Can new PCV box be defective?

Jotunn77 · Post by **Jotunn77** » 30 Oct 2025, 15:15

Used an aftermarket kit that I assume came with the cheap stuff. Replaced the PCV the system with no issues. Could not believe the state old system, btw. Did a test drive and had oil spray for the dipstick tube. Not the result I expected. Took everything back off to check my work and found no issues. It blows smoke from the dipstick and inflates a glove from the oil cap in the classic fashion. I am gonna try the 5/8 heater hose mod since I’m in here and it looks fun. But I’m curious if anyone has had a PCV box fail right off the shelf? Is there a way to find a fault with the box off the car?

Post by **scot850** » 31 Oct 2025, 08:38

Did you make sure the oil paths into the engine block are clear? The lower one in particular can block around the 90 degree corner. The only way to successfully clean it is to pull the oil pan and clean up from below.

Did you replace all the pipe work as well as the flame trap?

Sorry nearly forgot. The oil trap is a fairly simple device. It is just a series of baffles. If you can blow through it then it should work.

Neil.

Post by **erikv11** » 31 Oct 2025, 19:26

Make sure you didn't reverse the hook-ups for the two hoses to the top of the PCV box.

Jotunn77 · Post by **Jotunn77** » 14 Nov 2025, 10:43

Sorry, delayed reply. The hook ups are correct but I have not dropped the pan. As the tutorial mentioned, I blew into the oil return port and heard bubbling and assumed I’m good.

This was the PCV oil return on the old system and oddly crank case pressure was not an issue. I just did a compression test today with 150 across all cylinders. Should I be looking at the turbo? If so, I’m not sure where to start. Could it also be the ECU relearning and slowly adjusting?

Post by **erikv11** » 14 Nov 2025, 17:33

I don't see a clear reason why it would be the turbo.

Nothing for the ECU to "relearn" after PCV work, it's not that.

Most likely seems something not hooked up with but I haver no good ideas ...

Post by **misha** » 15 Nov 2025, 00:53

Compression test will tell you something and not telling you anything....leaving you to chase your own tail.

That said....if oil control rings are shot...compression will still be good but it will pouring oil into intake through pcv system.

Testing should be more intense...compression,leak down,dry & wet.

I had a car once which was pouring oil into intake...head was good,spark plugs nice & dry,no blowby.
After opening... the shop said that oil control rings were shot.
It was consuming 1l of oil per 400km...and exhaust was full of oil which transformed to grease at the end of the pipe.

Engine rebuilt was performed,head rebuilt(since it was off anyway,piston rings,seals....after that i got 100k km from that car wit ZERO oil consumption.
I sold it like that and it's still running strong.

Jotunn77 · Post by **Jotunn77** » 15 Nov 2025, 09:29

I am getting tired of chasing faults and it may be time to take it in. Thanks for all the advice. I’ll be sure to post the resolution later on.

Jotunn77 · Post by **Jotunn77** » 07 Feb 2026, 11:39

Just a follow up. I did not take the car in and ultimately got things right. Here’s a quick rundown of work done to stop the crankcase pressure.

Another smoke down revealed vac leaks at PTC and the bottom end of the intake hose that goes into turbo inlet. The PTC rubber boot was no longer sealing. The intake tube was cracked and had a ripple where the band clamp goes that prevented it from sealing. There was also a leak at the vacuum tree.

I tried liquid gasket to get things to reseal but it was no good as even more smoke dumped from the faulty connections. The vac tree simply needed a new o ring.

To address the intake hose, I ordered an aftermarket one from Do88. Out of the box, the fitment was pretty bad for a stock car. Took a few emails to Do88 to get what I needed to mod the intake for stock tolerances. Frankly, It was a pain for the cost of it. The part is definitely for the modding crowd but there’s really no OE replacement options. In the end everything sealed up.

So with all the vacuum leaks addressed, the car finally passes the glove test.

Post by **ZionXIX** » 08 Feb 2026, 05:25

Jotunn77 wrote: ↑07 Feb 2026, 11:39
To address the intake hose, I ordered an aftermarket one from Do88. Out of the box, the fitment was pretty bad for a stock car. Took a few emails to Do88 to get what I needed to mod the intake for stock tolerances. Frankly, It was a pain for the cost of it. The part is definitely for the modding crowd but there’s really no OE replacement options. In the end everything sealed up.

This was part of my hesitation in purchasing the do88 pipe. What mods were needed to get it to fit?