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What The #$%^ Is This Hose?


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#1 Dedaw

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Posted 10 January 2013 - 07:06 PM

Truck came with this hose cut off when first purchased, totally forgot about it until I was working on the valve cover yesterday. What's it for?

Posted Image
Talking about the one in front that's been cut.

. :MJ 2: .

 

1989 Comanche Pioneer, 4.0, 5 spd, 4x4


#2 Xacto

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Posted 10 January 2013 - 07:19 PM

Crankcase ventilation, it runs from the valve cover to the airbox as you can see here:

Posted Image

Looks like you have a non-stock airbox though and the previous owner just cut it off. Is there a plug in the valve cover opening?

#3 Dedaw

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Posted 10 January 2013 - 07:31 PM

I put in the cold-air, but the hose was already cut. :dunno:
No, there was a small air filter in the vent hole. Should I plug it, or try and run an OE airbox again? (Or mod it into the cold-air?)

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#4 Comanche County

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Posted 10 January 2013 - 08:10 PM

It's actually quite important.

#5 mvusse

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Posted 10 January 2013 - 08:31 PM

Small air filter on there will do the needed job just fine.
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#6 ftpiercecracker1

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Posted 10 January 2013 - 08:53 PM

It's actually quite important.


Really? How so, :hmm:

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#7 Biotex

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Posted 11 January 2013 - 08:51 AM

As the PCV sucks out blowby gasses from inside the crank case, there needs to be a filtered source of outside air to enter the crank case so there is neither a vacuum or pressure inside. That hose going to the air cleaner is the filtered sourse of air to enter the valve cover to replace what is being sucked out.

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#8 Pete M

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Posted 11 January 2013 - 09:04 AM

how important it is depends on how bad the blow-by is in a particular truck. I had a little filter on mine for a while. all it did was leak oil out that filter and fill my engine bay with stinky fumes that should have been sucked back into the engine. it didn't last long before I created a factory-like system again.

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#9 ParadiseMJ

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Posted 11 January 2013 - 10:59 AM

In states (or counties) that require emission inspections, that is a sure fail.

Just a breather filter does not suffice. It may not be key for running purposes, it may not be required in Texas, Ohio, Tennessee, or W.Virginia.

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#10 NotMatt

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Posted 11 January 2013 - 01:51 PM

As long as the filter is a good fit in the hole in the valve cover, so that the air that gets sucked in through the Crank Case Vent (CCV) system is filtered, it's alright to leave it like that. It's hard to find parts store ones that are a good fit though, usually. So if you want to leave it like that, clean it up and put some RTV around the hole and make sure all air going in is going to be filtered. Otherwise, hook it back up to the airbox like factory.

Here's the gotcha though... a lot of times people remove that tube and put an aftermarket filter there because their air box filter is getting soaked with oil. Usually what happens is then the whole engine bay gets soaked in oil, because their CCV system is not working right. This should not happen on a properly working system, even IF the motor has blowby. The fumes get pushed out the front valve cover hole and the airbox air filter gets soaked on a stock system when the small hole in the REAR grommet in the valve cover gets clogged. It's important that this small hole is not clogged and is connected to manifold vacuum. This manifold vacuum draws oil fumes from the rear grommet in the valve cover into the intake to be burned by combustion. The small vacuum also draws fresh air in through the front hole on the valve cover, which is why it's important that this front hole is filtered.

[EDIT]: And yeah, Like ParadiseMJ said... it will probably not pass an emissions inspection like that.

#11 Dedaw

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Posted 11 January 2013 - 05:36 PM

Went to get another grommet for the rear, since it was all puckered up. Also got a new PCV grommet and valve. Would it be acceptable to run the PCV to the back of the air filter (into the tube there) or just run another air filter with a properly fitting grommet? Also did the valve cover mod and will be painting it. Build thread coming when I'm done all finished up. :thumbsup:

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#12 Biotex

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Posted 11 January 2013 - 06:07 PM

In my experience, runningthe PCV tube into the air cleaner housing makes a mess and dirtys up your filter. You ideally want those fumes to go directly into the manifold out of sight.
I hope i'm reading your question correctly and are talking the actual PCV tube and not the other one.

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Military wrapped 2" rear leaf springs, Rubicon Express 4.5" coil springs,

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RE adjustable track bar, external slave cylinder.

 


#13 ParadiseMJ

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Posted 11 January 2013 - 07:26 PM

... will be painting it...


Well, that's more important than any dumb, stupid old hose!! Go for it!! :thumbsup:

1988 MJ 4.0 SWB  D30/D44 LSD

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OurChristmasTree.jpg

 

 

Nevermind, just saw you're in Communist California...

 

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#14 NotMatt

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Posted 12 January 2013 - 02:05 PM

Went to get another grommet for the rear, since it was all puckered up. Also got a new PCV grommet and valve. Would it be acceptable to run the PCV to the back of the air filter (into the tube there) or just run another air filter with a properly fitting grommet? Also did the valve cover mod and will be painting it. Build thread coming when I'm done all finished up. :thumbsup:


You're using confusing terms here, because these motors do not have a standard "PCV valve" like most motors. They have a "Crank Case Ventilation" system, or CCV system. No PCV valve needed. The rear grommet on the valve cover needs to be hooked directly to the intake manifold so that vacuum is applied to it with the motor running... but you can't run just any old grommet in there, it needs to be the one with the small 2.2 or 2.6 millimeter opening, otherwise it will create a huge vacuum leak and your engine will idle super high. Go to any parts store that carries Dorman products and get Dorman part number 46005, which is a kit with the right grommet and the tube that goes to the intake manifold.

The front grommet is the fresh air inlet, no PCV valve goes here or anywhere. This simply needs to be a filtered fresh air source so that when the vacuum sucks the fumes out the rear, the motor can take in fresh air to replace. You can put a grommet in it with a properly fitting small air filter, or you can get Dorman part numbers 46003 and 46004 which is the complete vaccum tube assembly for the front and includes the grommet for the front hole in the valve cover and has the entire tube that replaces the part that's cut in your original picture. This tube would then connect to the airbox for a filtered fresh air source. Either one works, the 2nd option is the way the factory did it, and if you have emissions inspections, probably the best way to fix it.

Go to rockauto.com and look at their parts catalog and drill down to the model/year of your rig and under "Emissions" section you can see a picture of the Dorman parts numbers I listed above. They are under "PCV Valve / Crankcase Ventilation hose" and "Vacuum Harness".

#15 Dedaw

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Posted 13 January 2013 - 06:29 PM

Well, that's more important than any dumb, stupid old hose!! Go for it!! :thumbsup:

Since the valve cover was off, and cleaned up to replace the gasket and do the mod, I'm taking the extra couple hours to paint it. :dunno:

Matt; thank you so much! I think I may just run the air filter on the CCV still, and got another grommet for the rear. However, I'm thinking I'll return it and grab up the full set you recommended. Thanks again.

. :MJ 2: .

 

1989 Comanche Pioneer, 4.0, 5 spd, 4x4