Can't Breath with the Breather Mod?

[cp99sr5]

So I just did the breather mod, got the kit from Yotashop, ran it through the gas filler area just like most everyone does and just before I attached the end to the diff, I decided to blow through the tube to ensure it could vent. Well it vented just fine so I thought what about the other way? So I tried to pull (suck) air through it and I got a little before the cap settled down and cut of the flow. I thought nothing about this and proceeded to finish up the job.

Then I got to thinking I read the following during my research - "The rear diff doesn't have a breather. For some reason, Toyota just installed a 1-way valve on the rear diff which allows gases to expand out, but not to contract when cooled rapidly. When you are driving around and the rear differential gets hot from normal driving and you splash into some water the sudden chill from the cool water causes the case to rapidly cool and contract, building a vacuum in the rear differential.

This sudden quick cooling can create a strong enough vacuum that it sucks in water through the rear diff seals. The rear differential does NOT have to be underwater to have this happen - water just has to be up to the level of the seals (roughly about a 1' deep if I remember correctly, I didn't measure). Obviously, a little bit of water in the rear differential is gonna cause some serious problems if it stays there for long!"

SO, if the diff cools rapidly and creates a vacuum the suction will cause the cap to seal and cut off the flow of air through the extended tube and could still pull water through the diff seals correct? OR is the air within the tube enough to prevent the vacuum from sucking water through the diff seals? Just want to understand the mechanics behind the theory.

Thanks - Chris

 

[mikey's2010SR5]

Pretty much the reason I will be going with the ARB filter breather. That way air can go both ways. That and the manifold has four ports.

 

[pluton]

SO, if the diff cools rapidly and creates a vacuum the suction will cause the cap to seal and cut off the flow of air through the extended tube and could still pull water through the diff seals correct? OR is the air within the tube enough to prevent the vacuum from sucking water through the diff seals? Just want to understand the mechanics behind the theory.

Thanks - Chris

This could be a serious issue for those that need to be able to park the truck with the rear axle in 20" of water.
All others, not so much.
Still, the two-way makes more sense if there are no other issues involved.
I extended my rear breather using the original one-way valve at the end of the extension.
But, I am haunted by the spectre of having been through a marathon rear axle seal failure/repair/failure/etc, so I'm hesitant to upset the original Toyota rear axle juju.

 

[cp99sr5]

Thanks for the replies, I guess the technical question is based on the volume of air inside the differential and how strong the vacuum created by rapid cooling is? I was hoping that the air contained in the 5 feet of additional tubing and the second it takes for the cap to seal is enough to "cushion" the vacuum force and prevent water being pulled in through the diff seals. Is the answer that it should be an open system and instead of a valve on the end, I should just put in a foam filter or does an open system create some other issues?

Thanks again - Chris

 

[3bears]

Pretty much the reason I will be going with the ARB filter breather. That way air can go both ways. That and the manifold has four ports.

what is this mod....the ARB filter breather

links?

 

[mikey's2010SR5]

what is this mod....the ARB filter breather

links?

ARB Link

 

[pluton]

The ARB unit looks cool.

 

[cashmoney]

Has anyone actually proven the whole vacuum theory? I understand metal contracts when it gets cold but I can't see it doing it enough to create any kind of vacuum.

 

[2014 Warthog]

Don't know if anyone has proven it. But it's not the metal contracting causing a vacuum, it would be the air inside cooling off.

For mine, I bought a cute little air filter from a parts store and ran it up to the top of my firewall. What I found amazing is how much air actually flows in and out of it! I bought an oiled filter and it is collecting dust at an amazing rate as well as misting oil out onto engine parts that are near it O.O

I think I'll change it out to a dry filter next time if I remember when I'm at the parts store again...

 

[pluton]

Has anyone actually proven the whole vacuum theory? I understand metal contracts when it gets cold but I can't see it doing it enough to create any kind of vacuum.

Come to think of it, I've never heard of, or seen it, actually happening. Good subject for Mythbusters, if you could trust Mythbusters.
I still say it shouldn't be a problem, as long you don't park the truck in cold water immediately after a long, hot drive.

 

[cp99sr5]

This is still unresolved for me, I ran the breather through the gas cap area, and have been looking for a small air filter that will fit on the end of the hose and work there before I go and take off the breather cap. So far no luck so I will most lkely have to re-route to another area and to accommodate the typical small filters that I am finding. My wife suggested using a small piece of foam and covering with a small piece of stocking to keep it in place over the hose, who knows might work!

 

[Snowb]

Dang I didn't know this was even a thing. Well I guess it might not be. I just extended my breather to my gas filler location on my '96.

 

[Myrunr2010]

So sitting here thinking about it, this is my theory on the whole vacuum thing and the mechanics of it all.

As you drive and everything heats up. The fluid would expand as it heats up. The metal would also expand, however, I don't think the thermal expansion of metal would be that significant. If that can be considered true, then you would only be concerned with the expansion/contraction of the fluid. So the "vacuum" that is drawn would be based on the difference in the volume of hot fluid to cold fluid. I'll have to look it up, but I can't imagine the difference in hot and cold fluid would be that significant.

Anyone else care to pick my logic apart?

 

[Myrunr2010]

So I just ran some numbers. If you used a temperature difference (I just used numbers that sounded like they might work) of 80 deg F to 212 deg F a 72" piece of steel (6') would expand to 72.0684". A 1/4" piece of steel would expand to a whopping 0.2502376".

The idea that the cooling of the metal would create a vacuum strong enough to cause your axle seal to break doesn't seem right based on the numbers.

 

[cashmoney]

Pretty certain this is another one of those internet rumors. Think about it. Every vehicle out there suffers from this (ever driven in the rain?) and every vent I've ever seen between 4 4wd vehicles and 3 2wd vehicles is just a rain cap on the end of a hose to let the air vent in and out and in all the years of mud bogging as a kid I never once had water get in due to hitting cold water. The metal case is not going to contract enough to create any type of vacuum and it's certainly not going to cool the fluid off enough to create a vacuum from the fluid contracting.

NOW, all that said, extending the breather up is a good idea but this whole vacuum notion is just silly. Toyota put a one way valve in to keep water out because it's located on the diff and not up high. Simple and easy. Just like how they built the 4runner.

 

[Myrunr2010]

Pretty certain this is another one of those internet rumors. Think about it. Every vehicle out there suffers from this (ever driven in the rain?) and every vent I've ever seen between 4 4wd vehicles and 3 2wd vehicles is just a rain cap on the end of a hose to let the air vent in and out and in all the years of mud bogging as a kid I never once had water get in due to hitting cold water. The metal case is not going to contract enough to create any type of vacuum and it's certainly not going to cool the fluid off enough to create a vacuum from the fluid contracting.

NOW, all that said, extending the breather up is a good idea but this whole vacuum notion is just silly. Toyota put a one way valve in to keep water out because it's located on the diff and not up high. Simple and easy. Just like how they built the 4runner.

Essentially the same conclusion I was trying to get at, just using logic and numbers in lieu of the "this is the experience I've had" route.

 

[KidVermicious]

This is still unresolved for me, I ran the breather through the gas cap area, and have been looking for a small air filter that will fit on the end of the hose and work there before I go and take off the breather cap. So far no luck so I will most lkely have to re-route to another area and to accommodate the typical small filters that I am finding. My wife suggested using a small piece of foam and covering with a small piece of stocking to keep it in place over the hose, who knows might work!

Leave it open. My front diff is extended to the firewall, my rear diff to inside the tail light enclosure, neither has a filter or jiggle cap or anything. Air is not constantly being drawn down the breather extension, so there's no way a statistically significant amount of dust will get down that breather tube and into your gear oil, and if you get water that high you'll have much bigger problems than a little water in the diff!

 

[cashmoney]

Essentially the same conclusion I was trying to get at, just using logic and numbers in lieu of the "this is the experience I've had" route.

100% agree. I was just going along with your thoughts.

 

[KidVermicious]

So I just ran some numbers. If you used a temperature difference (I just used numbers that sounded like they might work) of 80 deg F to 212 deg F a 72" piece of steel (6') would expand to 72.0684". A 1/4" piece of steel would expand to a whopping 0.2502376".

The idea that the cooling of the metal would create a vacuum strong enough to cause your axle seal to break doesn't seem right based on the numbers.

Has nothing to do with the expansion and contraction of metal, it's the air and gear oil. Here's how it plays out in a stock setup - the diff rotates, gear oil gets hot and expands, air gets hot and expands, extra air is pushed out the jiggle valve on the top of the diff, all good. Go to cross water above the axle, the cold water cools the gear oil and air enough to cause a contraction, the vacuum slams the jiggle valve shut and no water gets in, there's not enough vaccum to compromise the axle seals, all good. Fast forward a couple years, gear oil sloshes around and creeps up inside the jiggle valve, attracts dust, jiggle valve gets clogged and stops jiggling, not so good. Now when the oil and air heat up and need to expand, the jiggle valve doesn't relieve the pressure. The axle seals are normally the next weakest point, and air and gear oil will push through them - out, not in. But enough of being compromised like that will weaken them, and if you hit the next river with weak axle seals and a clogged jiggle valve you do stand a good chance of sucking water through the axle seals (or the jiggle valve, if it's clogged open), and that's got the potential to be very bad indeed depending on how much water gets in.

Answer number one is keep the jiggle valve clean and stay out of water above the centerline of the axle - your owners manual has a fording depth for your 4Runner for a reason. If you have to cross water much higher than that infrequently, a functional jiggle valve should still keep you in good shape, but it's a good idea to check your gear oil after. If you are crossing higher water frequently, or super deep water at all, extending the breather (and keeping it clean) is cheap insurance against water intrusion, but you should still check your gear oil frequently.

 

[cashmoney]

And for those putting filters on, you aren't helping anything. Think about it, even when the Toyota valve is open air is getting in there and nothing happens. Extending the tube isn't going to change that.