help please with PCV vapors - PeachParts Mercedes-Benz Forum

bricktron · #1 10-05-2013, 10:14 PM

switching the PCV vapors from the giant black drum air cleaner to a catch can has not worked out yet. the stainless steel scouring pad baffling in the can seems sufficient to catch vaporized oil, or at least a good fraction of it, but the can still emits a steady stream of smoky gas, which previously was directed back to the intake.

when i'm at a stop this gas builds up under the hood, leaking out at the sides, which kind of looks like there's a fire burning under there. it also wafts into my open windows.

i suppose i can just reattach this gas to the intake , but i'm under the impression that this is not totally awesome for combustion. is there any alternative?

yes, my engine may have a lot of blowby; i haven't tested the compression. whether i switch or rebuild engines later on, i'd like to do something better about this now.

vstech · #2 10-05-2013, 10:43 PM

pictures would help, but are you saying, you directed the vent tube to a can, that does not have a hose going to the intake??? of course the can is not capable of holding combustion gasses... 22:1 compression, along with several thousand psi combustion will certainly escape past the rings... the gasses have to go somewhere. and redirecting them into the intake is wise. if you are adamant about not getting the gasses in the intake, you could create a siphon in the exhaust tubing... downstream of the turbo, and dump them into the exhaust, but that'd just push the cloud out the tailpipe...

where does the oil go, that the can collects? are you dumping it out?

Codifex Maximus · #3 10-05-2013, 11:50 PM

Quote:

Originally Posted by bricktron

switching the PCV vapors from the giant black drum air cleaner to a catch can has not worked out yet. the stainless steel scouring pad baffling in the can seems sufficient to catch vaporized oil, or at least a good fraction of it, but the can still emits a steady stream of smoky gas, which previously was directed back to the intake.

when i'm at a stop this gas builds up under the hood, leaking out at the sides, which kind of looks like there's a fire burning under there. it also wafts into my open windows.

i suppose i can just reattach this gas to the intake , but i'm under the impression that this is not totally awesome for combustion. is there any alternative?

yes, my engine may have a lot of blowby; i haven't tested the compression. whether i switch or rebuild engines later on, i'd like to do something better about this now.

My opinion?

Burn those gasses. It's more economical, environmentally friendly and will keep condensates from building up under the hood and causing a grease film on everything.

Skippy · #4 10-06-2013, 12:02 AM

Quote:

Originally Posted by Codifex Maximus

My opinion?

Burn those gasses. It's more economical, environmentally friendly and will keep condensates from building up under the hood and causing a grease film on everything.

Either that or run a slobber tube somewhere. My* Paystar had one that vented over the left front leaf spring, as did the other trucks in the fleet. It wasn't uncommon for one of the less aware drivers to report an oil leak dripping on the left front leaf spring. Nope, just the slobber tube, and that was with trucks that only had about 40,000 miles on them.

*Ok, property of U.S. government, but I got to drive it.

Diesel911 · #5 10-06-2013, 12:37 PM

The below may or may not work. It depends on if the cause is sticking Piston Rings.

More Marvel Mystery Oil, said raised his compression
83 240d - no compression in #3 - Benzworld.org - Mercedes-Benz Discussion Forum

This is the begin of the above thread
Piston Rings Gummed Up? - Benzworld.org - Mercedes-Benz Discussion Forum

Marvel Mystery oil results sticky rings (not much info there)
Original thread also has + response
Compression Test...how low is low..... - PeachParts Mercedes ShopForum

Marvel Mystery Oil
http://www.benzworld.org/forums/w123-e-ce-d-cd-td/1619134-proof-results.html

Results of Marvel Mystery Oil soak by another member.
I didn't kill my motor after all. Maybe

Some of Our Members have said after driving 200-300 miles after switching to Synthetic Oil it freed up the Piston Rings.

Another Cause of Blow-by is worn Valve Stems/Guides/Seals on the Exhaust Valves. It allows Exhaust Gas to get into the crankcase.
Changing the Valve Stem Seals is a bit of work but the Parts are cheap. However, changing the Seals may on may not help of there is enough wear on the Valve Stems and Valve Guides.

My Father had a Gasser with that problem and if you left the Crankcase Breather Cap on the Crankcase Pressure built up to the extent that it pushed Oil between the Oil Pan Gasket.

charmalu · #6 10-06-2013, 12:42 PM

So what is wrong with the oil vapors going into the intake? The 78 and 79 W116 300SD had the oil vapors going straight into the U-Tube before the Turbo and burned them.
Then in 190 the invention of the EGR, and then the problems really started.

The inside of the Intake Manifold will just have a slight oil coating to it, and the burned vapors won`t cause any problems. after all look at all the crap people throw into the fuel tank, and it doesn`t seem to be a concern to a lot of people.

All older cars into the 60`s had a Draft tube hanging down from the side of the engine to let the Crank Case vapors out into the atmosphere, then the PCV valve appeared.

Interesting is my 82 Datsun 720 King Cab with the SD-22 Diesel engine has a Draft Tube.

Charlie

rscurtis · #7 10-06-2013, 01:51 PM

My 2003 Dodge still uses a draft tube. PCV was installed on the 2007.5 model year trucks with the 6.7 Cummins engine.

cooljjay · #8 10-06-2013, 02:55 PM

People disagree with my idea on how to stop blow by but it worked on my euro.....do oil changes about every 1500 miles or sooner and do valve adjustments a lot till the valves stay with in spec.....my theory is, that more frequent oil changes help to remove all the gunk that has built up in the engine over the years....plus have the injectors rebuilt....

bricktron · #9 10-06-2013, 03:21 PM

well, here are pix: 342790-my-catch-can-install.html (i am using a different breather than in the pictures now, but the principle is the same.)

maybe i have misunderstood something basic. why did the can come with a breather if a draft tube is the only convenient way to dispense with the gas? and if it's OK to burn the gas, why bother with the catch can at all?

bricktron · #10 10-08-2013, 03:28 AM

so can i hook the PCV tube directly from the valve cover into a bung on the intake manifold?

or is the "caught" waste oil in the can better on balance not to burn?

vstech · #11 10-08-2013, 09:34 AM

connecting the tube directly to the intake manifold on a turbo motor will NOT work. it has to go prior to the turbo.
the EGR fumes are fine to burn! our cars are equipped with OM engines... Oil is the O in the name.
the problem comes in, when EXHAUST gets dumped into the intake... that soot turns the oil vapor into carbon sludge/crust inside the intake... a bad thing.
so, sealing and eliminating the EGR system is a common tuning method.

charmalu · #12 10-08-2013, 11:54 AM

Yes, bad idea to plumb directly into the Intake manifold. Think Turbo = Pressure. so you will be putting pressure into the VC. You need a vacuum to draw the vapors out. So pre-turbo there is suction.

Charlie

DeliveryValve · #13 10-08-2013, 12:42 PM

From the looks of your setup.

You have this.

I think what you need to have is an air/oil separator that separates the oil from the gas and then routes the gas back to the intake. There are no problems in performance in doing it this way if you are separating the oil properly.

Here is a diagram of how it should be routed. Except you'll need a catch can for the separated oil since you don't have a provision to drain back into the sump with your '85 Cali motor.

Skippy · #14 10-08-2013, 06:36 PM

Maybe I'm missing something here. Why didn't you just leave it stock?

oldsinner111 · #15 10-09-2013, 04:58 AM

I put a dribble tube on my sd,blow by gases,are like breathing in a paper bag.