Clogged Front Diff Breather

Sometimes I can be dense, so I just want to clarify what you are saying here. The brand new OEM part for the larger diameter plug (part

$7 90930-03136 Toyota Breather Plug - 90930-03136

90930-03136) allows airflow in both directions. You can seal your mouth around the plastic end that gets inserted into the hose and blow air through the vent, and you can also suck the air back through the vent?

This is the OEM part that looks identical (at least in pics) to the smaller diameter plug on our 1st gens, but which the parts websites have been stating is not compatible with our generation, and is instead being sold for 2019-2023 models. When you say it is the wrong part, how did you determine that? Does it not physically fit into our smaller diameter hose, and/or does part 17810-51010 not operate the same as the 1st gen part?

 

Correct yeah all 3 allow airflow in both directions.

The only exception is if you take your fingers and push down on the little metal piece on top - in which case all 3 will not let air flow in or out. I could not replicate this behavior this my breath I had to push down on the metal cap with my fingers. Basically all 3 (OEM new part, Autozone part, currently clogged part) all behave in the exact same way for every test I did. I would go OEM because the part is super cheap and you know it's correct.

https://www.toyotapartsdeal.com/oem/toyota~filter~assy~air~17810-51010.html - Does not look like our part when you actually get it. Does not appear to let air in or out very easily. It seems to be serving a different function. I blew through my currently installed valve (which is super clogged this is the issue) and it does not perform in the same way.

 

I should say I disassembled the autozone part just to see how it works. You can pull the metal piece off the top with some pliers and pop it back on with your fingers. The metal piece just sits on top of an open orifice loosely and when air comes through it the air just pushes it up. We probably could just pull the metal piece off the top and clean the gear oil off from under the metal piece and put it back on and it might work like new. Just need to be careful not to damage the metal piece or really old plastic when pulling off the metal piece

 

I guess it makes sense for the breather plug to allow air flow in both directions, so that way it can equalize pressure in the differential as it heats and cools. And the metal cap is probably just something to keep the critters and dirt out.

The weather has been wet and cold here, which gives me a good excuse to keep procrastinating on cleaning mine up. The plan is to try and clean away all of the grime and figure out if I also have a leak at the driveshaft seal, which I strongly suspect.

 

Getting around to trying to address this. Did you ever find a new replacement for this smaller plug/vent? Did you happen to try disassembling the old one to clean it?

 

For anyone who might happen to be following this, I went ahead and took both of my plugs/vents apart. These are the original OEM parts from the factory. The larger one is indeed exactly as the OP described for his Autozone part. The metal cap just sits on top of the open orifice, so it is designed to allow flow in both directions.

HOWEVER, the smaller diameter plug/vent is designed differently. Underneath the metal cap is a weak spring that pushes a small rubber disc against the top of the plastic orifice, creating a one-way valve. So assembly is metal cap>spring>rubber disc>plastic piece. Pressure can easily escape the plug/vent (the spring is very, very thin), but it won't allow air back in if there was a vacuum being created. I didn't think to take pics while I had them disassembled, sorry.

Neither of mine appeared to be plugged or fouled up and appeared to be working as intended, so I am not sure what the problem is, but one of them (I don't know which) is still spewing gear oil.

 

I vividly remember when cleaning under my hood today seeing these two breathers thinking to myself(wtf are those things?). Now I know. Gonna clean mine up tomorrow they have earl all over em, following along happily with this thread.