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2.5 NA PCV question

3K views 24 replies 7 participants last post by  KGH 
#1 ·
Apologies in advance for another "is this normal" question..


2.5 NA PCV system / oil breather acting strange..

So theres pressure exiting the oil fill cap / screen and tube ..not excessive seems normal then tube attaches to inlet manifold. Should be suction there at manifold right? On my engine there is air pushing out and no suction. Lots of suction at the intake / filter side and nothing inside the inlet manifold clogging anything. The nipple on the intake manifold is pushing air out and not sucking it in..

Im stumped? Any suggestions or is this normal?
 
#2 ·
oil breather from top of engine should expel some gases and oil vapor but not at any real pressure. the intake will have suction/vacuum when the engine is running.

So the oil vapor from the breather will be sucked into the intake/inlet manifold as designed
 
#4 ·
I had blow by on my second 2.5 na once so I pealed 2 bananas and shoved them into the oil fill, then ran the truck for 30 minutes and no more blow by, it stopped smoking, ran smoother AND had 30 more hp!
 

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#5 ·
Naplm describes my setup . Small tube exits oil cap / vent then attaches to inlet manifold. The nipple on my inlet manifold that is supposed to have suction does not, but rather pushes air out instead.

There is suction from the air filter end of the manifold and there’s no blockage or obstructions..

Engine still seems to run strong but I’m stumped on where the pressure at inlet manifold could come from especially since the inlet at the air filter has enough suction to practically suck my hand thru
 
#14 ·
Haven't tried smoke but I held a piece of tissue against the nipple on the intake and it wasnt sucking, but rather blowing outward. I also plugged the hole with my finger and felt pressure...

Ill try again tomorrow with some smoke, buy would think that the tissue would be light enough that it would cooperate with the suction..Hopefully the smoke shows differently..

Cant think of anything that would create pressure there either that's why Im scratching my head and looking to the wisdom of the forum..

Even if there was severe internal engine damage, wear, etc there would still be suction right? And like I said its sucking like crazy thru the front of the intake manifold.

Maybe I should grab some bananas!
 
#16 · (Edited)


How well is the engine running? Steady idle, revs up fine, pulls OK under load?

The other end of hose labelled #7 in diagram connects to intake nipple. At idle, you have positive pressure out of intake nipple, ie, air coming out. One of my 2.5NAs does this, have not checked the other.

For OP, increase idle by manipulating throttle linkage on Injector pump, see if the positive airflow from nipple becomes negative/suction at nipple, mine does.

That said, I have no idea if this is normal. It defies what I would consider normal.

As a bonus, my motor runs oil out where 4,3,9 meet stud in diagram. Runs, not seeps.

(No bananas were injured in the creation of this post)
 
#17 ·
Ill check again today but it seemed as idle created no change, somewhat hard to tell as the fan starts to make a lot of wind one the revs increase. Blowing my tissue tester all over..

Whats interesting is that the damn thing runs great. Pulls strong, idles great, start with 10 - 15 seconds of glow in any temp so far, etc. Barely noticible stream of black smoke that increases with heavy throttle.

My setup is exactly diagram above
 
#20 ·
I don't think the 2.5 had a viscous fan, but don't really pay a lot of attention to them.
Generally we only put a chain on a 2.5 N/A to remove it so we can replace it with something more powerful and reliable.

To comment on the diagram regarding oil flowing from 4, 3, 9, there is suppose to be copper washers on the assembly that are not shown, that form a seal to prevent the oil from leaking.
.
 
#25 ·
On the 130, I have the copper washers, and lots of crankcase pressure, lol. My 110 2.5NA has the 200Tdi style retainers with rubber seals, no leak.

I am removing 50% of my 2.5NA inventory, so yes a chain will be involved!

OP - unless it is a second or third Defender, and used as a tool or runner, there is no reason to keep the 2.5! My 2.5 pulled 8 2” fence posts and concrete footings, and made a trip to the dump today. It is a truck for using as such. My 130 is getting the 200Tdi, and will not be hauling trash, unless I pick up Keys hitch-hiker chicks!

But I do wonder how the hell air pushes out an intake.
 
#24 ·
No viscous fan..

Was able to use some cardboard to make it less drafty in the engine bay and sure enough when revving it sucks all right!! Barely so if any at idle..

I swear yesterday the the suction was significantly less, if at all. Id expect lots of suction based on the amount of air the intake manifold pulls in..but alas I am no mechanic so maybe its normal.

Definitely some pressure / blowby from PCV crankcase breather cap but nothing Id call excessive. Have plenty of older worn out diesel truck for my business with lots of blow by..this is much less..

Guess what it all boils down to is that Im looking for reasons to keep this engine (dont ask me why), but Im paranoid the damn things gonna quit on me, even though it seems to be ok..

Thanks again for all the responses and suggestion.
 
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