I’ve seen posts of people just replacing the diaphragm as “preventative” measure or after it broke and call it a day. I think that’s not a correct fix, because only replacing the diaphragm doesn’t get rid of the carbon deposits and sludge accumulated inside the housing. Sure, if it was torn, it could get rid of the infamous squealing noise for a while. But more deposits will keep building up until the PCV eventually gets fully clogged and sends oil directly to the intake manifold and/or turbo, and that can cause major issues to the engine. Long story short, eventually has to be replaced or cleaned.
The oil filter and the new gaskets behind the housing are the only brand new parts.
Last year, while ordering around $300 in new parts to replace the PCV on my C70, I saw that FCPEuro has listed a “PCV Diaphragm Replacement Kit” for around $150. And that caught my attention, but I noticed it was including some parts that aren’t really needed, like for example 4 new bolts (Come on!, the old ones can be reused), and at least in my case: the diaphragm, both hoses and hose clamps. So after finishing replacing the PCV on the C70, the S40 was next. But this time I wanted to try cleaning and reusing the old parts of the other car, instead of spending another $300.
Now, the determining factors if you can get away by cleaning the PCV/Oil filter housing will be:
- In which shape is the plastic cap of the housing. (If it’s cracked, plastic crumbling apart, etc)
- If the PTC heater element is still working. You can test this by applying 12v to the plug and it should warm up.
- And if the plastic cap gasket is still in good condition (not brittle, broken, etc) It’s made of the same material as the oil filter cap o-ring, and should be still very flexible. However if the housing is too old, it may be a little bit squished. If you didn’t have any leaks in that area, you should be good.
If any those three parts are damaged, then you will either have to buy a new housing or somehow get used replacements (Junkyard, your neighbor’s car, whatever….)
Cleaning Process:
I started by taking completely apart the housing and then cleaning it to see in which condition it was. The plastic cap of the housing is attached with a series of plastic locks around it that grab the aluminum main piece. These can be done by carefully pushing the locks away from the aluminum with two flat head screwdrivers. Once you unlocked a few of them, the cap should come right out. It took me a few tries to unlock several of them consecutively, but eventually I managed to do so. Just keep in mind, the older the housing is, the more brittle the plastic it gets.
This is the PCV housing that came out of my S40:
Once this is apart, we carefully remove the seal and clean it to make sure is not damaged. With that seal out of the way, we can focus on removing the diaphragm cap with a flat head screwdriver. Under the cap, the orange diaphragm will come out pushed by a soft spring set those aside to be cleaned later, and now we can focus on cleaning the housing to reveal what manufacturing dates it has
Upper PCV hose:
It wasn’t clogged, but there was quite a bit of carbon inside.
As for degreaser, an aluminum safe degreaser is MANDATORY. I had good luck cleaning a cylinder head with this:
at a 1:3 mix ratio with water and submerged for 5-6 hours. It required minimal scrubbing on a few areas but overall, it did a great work cleaning that cylinder head. I think it should work just fine with the PCV. If not you can go with the good ol’ method of spraying it and brushing until clean.
As you may have guessed, the PCV plastic cap is the most important part of the system and it’s ABSOLUTELY VITAL to thoroughly clean the internals:
It has attached the cyclone separators and these have a key role in the system, which consists of separating the oil from the crankcase gasses. Unfortunately those cannot be taken apart, and neither the check valve below them:
So, the way I cleaned them, was by blocking the check valve and filling them via the diaphragm opening with degreaser at full strength and let it sat for a few minutes, then drain in a clear container and observe how much residue comes out. I kept repeating the process until the degreaser came out clean. Also, when done, you need to make sure the check valve is not stuck. If you shake it, you’ll hear the valve bouncing inside.
If you happen to have access to an ultrasonic cleaner, I think that could make the cleaning much easier and quicker. I would’ve give it a try if I had one.
Now, with everything clean, we can check the manufacturing dates and evaluate the condition of all the parts:
A simple way to know approximately how old the housing is by checking the assembly date here right under the nipple where the top hose connects to:
That copper-colored strip, is the part of PTC heating element, it warms up the cyclone separators. Most likely to improve oil separation when the engine is cold.
If you made it to this point, and you didn’t have to replace anything other than the two gaskets and dipstick o-ring, then lucky you!. The PCV is ready to be reassembled and put back into service. If you didn’t like the condition of the diaphragm, no worries, below is the link to order a new replacement. And if the cap was cracked or somehow damaged, then you can decide either to get a new housing, grab an used one at a junkyard and try this again. It’s up to you.
Now, I have to admit I made a mistake when I cleaned this housing. I used Super-Clean tough task cleaner & degreaser, which I applied with a spray bottle and scrubbed as necessary with an old toothbrush. This degreaser, being sodium hydroxide based, it causes damage to the aluminum. I didn’t notice any effects immediately after cleaning, but later the aluminum when exposed to moisture, it started developing some white chalky deposits on the exterior once installed (Honestly, it was just cosmetic issues). The interior of the PCV was perfectly fine (because it’s coated with oil once the engine is running). So, to avoid any further corrosion, I painted the exterior of the housing with leftover brake caliper paint I had from a previous project:
————————————————————————————————————
This part only applies for T5 engines:
I’ve never read or heard of this happening …..yet, but if the PCV housing was excessively dirty, you might want to check these two parts and make sure they are not obstructed:
That’s the tube that runs around the engine, behind the camshaft sprockets, and connects the lower intake manifold with the compressor intake of the turbo, via that check valve. The aluminum tube CANNOT be removed, unless you pull the timing belt and both camshaft sprockets first, needless to say, a major PITA.
If cleaning is required, one way I could think of doing it, while still on the engine is by pumping degreaser through it with a setup like this:
Just be careful to not bend it or move it too much, because as I mentioned earlier, it runs behind the camshaft sprockets and it’s only held by those foam sleeves. If in doubt, pull the timing belt cover and confirm it’s not rubbing against the cam sprockets.
And finally, the small piece on the right is the check valve threaded directly to the compressor housing of the turbo:
It only allows flow from the intake manifold towards the turbo. I know there are two versions of this check valve. The earlier version was a plastic diaphragm-style check valve, that caused some issues to a few owners. But later, it was superseded with a revised ball-style version. I think most of the cars have the newer version. If you’re already here, might as well remove it with a 19mm deep socket and clean it just in case. Be gentle when tightening it back, torque spec is 25 Nm / 18 ft-lbs.
If you did all of this up to this point, the congratulations! your car now has a brand new PCV system again and it’s ready to do thousands of miles more.
As you can see the process is not complex, just a bit time consuming. IMHO, this is the correct way of dealing with a clogged or really old PCV other than replacing everything with new parts.
————————————————————————————————–
Parts I used:
Additional parts that you might need depending on which condition yours are: