{"product_id":"ap-astro-pneumatic-tool-company-number-41-radiator-test-cap-for-late-gm-ford-direct-fit-oe-style-spring-loaded-seal","title":"AP Astro Pneumatic Tool Company Number-41 Radiator Test Cap for Late GM \u0026 Ford — Direct-Fit OE Style, Spring-Loaded Seal","description":"\u003cp\u003e\u003cstrong\u003eThe AP Astro 7858541 Number-41 radiator test cap is a direct-fit replacement cap engineered to restore correct cooling system sealing and pressure control on late-model GM and Ford engines.\u003c\/strong\u003e\u003c\/p\u003e\n\n\u003cp\u003eThis precision-made radiator test cap from Astro Pneumatic Tool Company (AP) replaces worn or missing caps to help maintain correct coolant system pressure and reduce fluid loss. Manufactured in Taiwan to compact dimensions, the cap matches OE-style fitment and is ideal for garage technicians, fleet maintenance, and DIY enthusiasts working on late GM and Ford vehicles that require a Number-41 style cap.\u003c\/p\u003e\n\n\u003ch3\u003eWhich vehicles and systems does this Number-41 cap fit?\u003c\/h3\u003e\n\u003cp\u003eThe Astro 7858541 Number-41 cap is intended for late-model General Motors and Ford cooling systems that specify a Number-41 style cap. It is built to the common size and sealing profile used on those applications, providing a straightforward replacement when the original cap is lost or damaged.\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eDirect fit for late GM and Ford radiator necks requiring Number-41 specification.\u003c\/li\u003e\n  \u003cli\u003eCompatible with closed cooling systems using spring-loaded pressure caps.\u003c\/li\u003e\n  \u003cli\u003eUsed as a service or spare cap in repair shops and maintenance fleets.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eHow does this cap help with cooling system performance?\u003c\/h3\u003e\n\u003cp\u003eA properly sized radiator cap maintains the cooling system's designed pressure, which raises the boiling point of the coolant and helps avoid localized boiling and boil-over during operation. The Astro cap restores the mechanical seal and spring function that prevent coolant loss and air entry into the system.\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eRestores the intended pressure boundary of the radiator filler neck.\u003c\/li\u003e\n  \u003cli\u003ePrevents coolant evaporation and loss under normal operating temperatures.\u003c\/li\u003e\n  \u003cli\u003eHelps reduce air intrusion that can cause hot spots and reduced heat transfer.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eWhat are the product dimensions, origin, and package details?\u003c\/h3\u003e\n\u003cp\u003eThe AP Astro 7858541 cap ships in compact packaging suitable for retail shelves or repair kits. It is a lightweight replacement part, produced in Taiwan and sized to the Number-41 specification for accurate fit and function.\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003ePackage dimensions: 6.3 cm L x 10.3 cm W x 12.0 cm H.\u003c\/li\u003e\n  \u003cli\u003ePackage weight: approximately 0.2 lbs for easy inventory handling.\u003c\/li\u003e\n  \u003cli\u003eCountry of origin: Taiwan, manufactured to industry tooling standards.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eHow should I install and inspect the replacement cap?\u003c\/h3\u003e\n\u003cp\u003eInstallation is a simple twist-on procedure after the radiator has cooled. Inspect the cap seating area and the cap's rubber gasket and spring before installation to ensure a reliable seal and correct pressure response.\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eAllow the engine to cool before removing the old cap to avoid scalding.\u003c\/li\u003e\n  \u003cli\u003eCheck the filler neck for corrosion or damage; clean before installing new cap.\u003c\/li\u003e\n  \u003cli\u003eVerify the cap’s spring and gasket compress and reseal under light pressure after installation.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eWho is this for: The Astro 7858541 Number-41 radiator test cap suits professional technicians, mobile mechanics, and vehicle owners maintaining late-model GM and Ford cars and trucks. It’s an appropriate spare part for service centers or fleet shops needing an affordable, OEM-style replacement cap that restores proper coolant system sealing and pressure control.\u003c\/p\u003e\n\u003csection class=\"product-faq-snippet\"\u003e\u003ch3\u003eFAQ\u003c\/h3\u003e\n\u003cdiv class=\"faq-item\"\u003e\n\u003cp class=\"faq-q\"\u003eQ: Is this radiator cap compatible with my GM or Ford vehicle?\u003c\/p\u003e\n\u003cp class=\"faq-a\"\u003eA: If your vehicle specifies a Number-41 radiator cap for late-model GM or Ford applications, this AP Astro 7858541 cap is a direct-fit replacement.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"faq-item\"\u003e\n\u003cp class=\"faq-q\"\u003eQ: Can I replace the cap while the engine is hot?\u003c\/p\u003e\n\u003cp class=\"faq-a\"\u003eA: No — wait for the engine to fully cool before removing the cap to avoid burns and prevent coolant spray.\u003c\/p\u003e\n\u003c\/div\u003e\u003c\/section\u003e","brand":"AP Astro Pneumatic Tool Company","offers":[{"title":"Default Title","offer_id":48084323958942,"sku":"B00TBA5FFA","price":30.28,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0781\/2041\/9486\/files\/astro-number-41-radiator-cap-front.jpg?v=1785849914","url":"https:\/\/northtrailauto.ca\/products\/ap-astro-pneumatic-tool-company-number-41-radiator-test-cap-for-late-gm-ford-direct-fit-oe-style-spring-loaded-seal","provider":"North Trail Auto","version":"1.0","type":"link"}