Greetings again Bfenty!

Silicone oil on them will make them last twice or three times as long as normal. I oil down the entire line outside and then both ends are soaked as well. I have been doing this on both of my Corvettes, it helps since my C3 has like 75' of vacuum lines in it and this way they look as new as the day I installed them in 1993. You want to be careful choosing a material to coat them with, certain petroleum based materials will make them break down even faster. Do Not use Petroleum Jelly or anything like that as it affects the life of the part and destroys rubber slowly. Even coating them with Armour All will work for a while but not last like the silicone does. I would imagine some of the tire shine products might even work as they are designed to last a while.

A friend who works for Xerox gave me a bottle like thirty five years ago and I still have some. I understand that Home Depot carries the silicone oil if you can't find it easily.

I wish you and your family a very Merry Christmas!

Chris

 

What about dielectric grease? I have a small tub that GM sells.They also suggest it for weather strip application. Ron B.

 

 

I apply it using a small rag that I wet with the oil and then I just coat the outside of the lines with the wet rag. You can usually reach every where but for those hard to reach vacuum lines I use a pair of 12" extended needle-nose pliers that hold the rag for me. If I have to I just spray the stuff onto the tubing if it is buried under the hood. The tire shine will work fine for most vacuum lines as well, spray it on let it sit for a minute and wipe off the excess. The tire shine works like silicone oil but does not last as long. Does it attract and hold dust under the hood?

Now I understand why your engine is so pretty... A little cleaning now and then makes for a very nice engine compartment. I have seen engines on this forum that look better than they did when they were made! With the engine sitting there when the hood is up sure makes it easier to clean and work on. I love the C4 models, I wish the newer cars let you have access to the engine like the C4's did, it would sure make owning one less expensive.

Good Luck!

P.S. The die-electric grease works great as well, if you have some feel free to use it, my only problem is that it holds dust and dirt to the grease if it is too thick, use sparingly but get good coverage if using Die-electric Grease!

 

Dielectric grease is silicone grease. Use it on rubber but keep it far away from any sensors.

 

OK, why don't you want to replace it? all of it is around 30 years old, and time is taking it's toll. I replaced all my vacuum, fuel emissions, and even the windshield wiper fluid tubing a couple years ago - well worth the effort. don't do a band-aid fix for something this simple. too much of the car's operation and performance depends on a good, leak free, vacuum system. just my 2-cents -

 

I agree with this and for some reason I am dreading the job on my LT1... maybe because I've been doing more work to the car lately... maybe because some of the spaces and access is so very tight.
I hope some of the lines through the firewall are solid enough to just cut and splice with new tubing.

 

 

to correct my previous post, "all tubing under the hood, and one line to the brake switch." never had my dash apart. can't recall how long it took - did it a couple years ago. i was in the middle of a minor mechanical restoration of my 85, and it was included within a bunch of other tasks. overall, i spent about (part time) 18 months - bumper to bumper and that included a valve job. cost for vacuum lines - not much. seems 90% of the lines are 5/32" tubing. i bought a 50 foot roll (gates vacuum) on fleabay - seems it was around $20 - used about 1/2 the roll. (fuel/oil resistant) fuel and emissions, by the foot (at NAPA). windshield wiper lines - 5/32" from the 50' roll. other sizes were purchased in 10 ft lengths - i'm thinking about $5 each. you shouldn't have to take the dash apart. the only significant piece is the cruise control line to the brake switch, and that can be optional. you don't have to do it all at one time - break it down to individual pieces, and replace one section at a time. remove one piece, measure, cut, and replace - plug and play. if it takes several days or weeks - so be it. the nice thing is the car won't be in-op for any length of time while you're doing this. you can do one or two pieces at a time, and still drive the car. i would say, you could knock it out in a weekend without much effort.

https://www.ebay.com/itm/Gates-Vacuum-Tubing-Non-Reinforced-27042-5-32-X-50-ONE-PER-PKG-27042/132600835354?epid=1523082811&hash=item1e dfa02d1a:g:MDwAAOSw9DJa465E:rk:11:pf:0

most of my rubber deterioration was around charcoal canister vacuum control lines, purge, and fuel emission system. my engine vacuum lines were a bunch of band aid fixes from over the years. everything under the hood is configured as new, and hopefully, will last for years.

 

 

This is probably as good a place as any to ask the question: is silicone vacuum hose a good or bad idea vs the standard stuff? I understand it's a no-no for oil lines, which means it's off limits for PCV lines. But what about dry vacuum lines?

 

 

Joe C, is the fleabay hose you linked the same size as the lines off the plenum? Stiff plastic? I had a hard time finding lines that were the right size, got stuck with some silicone in a couple of places, bright red to boot.

 

fairly sure about this - the hard plastic lines are the same as the rubber, but, the plastic stuff is O.D. and the rubber tubing is I.D.. when I did my 85, I was lucky to find a NOS assembly (rubber/plastic) that connects the A.I.R (smog pump) control solenoids. the assembly under the plenum to the EGR solenoid , I ran across an excellent used assembly. I have somewhat experimented with fabricating the hard plastic tubing sections with brass tubing and a small, hobby, tube bender. it looks like it will work, but I don't need anything at the present. maybe down the road. I didn't have much luck fabricating the bends with plastic -

also, vacuum nipples, tees, and elbows were purchased at o'riellys in kit form. there were a few places where I had to get creative. one section where the hard plastic goes thru the firewall for the HVAC control panel. I had to adapt the plastic to rubber - the section the goes to the 2-port check valve for the curise/HVAC. i used the 5/32 rubber over the plastic, and for protection, i took a section of 7/32" (or 3/16, 1/4" - ???) rubber tubing and made a slip fit, protective sleeve over the remaining plastic. if someone has to get into the harness that routes the HVAC plastic, that's going to be a problem, i tried to give it some extra protection.

 

PCV & brake booster hose will deteriorate on the inside of the hose. Replace with 11 / 32 vacuum hose available @ NAPA by the foot.

Rubber products continue to harden with age suggest changing the hoses. Vacuum hose is available in 50 ft rolls buy on line its cheap.

Good luck

 

I'd just knuckle down and change it all one day if it is that old.

Could it be that the ECM is adjusting in closed loop but cannot in open loop? Just a SWAG.

 

Not if they aren't coming from something that has oil in it.

 

Yeah that's exactly what I am thinking, since 140 degrees is when it goes from open to closed loop (I did my homework). Just curious if the first culprit to look at would be vacuum lines or not. I agree that changing out old rubber is probably a good idea regardless of whether it's acting up, just don't have a ton of time to play with my toys these days so I have to prioritize.