PCV Dilemma 1994 855T

HMS Surprise1 · Post by **HMS Surprise1** » 27 May 2010, 15:17

In 2009 I had disassembled my '94 855T with the intent to replace the radiator and do a complete PCV service. I had a serious oil leak which, based on everything I read on this forum, was probably the RMS. I was hopeful that a PCV service would correct my car's Mobil 1 incontinence. As it turned out I did not have the time to finish what I had started so I took the car to an inde Volvo shop to complete the job. I took my new radiator, new hoses and FCP-sourced PCV kit to them and they put everything back together. The car ran great. Despite all these new parts the inde diagnosed that the RMS was still leaking. Bummer. Because of this oil leak the car was not driven much in the past year. Maybe 1500 miles at the most. Mobil 1 replacement cost more than the fuel bill! So, the car has been parked. This past weekend I replaced my heater hoses. Thanks Ozark Lee for help with that!

Well, this week I bit the bullet and took the car back to the same inde to replace the RMS. The inde said that they would double check to make sure that the RMS was still the source of my oil leak. I was good with that as, hey, it would be much simpler and less costly to do rear cam seals, for instance, than the major surgery involved in RMS replacement. I received a call from the inde saying that the top of the engine had oil in the valley between the cams and they pronounced that the PCV system needed servicing and replacing. Huh!? I asked how that could be when so few miles had been accumulated since they installed the new parts. He said that they placed a vacum gauge on they PCV system and it showed a reading indicating 80% blockage of the system which would explain the oil in the cam cover valley. Okay, I can understand how a plugged up system could behave like this. But what part of the system could it be in that this service was just done so few miles ago?

1) How common is it to have a PCV system get blocked in no more than 1500 miles covered?
2) Assuming there is some blockage in the system where should I look first? The bosses where the oil seperator mounts to the block or some other spot?
2) Is this not something the inde should have caught before delivering the car back to me?
**Note: I am not maligning nor do I want anything out of the inde - at this point I just want to know how to move forward**
3) Where on or in the PCV hose circuit is he placing his gauge to check vacum or pressurization of the PCV system?

4) For those who might be using their cars for track day events - Does anyone who reads have any experience in either modifying or removing the PCV system for "off road use"? Would this involve a re-flash of the ecu to electronically turn off those PCV sensors that are no longer required to provide status inputs? Would love to hear from anyone who has successfully gone this route.

As always, thanks for the support from this great site!

Fair winds

850tech · Post by **850tech** » 27 May 2010, 18:01

HMS Surprise1 wrote: 1) How common is it to have a PCV system get blocked in no more than 1500 miles covered?
2) Assuming there is some blockage in the system where should I look first? The bosses where the oil seperator mounts to the block or some other spot?
2) Is this not something the inde should have caught before delivering the car back to me?
**Note: I am not maligning nor do I want anything out of the inde - at this point I just want to know how to move forward**

It's not, unless the bottom drain hole in the block from the oil trap was not properly cleaned. Other then that, I would be worried about the excess crankcase pressure being worn compression rings, they cause vary similar symptoms to the PCV system as both can increase crankcase pressure significantly.

Post by **FlyingVolvo** » 27 May 2010, 18:59

Make sure also that when they did the PCV job that they thoroughly cleaned the PTC nipple. Everything else can be perfect, but if the PTC nipple is clogged, then you'll still have pressure. It's where the pressurized blow-by fumes are put back into the air intake to be burned again.

Post by **jblackburn** » 27 May 2010, 19:03

Make sure also that when they did the PCV job that they thoroughly cleaned the PTC nipple. Everything else can be perfect, but if the PTC nipple is clogged, then you'll still have pressure. It's where the pressurized blow-by fumes are put back into the air intake to be burned again.

This.

And, since yours is a '94, check that the long metal EGR tube isn't clogged up. That might be the cause of it still having pressure.

HMS Surprise1 · Post by **HMS Surprise1** » 27 May 2010, 20:31

Thanks, guys for your replies. When I was replacing my heater hoses this past weekend I removed the PTC. I noticed that the nipple was solidly plugged up. I soaked it brake clean and used a retired dental scrapeing tool to reach as much crud as I could. Used a paper clip and the better part of a can brake clean to flush out the nipple. Cleaned the plug contacts with electronic parts cleaner. I would like to say that the inde cleaned/flushed out the long metal tube but I don't know if they did or not so perhaps this will be a good place to start. I's like to think too, that the inde cleaned out the drain back ports in the block before installing the new oil seperator but again, I don't know. Trying not to get steamed here. I'll pick up the car from the inde tomorrow and take my time checking out the system. Have any of you attached a vacum/pressure gauge to the system to evauluate its health?

Again, many thanks for your comments. I can't get to this until next weekend earliest but I will report what I find.

Cheers

Phaeton · Post by **Phaeton** » 27 May 2010, 21:18

I had mine done a while back, and I still get very light smoke from disptick.

Post by **wheelsup** » 28 May 2010, 19:32

I've got the same issue. I wrote to the Popular Mechanics "Car Clinic Q&A" editor for some possible answers. Here is the conversation:

I've been reading PM now for a year or two and the first page I turn
to is the Auto Clinic section. Reason being I am in no way a mechanic
but enjoy learning about auto repair.

I have hit a situation on my car, a 1995 Volvo 850 non-turbo (160k),
that I cannot figure out. I have searched and asked on specific Volvo
forums and no one can really come to a solid conclusion on what is
going on.

My 1995 Volvo 850 non-turbo has an oil leak, the "crank seal" aka rear
main seal or RMS. In addition there is crankcase pressure as evidenced
by unplugging the dipstick and sticking a balloon over the top of it
and then revving the engine - the balloon fills up with pressure. This
is typically why the RMS will leak. When I drive with the dipstick
unplugged, the leak is significantly reduced, as the pressure in the
crankcase is reduced and vents out the dipstick.

Generally the cause for this is a blocked PCV system, and in our cars
(93-97 850's and 98-2000 70 series cars) there is a "breather box" or
"oil separator" underneath the intake manifold. My entire PCV system
(oil separator, hoses, and connections) has been replaced and is brand
new. In addition there are two holes in the block that the oil
separator bolts to, and they are clear, including the one that goes to
the oil pan (confirmed by pouring oil thru - it doesn't pool).

Compression numbers taken on the car warmed up to operating temp, with
WOT, and cranking 10 rotations yields a range of 185 on the lowest to
200 on the highest.

Before I pull the motor and replace the RMS what can be done to
determine what is causing this over pressure in the system? I can
replace the RMS but it will only leak again without fixing the
crankcase pressure issue first!

I agree the PCV system isn't keeping the crankcase volume from pressurizing,
exacerbating your leaks.

Why? I've seen some aftermarket PCV valves that were not up to spec, a
result of concatenating several part numbers from different vehicles into a
one-size-fits-all package.

I'm going to guess the real problem is an engine that's generating enough
blowby to overpower the PCV system as the rings and valve stem seals wear
out.

As a temporary, diagnostic procedure, route the main PCV line into a milk
jug or something instead of back into the manifold, without any valve in the
way. This will keep the crankcase at atmospheric pressure instead of
overpressuring it, and I'll bet your leaks improve.

I actually use a flow meter on my racing engines to assess the volume of
blowby. I just check idle blowby after every race, and when it starts to
spike, time for new rings.

Finding some way to increase the capacity of the PCV system to suck blowby
back into the manifold will help in the short term. In spite of the good
compression numbers, I suspect your engine is just wearing out.

On the other hand, if you can vent it well enough, it may last a long, long
time before the oil consumption gets too bad.

MA

Thanks Mike.

No PCV valve on this car, just a big box and 1/2" or so diameter holes
in the block. When I pull the dipstick out 1/4" or so from sealing the
pressure vents out that way and very little oil is lost - in fact if I
replaced the RMS I bet it would cease.

Even with oil loss the car will run as long as you keep oil in it -
but I might attempt the valve stem seals. Is that a cause for
excessive crankcase pressure? If I replace those (which I can do with
the engine in the car) then I will see what I'm at. All else fails I
can take the engine out and rebuild it while running a temp. engine.
That will be fun!

Bad valve stem seals will indeed cause a lot of blowby, although replacing
the seals in situ will only help for a while, as the guides are probably
worn out, which is what wore out the seals. The extra clearance in the
guides/seals is letting exhaust gases enter the cam box.

Find the smallest annulus in the vent system before the air cleaner, and
make it bigger. This won't reduce the volume of gases, but it will keep the
pressure from building up.

I've seen really leaky engines blow the rear main seal inside out.

MA

Not sure what it means right now, I'm trying to learn about our engine in general and what the valve stem seals/guides are and where they are, if they are replaceable, and if changing them will in fact reduce blow-by.

850tech · Post by **850tech** » 28 May 2010, 20:44

Vary informative post wheelsup, I just replaced my engine due to a blown head gasket, but I had been fighting oil consumption and crackcase pressure for over a year. I had replaced the entire pcv with no success, I suspected rings as well, and even the turbo as it was soaked on the intake side. To the point, I changed the engine without replacing the turbo as I couldn't get a suitable one on short notice and using the PCV system from the old engine as well. All oil problems have ceased and I'm at last a happy camper. I completely disassembled the old engine, in part because I'm curious, but also because 'clean' aluminum is worth much more

I found that all the guides and seals in my case seemed ok, no play or visible signs of damage (that I could see atleast) and nothing to terrible in the cylinders or the rings, just wear from a lot of miles. Seems to me that even with good compression while testing, combustion pressure under load was just to much for the rings (or seals) to handle.

Post by **JRL** » 28 May 2010, 21:17

HMS Surprise1 wrote: Have any of you attached a vacum/pressure gauge to the system to evauluate its health?

Cheers

Always
I do it with a homemade qauge with every car I buy.
I lay it over the oil fill hole, takes 2 minutes