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PCV replacement questions.

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
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clarkerussell
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clarkerussell

PCV replacement questions.

Post by clarkerussell » Mon Feb 11, 2019 11:34 pm

Hey guys,

I'm replacing the PCV system in my S70 GLT with 285k miles and I have a couple of questions that I can't find answered in the walk through's.

1) When replacing the box, I understand that it says to clean out the ports on the block. Neither of the ports on my system seemed to be clogged... at all... Is there a picture somewhere of what I should be looking for? Is it normal for there to be no meaningful sludge buildup in those ports?

2) the breather box/catch can was completely empty, but I replaced it just to be safe. Again, is that typical?

3) With the engine block ports clear, and the breather empty, what would cause the positive pressure? Is it that the hoses were broken and it requires vacuum from the intake to eliminate the positive pressure?

4) Finally, I realize that I have never cleaned the PCT valve... If that is clogged (I'll check tomorrow) does that basically defeat the entire purpose of the PCV system?


Thanks in advance guys.



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oragex
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Re: PCV replacement questions.

Post by oragex » Tue Feb 12, 2019 2:19 am

There is a lower port in particular (the lowest towards the bottom of the engine), needs a hose that fits tight in there (may wrap the end of it with some duck tape), then blow at the other end and listed for oil bubbling inside the oil pan. Should be quite easily to blow through it.

Very wise decision to replace the breather box even when perfectly empty. Had the same and put it back, the glove was still inflating slightly, removed everything again then put a new breather box, not it sucks the glove with force. These breather boxes do also crack or fail inside at some seal or diaphragm (such as on non turbo engines).

Positive pressure would be from another clogged passage on the pcv hoses, in particular the turbo engine needed everything really cleaned up or better, replaced. So possible for the PTC valve indeed.

The glove should suck in quite nicely On my S60:


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Re: PCV replacement questions.

Post by abscate » Tue Feb 12, 2019 4:29 am

Broken hoses will cause positive crank pressure

The PTC isn't a valve, it's just an orfice. It needs to be cleaned every 50,000 miles. If it's plugged, the PCV system fails, correct.

Replace all the 16 year old , oil soaked, baked plastic pieces with new Volvo stuff. If you enjoyed the Labour part of this job, use the cheap parts and then you can do it again in one year.


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Re: PCV replacement questions.

Post by tardcart » Tue Feb 12, 2019 6:13 am

PTC I wounder what that stands for. the T must be temperature. I hate calling it a valve too, maybe restrictor would be a better term for it. or heater. I hope you got the new long lines, they are always brittle and cracked in their insulating sleeve if original.



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Re: PCV replacement questions.

Post by clarkerussell » Tue Feb 12, 2019 9:03 am

I got the whole original Volvo kit from FCP. I used URO last time (many moons ago) and they were basically dust when I took it out. I'm not sure how long they had been that way, but I'd say it's been quite some time...

I'm not messing around with questionable parts as I want to use it for my daily driver again. At least for another year to get it to 300k miles! My dad bought the car new and it's certainly not as pretty as before, but it has a special place in the family. I've replaced the starter + wire, I'm doing the PCV/PTC, replacing the leaking power steering pump, replacing all motor mounts, and wires/plugs/cap. The timing belt was done about 10K miles ago, so I'm good there...



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Re: PCV replacement questions.

Post by greg850r » Tue Feb 12, 2019 12:40 pm

The last one I did I decided to upgrade the long pipe. I obtained some soft copper from an A/C supply that was the same size as the black plastic pipe and bent it to match, then put the elbows on it and wrapped it in the insulating sleeve. I expect it won't ever crumble now.


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Re: PCV replacement questions.

Post by tardcart » Tue Feb 12, 2019 1:23 pm

the metal lines will, I'm guessing, clog up with condensation mixed with oil unless you insulate them like the factory did. but it will take 6 years and most of these cars won't be on the road in 6 years.



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Re: PCV replacement questions.

Post by clarkerussell » Wed Feb 13, 2019 9:36 pm

So I pulled the PTC and it was clear. There was a little bit of buildup, but I could see straight through. I still spent some time scraping and spraying cleaner on it. The rubber boot for the PTC was in near perfect condition and there was minimal oil in the tube itself.
I'm hoping that the rigid hoses from the PTC to the box were at fault originally and that's what was causing the positive pressure...

Do all the hoses on the air intake (PTC valve hoses, and the other ones) need hose clamps, or just the large hose to the breather box?



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clarkerussell
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Re: PCV replacement questions.

Post by clarkerussell » Wed Feb 13, 2019 9:37 pm

oragex wrote:
Tue Feb 12, 2019 2:19 am
There is a lower port in particular (the lowest towards the bottom of the engine), needs a hose that fits tight in there (may wrap the end of it with some duck tape), then blow at the other end and listed for oil bubbling inside the oil pan. Should be quite easily to blow through it.
So is this the test? Basically attach a hose to the lower port (the oil return, right?), seal it up, and blow through it to make sure the port is clear?



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