Searching vacuum check valve Audi usually means your 3.0T is doing something vague and annoying: an idle that hunts, a brake pedal that feels firmer than it should, or a lean code that survives a new PCV valve. A check valve is a tiny one-way gate, and when it leaks or sticks it can impersonate much more expensive failures. This guide explains the vacuum check valves on the supercharged EA837, how to test them in ten minutes, and why the Vorsprung 3.0T oil check valve set belongs on your list whenever the supercharger comes off.
What a Vacuum Check Valve Does on an Audi
A check valve lets air flow one way and blocks it the other. Inside is a small flap, disc or ball on a light spring. When pressure on the inlet side is higher, it opens. When pressure reverses, it seats and seals. That is all it does, and it is exactly why it matters on a supercharged engine: the intake manifold switches from vacuum at idle to boost under load, many times per drive. Anything that should only ever see vacuum needs a one-way valve to keep boost out.
Where the 3.0T Uses Check Valves
| Circuit | What the check valve does | What happens when it fails |
|---|---|---|
| Brake booster | Holds vacuum in the booster and keeps boost from pushing back into it | Hard pedal, less assist after repeated stops, hiss at the booster |
| PCV (crankcase ventilation) | Routes crankcase gases to manifold vacuum off boost and to the supercharger inlet side on boost | Rough idle, lean codes, oil in the intake, crankcase pressure |
| EVAP purge | Sends fuel vapor to the manifold under vacuum and to the inlet side under boost | EVAP codes, rough idle right after a cold start, fuel smell |
| Engine oil (valley) | Stops oil draining out of the heads and chain tensioners when the engine is off | Rattle for a second or two on cold start |
That last row is not a vacuum valve, but it lives in the same valley and it is the one our 3.0T oil check valve set replaces. More on that below.
Symptoms of a Bad Vacuum Check Valve
- ✅ Rough or hunting idle that the ECU cannot trim out.
- ✅ Lean codes (P0171/P0174) that return after other leaks are fixed.
- ✅ Firm brake pedal or reduced assist, especially after a hard run or several stops.
- ✅ Hissing that changes when you press the brake pedal.
- ✅ Oil in hoses that should be dry, a sign boost or crankcase pressure is getting where it should not.
These overlap with a torn PCV diaphragm, a cracked breather hose and leaking intake gaskets. Our Audi PCV valve guide and PCV breather hose guide cover those, so work through them together.
How to Test an Audi Vacuum Check Valve
- Find the flow arrow. Every check valve is directional. Note the orientation before you pull it.
- Blow test. With the valve off the car, air should pass one way and stop completely the other way.
- Hand vacuum pump. Apply vacuum to the side that should hold it. The gauge should stay put. A slow drop means the valve leaks internally.
- Smoke test the circuit. A valve that passes on the bench can still leak at a cracked barb or a brittle hose end.
- Booster check. Engine off, pump the brake pedal until firm, hold light pressure, start the engine. The pedal should sink slightly as assist arrives.
If trims still look off after that, rule out airflow issues with our Audi MAF sensor guide and decode codes with our check engine light causes guide.
The Other Check Valves in the 3.0T Valley
Here is the part most vacuum check valve Audi guides skip. Under the supercharger sit two oil check valves that keep oil in the cylinder heads and hydraulic timing chain tensioners when the engine is off. When they are missing or tired, the tensioners start empty and the chains slap the guides for a second or two on a cold start. Some 3.0T engines left the factory with blank plugs in these positions. Every rattle is wear on the plastic chain guides, and the timing chains on this engine live at the back, which is the last place you want to go.
The Vorsprung 3.0T Oil Check Valve Set ($39.99) is an oil part, not a vacuum part. It includes two valves with quality internal springs and seals for a complete valley service on 2009-2017 EA837 S4, S5, SQ5, A6, A7 and Q7 models.
Oil Check Valve Set: Vorsprung vs Generic vs Dealer
For the two oil check valves in the 3.0T valley, it comes down to three choices: dealer parts at dealer prices, a generic plastic valve of unknown spec, or a platform-specific part from people who work on these engines.
| Vorsprung 3.0T Oil Check Valve Set | Generic check valve | Dealer/OEM | |
|---|---|---|---|
| Built for | EA837 3.0T valley, 2009-2017 | Universal, barb sizes vary | Per part number |
| Contents | Two valves for a full valley service | Usually one | Individual parts |
| Fitment help | Email us with your build | None | Parts counter |
| Price | $39.99 | Varies | Dealer pricing |
If the supercharger is coming off for anything, add the Audi 3.0T oil check valve set to the cart. It is one of the cheapest parts in the job and stops the cold-start chain rattle.
Shop the 3.0T Oil Check Valve Set, $39.99
✅ Platform-specific EA837 parts ✅ Fitment help from real 3.0T owners ✅ Fast US shipping
What to Look for in a Replacement Check Valve
- ✅ Correct flow direction and a clear arrow.
- ✅ Barb and hose sizes that match the original. A stretched hose leaks at the clamp.
- ✅ Seals and diaphragms that survive heat and oil vapor. That is why we mold our GLT TruSeal PCV diaphragm ($19.99) from Viton GLT rated -40°F to +400°F.
- ✅ Fitment by engine code. A valve from another platform may look identical and still have the wrong opening pressure.
Fitment and Related Parts
The oil check valve set fits 2009-2017 EA837 3.0T supercharged S4, S5, SQ5, A6, A7 and Q7 models. For the brake booster and EVAP valves, use the Audi parts catalog by VIN, since part numbers vary by model and year. For the PCV side, pick the right Hengst OE PCV valve or go billet with the Billet PCV Housing Adapter. Cracked pipes? See the 06E103207P / AM PCV pipe. More valley parts live in our OEM+ upgrades and fixes collection.
Install Notes
- ✅ Mark hose orientation and valve direction with a paint pen before removal.
- ✅ Warm brittle hoses before pulling them off barbs, or just replace them.
- ✅ While the supercharger is off, reseal it with the GLT TruSeal intake manifold gasket set and look hard at the thermostat housing.
- ✅ Also check the oil filter housing seals. Our oil filter housing gasket guide and replacement walkthrough show how.
- ✅ Smoke test and clear codes after the job, then log trims on a drive.
Vacuum Check Valve Audi FAQ
What does a vacuum check valve do on an Audi?
It lets air flow only one way. On a supercharged 3.0T it keeps boost out of circuits that should only see vacuum, like the brake booster, and routes PCV and EVAP flow correctly on and off boost.
What are the symptoms of a bad vacuum check valve?
Rough or hunting idle, recurring lean codes, a firm brake pedal or reduced assist, hissing, and oil in hoses that should be dry.
How do I test a vacuum check valve?
Take it off, confirm air passes one way only, then apply vacuum with a hand pump to the side that should hold it. The gauge should not drop. Smoke test the hoses and connections too.
Can a bad check valve cause brake problems?
Yes. A leaking brake booster check valve lets stored vacuum bleed off, so the pedal feels harder and assist drops, most noticeably after repeated stops.
Is the Vorsprung 3.0T check valve set a vacuum check valve?
No. It replaces the two oil check valves in the engine valley that keep oil in the heads and timing chain tensioners, which helps prevent cold-start chain rattle. It is a smart add-on whenever the supercharger comes off.
Where are the check valves on an Audi 3.0T?
The oil check valves are in the valley under the supercharger. Brake booster, PCV and EVAP check valves sit in their respective hose runs; locations vary by model, so check the repair information for your car.
Can I clean a vacuum check valve instead of replacing it?
Cleaning rarely restores a hardened seal or tired spring. Given the low cost of the part and the labor to reach some of them, replacement is the better call.
Bottom Line on the Vacuum Check Valve Audi Owners Should Know
A leaking vacuum check valve on an Audi 3.0T can make a healthy engine look sick. Test the booster, PCV and EVAP valves before replacing big parts, and when the supercharger comes off, replace the valley check valves too. The Vorsprung 3.0T Oil Check Valve Set keeps oil where it belongs and your cold starts quiet.
Shop the 3.0T Oil Check Valve Set, $39.99
Drive the difference. Drive Vorsprung.
Prices checked September 25, 2026 and subject to change.
