Parts for your 1998 Daihatsu Gran move-Radiator cap

1998 Daihatsu Gran Move radiator cap — purpose, care, and when to replace

Yes, the 1998 Daihatsu Gran Move (also known as the Pyzar, M100/M101 series) is fitted with a conventional, pressurised radiator cap on the radiator itself. This is shown in the Daihatsu Pyzar/Gran Move Workshop Manual cooling system diagrams and procedures (M100/M101 Cooling section), and in the Daihatsu Electronic Parts Catalogue, which specifies a pressure cap for the model. So a radiator cap is very much relevant to this vehicle’s cooling system.

The radiator cap on a Gran Move does more than just close the filler neck. It holds system pressure (typically around 0.9 bar), which raises the coolant’s boiling point, keeps temperatures stable on hot Aussie and Kiwi days, and manages expansion and recovery via the overflow bottle. It also includes a vacuum valve so coolant can return to the radiator as things cool down, preventing hoses from collapsing.

As part of routine servicing, the cap deserves the same attention as hoses, coolant, and the thermostat. If the spring weakens or the seals harden, pressure control suffers, which can show up as creeping temps in traffic, coolant push-out into the overflow, or a collapsed top hose after cool-down. A simple pressure-cap tester can confirm if it holds the rated pressure and releases correctly.

Owners should consider replacing the radiator cap every 2–4 years or at any cooling-system service, especially if the vehicle tows, sees long highway runs, or lives in hotter regions. Stick with an OE-quality cap of the correct pressure, the rating is usually stamped on the cap and matched in the service manual. Always check and remove the cap only when the engine is stone cold — under pressure, hot coolant can cause nasty burns.

Good practice when fitting a new cap:

• Inspect the filler neck for nicks or corrosion that could compromise sealing.
• Lightly clean the seat, fit the cap squarely and twist until fully seated.
• Verify the overflow hose isn’t cracked or blocked so expansion and recovery work properly.
• Refill with the correct long-life coolant for alloy engines and bleed air as per the manual.

Done right, a fresh, correct-spec radiator cap helps the 1998 Gran Move keep its cool, reduces boil-over risk, and protects the alloy components from heat stress.

What pressure rating should the Gran Move’s radiator cap be?

Most 1998 Gran Move/Pyzar models specify a cap around 0.9 bar. Always confirm by checking the marking on the existing cap and the cooling section of the workshop manual for the engine code fitted. Matching the rated pressure is important for proper boiling-point control.

Where is the radiator cap located on a 1998 Gran Move?

It’s mounted on the top of the radiator, at the filler neck near the upper tank. Only open it when the engine is completely cold to avoid sudden release of hot, pressurised coolant.

What are the signs the radiator cap needs replacement?

Common clues include coolant pushing into the overflow bottle and not returning, a collapsed upper hose after cooling down, slow overheating in traffic, or visible perishing on the cap’s rubber seals. A cooling-system pressure test and a cap test will confirm the fault quickly.