Coolant: type, change, bleeding
Why phosphate-free coolant, why the radiator drain does not empty everything and how bleeding works in principle.
In short: For the alloy engine Porsche recommends phosphate-free antifreeze. Every time the circuit is opened, it has to be bled carefully.
Coolant
The label should explicitly say “phosphate free”; “safe for aluminium engines” alone is not enough. A 50 : 50 mix with water is usual.
Draining
The radiator drain does not empty the system completely; some coolant stays in the block. For a full drain there is a drain plug on the block (on the passenger side of left-hand-drive cars).
Bleeding in principle
At the highest point – a bolt on the coolant nozzle at the front of the cylinder head – the system is bled until coolant comes out without air, with the heater on full. A pressure tester works best; do not exceed 10 psi. Then drive the engine to temperature and bleed again.
Air in the system can cause overheating – if in doubt, use the workshop manual or leave the job to a specialist.
Technical values
Only work with the workshop manual and the correct tools. Do not use unverified values without checking them – wrong tension values can destroy the engine.
| Value | Figure | Condition | Status | Source |
|---|---|---|---|---|
| Antifreeze | phosphate-free | – | unverified | [1] |
| Mix ratio, general | 50 : 50 (follow the product's instructions) | – | unverified | [1] |
| Volume to catch when draining | have about 7.8 litres ready | Not an exact capacity | unverified | [1] |
| Maximum pressure when bleeding with a tester | 10 psi (about 0.7 bar) | – | unverified | [1] |
Sources
- Secondary source Cooling System Draining, Filling, and Venting
Coolant, draining and venting.