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  1. #11
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    Quote Originally Posted by Pennhaven View Post
    I was able to get my bore scope into the neck of the PTC nipple without too much disassembly. (Good thing because I couldn't even get the intake tube to release from the filter box cover. If there is an easy trick, I'd love to hear it.)

    The PTC looks pretty darn clean to me, unless I don't know what to look for. https://photos.app.goo.gl/9GrE69ptzh8opeWA7

    Any opinions? Should I shoot some brake cleaner down there while the hose is off?

    I also did a glove test at the oil filler at idle, and the dealer tech appears to be correct. It seems to me that there is noticeably more suction than in the past. It pulls the glove down at least a quarter inch. Where if my memory is correct, as FirstVolvo noted, earlier it just barely pulled it down.
    From the photo the PTC opening does look clean. As I recall this was a decent size opening and the PTC area in my car was clean too even after 125K miles. I'm not sure what else may be causing too much vacuum. Was there ever any work done on the PCV system previously? The vacuum source at idle is just the small line from the intake manifold (banjo bolt) through a small diameter hard hose to the top the of the oil trap hose, the long hose that goes the PTC and air intake tube.

    For easier removal of the intake tube from the top cover of the air cleaner box I hold the intake hose and pull the cover at an angle to the intake tube rather trying to pull it straight out. Hold the top of the intake tube and using the furthest edge of the cover pull up on it to pry it out of the tube.

  2. #12
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    Quote Originally Posted by FirstVolvo View Post
    From the photo the PTC opening does look clean. As I recall this was a decent size opening and the PTC area in my car was clean too even after 125K miles. I'm not sure what else may be causing too much vacuum. Was there ever any work done on the PCV system previously? The vacuum source at idle is just the small line from the intake manifold (banjo bolt) through a small diameter hard hose to the top the of the oil trap hose, the long hose that goes the PTC and air intake tube.

    For easier removal of the intake tube from the top cover of the air cleaner box I hold the intake hose and pull the cover at an angle to the intake tube rather trying to pull it straight out. Hold the top of the intake tube and using the furthest edge of the cover pull up on it to pry it out of the tube.
    Thanks. It would probably help if I had bigger hands to get more leverage on the end of the hose. For a mechanic my hand size is fine for getting in tight spaces, but not so good for grip needed to apply a lot force.

    No PCV work done previously. As stated in my earlier post, while this car doesn't have a lot of miles, it has a greater than usual proportion of short trip driving, so I guess it's feasible that lines could be getting blocked. As I mentioned in my previous post, a poster at Swedespeed https://www.swedespeed.com/threads/c...1/post-2673465 suggests the high vacuum condition is caused when that long top line from the oil trap banjo bolt gets clogged. It would nice though to hear that from someone who had that symptom and actually corrected it with a clean line. In the meantime, I'm going to try and reason it out whether that makes sense.
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  3. #13
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    Quote Originally Posted by Pennhaven View Post
    Thanks. It would probably help if I had bigger hands to get more leverage on the end of the hose. For a mechanic my hand size is fine for getting in tight spaces, but not so good for grip needed to apply a lot force.

    No PCV work done previously. As stated in my earlier post, while this car doesn't have a lot of miles, it has a greater than usual proportion of short trip driving, so I guess it's feasible that lines could be getting blocked. As I mentioned in my previous post, a poster at Swedespeed https://www.swedespeed.com/threads/c...1/post-2673465 suggests the high vacuum condition is caused when that long top line from the oil trap banjo bolt gets clogged. It would nice though to hear that from someone who had that symptom and actually corrected it with a clean line. In the meantime, I'm going to try and reason it out whether that makes sense.

    The post referenced about the long tube being clogged is also the hose/tube I thought could potentially be clogged and could be causing the high vacuum. This is why I thought looking at the PTC opening was a good idea, the PTC is in the path from the top of oil trap (where this long hose connects) to the inlet near the turbo area and the PTC opening is a more restricted opening than the rest of the long hose so a good area to check out. It's not the banjo bolt area on the underside of the manifold though, this is the source of the vacuum at idle/low loads and you wouldn't have too much vacuum in the crank case if this area was blocked.

    One other thing that you could do to check the rest of the hose is with the hose disconnected as before, remove the oil filler cap on top of the engine and blow very low pressure air into the removed hose end to check if the hose is blocked up or not. You have to be very careful to use low volume, low pressure air but that's all you would need to see if there's any blockage, if any pressure built up at all you would know this hose is clogged up. If all is clear, air should flow through the long hose/tube, into the oil trap, into the engine crankcase and out the open oil filler opening. You could also blow air into the PTC and make sure air flows freely into the air intake tube.

  4. #14
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    Quote Originally Posted by FirstVolvo View Post
    The post referenced about the long tube being clogged is also the hose/tube I thought could potentially be clogged and could be causing the high vacuum. This is why I thought looking at the PTC opening was a good idea, the PTC is in the path from the top of oil trap (where this long hose connects) to the inlet near the turbo area and the PTC opening is a more restricted opening than the rest of the long hose so a good area to check out. It's not the banjo bolt area on the underside of the manifold though, this is the source of the vacuum at idle/low loads and you wouldn't have too much vacuum in the crank case if this area was blocked.

    One other thing that you could do to check the rest of the hose is with the hose disconnected as before, remove the oil filler cap on top of the engine and blow very low pressure air into the removed hose end to check if the hose is blocked up or not. You have to be very careful to use low volume, low pressure air but that's all you would need to see if there's any blockage, if any pressure built up at all you would know this hose is clogged up. If all is clear, air should flow through the long hose/tube, into the oil trap, into the engine crankcase and out the open oil filler opening. You could also blow air into the PTC and make sure air flows freely into the air intake tube.
    Thanks. I really appreciate your input. But if this diagram from Matthews Volvo is accurate (maybe it's not?), then isn't all of the vacuum at idle being supplied by the short section of hose from the intake manifold? Isn't the long section only there to supply vacuum once the throttle is open and there is positive manifold pressure? In either case I can't see how a blockage in the hose is causing increased crankcase vacuum.
    '04 XC70, Ash Gold / Taupe, Premium, Touring, Tinted Rear Glass, Rear Skyddsplåt, Wing Profile Load Bars, USA Spec 11,
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  5. #15
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    Quote Originally Posted by Pennhaven View Post
    Thanks. I really appreciate your input. But if this diagram from Matthews Volvo is accurate (maybe it's not?), then isn't all of the vacuum at idle being supplied by the short section of hose from the intake manifold? Isn't the long section only there to supply vacuum once the throttle is open and there is positive manifold pressure? In either case I can't see how a blockage in the hose is causing increased crankcase vacuum.

    The short hose from the manifold attaches to the elbow of the long hose above the oil trap, the elbow connects the long hose to the oil trap. The short, small diameter hose does provide PCV vacuum during idle and because it is also connected to the long hose, which goes to the air intake tube in front of the turbo, the long hose will limit the amount of vacuum in the hose and crankcase because air can be drawn in from the air intake tube. The air pressure in the air intake tube at idle near the long hose opening in front of the turbo is probably at a very slight vacuum and what will balance out too much vacuum in the crankcase. If the hose is clogged then air couldn't be drawn in to limit the crankcase vacuum. At higher speeds and under boost (in the manifold) the vacuum must come from the long hose near the turbo. If the long hose is clogged you won't have enough vacuum at higher speeds and higher loads.

  6. #16
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    Quote Originally Posted by FirstVolvo View Post
    The short hose from the manifold attaches to the elbow of the long hose above the oil trap, the elbow connects the long hose to the oil trap. The short, small diameter hose does provide PCV vacuum during idle and because it is also connected to the long hose, which goes to the air intake tube in front of the turbo, the long hose will limit the amount of vacuum in the hose and crankcase because air can be drawn in from the air intake tube. The air pressure in the air intake tube at idle near the long hose opening in front of the turbo is probably at a very slight vacuum and what will balance out too much vacuum in the crankcase. If the hose is clogged then air couldn't be drawn in to limit the crankcase vacuum. At higher speeds and under boost (in the manifold) the vacuum must come from the long hose near the turbo. If the long hose is clogged you won't have enough vacuum at higher speeds and higher loads.
    Thanks again. I woke up this morning with the thought that the long hose to the air tube would do just as you say, limit the amount of vacuum supplied by the manifold at idle. So your post must have reached me telepathically in my sleep.

    I just attempted to apply a vacuum to the end of the long hose where it attaches to the PTC. If it were clogged that should be easy to do with my MityVac. However, I could not get any vacuum at all with the hand pump. So, to me, that says that if the line has blockage it is only partial. It would be nice if there was some sort of thin flexible, yet stiff along its length, tool that I could push up around the bend of the hose and along its length (like a plumbers snake) to clear away any partial blockage. Maybe some hollow tubing that would collect gunk, instead of just pushing it ahead. I'm going to see what I can come up with. Suggestions welcome!

    In the meantime, the one thing I still don't understand about this system is the function of the PTC. It seems to me it must be there to limit the flow through the long tube, but why/when I don't get. Is there any chance that even though it isn't blocked, it may be closing too much at idle?
    Last edited by Pennhaven; 03-23-2022 at 12:12 PM.
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  7. #17
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    Following up, I used a variable speed vacuum cleaner's nozzle blowing into the oil filler (and sealed to it with duct tape) and got air flowing out of the long line to the PTC even at the lowest speed setting. The flow increased linearly as I increased the vacuum speed, so there definitely is not a complete blockage. I can't say though whether it was flowing as much air as it needs to function properly. My sense is that the vacuum cleaner might possibly have pushed out more than it did, but then the tubing diameter is much smaller than the vacuum hose, so at relatively low pressure coming out of big hose venting into a smaller hose it's difficult to judge.

    I also ordered a narrow flexible pipe cleaning brush, and should have tomorrow. Whether it can go around a 90° bend and sufficiently clean any blockage remains to be seen.
    '04 XC70, Ash Gold / Taupe, Premium, Touring, Tinted Rear Glass, Rear Skyddsplåt, Wing Profile Load Bars, USA Spec 11,
    StonGard Light Protection, Yokohama YK740 GTXs, Meyle HD Sway Bar Links, ipd HD TCV, subframe & top brace poly bushing inserts,
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  8. #18
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    Quote Originally Posted by Pennhaven View Post
    Thanks again. I woke up this morning with the thought that the long hose to the air tube would do just as you say, limit the amount of vacuum supplied by the manifold at idle. So your post must have reached me telepathically in my sleep.

    I just attempted to apply a vacuum to the end of the long hose where it attaches to the PTC. If it were clogged that should be easy to do with my MityVac. However, I could not get any vacuum at all with the hand pump. So, to me, that says that if the line has blockage it is only partial. It would be nice it there was some sort of thin flexible, yet stiff along its length, tool that I could push up around the bend of the hose and along its length (like a plumbers snake) to clear away any partial blockage. Maybe some hollow tubing that would collect gunk, instead of just pushing it ahead. I'm going to see what I can come up with. suggestions welcome!

    In the meantime, the one thing I still don't understand about this system is the function of the PTC. It seems to me it must be there to limit the flow through the long tube, but why/when I don't get. Is there any chance that even though it isn't blocked, it may be closing too much at idle?
    I've read the PTC is sized to meter a known amount of air because it is after the MAF sensor so there has to be a way for the ECM to account for a known amount of air being supplied past the MAF. It's heated to prevent moisture from freezing and clogging it up.

  9. #19
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    Quote Originally Posted by Pennhaven View Post
    Following up, I used a variable speed vacuum cleaner's nozzle blowing into the oil filler (and sealed to it with duct tape) and got air flowing out of the long line to the PTC even at the lowest speed setting. The flow increased linearly as I increased the vacuum speed, so there definitely is not a complete blockage. I can't say though whether it was flowing as much air as it needs to function properly. My sense is that the vacuum cleaner might possibly have pushed out more than it did, but then the tubing diameter is much smaller than the vacuum hose, so at relatively low pressure coming out of big hose venting into a smaller hose it's difficult to judge.

    I also ordered a narrow flexible pipe cleaning brush, and should have tomorrow. Whether it can go around a 90° bend and sufficiently clean any blockage remains to be seen.
    Blowing air into the oil filler with a vacuum cleaner is a good idea as long as the air is clean and you've confirmed there's not a complete blockage in the long line. Did you also check with the hose connected to the PTC? May be more difficult to check air flow into the large intake tube but worth a check to see if you can least hear or feel some air flow through the PTC into the intake tube. Maybe also try blowing air through the intake tube with the long line connected and with the MAF removed to see if there's some air flow out the oil filler opening. There would be air loss through the turbo and intake manifold so limited air flow through the PCV system but if any air flow is detected out the oil filler opening the long line and PTC wouldn't be clogged up.
    At idle, when you're seeing what appears to be too much vacuum with the glove, I wouldn't think there would need to be very much air flow through the PTC and long line to limit the crankcase vacuum.

  10. #20
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    Quote Originally Posted by FirstVolvo View Post
    Blowing air into the oil filler with a vacuum cleaner is a good idea as long as the air is clean and you've confirmed there's not a complete blockage in the long line. Did you also check with the hose connected to the PTC? May be more difficult to check air flow into the large intake tube but worth a check to see if you can least hear or feel some air flow through the PTC into the intake tube. Maybe also try blowing air through the intake tube with the long line connected and with the MAF removed to see if there's some air flow out the oil filler opening. There would be air loss through the turbo and intake manifold so limited air flow through the PCV system but if any air flow is detected out the oil filler opening the long line and PTC wouldn't be clogged up.
    At idle, when you're seeing what appears to be too much vacuum with the glove, I wouldn't think there would need to be very much air flow through the PTC and long line to limit the crankcase vacuum.
    Thanks again.

    Not able to check whether pressurized air will actually flow through the PTC into the intake tube, as I still haven't been able to get the tube off the air filter housing. Hopefully the fit is only so tight due to being cold. Will plan to try later on after the car is driven and hopefully warming it up will loosen it enough to easily remove.

    I did put the new air filter in and I think that has reduced the vacuum at idle. The old one was not super dirty, but probably dirty enough to impede air flow and possibly raise the manifold vacuum. This change did appear to reduce the suck-in of the glove.

    I couldn't get the tube cleaning brush I bought to go around the 90° bend. But it came back with absolutely no residue from that end of the line. So it appears to be just as clear (at least at that end) as the PTC is. (I really doubt there is any restriction in the PTC, so testing again for pressurized flow through it, I think, is a real long shot.) So now I'm wondering if combination of the dirty air filter and perhaps an inexperienced tech doing the vacuum check may be all we're dealing with here, and maybe all this is just an overreaction.

    I got a lead on a reputable indy shop with an experienced Volvo tech. (We moved last year, and no longer near the indy I had relied on.) So my plan is to get an opinion from him before assuming any work needs to be done.
    '04 XC70, Ash Gold / Taupe, Premium, Touring, Tinted Rear Glass, Rear Skyddsplåt, Wing Profile Load Bars, USA Spec 11,
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