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http://www.freewebs.com/howardsvolvos/engine.htm

Postive Crankcase Ventilation (PCV)

The PCV system on this car seem to get clogged up around 100k miles for some cars. Usually, cars using synthetic will be cleaner while cars using non-synthetic will have greater clogs. Here are the statistics I've had personal experience with

2001 V70 T5 using synthetic. No clog at 100k+ miles
2001 V70XC using synthetic. Banjo nipple clogged at 100k+ miles
2002 V70XC using non-synthetic. Oil drain port on the oil trap completely clogged at 100k+ miles

Why is PCV necessary? How does it work?

Here is a little diagram of how the PCV system works in all cars. Basically, some gases will leak by the rings on the pistons and enter the crank chamber. This vapor pressure must be vented to not blow out the seals. Emissions regulation prevents us from dumping this vapor pressure into the atmosphere so it is fed back to the intake and back into the the combustion chamber. This is why there is negative pressure in the engine's chamber where the oil flows. Engine's own air suction power is the force that creates this negative pressure in the oil chambers.

http://www.aa1car.com/library/pcv.htm

So how do you know if your PCV system need servicing? Here is a summary

There are 2 different circuits to vent the blowby pressure in this car. I believe this is probably common to turbo cars as my VW 1.8T turbo engine also has 2 circuits.

Idle circuit: Intake manifold provides the vacuum source during idle. An easy test is to put a latex rubber glove over the oil filler hole with the engine idling. If the rubber glove gets a little air sucked out of it, there is vacuum and a healthy unclogged idle circuit. If the rubber glove blows up, then there is no vacuum and you have a clogged idle circuit.

Boost circuit: Intake manifold on turbo charged cars switches from vacuum to pressure under boost so can not be used as the exclusive source for vacuum like normally aspirated cars. There is a vacuum source in front of the turbo called the PTC nipple that provides vacuum under boost conditions. The PTC nipple also has an electrical connection to power a heater in the nipple. I heard this is to prevent condensation/clogging. Here is a good explanation

http://www.matthewsvolvosite.com/forums/viewtopic.php?f=1&t=38413#p182659

The following link shows a home made device and tested while torquing the brakes (applying both brake + acceleration to create load and therefore boost).


Other signs of a plugged PCV is the dip stick being forced out of its hole and oil leaks that aren't the common ones (turbo return line, oil filler gasket) This is because the engine chamber where the oil is should have negative pressure (caused by PCV system) If the PCV system is clogged and there is positive pressure present in the oil chambers in the engine, there is force to push out the seals and cause leaks.

Oil Leaks

From reading the Volvo forums and my personal experience, it seems a clogged idle circuit don't usually cause seals to leak. I had some oil in my #2 spark plug as the oil forced its way past the seams between top and bottom half of the head. Note this is just the sense I get from reading these boards. Certainly not based on many hands on diagnostic and repair experience.

I would guess a clogged boost circuit will cause seal leaks pretty quick due to the higher blowby pressure.

Directions

I will outline my directions below. I have found additional excellent online writeups and will share them here as well. Here is a link for a XC90 with the 2.5T engine. PCV system is basically identical to the XC70. This direction seems pretty good. You might look over my write up below on additional tips to handle the more difficult part of the job.

http://www.volvoxc.com/0/resources/how-to/pdf/VOLVOXC90PCVSYSTEMREPLACEMENT.pdf

Servicing the PCV System

Now onto how to the service of your PCV system. A warning before you begin, this is one of the bigger jobs on this car and can take 6+ hours for a first timer with reasonable experiencing doing their own car's maintenance. This is because Volvo's design decided to bury the PCV components under the intake manifold.

First, there is a banjo fitting that commonly clogs. It clogs because there is only a 2mm diameter channel where the oil vapor runs through. So it doesn't take much to clog it.

What does the PCV look like on this car

Here is the airflow directions for reference

Cleaning the Banjo Fitting Under the Intake Manifold

http://www.volvoxc.com/resources/how-to/pdf/VOLVOXC90PCVSYSTEMREPLACEMENT.pdf

This is the direction on an XC90. It is largely similar but may have slight differences. On my 2001 V70 T5 and 2001 V70XC, the differences are

Fuel line has a quick disconnect above the manifold
Lower bolts on the intake manifold isn't difficult to get to (even the one nearest to the passenger side). They also didn't need to be removed as the intake manifold bold holes have an opening on the bottom.
didn't need to remove the thermostat housing components

This writeup will avoid the directions already in this document. Rather, just focus on the differences in my cars and tips for short cuts.

Here is the directions for removing the intake manifold

http://www.volvoxc.com/resources/how-to/pdf/intake-manifold.pdf

Simple Short Cut Without Removing Manifold

Here is a post on cleaning the banjo fitting nipple that often clogs without removing the intake manifold. It does require ETM/airpipe to come off. NOTE This direction appears to be for pre 2002 cars. More explanation below.
http://volvospeed.com/vs_forum/topic/59545-cleaning-pcv-on-99-v70xc/#entry759758

Here is what the nipple look like. Note the hose with the weed wacker line coming out of it. That is the hose that need to be removed from the nipple so the nipple can be cleaned. The channel is only 2mm inside the nipple. I used a paper clip and a 2mm nail to clear it. On one of my cars, it was completely clogged.



Important NOTE

Recently worked on a 2002 V70XC, the hose that connects to the nipple is constructed differently than my 2 01s (The middle hose connecting to the bolt/washer assembly numbered 14,9,10 in the diagram above). The connection is basically has the banjo nipple on one end and a plastic fitting to an Y junction on the rubber pipe on the other end. The 01s just had a rubber hose connecting the both end. The 02 had a hard thin plastic pipe that is on very tight (like shrink tubing tight) onto the nipple and the fitting. Then there is a rubber hose covering this tube like a jacket for more protection. The problem is this hard thin tube is super brittle after many miles near the heat and basically breaks apart when you try to disconnect it from either end. You can purchase a replacement hose at local auto parts store. There is a plastic fitting on the end that connects to the big L shaped PCV hose, need to carefully take off the clamp (avoid ruining the rubber) and remove the the plastic fitting (didn't seem possible to remove it non destructively) and buy a new replacement fitting at your local auto store.

All of this have to be done with the manifold removed. So it appears the 02s can not benefit from the simple banjo bolt cleaning short cut described above.

Lets Begin

A few notes before you begin this job. You will need the following

o-ring for the pressure side of the power steering pump connector. Get a couple and read on for the reasons below.
ETM gasket (my car was an 01, not sure what 02+ will be)
paper towel to catch the spilled PS fluid (only a little bit) and plug the hole after removal PS pressure side pipe.

Also take the belly pan off as this is a long job and you probably will drop a bolt here and there. Have a telescopic magnetic pickup would come in handy as well.

Fuel Line Disconnect
My 01s had a fuel line connection above the manifold that requires a fuel line disconnect tool (3/8 tool, my local O'Reillys had them for $3.50). Be sure to bleed the fuel pressure first (remove the cap on the end of the fuel rail, press middle pin and release the fuel pressure into a jar)


PS Pump Short Cut

I was able to avoid removing the PS pump. Just remove the pressure side (metal) hose at the top. You don't really need to clamp the PS hose since not much fluid will come out because the PS pump won't be turning. But definitely have some paper towels and rags handle when you disconnect the PS pressure line. You want to keep the disconnected pressure line fitting higher than the rest of the line so no fluid leaks out. The metal pressure line turns into a rubber hose so it can be pushed towards the belly and and keep it out of the harms way in case the hood accidentally closes.
https://lh5.googleusercontent.com/-hWEx3cP2flo/T51ppsGFK2I/AAAAAAAACww/TSQj5RMP2W0/s400/DSCF5792.JPG

Remove Air Pipe and ETM

See the throttle body cleaning directions here.

Manifold Removal Short Cut

My 01's lower manifold bolt holes have openings on the bottom so the bolts don't need to be removed completely. I'm not sure this is the case on the newer year models. This makes the job very easy. You will need a universal swival for the tricky angles. For the bolt nearest to the passenger side, I used 2 extensions (6"+4") and snuck it just above the alternator to loosen this bolt.

You have to remove a couple of vacuum fittings and use a 17mm wrench to remove the banjo bolt from the bottom (near alternator). This step is blind and limited space with the wrench and your arm under the manifold. Remove/loosen the manifold bolt first so the intake manifold can move and give more space to access the banjo bolt. There are 2 copper washers between the bolt/round fitting and round fitting/manifold. Be sure not to loose the copper washers.

Banjo Bolt

Volvo changed the banjo bolt design over the years. I believe 2005+, the banjo bolt evolved to include a check valve. This is to eliminate the pressure from entering the PCV system when intake manifold is pressurized under boost. I guess on cars without check valve, the boost circuit is expected to produce vacuum to over come this pressure and the blowby.

I personally think the checked valve design is a better design rather than to rely on the boost circuit's vacuum to remove this pressure and blowby pressure. So if you have a banjo bolt without the check valve, you might consider replacing it with the new design on any Volvo PCV system for the turbo charge cars. The new design is part number 31325709.

Cleaning the 2 ports on the engine block

After the oil trap is removed, the 2 ports that connects engine block to the oil trap is visible. The top port is where the blowby gasses in the crank case need to exit into the oil trap. The bottom port is to drain back the filtered oil from oily vapor back into the oil pan. Usually, the blockages are found on the bottom port.

In addition, the bottom port runs through interior channels in the engine block that maybe plugged as well. This may require removing the oil pan to clean. Here is a link with a tip on how to clean this interior channel.

http://www.volvoxc.com/forums/showt...water-pump-and-serpentine&p=165636#post165636

Replacing the Oil Trap and Hoses

Here is where the oil trap and hoses are located

P2 PCV System

I replaced everything except the complicated L shaped hose/pipe assembly with the banjo fitting on it (#8 in this diagram). I just cleaned the banjo fitting on it and blew air through it to make sure it was clear. But my car was 2001s and had a simpler design that allowed for easy cleaning compared to 02+. On 02+, its probably best you replace that whole L shaped hose/pipe even though its expensive.

Clean the banjo fitting nipple
Blow air through the hose that connect through the banjo fitting after the oil trap and hoses are back in to make sure everything is clear
The hose connecting the bottom of the oil trap to the engine block has a newer design on my car. It is now a solid metal tube with molded on rubber press fittings.

Reattach The Banjo Fitting

This is probably the hardest part of this job. Here is how I did it without loosening the alternator and AC pump.

First, you need 2 new copper washers or resand the surface of the old ones.

Don't connect the hose between the banjo fitting and the oil trap. This gives the banjo fitting a little more room to move and allows the banjo bolt thread to catch the thread in the intake manifold. Your entire arm will be under the manifold trying to get the bolt's head to catch by feel without loosing the top washer. It seems right handed person is required to do this given the space allowed.

Put in a new intake gasket, thread in the lower intake manifold a little bit so the manifold can rest on it (if you have the manifold with an opening on the lower bolt hole).

Now try to put the manifold in its near final position. The 2 coolant hoses connecting the banjo fitting will prevent it from moving very far from the engine block. But disconnecting the connection at the oil trap give you a little more freedom to move.

Put the copper washers on and hunt by feel to thread the bolt into the manifold. The top washer falls off easily so after you catch the thread for a few turns, stop and look and make sure the washer is still there.

Work a 17mm wrench under the manifold and tighten the banjo bolt. It could be easy to cross thread so make sure there isn't huge resistance as you tighten.

Loosening The Alternator

If you are unable to reattach the banjo bolt per direction above. You may have to loosen the alternator. Serpentine belt has to come off (read here). There are 4 bolts that hold the alternator and AC pump together. The top 2 bolts is easy but the bottom 2 bolts are harder. You probably have to take off the rubber hose that connect the intercooler to the charged air pipe (the one over the top of the engine) The top 2 bolts need to come out and the bottom 2 need to be loosened to tilt the alternator forward and get it out. Now finally, you can get to that banjo fitting if you weren't successful before.

Reconnecting The PS Tube

Put the new o-ring on the PS pressure side metal tube. Don't over tighten as it will smash the o-ring and PS fluid will leak out. The o-rings are cheap so get a couple just in case.

My oil trap was clear and all of the hoses and engine block inlets were clear even at 122k miles on the V70 T5 (the banjo fitting was cleaned at 90k or so). There was only a 1/16" thick of gunk at the bottom of the 2 engine block inlets. I just used a paint can opener to scrape it outwards. I always ran synthetic and I'm guessing that helped. Here is a picture, it looks worse in the picture, I should have taking a picture face on to show you how clear the engine block inlets were.

From PCV

However, my V70XC had a clogged PCV system at 116k miles. The banjo fitting was completely clogged and hardened. When I took the banjo bolt out, a little puddle of oil came out. I guess they had collected inside that portion of the intake manifold unable to get vacuumed out due to the clog.

Before reassembly, it is probably a good time to use some carb cleaner and clean the butterfly and the throttle body opening.

Nothing too tricky about reassembly. Read the ETM and air pipe directions to familiar how to reassemble the ETM and reconnect the pipe to ETM's intake.

Here are some more notes on this job.

http://www.volvoxc.com/forums/showthread.php?t=17284

Torque Specs

ETM to manifold bolts (10Nm)
Intake manifold bolts (20Nm, start from center bolt)

Boost Circuit

There are 2 vacuum circuits on the turbo cars. What I outlined in previous sections take care of the "idle" circuit which seems to be the most common clog. The big L shaped hose is just a sleeve that houses both coolant lines and vacuum lines. The vacuum lines end at the PTC nipple and I believe another another banjo bolt. Both of my Volvo's had a clear PTC nipple and I've not bothered service that banjo bolt. Here is an explanation and test on the boost circuit.
 

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If you've never done it before, it is not easy. Feasible, but not easy. Try doing it over a weekend, not something you are going to bang out after work one day if you've never done it before.
 

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im almost 100% sure it's clogged, but how much longer could I drive it until it really starts to give me problems
Who knows? Because of the positive crankcase pressure caused by the clogged PCV system... best case scenario is that it will seep oil out of a seal. But an oil seal can blow at any moment and leave you stranded. It has happened a lot and leads to a much more costly repair.
 

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Could be tomorrow!

Could blow a seal and spew out all the oil which will be more expensive (very expensive if it's the rear main seal). Don't catch the oil loss in time and buh bye rod bearings, buh bye engine. This is the worst case scenario.

If you must drive it I'd leave the dip stick popped up to relieve pressure and drive with a light foot, but you've been warned.
 

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Could be tomorrow!

Could blow a seal and spew out all the oil which will be more expensive (very expensive if it's the rear main seal). Don't catch the oil loss in time and buh bye rod bearings, buh bye engine. This is the worst case scenario.

If you must drive it I'd leave the dip stick popped up to relieve pressure and drive with a light foot, but you've been warned.
That'll help but it'll probably also cause a huge oily mess under the hood.
 

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Better than a blown seal which will do the same thing.
Agree. I just didn't want him to think there were no consequences to leaving the dipstick loose.
 

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I'm an experienced mechanic with a good set of tools and it took me about 4-5 hours my first time. There are a few banjo bolts that are very frustrating. But overall it's simply unbolt and replace. Not too complicated, but set aside a lot of time and just follow the steps.
 

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As long as the job is done properly and thoroughly, (making sure the port to the oil pan is also cleaned out and also not plugged up with ****), install a new set of spark plugs and then start using synthetic oil, you should be good to go for another 100K miles if the rest of the XC is in reasonably good condition.
How many miles on your 04?
If you decide to do this, let me know and I will tell you the PN to use so that you don't have to buy the large and expensive tube
 

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Not a bad job to do yourself - I did it on my parents 04 XC70 at around 200k and it took me about half a day working carefully. Don't let this go unchecked too long. You're gambling with blowing something like your rear main seal, cam seals, etc. Replace it!
 

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If I had to do it over again I would pay someone to do it for me. It's not a complicated procedure but tight spaces make it an aggravating job.
 
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