Yesterday I replaced the Coolant Temperature sensor on my daughter's 95 Legacy. So that big vertical hose by the Idle Air Control valve was super brittle and broke and I had to make a trip to Napa to get some new hose. The top the the hose has two connecting hoses. One goes to the PCV valve and the other goes to the air intake plastic system. I'm just wondering what it does and what symptoms you can get if it is leaking. 

Tonight I'm going to do the same procedure on my 95 Legacy so I have enough hose to replace that big hose too.

It goes down to the air oil seperator area on the back of the block, which goes to the oil pan.

Yes they often get very brittle from the engine heat.  I've found the IAC hose is a perfect fit.  When I'm in the self server yards, I'll pull a couple.  You get 2 breather hose sections from each IAC hose.

40 minutes ago, lmdew said:

It goes down to the air oil seperator area on the back of the block, which goes to the oil pan.

Yes they often get very brittle from the engine heat.  I've found the IAC hose is a perfect fit.  When I'm in the self server yards, I'll pull a couple.  You get 2 breather hose sections from each IAC hose.

Thanks for the information. What happens if they leak air?

Oil leak.  It's venting into the block.  The PVC valve is controlling how much air goes in there. 

 

12 hours ago, lmdew said:

Oil leak.  It's venting into the block.  The PVC valve is controlling how much air goes in there. 

 

I replaced my Coolant Temperature sensor last night as planned. The big vertical hose wasn't brittle yet but I did replace it. The connection into the engine was full of greasy crud and almost blocked. The line to the PCV valve also full of crud and nearly blocked. I cleaned that all out and took the PCV valve out and cleaned it with carburetor cleaner.

After I got the car all back together I didn't bother test starting it. So this morning when I started it the engine would die after a few seconds. Turns out I neglected to reconnect the big horizontal hose from the Idle Air Control Valve when it connects near the MAF sensor. Got that reconnected and now the car runs normally. 

PCV hose. If it leaks, you get a post-MAF air leak, which will cause running issues.

 

You can replace it with generic hose, but be sure it is PCV rated (oil and vacuum resistant. coolant hose will break down and become gummy).

6 hours ago, Numbchux said:

PCV hose. If it leaks, you get a post-MAF air leak, which will cause running issues.

 

You can replace it with generic hose, but be sure it is PCV rated (oil and vacuum resistant. coolant hose will break down and become gummy).

I have a feeling the hose I got is not oil resistant. I think it said “Heater Hose.”  So probably I will need to get proper oil resistant vacuum hose.