Vacuum Hoses 101

[redcoupe86]

Here are some pics of some vacuum lines I am dealing with.

Im trying to determine if the hose I have labled Hose #1 is the same one you see in the engine bay in the pic below. The one in the engine compartment goes to the charcoal canister. It is dryrotted and has snapped. I will need to run a new line, but i do not know what route this line takes.

Can someone explain how to change this line, and tell me if indeed it is Hose #1?

[dentist90]

Your Hose#1 looks a lot like my windshield washer hose. If you follow it up the fender and it turns in toward your "squirters", it probably is yours, too. Try pinching it off and see if your washer still squirts. I'll have a look at mine and see if I can figure out what you're broken hose is.

[redcoupe86]

the windshild wiper hoses are the ones below the one i have the arrow pointing too.

I just came back frm inside the garage and it appears that this line (hose #1) connects to the brake fluid reservoir.

The only thing i've found on the charcoal canister in the Bentley is one little diagram that shows the line running to a evaporation chamber to the charcoal canister.

If i look under the left front fender I see two black canisters. One large one that is under a smaller one. Im assuming the evaration chamber is the one on top (i have no idea what the big one below is for?), however i cant figure out which line is the one coming from the the charcoal canister. If i look in the trunk there is an expansion chamber (a whitish plastic rectangle thing) that has a line from the tank, a line that goes to the filler neck and a line that connects to a hard metal line that seems to be welded to the body. That metal line then goes behind the fuse box and then I don't know where it goes - can someone clue me in hear - I think it connects somehow to the evaopration chamber. And Im still trying to find where the charcoal cansiter line connects to all of this.

[shbop]

The large one is probably your washer fluid resevoir.

[dentist90]

Ya, that top black box is the fuel expansion tank and I'm sure it does connect with the smaller white vent box in the trunk. The larger black box below it is the windshield washer reservoir. That hose #1 is a brake fluid overflow hose. I can't trace mine all the way, but I believe that just drains under the car somewhere... allows for thermal expansion of brake fluid. Still looking at my car to see if I can help

[redcoupe86]

the diagram on page 240-23 of the Bentley shows the diragram of im talking about. It shows the charcoal canister going to the evaporation chamber, i just cant figure out where that line conncects and then runs to get to the charcoal canister (CC). Does the line from the CC run through the center tunnel or does it just run under the car somewhere. I followed the line from the CC into the engine compartment, then it the line goes behind the curise control throgh or behind the firewall somehow. Thats where I loose it. . .

[JTL]

I had a u shaped rubber line fall out. I think it goes to the back of the throttle body? Anyone know what it is.

Thanks, jt
-84 targa

[dentist90]

RedCoupe,
I can see where you're at. I traced mine around behind the air filter and across the firewall to the left rear shock tower, where it dives down into a place I shall call 'The Abyss'. Unfortunately I can't see if it connects to a hard line running under or thru the chassis or if it stays the same material (GOD I hope not). It must obviously draw from the evaporation cannister somehow. Try taking your left front wheel off and see what hoses are coming from the cannister. Its too dark for me to see right now, but my curiosity's got me. I'll take a peak again tomorrow. If all else fails, maybe a splice to the existing hose and hope for the best?
PS: that tube sure broke cleanly... I thought the fiber wrap would fray or perhaps keep the brittle tubing from completely falling apart!

[dentist90]

JTL,
A picture might help. I have a vacuum tube going from behind the throttle body over to the vacuum diaphragm seen in redcoupe's 2nd photo (on top of that oil breather hose). It's cloth covered all the way, though. Is that it?

[redcoupe86]

I felt arond this morning and I think I "felt" a "U" shaped vacuum line too behind the throttle body - it come out of the TB and then goes right back into the TB about 2" or so below the one it came of. I have no idea what this is for.

Originally posted by JTL
I had a u shaped rubber line fall out. I think it goes to the back of the throttle body? Anyone know what it is.

Thanks, jt
-84 targa

[redcoupe86]

i know, it just snapped in two, with very little force. Curriously enough all the other hoses arn't in near this bad of conddition. But Im going to Autozone today and replacing as many as seem feasible.

thanks for your help!!!

[i]
PS: that tube sure broke cleanly... I thought the fiber wrap would fray or perhaps keep the brittle tubing from completely falling apart! [/B]

[JTL]

The one I'm talking about is very small diameter, even smaller than one would use for brake bleeding. It is black rubber with no cloth cover.
I decided to replace the stock airbox with a k&n cone, which left the crankcase breather hose unplugged. Is there any harm is this besides a possible mess if you overfill oil?
Sorry, don't mean to get sidetracked on the original thread. I also have some unplugged cloth covered lines in the engine comp.

Rednine,
Do you have the cruise control actuator installed. Might hose#1 in the back belong to it?

jt

[dentist90]

JTL... looks like that small U-shaped hose does go behind the throttle body. Mine is exactly as redcoupe descibed. Need a small mirror to see back there.

[redcoupe86]

Well, 5 hours of work cleaning and replacing all the vaccuum lines I could. Never ended up finding where the hose runs off to, just ended up splicing it. Whenever I drop the engine I deal with it at that time.

JTL: By not using the breather hose the gas fumes from your tank wont get pulled through to the charcoal canister. From what I've read this will cause you to have a smell of gas you park the car. This doesn't sound like a good thing to me, but if you park in a well ventilated area or if the smell isn't that bad then it might be alright.

Hose #1 is definately the break overflow line - I traced it down to confirm that.

Originally posted by JTL
I decided to replace the stock airbox with a k&n cone, which left the crankcase breather hose unplugged. Is there any harm is this besides a possible mess if you overfill oil?
Sorry, don't mean to get sidetracked on the original thread. I also have some unplugged cloth covered lines in the engine comp.

Rednine,
Do you have the cruise control actuator installed. Might hose#1 in the back belong to it?

jt [/B]

[Bill in OKC]

Originally posted by JTL
I had a u shaped rubber line fall out. I think it goes to the back of the throttle body? Anyone know what it is.

Thanks, jt
-84 targa

I believe that is a thermal vacuum switch that opens when the engine is cold. The vacuum is then directed to the Ambient air valve pictured above (just above the yellow oil filler cap) and this is somehow related to starting the engine in cold weather.

[JTL]

Thanks Bill. These vac lines have always been a mystery to me. The car seems to run just fine without some of them connected. However, everything in a p-car has a function.

jt

[2ndTARGA]

Redcoupe86:

I ran across your old thread because I had the same question and because you said you never found out where the small broken line went. (the one that dove down into the left rear corner of the engine compartment.)

I had the same disconnected line (brittle and broken) and followed it to the rear bulkhead of the shifter tunnel. There, just above the fuel lines where you can't see it, it is clamped onto a steel nipple. I'm guessing that the other end of this small conduit is what you found near the fuse box in the trunk. So, it's no-doubt the vacuum line from the canister system to the engine.

Since a PO cut my line off, my question still is, where is it supposed to connect to the engine?

Help anyone? I've checked all the workshop manual diagrams with no luck.

Thanks,

Ron

[randywebb]

People are calling these vacuum lines, but some of the ones being discussed are NOT - they are gasoline vapor lines and ordinary PVC will NOT be safe in this application.

There are threads on what to use - search will pop them up. Be sure to use the correct type of hoses; you don't want the things dissolving and venting gas fumes towards the battery terminals...

[2ndTARGA]

Very good point!

You're right, the line I'm asking about is actually a fabric covered fuel line - approx 5/16" O.D. From the charcoal canister to the (still unknown to me) connecting point at the engine.


Ron