Parts for your 2020 Holden Colorado-Radiator cap

Radiator cap for the 2020 Holden Colorado

Based on technical sources — the Holden Colorado RG Owner’s Manual (MY20) cooling system guidance, GM Service Information for the 2.8L diesel cooling system description and operation, and Australian parts catalogues from ACDelco, Tridon and Dayco for RG Colorado (2016–2020) — this model does use a pressure cap, but it’s mounted on the pressurised surge/expansion tank rather than directly on the radiator. So a “radiator cap” is relevant to the 2020 Holden Colorado, it’s simply located on the coolant reservoir under the bonnet.

The cap’s job is bigger than it looks. It seals the system, holds a set pressure so the coolant’s boiling point is raised, and manages vacuum when the engine cools so coolant is drawn back from the reservoir instead of collapsing hoses. It also provides a safety relief path if pressure spikes. If that cap can’t maintain its rated pressure or seal properly, the ute can run hotter than it should, push coolant out, or pull air into the system — none of which is ideal for a hard‑working Colorado.

Owners should treat the cap as a service item. Check it at each service (or roughly every 10,000–15,000 km):

• Only open when cold, twist slowly to the first detent to release any residual pressure.
• Inspect the rubber seals for nicks, flattening or hardening, and the spring/valve for smooth movement.
• Look for crusty deposits or corrosion on the cap and surge tank neck, clean the neck before refitting.
• Match the replacement to the factory rating stamped on the cap (often around 100–140 kPa/15–20 psi). Don’t guess.

Common signs a cap is done: unexplained coolant loss, overflow bottle repeatedly overfilling or running dry, temperature swings, sweet smells, dried coolant tracks near the tank, or hoses that collapse as the engine cools. A cooling‑system pressure/vacuum test will confirm it quickly, and caps are cheap insurance compared with head gasket dramas.

When replacing, fit an OE or premium equivalent cap with the correct kPa rating. After any cap change, top the surge tank to the COLD mark, start the engine with the heater on hot, let it idle until warm, squeeze the upper hose a few times to burp air, switch off, allow to cool fully, and recheck the level. Dispose of old coolant responsibly.

As preventive maintenance, many workshops replace the cap every 3–5 years or 60,000–100,000 km, sooner in hot or heavy‑towing conditions. It’s a small part that keeps the Colorado’s cooling system on song.

FAQs

Where is the radiator cap on a 2020 Holden Colorado?
It’s on the pressurised surge/expansion tank on the passenger side of the engine bay, not on the radiator itself. The cap performs the same pressure‑control job — the radiator is part of a sealed system that’s filled via that tank.

What pressure cap should a 2020 Colorado use?
Use a cap that matches the rating printed on the original (typically around 100–140 kPa, or 15–20 psi). A lower rating can cause boil‑over, a higher rating can stress hoses and the tank. If unsure, check the vehicle’s build plate and parts catalogue against the VIN.

How often should the cap be replaced?
Inspect at every service and replace at the first sign of seal damage, corrosion, weak spring action, or test failure. As a rule of thumb, replace every 3–5 years or 60,000–100,000 km, especially if the vehicle tows, works off‑road, or lives in hot climates.