PTC's role in the PCV system - can clogging cause positive pressure?

[timetobakethedonuts]

I just discovered that I have positive pressure in my crankcase, with a partially inflated latex glove at warm idle. When discovered, I was in the process of trying to determine if my '98 S70 T5 still had all the stock valves/connections after being brought to level 0.

The good news is, it appears I do have all the stock connections, the turbo boost valve, and what I discovered is called the PTC port (sometimes referred to as valve). The routing of the air snorkel between the MAF and turbo and all the tubing at the rear corner of the motor near the turbo is all pretty tight, but I have been able to verify the routing of everything except RIP intake and air tubes, and air filter seem to be stock.

Now I am trying to put my new "knowledge" to work, as pertains to the PCV pressure I discovered, where I am supposed to have a slight vacuum. The car has only 16k miles on it since the PCV box and dual line (one small tube, one larger tube for oil vapor) from the box/intake manifold to the PTC were replaced with new OEM parts from Volvo.

I had the oil pan off a few years ago to replace the O-rings and successfully eliminated a tapping at idle, but when I cleaned the pan I did not understand the PCV passage's function, and that I should check it to make sure it was clear. So it may have been cleaned, or maybe not. I recall it draining slowly at one point when cleaning, and wondering why.

The question in my mind is, could the PTC port be clogged, and could that cause the pressure? This appears to be where oil vapor is released to the intake, so logically it seems like it could be. My thought is, try to service the PTC first (remove the snorkel from the car, and then carefully remove the PTC from it to clean) to see if this fixes the problem, and only if this fails, dive into the standard PCV service and while doing that the oil passage to the pan could be checked at that time by blowing into the passage at the block, and listening for gurgling in the pan.

Thoughts would be appreciated. I am intimidated by this corner of the motor with the turbo since it is so tight. But Robert DIY posted a video on a P2 car today where he was able to get the snorkel out with the PTC in it.

Don

[scot850]

The PTC is not really a valve. It is a preheater orifice. It does need to be kept clear. It is part of the snorkel tube to the turbo. Removing the snorkel tube you can clean the orifice tube using a small drill bit turned by hand.

Neil.

[abscate]

The PTC orfice provides vacuum to the PCV system under boost, so if you have pressure under idle you need the whole PCV job done. It’s a Volvo specified 60k maintenance item, and 30k makes sense on high mileage motors

[erikv11]

Your plan sounds spot on. One thing I would add is that is you can check for gurgling at the outset by blocking the hose leading away from the trap.

Unfortunately clogged oil passageway into the pan is more likely than clogged PTC but for sure worth checking.

[magna224]

Mine always had slight pressure even after fresh pcv with oem parts and cleaning out the block with wire brush at 130k miles.