sealing vacuum lines to fittings

[Robert G.]

Hello,
what is recommended for sealing vac lines to fittings? I want to prevent vac loss and in some cases bond loose connections.
I think they used something during assembly on least some fittings.
I have heard of people using silicone spray, and also RTV
Thank you

[Michael L.]

Re: sealing vacuum lines to fittings

FWIW I used a LIGHT coat of RTV. I placed it on the male end of connections and not close to the tip. I believe this type of application prevents any sealant from entering the tube and clogging the line.

Mike

[Robert G.]

Re: sealing vacuum lines to fittings

Thank you Mike, the application tips are very helpful too

[Patrick H.]

Re: sealing vacuum lines to fittings

Most connections require nothing, even with old hoses, at least in my experience.

However, I have found that using a piece of heat shrink tubing (black) on the hard object will increase the diameter just enough that an old hose will now fit just fine. Personally, I do not trim old hoses as many of them don't have extra length, and using the heat shrink trick works just as well without permanently modifying the hose.

[Duke W.]

Re: sealing vacuum lines to fittings

Silicone spray or a very light film of silicone grease will keep rubber hoses from seizing onto fittings. RTV is a weak glue and I don't advise using it on hose connections.

On heater hoses you want to make sure that the clamp is inside the "upset" on the nipple, or the hose could blow off. It happened to me once. Live and learn!

You don't have to worry about vacuum hoses blowing off. That's why they typically have no clamp of any kind, and as long as they fit snugly on the nipple they won't come off without some outside mechanical force.

Trying to remove old heater hoses from heater core nipples is a sure fire way to cause a leak at the nipple solder joint, Then you will have to remove the heater housing, to repair or replace the core, which is NOT a fun job. With a thin film of silicone grease, once the clamp is off you should be able to twist and pull the hose with very little force until it slides off the nipple. If the hose won't co-operate, slit it longitudinally past the end of the nipple and peal it off.

Heater hose is inexpensive and easier to replace rather than removing the heater housing and repairing or replacing the heater core, and if you don't know how old they are, replacement is a good idea if they have to be removed.

Duke

[Patrick H.]

Re: sealing vacuum lines to fittings

You don't have to worry about vacuum hoses blowing off. That's why they typically have no clamp of any kind, and as long as they fit snugly on the nipple they won't come off without some outside mechanical force.

Duke

Duke,

It's not them blowing off, it's that they can seal poorly after 50 years. The rubber hose stretches to the diameter of the solid connection, they harden to the new shape and they leak vacuum. I think you understand how bad a vacuum leak can be on these cars, even if small.

RTV as glue is just fine if it seals; as noted I do it in other ways.

[Duke W.]

Re: sealing vacuum lines to fittings

As long as a vacuum hose fits snugly on the nipple they should be okay to use. If the hose ID has stretched, it probably also shows on the outside via a larger OD or cracks.

At least on C1/2 Corvettes there aren't than many vacuum hose connections. C3s have more and modern cars are a nightmare.

I recently had a "check engine" light on my '91 MR2, ran diagnostics that told me it had something to do with the EGR system. A visual inspection showed a disconnected hose on the vacuum switching valve that controls the EGR valve. The hose was in fine shape and fit snugly back on the nipple. I don't now how it came loose, but I must have somehow inadvertently knocked it off doing something else in the engine compartment

Duke

[Robert G.]

Re: sealing vacuum lines to fittings

Thank you Patrick and Duke. Helpful insights !

[Terry M.]

Re: sealing vacuum lines to fittings

Remember, whatever you choose to use, if anything, will have to be removed at some point down the road. Whether you own the car, or someone else has it. So resist the temptation to use something permanent and think twice about something that may be semipermanent. After 25 or 50 years what today is semipermanent can be much more permanent, Think long-term. We are only custodians of these cars for a brief part of their history. I suggest you try to be the best keeper you can be.

[Robert G.]

Re: sealing vacuum lines to fittings

Well said Terry.
Thank you