121283; from VIN J-000001)
• Right (part#155121284B; from VIN J-000001; cars with A/C)

• All (above templates in one file)

AutoCAD

• All Three (above templates in one file)

Thank you to Thomas for creating and sharing these files!

Oil Coolers

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.

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.