One of the most common failures in older Boxsters is the leaking of coolant from a cracked coolant reservoir.
The reservoir is made from plastic which with age, heat and coolant pressure eventually develops minute and almost invisible cracks.
If your coolant level has dropped, and you can’t the obvious reason such as a loose coolant cap or an overflow, check in your rear trunk. You may have a cracked reservoir and not know it.
You will have to peel back the rear trunk’s carpet liner in order to check.
It is held in place with push-type plastic fasteners.
Start by removing the rear trunk’s latch cover, disconnecting the light and then pulling back the liner from under the coolant reservoir
If your reservoir is cracked, you will easily see small coolant puddles under the carpet in the rear trunk.
You’ll have to replace the reservoir.
It is recommended that you drain a couple of gallons of coolant in order to avoid spills.
To avoid burns, this job is best tackled when the car is cold.
Using a small hand pump (at most auto-parts stores) pump out the coolant from the reservoir.
Now it’s time to remove the tank.
Start by removing the rubber gasket around the reservoir’s top. Remove the coolant cap and oil cap. Using a small screwdriver, slide it under the flat cover and lift it out exposing the pressure relief valve.
On the older cars, disconnect the oil dipstick. It is held in place with small pressure tabs.
Remove the fastening ring on the oil filler tube by turning 1/4 turn ccw.
Finally remove the hex bolt securing the top of the flange.
Disconnect the coolant level indicator connector on the bottom and remove the hex bolt which hols the coolant’s support leg to the trunk.
Now, you need to remove the hoses which are connected to the coolant’s plenum.
The overflow hose can be just pulled out. It’s held in place by pressure.
The other hoses are held in place with spring clamps. Some of these clamps are readily accessible and can be best removed with simple pliers.
Now you’ll need access to the top of the engine in order to remove the rest of the hoses.
To be able to disconnect the remaining hoses without too much hassle it’s highly recommended that you use a cable-operated spring clamp plier available at many automotive stores.
This specialized tool will save you hours of work and is also safer to use on hard-to-access spring clips which can break a finger if it slips in your hand.
Remove the two fasteners that secure the plastic distributor to the trunk’s bulkhead.
Now remove the hoses on the distributor on the inside of the trunk.
Now breathe in deeply and be as patient as possible.
Pull the distributor into the inside of the trunk which will allow access to the spring clamps on the engine’s side.
Carefully remove the spring clamps and remove the distributor.
You can now finish removing the damaged reservoir and start installing the new one by reversing the above steps.
Using the cable-operated spring clamps comes in very handy on the installation as well.
Don’t forget to reconnect the coolant level sensor.
Finally, when all hoses and fixtures are back in place you’ll need to refill the system with new coolant (or with the one you saved).
You can use the instructions on another one of my pages, Flush the Coolant System which also shows the use of a vacuum system that tests for leaks.
Replace Coolant Reservoir