# Diesel Engine Valve Adjustment in Upland > Diesel valve adjustment in Upland to the maker's lash spec. Quiets ticking, protects valves and restores smooth running on engines that need it. Source: https://route66autorepairshop.com/diesel-engine-services/diesel-engine-valve-adjustment 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:** Valve **lash** drifts as parts wear. We measure every valve and adjust to spec, which quiets **ticking** and protects the valves. A diesel engine valve adjustment at Route 66 Auto Repair in Upland sets the small gap between the rocker and valve, called lash, back to the maker's specification. Many diesels need this on a schedule, especially engines with solid lifters. Our ASE-certified technicians measure each valve, adjust only what is out, and record the readings on your repair order, with a written estimate first. ## Why do some diesels need valve adjustments? Valves open and close hundreds of times a minute, and the parts that move them wear slowly. On engines with adjustable rockers, that wear changes the lash. Too much lash causes ticking and lazy valve timing. Too little can hold a valve slightly open, which burns the valve seat and lowers compression. Some diesels use hydraulic lifters that adjust themselves, and those need no routine lash service. We check your engine's requirement before recommending the job, so you are not paying for an adjustment your engine does not need. ## What are the signs your diesel needs a valve adjustment? - A steady ticking from the top of the engine that follows engine speed - The maker's scheduled lash interval has come due - Rough idle or a harder start with no fuel or glow plug fault - Lower compression on a cylinder during testing ## Our valve adjustment process 1. **Confirm the schedule:** We check your engine's lash requirement and interval. 2. **Remove covers:** Valve covers come off, and gaskets are inspected or replaced. 3. **Measure:** Each valve is measured with feeler gauges at the correct crank position. 4. **Adjust:** Out-of-spec valves are set and locked, and readings are recorded. 5. **Reseal and run:** Covers go back on with new gaskets as needed, and the engine is run and checked for leaks. ## What's included in a diesel valve adjustment - Lash requirement check for your engine - Measurement of every valve - Adjustment of out-of-spec valves - Before and after readings on the repair order - Valve cover gasket inspection or replacement - Leak check and test drive ## Is a valve adjustment need-now or need-later? **Need now:** - Loud ticking with low compression on a cylinder - A valve that is far past its interval on a working truck **Need later:** - An interval coming due in the next few thousand miles - A faint tick with normal compression ## How pricing and timing work Price depends on the number of valves, how much must come off to reach the covers, and whether new gaskets are needed. Most adjustments are a drop-off job that finishes the same day when the board allows. AAA members get 10% off parts and labor, up to $75. ## Aftercare The engine should sound quieter at idle right away. Watch for any oil seepage at the covers over the next week; see [diesel engine valve cover repair](https://route66autorepairshop.com/diesel-engine-services/diesel-engine-valve-cover-repair) if it appears. Low compression that stays low after adjustment needs a [diesel engine compression test](https://route66autorepairshop.com/diesel-engine-services/diesel-engine-compression-test). Gas engines are covered on [engine valve adjustment](https://route66autorepairshop.com/engine-services/engine-valve-adjustment). ## Frequently asked questions ### How often does a diesel need a valve adjustment? It depends entirely on the engine. Some list an interval in the owner's manual; others have hydraulic lifters and no interval. We check your engine before recommending it. ### Is valve ticking always a lash problem? No. An exhaust leak or injector noise can sound similar. We listen and measure before adjusting. ### Can I drive with loose valves? For a short time, usually, but the problem can worsen. Tight valves are more urgent because they can burn a valve seat. --- Call (909) 608-7699 or visit https://route66autorepairshop.com/contact for a written estimate.