Front Diff Hose

I had to replace the hose going from the front differential to the firewall today because the front driveshaft had chaffed it. I had a difficult time putting the white cap back on the top end of the hose. Can someone tell me what this cap is for and why it looks the way it does? It's got a top that sort of wiggles around for no apparent reason. Thanks!
Matt

That cap is a check valve, and the hose is an air breather. When the oil heats up, the air overtop of it expands and needs to be vented so you don't pop the gasket (it can happen,) and the valve on the end is to help prevent water ingestion as well if you "swim" your XJ. The wiggly part is the actual valve proper.

For your other question, the transmission breather hose (same basic function) is found, IIRC, bolted with one of the two bolts at the driver's rear of the engine, same place where you find the engine grounds (near and aft of the distributor.) I don't recall the proper orientation of the pipe end, but pointing it more or less downward wants to sound correct (so it won't accidentally catch anything, and anything that might get spit out goes down and away from the windscreen.) HTH

5-90

I was under my '88 and noticed the hose - only 12" long - zip-tied to the control arm. There is oil all over the place in that area. Did it come from the breather hose? If so, what is the supply for the oil?

phead50 said:

I was under my '88 and noticed the hose - only 12" long - zip-tied to the control arm. There is oil all over the place in that area. Did it come from the breather hose? If so, what is the supply for the oil?

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The oil in the differential case gets strewn around when the axle is turning - that's how the gears are lubricated ("splash lubrication.") It's possible that some of the oil would get lightly blown out of the hose in normal operation.

If there is a downward bight in the hose (think "drip loop," like on your electrical service entry for your house,) it's possible that oil will collect in that loop until there is enough to blow out the other end of the hose. The hose is there to allow for the expansion and contraction of the air over the gear oil - otherwise, you'd blow gaskets at freeway speeds. That would provide the "pumping action" through the hose.

So, the "source" of the oil blowing out would be the axle itself, and there's no mechanical cause for it - simply physics and random chance.