Diff breathers

[stickshifter]

What if we are overthinking the problem? Carraro builds axles for a whole range of heavy equipment. Most of them are used in construction/hauling machines, and I've never personally seen raised diff breathers on such machines. It doesn't make sense to raise a breather which only vents out. Maybe it has a lot to do with the beam axle internals and type of the seals. I think that some positive pressure inside the diff is a very desirable thing to have by design, this actually prevents the water getting inside through the seals more than having it at atmospheric pressure and submerged in 80cm of water (if using atmospheric breathers - because it makes no sense to extend the breathers if using the same one-way vent).
Ineos never said that you can park your car in 80cm of water. As long as the engine is running, the air fan is on max on fresh air and you are moving, there is no time for sufficient water to get in anywhere to cause damage.
But if you stall, or stop, or park in 80cm of water, then it becomes a problem.
Maybe we need a more complex mathematical model of why we are doing raised breathers, myself included in my LC80. What are the pressure differences inside the diff between atmospheric breathers and closed one-way breathers when submerged in different depths of water, for example.
Maybe we are wasting our time and resources to solve problems that do not exist. Dunno, just sayin...

This is what I learned many years ago:

The factory-installed differential breather - which is not raised but is located on the differential housing - can get clogged by driving thorough mud, or under other circumstances. If the breather gets clogged, and you are driving under conditions in which the inside of the differential is heating up, the rising pressure cannot escape through the breather. Under such conditions, differential oil typically gets forced down one axle shaft, and out the axle seal.

When driving through cold water, pressure inside the differential can drop. If the breather is plugged with mud or sludge, it is possible that the pressure will equalize by sucking water in through the axle and pinion seals.

 

[AnD3rew]

And even if they are not clogged, they will release pressure when hot, but then close as they cool which will result in negative pressure, not positive pressure inside the diff. When axle seals etc are new, probably not a major issue, but as they start to wear chances are that you are out bush doing a hot hard slog and then you drive through a stream with cool water, the diff cools very quickly and the already negative pressure becomes a pretty strong vacuum and pulls water in through the axle seals. Are they really necessary????? Maybe not if you offroad rarely, drive in water rarely and change diff oil regularly and or don’t plan to keep the vehicle longer than a few years. But it’s pretty cheap and easy insurance otherwise. Of course you should also be aware when you do it you also add a new point of failure if you tear off a hose, or drop into water deeper than your breather top you may end up putting a lot more water in your diff. . I put the breathers on mine.

 

[alexandruast]

I'm curious if anyone can test and butcher an Ineos breather to actually see the pressure release valve material working. I know for sure there are porous materials for valves that can pass air slowly in one direction, faster in the other (for pressure release), but won't pass water in any. This is how newer toyota models use in their breathers. I think it's easy to test with a simple pressure rig setup. Clogging it should not matter because mud is porous and can, albeit slowly, escape air.
Usually, aftermarket or DiY solutions in a vehicle do not solve an engineering defect, only change the manufacturer's tradeoff variables in the equation. It's absolutely reasonable to DiY or aftermarket a system or part if the manufacturer's tradeoff was cost. But I personally do not think this is the case (we are only talking about some additional hoses). Unless I know what are the tradeoffs we are talking about with raised/open breathers design vs closed, I won't change mine.
Messing with the manufacturer's engineering design without understanding all the variables, usually, will lessen the reliability. Unless the engineering was plain stupid. But I am reserved in calling any engineering stupid, unless I perfectly understand how that system was supposed to work, and in under which conditions.

 

[Miki]

<snip>
Maybe we are wasting our time and resources to solve problems that do not exist. Dunno, just sayin...

Yeah ...

 

[Tom109]

The Carraro breather appears to have similar construction to a Schrader valve (tire). I didn’t really investigate, just threw them in my parts bin after removal. I ran breather tubing into the engine bay just like I have, problem-free, on my LR’s for decades.

I am a little curious on the Carraro breather, but not enough to cut it apart or reverse my raised breather tubes. I am not comfortable with the idea of any breather venting while submerged.

 

[Greasemonkey]

My Same 4WD vintage tractor from 1965 had a simple breather in the front axle, which consisted of a 6mm pipe with a plastic cap. Through small channels in the cap, both warm air could get out of the axle and cold air could get into the axle. Since I was afraid that water could get into the axle when driving through water, I put a transparent plastic hose on the pipe of the axle and led it up over the engine. But now you could see what was really happening. The front axle was breathing ! What I mean is, that condensation has now formed in the hose, which has run back into the axle. This is certainly not much for daily use. But every time the tractor is parked, condensation forms and runs back into the axle. How much ? No idea. Is it a problem ? I do not know either. The breather used in the Ineos - Nostrali 33A - has an NBR seal on the inside, which is pressed onto its seat using a stainless steel spring and which opens at 0.25 bar overpressure. Provided this breather and the axle seals ! work, there is no way water can get into the axle. If both items are worn out, different story.

 

[alexandruast]

Provided this breather and the axle seals ! work, there is no way water can get into the axle. If both items are worn out, different story.

If one is using atmospheric breathers, there is an unfortunate corner case where you might have worn seals (but not actually failed) and the water will be pushed through because of the pressure difference while submerged. This would not happen with the original breather.

 

[Tazzieman]

We should be asking for diff pressure and moisture sensors, all displayed on the centre screen
That would alleviate all anxiety

 

[Tom109]

If one is using atmospheric breathers, there is an unfortunate corner case where you might have worn seals (but not actually failed) and the water will be pushed through because of the pressure difference while submerged. This would not happen with the original breather.

Actually, there should be near zero pressure difference with raised (atmospheric) breathers. Your worn seal analogy would apply to the original breather.

 

[Ovrland Bill]

Actually, there should be near zero pressure difference with raised (atmospheric) breathers. Your worn seal analogy would apply to the original breather.

Is alexandruast perhaps saying that the original breather could maintain enough positive pressure that the seals would remain seated (enough to prevent water ingress)?

 

[Jmccmick]

it seems to me that an air-permeable waterproof filter/valve at the engine end of a breather tube would solve everyones, including the possibility of condensation within the tubing draining back to the diff. There are PTFE or similar membranes that would serve though i havent seen any with pipe fittings. I expect theyd become contaminated and fail over time being connected to a pool of oil, anyone whos ruined an expensive goretex jacket will understand exactly what im talking. For myself, I think i will be satisfied with secure tubing and a sintered filter in a clean-ish area of the engine bay

 

[Tom109]

it seems to me that an air-permeable waterproof filter/valve at the engine end of a breather tube would solve everyones, including the possibility of condensation within the tubing draining back to the diff. There are PTFE or similar membranes that would serve though i havent seen any with pipe fittings. I expect theyd become contaminated and fail over time being connected to a pool of oil, anyone whos ruined an expensive goretex jacket will understand exactly what im talking. For myself, I think i will be satisfied with secure tubing and a sintered filter in a clean-ish area of the engine bay

I agree. This shows a sintered filter on my diff breather lines.