Cleaning the PCV system on a Volvo V70 XC

anyone know how to clean the PCV system on a Volvo V70 XC? I replaced the oil filler cap, but still leaking oil.

You need to locate the PCV valve, and while it is detached from the engine (but still attached to its hose), you should squirt PCV valve cleaner into the valve. This should be done while the engine is running. A few doses of this should free-up the valve and remove a lot of the crud from the PCV hose.

Regarding the oil filler cap, I’m not sure why you would have replaced that part. Unlike years ago, when oil filler caps were vented to the outside air, modern oil filler caps normally form a very tight seal when they are screwed-in properly. Unless the oil filler cap had somehow been damaged, I don’t understand why you would replace this item.

If careful cleaning of the PCV system does not resolve your oil consumption/oil leak problem, you need to take a careful look at all of the many seals and gaskets on the engine.

By the way–what is the model year and the odometer mileage of your mystery Volvo V70?

I have seen some recent model Volvos with PCV valves failing and losing a great deal of oil. The valves were called anti-backfire valves and were very much similar to the British valve using the same name that dates back to the early 60s. That type valve would require disassembly to clean as spraying cleaner into the ports would likely damage the rubber diaphram.

this is a 1999 with about 150k miles.

At that age and mileage it could be anything from a faulty PCV system to excessive blow-by to hardened crank seals and worn crank journals.

Considering the miles on the car, I’d run a compression and/or leakdown test and go from there.