BMW 1 Series: B58 valve cover PCV diaphragm failure and valve cover gasket leak (M140i)
B58 valve cover PCV diaphragm failure and valve cover gasket leak (M140i) is a common engine fault on the BMW 1 Series on the 2016–2019 cars, and we rate it major. Putting it right costs $300 to $2,500 at New Zealand independent workshop rates. Below is what goes wrong, the symptoms to notice on a test drive, where to look, and what to ask the seller before you hand over any money. It is one of 50 documented faults on the BMW 1 Series.
- Vehicle
- BMW 1 Series
- Engine
- B58
- Years
- 2016–2019
- Fuel
- petrol
- System
- Engine
What you are looking at
No photograph available
What goes wrong
The first-generation B58 (B58A) builds its crankcase ventilation (PCV) valve into the plastic valve cover, using a spring-loaded rubber diaphragm to control crankcase pressure. The diaphragm wears or tears, which lets oily vapour into the intake and can cause whistling, rough idle, smoke and higher oil use; separately the valve cover gasket hardens and seeps oil. BMW sells a diaphragm repair kit for the B58A, but many cars end up with a whole new valve cover. Owner reports on Bimmerpost include a 340i needing a valve cover and oil separator for a smoking exhaust.
What you would notice
- Whistle or squeal from the engine at idle
- Rough idle or misfire
- Blue or white smoke from the exhaust, worst on start-up
- Oil seeping around the valve cover or burning oil smell
- Oil level dropping between services
How to check it
Where to look. Top of the engine: plastic valve cover with the integrated PCV valve
With the engine idling, listen at the top of the engine for a whistle or squeal that is not the belt. With the engine off, look under the oil filler cap for a creamy white or yellow residue, and note if the cap is very hard to lift off with the engine running because of suction. Use a phone torch along the edges of the valve cover for oily wetness or dust caked on oil. Watch the exhaust on start-up and after the test drive for blue or white smoke. Ask how much oil the car uses between services and whether the valve cover or PCV has been replaced. If a workshop inspection is possible: have the fuel trims and misfire counters read and crankcase pressure checked.
What it costs to put right
$300 to $2,500 at New Zealand independent workshop rates. That is for this job on its own, not for the car.
Ask the seller
- “Has the valve cover or PCV valve been replaced?”
- “How much oil does it use between services?”
- “Does it ever smoke or whistle at idle?”
Now check the BMW 1 Series you are actually looking at
Everything above is true of the model, and it is free. What it does not tell you is whether THIS car has been looked after: its odometer history and whether the reading has ever gone backwards, whether there is still money owing on it, whether it has been reported stolen, how many owners it has had and what it is really worth today. That comes from the official records for that plate. Enter the plate for the free details, or get the full history and a market valuation from $13.49.
Where this comes from
- BimmerWorld Genuine BMW PCV diaphragm repair kit 11121025447, B58A (F22 M240i, F3X 340i/440i)
- SlashGear "Common Problems With BMW's B58 Engines (According To Owners)" citing a Bimmerpost 340i valve cover and oil separator replacement
- BMWTuning.co "The 5 most common BMW B58 engine problems" (valve cover gasket and PCV, M140i/M240i/340i/440i)
BMW 1 Series buyer questions
Is b58 valve cover pcv diaphragm failure and valve cover gasket leak (m140i) serious on a BMW 1 Series?
We rate it major and common on the BMW 1 Series. The first-generation B58 (B58A) builds its crankcase ventilation (PCV) valve into the plastic valve cover, using a spring-loaded rubber diaphragm to control crankcase pressure. The diaphragm wears or tears, which lets oily vapour into the intake and can cause whistling, rough idle, smoke and higher oil use; separately the valve cover gasket hardens and seeps oil. BMW sells a diaphragm repair kit for the B58A, but many cars end up with a whole new valve cover. Owner reports on Bimmerpost include a 340i needing a valve cover and oil separator for a smoking exhaust.
How much does it cost to fix on a BMW 1 Series?
$300 to $2,500 at New Zealand independent workshop rates. That figure is for this job on its own. A car showing the symptoms on this page is usually worth either walking away from or negotiating down by at least the repair figure.
Which BMW 1 Series years are affected?
Our research records this fault on the 2016–2019 BMW 1 Series. Build dates move around, especially on imported cars, so treat the range as the years to look hardest at rather than a guarantee either way. The official records tell you the exact build and first registration date for the car in front of you.
How do I check for it before I buy?
With the engine idling, listen at the top of the engine for a whistle or squeal that is not the belt. With the engine off, look under the oil filler cap for a creamy white or yellow residue, and note if the cap is very hard to lift off with the engine running because of suction. Use a phone torch along the edges of the valve cover for oily wetness or dust caked on oil. Watch the exhaust on start-up and after the test drive for blue or white smoke. Ask how much oil the car uses between services and whether the valve cover or PCV has been replaced. If a workshop inspection is possible: have the fuel trims and misfire counters read and crankcase pressure checked. Look here: Top of the engine: plastic valve cover with the integrated PCV valve