Replacing Vacuum Hoses --- Tips & Techniques

[Wade Nelson]

I found myself replacing a # of rock hard (baked) vacuum hoses yestiddy, and thought I'd share a few tips.

The # trick is NOT to bust off the "barb" or nipple it fits onto. Some of these small plastic pieces are ir-replaceable.

What I'll do is take a tubing cutter, and cut the old hose in half 1" away from the barb. Now i'm only fighting with one end. Next I'll take a boxcutter, and slit the hose ALONG the barb, in two places, 90 degrees from each other. If it's a plastic barb, be very, very careful.

(Try also never to pull the boxcutter TOWARD yourself, some nasty cuts can result. Ask how I know this...)

Usually with two slices, you can then TWIST the remaining piece of hose off the barb.

I have something similar to an icepick, but with the last 1" bent 90 degrees, that I use for radiator and other large diameter hoses. You stick it between the outlet and the hose and run it around in a circle, breaking the rubber loose from the outlet. Best tool in my box -- NAPA sells 'em.

I'll grease most barbs with "Silglide," a pure silicone lubricant available from NAPA, before trying to slide a new piece of hose on. If your local store doesn't have Silglide, try your local adult video & toy store. Adult silicone lube will work just as well. Beware, silicone in any form can contaminate an 02 sensor, so either use it sparingly, or just use petroleum grease (or jelly) if some of it is possibly going to end up in the intake of the engine. AC/Heater control hoses --- no worry.

Usually brittle hoses crack right at the end, and there's always ONE I don't have the right size tubing to replace. So what I'll do is cut off the last 1", and just slide it down a bit until I can get to the parts store.

When you go to the parts store, they've got several varieties of hose:

Vacuum hose

Coolant hose

Emissions hose

Fuel hose

Fuel Injection hose (green, low -emissions)

The two most common mistakes are using 5/8" coolant hose for emissions applications, like the PCV line, and paying for 50-100 psi fuel injection hose ($7 a foot) if all you need is fuel hose (carbureted) $4 a foot.

Coolant hose can't withstand heated, fuel and oil laden fumes. Sometimes that's all they've got in the larger sizes and you use it anyway until you can get what you need.

I see someone selling complete vacuum hose kits on ebay, in neon colors. Like wow, man! He claims to have vacuum diagrams for all the different Z models, Federal vs California, etc.

I currently have a problem with my AC going to the floor vents whenever I romp on the accelerator. Most likely this is a cracked hose, or leaking vacuum motor somewhere under the dash.

The way I intend to locate it is using a smoke machine, which most garages today have. These pump smoke in at a very low (1-3 psi) pressure, and you simply look for the leak as you dial the heater control to the various positions. You can also use a cigar/cigarette and someone with big lungs accustomed to exhaling large quantities of that *hit!

Hose clamps come in 3 primary varieties, the wire-style originally on the Z's for those purists doing restorations, the ubiquitous stainless steel screw clamps you see under most hoods, and specific FUEL INJECTION clamps for FI lines. These do a better job of compressing the entire hose than the screw clamps. they're worth the extra buck or two compared to an engine bay fire, imho.

HTH.

[stiletto660]

Hi Wade,

I would check for a cracked hose at your vacuum tank chances are one of the 4 Vacuum hoses has a length wise split in it. I have seen this on many occasions and about 1/2 the time the split in the tube is not visible unless you remove it and bend it. The crack or split is usually within 1/2" for the end of the vacation line.

[Wade Nelson]

Hoses were ok, even so I "freshened" the ends by chopping off 1/4".

I put an aftermarket 1-way valve between the tank and the dash. That will help me determine where the problem is. I suspect the 1-way valve at the tank itself is stuck open, or intermittent.

[Wade Nelson]

Just to finish this thread out the leak was two-fold, one, a leaking vacuum actuator under the dash, and the hose supplying vacuum from the motor repeatedly cracking.