question about leaking vacuum hose ID?

[EMBPilot]

There is a large vacuum hose that plugs into the back of the J boot... it is only a few inches long and very thick rubber. While installing the new jboot on the car i noticed that just after the clamp on this hose, the hose is badly cracked.

the hose runs from the jboot back (under the intake manifold), to a large round circular thing. The circular thing sits just behind the idle stabilizer valve. this vacuum line plugs into that round thing.

- whats that round thing this line plugs into?
- what hose is this?
- do you think i can change this hose without having to remove the intake manifold?

can i find this hose locally (just a generic rubber hose) at advanced? or is this something i should get from pelican?

[Razorback1980]

Hey Kevin,

The large black thing if I understand everything correctly is the oil/air separator (also where you put oil in your car) and this is why it's there. Piston rings don't seal all the compression in the cylinders as the pistons come up on compression....some of it seeps by the rings and goes into the crankcase area (oil pan). If the crankcase were unvented, the pressure would build up and have to blow gaskets somewhere. The oil air separator is the "vent" that lets this escaped compression out of the crankcase. Because this air also has unburned fuel (it escaped the cylinder before ignition), they attach a hose to the separator and send the escaped compression with the unburned fuel back through the engine and burn the fuel at the same time venting the crankcase using a vacuum source. This helps reduce emissions on your car. Older cars used to just vent it to the outside dumping unburned fuel into the air...so I've read. So, what was your question again? Sorry, I know you didn't ask for the long lecture. Anyway, this hose is the crankcase ventilation hose. I'm not sure if you can change it without removing the intake or not but I believe you can. The problem with the hose (if I remember correctly) is that it has a 90 degree bend in it just before the separator. There are several options to fix the hose. You can go to the local auto parts and they can sell you a generic hose and a generic hose with a bend and you can buy a splice and put it all together and MAKE a complete new hose. When I priced all that out before, it was cheaper to buy the right part. Because only the end is bad, you can also buy a generic hose the approximate size of yours about four to six inches long and a small splice and replace only the end leaving the original 90 degree part...silicone the splice to prevent leaks. It's not that the hose is special in any way, it's that it has a 90 degree bend in it and you can't allow the hose to have restricted air flow. I am guessing the cheapest to the most expensive is like this...1)replace only the end 2) replace with OEM part 3) replace with generic parts. I am not sure of those prices, but I'm guessing that is how it would go.

Here is another thread on this same hose along with a diagram showing how it all fits together. I was wrong about the two piece part and I never did get an actual part number from PET, so I would just call Pelican. Zero mentioned an interesting fact in all this...the hose changes sizes from one end to the other.

Crankcase Breather Hose

[p-talk]

Thanks, I was just wondering the same thing. I found this hose disconnected last night at the separator while replacing the O2 sensor, so I put it back on.

[Techno Duck]

Take the intake manifold off. Getting at anything underneath the intake is a pain in the ass with it still on, i couldnt imagine cutting off the compression clamps and putting on hose clamps with it still on. Take the intake off and change every hose under there for peace of mind. There aren't to many. Change the air oil seperator o-rings while your at it and the heater control valve if you dont know when it was last changed. Pulling the intake really isnt to bad of a job and there are a dozen things that can be addressed while its off that will make your car run better.

One of the annoying things that Porsche did was they did not put a barb on the end of the air oil separator.

[EMBPilot]

Tom, Awesome write up!! thanks so much to both of you! i noticed after looking closer that it was attached to the oil filler neck and that really peaked my curiosity. it all makes sense now.

That hose has some minor cracking. However, after looking closely at the three way elbow on the front bottom of the jboot, the plug on the end of that elbow was REALLY bad. One side of it was cracked all the way open. I replugged it with a new plug, and put new hose clamps on those fittings. After that minor fix, and the new jboot the idle has smoothed out considerably. theres still a very minor hunt, maybe 25 rpm or 50 at the very most. but its really calmed down from what it was before. And I can swear I think I can hear another vac leak from someplace, it’s a very faint hissing. I put a funnel up to my ear and searched but just couldn’t find anything that wasn’t plugged in.

I adjusted the idle per clarks garage to right around 950, when the jumper is on the test plug, the idle is super smooth. Once i remove the jumper the dme for some reason lowers the idle to just around 800. ? not sure why. maybe i need to readjust the idle after i fixed the above hoses again.

another point of interest for today. I shot some brake cleaner into the vac line that goes into the Idle stabilizer valve. the idle would go up a lot, and stay there. then id smack the ISV a few times and it would come back down to normal over a minute or so. Im not sure if thats an indication that the ISV may be sticking or on its way out. clarks says to check it to clamp off the out going vac line from it but its impossible to get to, i cant even tell where it goes to reach it.

[Razorback1980]

I would say that any man that can change timing belts could easily do this job. Loosen the bolts and just swing it back and tie it up out of the way and just start replacing hoses one by one until you have them all replaced. Lindsey racing has a great silicon replacement kit, purchase the hose you mentioned from Pelican along with intake gaskets and I think the rest you could get locally. Clean the mating surfaces of the intake and head after replacing hoses and put the bolts back in. Anyone with your mechanical abilities could do it blindfolded! More good advice from Techno Duck.

[Techno Duck]

If you think the ISV is bad but do not want to buy a new one, you can try shooting carb cleaner into it. Many people have had success with doing this. I personally felt the $150 is peace of mind to just change the thing.

I have since pulled the intake manifold so many times i would probably just clean it out if i ever had idle problems again.

Consider rebuilding the throttle body while you have everything apart. Bruce Arnn has a nice kit with all the o-rings you need.

Also buy a good assortment of hose clamps as you will need many of them. Almost every vacuum hose uses a one time use compression clamp to secure it on the barbs.

Also a good time to change the funky size 15/32 (i think thats the size) hose that comes off the brake booster onto the venturi thing-a-mabob. That hose is always really brittle i find.

And of course with the intake manifold off, also a great time to clean up the grounds on the bellhousing. Just make sure you put a piece of duct tape over the bell housing window or you will be fishing out a nut with a magnet in a hard place .

[EMBPilot]

thanks guys, i'll look into all this.. ive been slowly stock piling away parts...
currently on hand i have -
intake gaskets
a working ISV from a 89 that had about 70K on it.
4 reseal kits for the injectors (i'll send them out to be cleaned while they're off)
the big ring gasket for the TB
i'll get that hose off pelican part number 944-107-187-01 (25 bucks), the vac kit from lindsey, send the injectors out and look into the kit from bruce. but bruces kit looks like i could easily screw up my 100% working TB, i may hold off on that...

what do you mean 'just swing away the intake manifold"? are there any tricks to getting it off easily or just moving it out of the way?

how do you clean gasket surfaces properly?

[Razorback1980]

Just pull the top back toward the fender to expose the vacuum lines. You'll figure out where it works the best. No tricks, that's the easy part. I use a gasket scraper, but you have to be real careful on aluminum not to take away the metal with it. Basically a razorblade scraper with a handle. You can also buy some solvent stuff that is suppose to help loosen it but I have never done that. It's not hard and you'll have no trouble with that part either. Just make sure it's clean when you are done. If you leave small pieces, it's a small bump in the sealing surface and may not seal although the gasket does allow for some imperfections. Suddenly your broken hose has turned into an all day job costing a lot of money! But it will be good experience and run better when you are done. It's nice to know there are no vacuum leaks. You could however just put a four inch piece of hose on the broken place for about three dollars and not have the vacuum leak until you get around to do all the other stuff.

[EMBPilot]

if i choose to just do this line for now, and just rotate the head out of the way, sounds like your just rotating it from the pax side towards the drivers side fender.

i dont think pelican has the hose im looking for...
part number i listed above only shows fitment for
Breather Hose from Oil Separator, 924S, 944 (through 1987), 944S, Each

and my cars an 88....

hard to tell if they are different. looks like they are cause that ones got a little bend in it. i think mine just has the 90 and its straight from there.

[Techno Duck]

944Online.com usually has everything in stock though i find they are a bit more expensive for select items. May want to double check elsewhere.

Pelican can probably special order them.

Try Sunset Porsche also. They are a dealer out of California, they are always very cheap in there prices. No markup at all. Google the dealer and they should show up.

[EMBPilot]

Thanks Jon!

i stand corrected, i checked on the car and although i cant match up measurements, the hose "looks" the same as the one pelican has under the part number i listed, only they show it up to 87, but it looks like the identical part.

[Techno Duck]

These are the o-rings for the air oil seperator
999.701.661.40 - 24x5 seal
999.701.613.40 - 20x5 seal

Two vaccum hoses on either side of the ISV
944.110.214.01
944.110.217.00

Hose on side of venturi tube
944.110.361.02

All part numbers are for the same hose that runs from the top of the air oil seperator to the j-boot.
944.107.311.00
944.107.187.01
944.107.311.01
944.107.187.02

Which one you need is beyond me, may want to double check with your engine code.

[EMBPilot]

Jon,
Thanks for the help, i ordered most of the stuff above, with the execption of the seals, im not sure that i need them because im just going to be doing the hose to the filler neck. i dont think that needs seals correct?

the hose for the breather tube i got was 944-107-187-01-M100 it looks identical to the one on my car. hopefully it will work. i guess i'll find out when it gets here.

Jon did u install the lindsey silicone vac kit on your car? i just ordered it. searching the board there were a few posts to people that were saying the porsche stuff was better, which i find tough to swallow considering how old the stock stuff is.

[Razorback1980]

The seals go between the oil air separator and the block. There are only two bolts that hold it on and they are easy to replace which is why he is suggesting that you replace them if you are already there. You may want to just call Pelican in the morning and talk to a parts guy who should be able to tell you if that hose will work or not so you don't have to wait until you get it to find out if it's wrong. I'm not sure why PET makes the stupid hose so hard to figure out but when I tried before, I remember it being almost impossible to tell which one you need. I'm sure it will all work out well for you.

[Techno Duck]

Kevin, like Tom said you dont need the o-rings, but they are less than $10 for both and only 3 bolts away from changing them with the intake manifold off. When they harden the seals shrink. This allows air to leak past them which for some reason (i never figured this one out) causes huge amounts of oil to get sucked into the j-boot. Pull your throttle body off and you may or maynot see it covered in oil. Your typically going to see the oil burning off only at higher RPM.

This is how mine looked..



The o-rings i took off litreally crumbled into pieces as soon as i tried to remove them with a pick. They were also leaking bad enough i had a substantial leak from the drivers side rear of the oil pan.

I do have the Lindsay Racing kit on my car. The reason some people do not like it is because the hose can kink easily. This isnt a problem as long as you watch how you route everything.

The stock stuff isnt bad..and to tell you the truth would probably cost you the same amount buying the packs of 3ft plastic vacuum tubing from Pepboys at $5 each. You would probably need 3-4 packs of the tubing including finding the y connectors and t connectors. I figure the $25 (or whatever it is) for the Lindsay kit wasnt a bad deal.

Also consider checking the heater control valve. They tend to crack with old age and it will destroy your clutch as its right above the bell housing.

[Panzer909]

EMBPilot, I have what looks to be a massive leak in that area as well. Is this what you are talking about?:

[EMBPilot]

thanks guys,
Jon, the boot and TB intake were clean of any oil, the only sign of oil was around the lip of the vac line that goes back to the filler neck. the seals on the filler neck look good its pretty dry all around there. there is however a small leak though several inches infront of it though leaking down the pan

i liked the lindsey kit cause it comes with most of the connectors i'll need, all in one stop, and it was just 30 bucks.

it depends how i feel going into this, whether or not i'll take the intake off and dive in, or just try and replace what i can without taking the -intake- off. i have two sets of intake gaskets here, including the big rubber ring that goes onto the TB to intake. im going to play it by ear but i think i need to change out the suspect hose that we've been talking about.

right now the car is running well (knocks on wood), i know once i take the manifold off it wont move from the garage for at least two weeks.

[Razorback1980]

Kevin, Please do not remove the head only take off the intake manifold. This whole procedure will only take a few hours. I'll send you some pictures that will hopefully help clarify this.

[EMBPilot]

why did i say head? i didnt mean that! but thanks for calling me out on it tom!! been a long day!