Can someonesuges recommend something to spray on the vacuum lines to test for a leak?

Thanks
Doug

 

try a cigar!

Finding Engine Vacuum Leaks With A Cigar - YouTube

 

Thats one way. A good general rule is if in doubt, throw it out. If the hose seems suspect, it probably is. A common place to break is in the semi-rigid lines where they wrap around the back of the engine, where the semi-rigid lines pass throughout the firewall to the defrost and blend door controls, or right nest to the check valve.

Also the evap hose that runs from the purge canister to the throttle body tends to rot and is a common failure point. The PCV valve and elbow are also problem areas, check the PCV valve, and for the most part, stick with high end replacement PCV valves like Motorcraft or AC Delco.

Must harder to find are the upper and lower intake plenums. Some will go for hundreds of thousands of miles without an issue, but the average failure mileage for the intake gaskets or an injector o-ring is about 150-170K miles, though this does depends on which engine you have, the 4.0L is more prone to have gasket failure than the 3.0L When replacing those gaskets, it is best to go all out and replace both the upper and lower gaskets and all of the injector o-rings.

The cigar method does work, but obviously not a good idea if you don't smoke. If you do smoke, its probably a good idea to quit, but if you are gonna get lung cancer, you might as well find a few vacuum leaks along the way.

 

best way i've found from experience is visual, pull the hose out-bend and flex. use strong reading glasses. any sign of hose decomposition and cracking. time to replace.

smoke test does not catch the cracked hose intermittent leakers that only leak after the engine is heat soaked and the hose rubber expands.
you'll also see any cracks and decomposition in the ends which along with bends are the failure points. end often will be intermittent sucker until fan wind flexes the hose opening the cracks.

mechanics like the smoke machine test because it looks so high tech and they can charge a fortune for it. plus they get all those repeat intermittents back again for another $200 try.

time for mechanic gloves and hose pulling.
use high quality gas rate neoprene or vitron hose, no cheap stuff or you'll be doing it again in a yr or 2. the molded hose from the purge tank system to the throttle body is buried and often overlooked because of all the work to take it out. flex the bends in it, my failure point that took 2 years of chasing to find because I was lazy and didn't want to do the hard work analysis to pull it out and completely close examine it.

thank god we're out of the 90s and all the vacuum engine/powertrain control garbage. works great first 5 years then it's a mechanic's shop gold mine

 

I don't own a smoke machine, but I really like them. And I have never been charged anywhere near $200 for a smoke check. The machines found leaks that would have been difficult or near impossible to find. The only problem is the machine will often only find the worst leak in a system that has multiple leaks. For leaks in the intake gaskets, or injector o-rings, the smoke machine is often the only method that will find them. On my '97, I had a massive leak that you could hear, but couldn't see. When we hooked up the smoke machine, it was immediately obvious where it was. In mine there ended up being two leaks. One was the o-ring that sealed the EGR tube to the up err intake, the other was one of the gaskets where the upper intake meats the lower. Neither leak could really be seen otherwise, in fact we used the fluorescent smoke, and you could see the trail on that one, you otherwise couldn't see the smoke. Once we spotted the EGR tube leak, which was the big one, I wanted to try the famous starter fluid spray test, which will supposedly increase idle. So I sprayed all around that leak, and guess what. That test revealed nothing, no change whatsoever. A broken hose might have revealed more of a change, but most other leaks just won't pull in enough fluid to make any detectable difference, making the test almost worthless.

 

what i hear is that there is no foolproof way to find vacuum leaks, one way might work with one type of leak, and another won't. I think experience with a particular vehicle is the fastest way to find them, otherwise it's mostly guesswork, trial-n-error, stroke-of-luck, amen, ad infinitum.

I would like to know how many vacuum hoses there are in my 4.0, where they are, and believe me, I will replace them all!

 

There is on hose that goes to the brake booster, one to the PCV valve, one that runs to the fuel pressure regulator, and one that runs to the vacuum reservoir/climate controls. If you have an older model, there will also be a hose that runs to the vacuum modulator on the transmission.

In addition, there is an evap hose that runs from the purge canister to the underside of the throttle body. I think thats all of them.

 

thanks, I will start to find them one by one; I am familiar with the purge canister hose located below the air filter housing; When I was installing the Putco headlamps wiring harness I removed the air filter box and noticed the hose was almost disconnected from the canister; the hose has a formed "L" shape, but it is stretched and very deteriorated, won't stay connected. I put a small clamp temporarily.

 

There is one more if you have an EGR valve. It runs from the vacuum tree to an EGR solenoid, and then to the EGR valve itself. The computer uses the solenoid to allow vacuum to operate the EGR valve.

 

that's exactly what I can't find: the vacuum tree or "tank". where is it??

I don't have the Ford Shop Manual, looking for one. there must be a diagram showing the routing of all vacuum hoses.

 

The Vacuum Tree on a 3.0L is best found through the Doghouse opening with a lamp. It's at Driverside, approximately at the depth of the Firewall. Looks like a Christmas Tree attached to an Oil Wellhead..often seen so in Texas A vertical mounted Pipe with Fittings all around.

Schematics for the Vaccum System are attached inside the Hood on a Sticker.

 

thanks again waterbear! yes I know about the label on the hood showing the vacuum routing diagram, but I can't understand it. I'll look through the doghouse with my cowboy hat, maybe I'll get lucky and see a Texan girl in there !

 

If you are going to replace vacuum lines, you might consider replacing them with fuel lines instead of vacuum lines. Fuel lines are built more sturdily, and will better resist gasoline (obviously!), so it will work particularly better for that evaporation canister return line.

 

ok, sounds like a plan, the only concern I have is the L shaped formed hose that connects to the bottom nipple of the canister, I don't want to install a new straight hose that ends up kinked. And I noticed there is another L shaped formed hose near the coolant temp sensor, in a very tight/difficult spot under the intake which also is very lose, obviously old and stretched.

 

How many inches of Vacuume should a 1999 F350 Superduty have.
I measured 19 inches cold and 18 after the engine was at operating temp.