# Engine Valve Cover Replacement in Upland > Cracked or warped plastic valve cover, or a failed built-in PCV? Engine valve cover replacement in Upland, confirmed with a smoke test first. Source: https://route66autorepairshop.com/engine-services/engine-valve-cover-replacement Updated: 2026-09-17 Business: Route 66 Auto Repair, 1775 W Foothill Blvd, Upland, CA 91786, (909) 608-7699 Hours: Monday to Friday 8 AM–5 PM, Saturday 8 AM–2 PM, Sunday closed **TLDR:** When a **plastic valve cover** cracks or its **built-in PCV** fails, a gasket will not fix it. A **smoke test** confirms the cover before we replace it. Engine valve cover replacement at Route 66 Auto Repair in Upland is for covers that a new gasket cannot save. Many modern engines use plastic valve covers with the PCV valve and oil separator built in. Years of heat cycles make them crack, warp or lose the internal diaphragm. We confirm the cover itself has failed, often with a smoke test, before replacing it. ## Why do valve covers fail? Plastic covers save weight and cost, but they sit on the hottest part of the engine. In Inland Empire summers, they can go through thousands of hot and cold cycles. The plastic gets brittle, bolt holes crack, and the sealing flange warps so no gasket can seal it. Many covers also hold a small rubber diaphragm that regulates crankcase ventilation. When it tears, the engine pulls unmetered air. ## What are the signs the cover itself has failed? - A whistle or hiss from the top of the engine at idle - Lean codes or rough idle that improve when the oil cap is removed or reinstalled - A visible crack near a bolt hole or baffle - A leak that returns soon after a gasket replacement - Rising oil use with oily residue in the intake tube ## How do we confirm it? A smoke machine pressurizes the crankcase and intake with visible vapor. Smoke from a crack or from the PCV port tells us the cover is the leak. We also check whether the engine's fuel trims return to normal with the PCV port capped. Covers with metal bodies are often reusable, in which case [valve cover gasket repair](https://route66autorepairshop.com/engine-services/valve-cover-gasket-repair) may be all you need. Vacuum leak testing is covered in more depth on the [engine diagnostics](https://route66autorepairshop.com/engine-services/engine-diagnostics) page. ## Our valve cover replacement process 1. **Smoke test:** Confirm the crack or PCV failure and photograph it. 2. **Source the cover:** Match the cover to your engine code, including the correct PCV design. 3. **Swap and seal:** Install the new cover with its gasket and tube seals, torqued in sequence. 4. **Verify:** Clear codes, check fuel trims at idle and road-test. ## What's included in valve cover replacement - Smoke test with photos - Replacement valve cover matched to engine code - New gasket and tube seals - Fuel trim check after repair - Road test ## Need-now or need-later? **Need now:** - A torn PCV diaphragm causing rough idle or oil consumption - A crack leaking oil onto the exhaust **Need later:** - A small cosmetic crack away from sealing areas, rechecked at each oil change ## How pricing and timing work Cover prices vary widely by engine, and some are dealer-only, which can add a day. Phone quotes are ranges until we see the part number. AAA members save 10% on parts and labor, up to $75, with the card at time of service. ## Aftercare Idle may take a few drives to settle while the computer relearns. If oil use was high before, track it for a month. Continued use points to other causes such as [piston ring replacement](https://route66autorepairshop.com/engine-services/piston-ring-replacement) needs. ## Frequently asked questions ### Can a cracked plastic valve cover be glued? Adhesives rarely hold up to engine heat and oil for long. Replacement is the reliable fix for cracks near sealing surfaces or bolt holes. ### Why is my engine whistling? A whistle at idle often points to a vacuum leak, and a torn PCV diaphragm in the valve cover is a common source. A smoke test confirms it. ### Do I need a new gasket with the new cover? Many replacement covers come with a gasket installed. If not, we supply one. Tube seals are usually replaced at the same time. --- Call (909) 608-7699 or visit https://route66autorepairshop.com/contact for a written estimate.