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Engine valves open and close to let air in and exhaust out. A burnt exhaust valve leaks compression, and a snapped timing belt can bend several valves at once. Route 66 Auto Repair in Upland confirms valve damage with compression and leak-down tests before the cylinder head comes off. ASE-certified technicians then replace the damaged valves and check the parts that work with them. Your written estimate shows every step, so nothing is a surprise.
Signs of a damaged valve
- A steady misfire on one cylinder that plugs and coils do not fix
- Low compression on one or more cylinders
- Air hissing from the tailpipe or intake during a leak-down test
- An engine that cranks fast with no start after a timing belt break
- A puffing sound from the exhaust at idle
How does a leak-down test find a bad valve?
We bring a cylinder to the top of its stroke and fill it with shop air. A gauge shows how much leaks away. Then we listen: air at the tailpipe points to an exhaust valve, air at the throttle body points to an intake valve, and air at the oil filler points to rings. Bubbles in the coolant point to a head gasket. This test tells us where the loss is before any teardown.
Burnt valves vs bent valves
A burnt valve usually comes from heat: a lean mixture, a valve that is not closing fully because of tight clearance, or deposits on the seat. A bent valve is mechanical, often from a timing failure on an interference engine. Bent valves often mean the valve guides need checking too, and burnt valves often need valve seat repair.
Our valve replacement process
Step 1: Test first
Compression and leak-down tests identify the affected cylinders.
Step 2: Remove the head
The cylinder head comes off, and the head gasket is replaced with it.
Step 3: Inspect the valvetrain
Valves, seats, guides and springs are checked and photographed.
Step 4: Replace and seal
New valves are fitted to properly finished seats, with new stem seals.
Step 5: Reassemble and verify
Head torqued in sequence, timing set, compression rechecked and road-tested.
What's included in valve replacement
Included on the work order
- 01Compression and leak-down tests
- 02Cylinder head removal and new head gasket set
- 03New valves as quoted
- 04Valve stem seals
- 05Seat and guide inspection with photos
- 06Post-repair compression test and road test
Need-now or need-later?
Need now: call
- Bent valves after a timing failure: the engine should not run
- A burnt valve causing a constant misfire
Need later: book
- Slightly uneven compression still within spec
- Valve cover gasket seepage found during testing
How pricing and timing work
Head removal is the core labor. Overhead cam engines with complex timing take longer, and V engines may need one or both heads. Seat and guide work are added only if measurements call for them, and your written estimate shows every step. AAA members save 10% on parts and labor, up to $75, with the card at time of service. Expect several days. More on the head itself is on cylinder head repair.
Aftercare
Follow the early oil change on the invoice and watch coolant level for the first weeks. Some engines need a valve clearance check after a set mileage, which we note if it applies.
Frequently asked questions
Can a burnt valve be fixed without removing the head?
No. The valve and seat are inside the head. The good news is that a leak-down test confirms the problem before you commit to the teardown.
Will all my valves be replaced?
Only damaged ones unless you choose otherwise. If most valves show wear, the estimate may offer a full valve job as an option.
Why did my valves bend?
On an interference engine, a timing belt or chain failure lets pistons strike open valves. That is why timing belt intervals matter.