Diff Breathers

[Fozzy Senior Member Find all posts View Profile Close Fozzy]

Re: Diff Breathers

Yes, on mine the hose is long enough so that they curl over in the engine bay and point down. They'd have to be actively sucking air (and the water to be around 1200mm deep in the engine bay) for any moisture to go down the pipes. The rear diff breather is straight up and down but it's tucked in behind the rear tail light - I'm prepared to bet it won't have problems at that height!

Dave

[RogueAussie Senior Member Find all posts View Profile Close RogueAussie]

Re: Diff Breathers

Just remember the breather filter (silencer) should be facing down so when you wash under the bonnet water doesn't enter the line.

I hadn't thought of that... But it makes sense! Does anyone have them installed in this fashion?

Matty

Or, as I do with the pod filter on my Harley when I wash it, just put a bag or something over it while you wash it and take it off when you are finished. I'd prefer to do that then have a risk of kinking hose or adding un-wanteded pressure to the joints by inverting the filters.

You could go as far as fitting a check valve inline before the filters. Make sure it's fitted the right way and that will add that little bit of insurance. Looking at the hosing you have used, a good quality aquarium grade check valve would work a treat! (excuse my ignorace, but does air need to be able to pass both ways or just exit the diffs? is so then the check valve is a Fail lol)

[Rusty62 Advanced Member Find all posts View Profile Close Rusty62]

Re: Diff Breathers

Just remember the breather filter (silencer) should be facing down so when you wash under the bonnet water doesn't enter the line.

What the? Next thing Rusty you're going to tell me you wash the outside of the car too! Unbelievable!

:lol:

Only when i have to. Or when the cook complains she get dirt on her legs.

[FLexus Lurker Find all posts View Profile Close FLexus]

Re: Diff Breathers

Here are a couple of other useful part numbers for you all.
http://www.larsdennert.com/4runner/breather/index.html

[prado_chia Lurker Find all posts View Profile Close prado_chia]

Re: Diff Breathers

Just remember the breather filter (silencer) should be facing down so when you wash under the bonnet water doesn't enter the line.

Does the diff oil circulate? Not trying to be difficult I want to do this mod soon. Was wondering if you could use maybe a balloon/bellows of oil to expand and contract with temperature change and be totally sealed?

[stevensr34 Senior Member Find all posts View Profile Close stevensr34]

Re: Diff Breathers

Actually if you extend the diff breather using fuel hose (which has a bit of give in it) you can just seal up the end of the hose with a bung/plug... the difference in air pressure in the diff between cold and hot is bugger all...this would be taken up with the hose expanding very slightly over its length. Much easier than getting breather plugs/fuel filters/etc...

[RogueAussie Senior Member Find all posts View Profile Close RogueAussie]

Re: Diff Breathers

Actually if you extend the diff breather using fuel hose (which has a bit of give in it) you can just seal up the end of the hose with a bung/plug... the difference in air pressure in the diff between cold and hot is bugger all...this would be taken up with the hose expanding very slightly over its length. Much easier than getting breather plugs/fuel filters/etc...

To extend it in the first instance you need to replace the plugs, then adding the fuel line as mentioned. So the adding of a fuel filter isn't exactly hard or expensive. If just sealing up the end of the hose was the answer then why do the proper "of the shelf" kits not do that? They provide a form of filtration as apposed to just sealing the hose. I'd just for out the extra $10-$12 and plug a filter on the end ... is it really that hard after crawling under the car and running the hose in the first place?

[stevensr34 Senior Member Find all posts View Profile Close stevensr34]

Re: Diff Breathers

If just sealing up the end of the hose was the answer then why do the proper "of the shelf" kits not do that?

Why indeed? Probably they haven't thought it through! Or else they have a great markup on a sexy-looking blue $4.75 air-compressor filter...

They provide a form of filtration as apposed to just sealing the hose. I'd just for out the extra $10-$12 and plug a filter on the end ... is it really that hard after crawling under the car and running the hose in the first place?

No - however it means you don't have to run a hose up to the front engine bay, or up through a grommet to the fuel filler, or inside the jack storage cavity. Instead the hose can stay entirely under the car, strap-tied up above the diff, if that looks a good spot.

Remember - there's really nothing to "filter". The air that is put under pressure (via expansion when the diff heats up), also cools down and returns to it's original volume once you stop.

[Matty80 Avid PP Poster! Find all posts View Profile Close Matty80]

Re: Diff Breathers

Why indeed? Probably they haven't thought it through! Or else they have a great markup on a sexy-looking blue $4.75 air-compressor filter...

Technically they are an 'air suppressor' not a filter, and buying these individually over the counter isn't actually that cheap. The guys that I dealt with at Adelaide Pneumatic Sales indicated that an average of $5 per fitting would be standard. With 8 connectors and 4 suppressors thats $60, custom manifold say $50, hose? few bucks a meter? Markup for packaging it into a kit and inc GST ontop. $180 to $200 probably about right. Only issue i had with it was all the fittings that i couldn't actually use from the kit, and having to fork out for more.

They provide a form of filtration as apposed to just sealing the hose. I'd just for out the extra $10-$12 and plug a filter on the end ... is it really that hard after crawling under the car and running the hose in the first place?

No - however it means you don't have to run a hose up to the front engine bay, or up through a grommet to the fuel filler, or inside the jack storage cavity. Instead the hose can stay entirely under the car, strap-tied up above the diff, if that looks a good spot.

Remember - there's really nothing to "filter". The air that is put under pressure (via expansion when the diff heats up), also cools down and returns to it's original volume once you stop.

Having a sealed hose defeats the purpose of having a "breather" as it lo longer releases the expansion or suction pressures from the dif completely. Which is kind of the point really - so that these preasures are completely removed from the seals within the diff and thus knowing that water/mud will not be drawn past them.

Interesting concept though, I am very interested to see this type of setup in action and hear the results of how it stands the test of time (and river crossings)... Is this how you have fitted them in your rig mate (or planning to fit)? Do you have some photos as examples?

Matt

[Schaffer Addicted PP Member Find all posts View Profile Close Schaffer]

Re: Diff Breathers

Technically they are an 'air suppressor' not a filter, and buying these individually over the counter isn't actually that cheap. The guys that I dealt with at Adelaide Pneumatic Sales indicated that an average of $5 per fitting would be standard. With 8 connectors and 4 suppressors thats $60, custom manifold say $50, hose? few bucks a meter? Markup for packaging it into a kit and inc GST ontop. $180 to $200 probably about right. Only issue i had with it was all the fittings that i couldn't actually use from the kit, and having to fork out for more.

I purchased my gear from them and picked up everything other than a small piece of aluminium angle for less than $20.00. The local hardware store had a short peice of the angle which I drilled to fit the silencers and that cost maybe $5.00.

[stevensr34 Senior Member Find all posts View Profile Close stevensr34]

Re: Diff Breathers

Having a sealed hose defeats the purpose of having a "breather" as it lo longer releases the expansion or suction pressures from the dif completely. Which is kind of the point really - so that these preasures are completely removed from the seals within the diff and thus knowing that water/mud will not be drawn past them.

Interesting concept though, I am very interested to see this type of setup in action and hear the results of how it stands the test of time (and river crossings)... Is this how you have fitted them in your rig mate (or planning to fit)? Do you have some photos as examples?
Matt

At present I've gone down the path everyone else does, and have poked the rear breather extension hose pipe up through a grommet to the jack cavity in the back.
However I am going to try changing the design so that the hose stays in a loop under the car, assuming I have enough pipe to allow for the gentle expansion of the air...

Now to my calculations:

Air expands by 1/3 it's volume if heated from 0 degrees to 100 degrees C.

If we assume air at 0 degrees is at normal atmospheric pressure (say 15psi "Pounds per square inch") then it will expand inside your diff to 20 psi at 100 degrees. (what is the operating temperature of a diff anyway? - must be less than 100 deg C?) This increase of 5 psi causes air to be expelled through the one-way breather valve on the diff. When the diff cools back to (say) zero degrees, the air contracts causing the pressure in the diff to now be below the outside air pressure, by about 5psi. This is what causes the breather valve to briefly suck air in when you remove it.

So we just need enough hose to expand very slightly when the diff pressure increases by up to 5psi...

So - next question: How much volume of air is actually in the diff? (I reckon much less than a litre)

...to be continued...

[Schaffer Addicted PP Member Find all posts View Profile Close Schaffer]

Re: Diff Breathers

If we assume air at 0 degrees is at normal atmospheric pressure (say 15psi "Pounds per square inch") then it will expand inside your diff to 20 psi at 100 degrees. (what is the operating temperature of a diff anyway? - must be less than 100 deg C?) This increase of 5 psi causes air to be expelled through the one-way breather valve on the diff. When the diff cools back to (say) zero degrees, the air contracts causing the pressure in the diff to now be below the outside air pressure, by about 5psi. This is what causes the breather valve to briefly suck air in when you remove it.

The standard breathers ARE NOT a one way valve. What they are is a spring load valve that if the pressure inside of the diff is much higher than the outside temperature, due to a rapidly cooling the diff by submerging it in cold water, then the flow of air through the breather has enough force to pull the cap compressing the spring and sealing the valve. It should, in theory, remain like this, until the temperatue increases and the seuction is no longer there. This would presumably only occur when the temperature increase approaches the outside temperture and the force on the spring drops below the strength of the spring.

Now if you have a close look at the breathers you will probably find that they are crap and don't fully seal adequatley (IMO). You may be lucky but I've got at least one that air can pass through in both directions when fully closed. I recommend you skip the physics and just plus the breather up as high as you can and just use some sort of filter to prevent dust and dirt being drawn into the hose and eventually the diff housing.

[RogueAussie Senior Member Find all posts View Profile Close RogueAussie]

Re: Diff Breathers

Not being and engineer or nuclear scientist I can't put money on anything. However, you are talking about the "bellow" effect being adequate ... my question, point, statement (however you want to take this) is this: The explaination has been made about the expansion of gases due to the rise and fall of ambient and friction heat and cooling. So you are suggesting that with an adequate length of fuel hose, flex in the walls of the hose will be sufficent to cope with the gases being expelled then sucked back in. The problem is two-fold ...

1. The issue isn't the sudden expelling of gasses but the sudden intake. You'd want to be sure that there was sufficient air and flex in the hose at ALL times so that when you hit the first water crossing and it rapidly cools and tries to SUCK air in it doesn't act as a seal causing the gaskets to be sucked in in an attempt to get a sufficent supply of air.

2. Have we taken into account ambient temperature variation season to season, day to night and caused by short and long distance driving. The flex in the hose is going to be GREATLY effected by those temperatures. The point I am trying to make is that we all know that when things are hot they have more give and by rights that hose may have enough flex in it. But what about those cold days or short drives and the hose remains cold. The hose will be lucky to flex at all bexause again we all know that cold things DON'T flex or give as hot things do. Take the hose at room temperature and bend it then put it in the freezer for 10 mins and feel the difference. Hopefully I am getting my point across .. it has been a looong day.

Again, I ain't no scientist but they are a coupld of CDF points I though I might air for the sake of trying to save yourself 10mins and $12.

And just in case you think about using a more flexible / giving hose, remember that the gases alone coming from the diff are corrosive to the hose. The hose I have used is not fuel hose and I know I will have to keep and eye on it and change it before it wears out.

[nika Member Find all posts View Profile Close nika]

Re: Diff Breathers

Having a sealed hose defeats the purpose of having a "breather" as it lo longer releases the expansion or suction pressures from the dif completely. Which is kind of the point really - so that these preasures are completely removed from the seals within the diff and thus knowing that water/mud will not be drawn past them.

Interesting concept though, I am very interested to see this type of setup in action and hear the results of how it stands the test of time (and river crossings)... Is this how you have fitted them in your rig mate (or planning to fit)? Do you have some photos as examples?
Matt

At present I've gone down the path everyone else does, and have poked the rear breather extension hose pipe up through a grommet to the jack cavity in the back.
However I am going to try changing the design so that the hose stays in a loop under the car, assuming I have enough pipe to allow for the gentle expansion of the air...

Now to my calculations:

Air expands by 1/3 it's volume if heated from 0 degrees to 100 degrees C.

If we assume air at 0 degrees is at normal atmospheric pressure (say 15psi "Pounds per square inch") then it will expand inside your diff to 20 psi at 100 degrees. (what is the operating temperature of a diff anyway? - must be less than 100 deg C?) This increase of 5 psi causes air to be expelled through the one-way breather valve on the diff. When the diff cools back to (say) zero degrees, the air contracts causing the pressure in the diff to now be below the outside air pressure, by about 5psi. This is what causes the breather valve to briefly suck air in when you remove it.

So we just need enough hose to expand very slightly when the diff pressure increases by up to 5psi...

So - next question: How much volume of air is actually in the diff? (I reckon much less than a litre)

...to be continued...

Question, do you have or intend to have a ARB air locker fitted?

[stevensr34 Senior Member Find all posts View Profile Close stevensr34]

Re: Diff Breathers

The standard breathers ARE NOT a one way valve

I think you'll find they are supposed to be! - they let air out but NOT in (under any circumstances)... sounds like one-way to me...

...if the pressure inside of the diff is much higher than the outside temperature, due to a rapidly cooling the diff by submerging it in cold water, then the flow of air through the breather has enough force to pull the cap compressing the spring and sealing the valve. It should, in theory, remain like this, until the temperatue increases and the seuction is no longer there.

I am saying the same thing as you: no need to argue with me!

PS it's easier to explain by taking a simple example, using the standard Toyota setup:
1. With every component at room temperature, loosen breather valve to equalize pressure.
2. Tighten valve.
3. Drive for a while to get things hot. At this point the pressure increase in the diff has been bled out via the valve (never to return).
4. Drive through a creek. As the diff cools quickly, the air in the diff cools too, and contracts. This leaves the air in the diff at a lower pressure than outside. This causes potential suction of water/dirt/etc through any seals in the diff.

Cheers,