1996 850 PCV Problem - Simple Fix?

PeteB · Post by **PeteB** » 03 Oct 2016, 14:46

Our 850 is now failing the glove test and we just don't have time to do a
full PCV job - maybe in the Spring. I currently have the dip stick out a bit.

I am really tempted to cut hoses (where ever?) and put in an old style PCV
valve. I have one here from a Mazda 626 to just try for a fit.

Could we just go old school where the vent went into the atmosphere by
pulling the hose near the oil filler cap and running one down the side of
the engine or will that spill oil?

I suppose this is considered tampering with the emissions control, and
therefore illegal?

Post by **Ozark Lee** » 03 Oct 2016, 17:36

You can't really use a PCV valve with the oil trap system and cutting the lines causes a massive vacuum leak. They can get bad enough that it will spew oil out of the dipstick but short of that leaving the dipstick loose will help keeping the pressure down and hopefully save the seals.

...Lee

PeteB · Post by **PeteB** » 03 Oct 2016, 17:49

Are there diagrams online somewhere explaining the difference between a PCV and oil trap system?

Has anyone thought of blowing the lines out with compressed air, would that push the sludge into
the oil pan or ???? I'm not sure exactly what the cause is of the problem.

Post by **misha** » 03 Oct 2016, 18:14

Do you still have flame trap disc attached?

Post by **erikv11** » 03 Oct 2016, 19:01

What misha said - assuming this is an NA, if the flame trap disc is still installed then pull it out and throw it away in a hurry.

Lots of people have vented the crank case tho the atmosphere on these cars, it is not emissions-friendly but can get you through the winter. As alluded to, you will want to make sure the intake side is not open to the atmosphere, just the crankcase side.

Post by **erikv11** » 03 Oct 2016, 19:04

Search on "vent to atmosphere catch can volvo 850" you will find a bunch of hits all over the innerwebs.

Post by **rspi** » 03 Oct 2016, 19:59

Post by **tryingbe** » 03 Oct 2016, 20:13

PeteB wrote:Are there diagrams online somewhere explaining the difference between a PCV and oil trap system?

PCV valve - Usually one end goes to the intake manifold to get vacuum, the other end goes to valve cover to access crankcase gases.

Oil trap system - Usually one end does not go to the intake manifold, but to the intake box or hose instead, there is no vacuum there. The one end goes to a box that drips oil back to the engine block.

PeteB wrote:I'm not sure exactly what the cause is of the problem.

Lots of short drive, not using synthetic oil, not changing oil regularly, not servicing PCV system regularly, old worn out engine, etc.

PeteB wrote: Has anyone thought of blowing the lines out with compressed air, would that push the sludge into
the oil pan or ????

Replace the parts, don't clean.

From two different cars.

I found with the older engines, even with new PCV parts, it is not enough. The stock PCV pipe from the separator to the intake is severely undersized for an older engine. Also, the hole at the heating element at the PTC valve is tiny, like smaller than 1/4 inch tiny. Both will restrict the flow of the crankcase gases.

To address those issues, here is what I do. Get the below parts.

A 3ft 5/8 oil compatible hose. Do not use silicone hose, as it will "sweat" oil. Do not use heatercore hose, it is not rated for oil, it will become soft and you'll have to replace it sooner. This is what I use. Buy 3, as it is sold by the foot.
10 An Push Lok Loc Lock Hose Oil Coolant 5 8? Black 250 P s I Industrial Hose | eBay

One 3/4 elbows from your local hardware store. (5/8 will be the wrong size!)

A 3 feet 3/16 vacuum hose to replace the small hose from the intake manifold to the PTC valve. I prefer silicone hose for this.

Optional, get 6 of this. I like their clamps.
https://www.ipdusa.com/products/4768/10 ... 12mm-width

Optional, wireloom to protect the hose.

Take a unibit and drill out the PTC valve holes to as big as you feel comfortable. I think I drilled mine out to about 1/2 inch.

Remove the intake manifold and replace that stock PCV hose, I cut a short hose and then use a 90 degree elbow, than a long hose to the PTC valve. Replace the vacuum hose to the intake manifold to the PTC valve with the new one. Then reinstall the intake manifold.

All the crankcase gas have to go thru that tiny PTC hole!!!

Installed on car

Post by **rspi** » 03 Oct 2016, 20:34

PeteB wrote:Our 850 is now failing the glove test and we just don't have time to do a
full PCV job...

You can actually do the job in 2 hours. Is the car turbo?

I usually cut things out to find time to have fun with the car. No TV, movies, eating out, FaceBook, etc.

PeteB · Post by **PeteB** » 04 Oct 2016, 22:02

Thanks everyone! The car is NOT turbo.
Flame trap? That is the plastic screen disk, right? If so yes I removed that.

erik: thanks will do: "Search on "vent to atmosphere catch can volvo 850" you will find a bunch of hits all over the innerwebs."

OK Robert, I get that it can be done in two hours, BUT I'm tired of putting so much money into
this car so I want to do it with heater hose, reuse the trap box, etc. So, I have to plan better
to have all the parts ready to do the job.

Tryingbe, thanks that helps a lot to use your more cost effective way to do the fix.