To plumb or not to plumb (breather lines to air box)
- Thread starter outsidr
- Start date
On my FJC, the front diff has an extension on it from the factory, with a check valve on the end up near the top of the engine. the rear diff was right on the diff itself, so I ran a line up to where my fuel filler is with the stock check valve attached to the end of the hose.
the manual trans has no breather on my truck.
the manual trans has no breather on my truck.
overlander
Expedition Leader
I've heard people talk about tying those lines into their airbox or snorkels direct, but it doesn't make sense to me. Is that something you want to hook up to a vacuum source?
For me, I'm going to be extending them all and tying them all into a single plumbing manifold like this http://www.sierraexpeditions.com/index.php?l=product_detail&p=193, and then running the single continuing line up my snorkel to my roll cage top, with a small breather filter element. All the lines running up to the manifold will have a one way check valve, so that they all don't leak/mix in event of a rollover.
For me, I'm going to be extending them all and tying them all into a single plumbing manifold like this http://www.sierraexpeditions.com/index.php?l=product_detail&p=193, and then running the single continuing line up my snorkel to my roll cage top, with a small breather filter element. All the lines running up to the manifold will have a one way check valve, so that they all don't leak/mix in event of a rollover.
ntsqd
Heretic Car Camper
One thing you have to kepp in mind when extending the vent hoses is the "Garden Hose Syndrome". The longer the hose for a given ID, the more restrictive it is to flow. I know we're talking about a vent, but I've seen issues with too small of a hose. This can cause a small vacuum in the axles.
A vacuum makes it easier for the diff oil to cavitate & form air bubbles entrapped in the oil. Air is not a very good lubricant. This seems like a really trivial thing, but I've seen it cause problems.
I built a manifold for a friend. Both axles, the trans, and the t/c are plumbed into the bottom of it. The crankcase breather hose from one valve cover is connected to one and and the hose to inside the air filter is connected to the other end. He hasn't rolled it (yet), but he has flopped it on it's side (downhill no less) and gear lube into the intake has yet to be a problem.
I have both axles on my '84 yota vented to a filtered breather, but the trans & t/c venting are very odd and I've yet to find a satisfactory method of porting them to my breather. Since water crossings aren't high on my list of things to encounter in the Mojave I've not pursued it further.
You don't want a vacuum in the axles if you are making water crossings. That will just make it easier for the water to gain entrance. If anything you want a couple psi (At MOST!) of positive pressure in the axles.
A vacuum makes it easier for the diff oil to cavitate & form air bubbles entrapped in the oil. Air is not a very good lubricant. This seems like a really trivial thing, but I've seen it cause problems.
I built a manifold for a friend. Both axles, the trans, and the t/c are plumbed into the bottom of it. The crankcase breather hose from one valve cover is connected to one and and the hose to inside the air filter is connected to the other end. He hasn't rolled it (yet), but he has flopped it on it's side (downhill no less) and gear lube into the intake has yet to be a problem.
I have both axles on my '84 yota vented to a filtered breather, but the trans & t/c venting are very odd and I've yet to find a satisfactory method of porting them to my breather. Since water crossings aren't high on my list of things to encounter in the Mojave I've not pursued it further.
You don't want a vacuum in the axles if you are making water crossings. That will just make it easier for the water to gain entrance. If anything you want a couple psi (At MOST!) of positive pressure in the axles.
robert j. yates
Explorer
Whats wrong with simply extending the vent tube and adding a small breather or check valve to it? I've re-done both axles, the transfer case and transmission using this method and its simply never been a problem.
robert j. yates
Explorer
ntsqd said:
ntsqd said:
Pardon my editing but I needed to re-arrange a bit to make my point...running a maze of hoses to the engine bay IMO needlessly complicates things. I have a rear axle breather extended up my gas tank filler hose same as in the stock postion...all that took was 12" of hose to accomodate the lift and increased articulation. I did the same with the front axle. The transmission involved the most work but that is due in part to the fact that Jeep did not see fit to provide a real vent for the 32rh 3 speed automatic I am running. That vent is now located in the bellhousing and terminates on the firewall in the engine compartment. As for the t-case...I simply augmented the existing ventline so that it to terminated on the firewall. Simple, cheap and effective.
ntsqd
Heretic Car Camper
You partially make my point. I would call a 12 inch extension reasonable.
I did it for dust entry control into the axle lube. Did I NEED to since I rarely cross streams? Probably not.
However, my friend does as do some of those more Easterly of me. Do they need to? My friend does as he has no sense. For others it depends on their intended max fording depth. That's not something I have a lot of experience with, nor do I care to. I merely point out that extending a small diameter hose can be a problem spot. If you are going to extend the rear axle vent into the engine bay I suggest increasing the size of the hose.
FWIW I do NOT think a check valve is a good idea. The reason why is this sort of scenario:
A warm to hot axle is plunged into a cold stream. The hot air in it contracts, the check valve seals off the vent line. Now you've got a submerged axle with a vacuum inside it. That makes water entry into the gear lube much easier than if the axle were simply vented.
I did it for dust entry control into the axle lube. Did I NEED to since I rarely cross streams? Probably not.
However, my friend does as do some of those more Easterly of me. Do they need to? My friend does as he has no sense. For others it depends on their intended max fording depth. That's not something I have a lot of experience with, nor do I care to. I merely point out that extending a small diameter hose can be a problem spot. If you are going to extend the rear axle vent into the engine bay I suggest increasing the size of the hose.
FWIW I do NOT think a check valve is a good idea. The reason why is this sort of scenario:
A warm to hot axle is plunged into a cold stream. The hot air in it contracts, the check valve seals off the vent line. Now you've got a submerged axle with a vacuum inside it. That makes water entry into the gear lube much easier than if the axle were simply vented.
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cruiser guy
Explorer
Mine are vented to the underside of the hood. No filter or check valve on them just a cover to keep stuff from falling down them. It still leaves the manual tranny which, as far as I know, all vent through the shift tower.
If I'm going that deep I guess I'm changing tranny oil.
If I'm going that deep I guess I'm changing tranny oil.
robert j. yates
Explorer
I guess the part I was scratching my head about was plumbing everything into the airbox........I am usually concentrating on keeping stuff out....
viter
Adventurer
I got rear, front diffs, auto tranny and t-case all plumbed into "roof" of the airbox (that has snorkle connected to it) on my 2003 taco. All lines are joined into one before entering the air box, then that single line goes thru a VW type fuel filter (the small plastic clear one with yellow paper? filter inside), and then into the airbox. This way there is no check valve so when diffs cool off quickly when entering cold water they can suck in air from the box, but the filter will not let dust in. I was a bit worried about fluids mixing but since each one would have to travel at least 3 feet up it's own tube before the "joint" I really doubt any of the fluids will expand enough to get that far... The fact that the line is plumbed into "roof" of the airbox means water will get to it only if the whole airbox is filled with it - which is quite unlikely even if I do get some water into airbox from splashes or seep in. And the clear vw fuel filter allows you to see if it has water inside. 
so far (a couple years) it seems to work...
so far (a couple years) it seems to work...
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Nullifier
Expedition Leader
Mike I saw on the ttora forum that someone was using a diff breather balloon off of a Kawasaki side by side. I will try to dig up the link but I have to say that if I was doing breather work, that is the only way I would go. It requires running no lines. It is basically a balloon over the vent nipple that will expand and contract as needed and prevent water from getting into the diff.