Skip to main content ↑ ↓
Topic: Find air intake system leaks (Read 907 times) previous topic - next topic

Find air intake system leaks

We would like find air intake 'plumbing' leaks between air filter and intake manifold.  While engine is idling, we figure that spraying something flammable along the air flow including intercooler, if there is a leak the RPM's would increase.

What do  you recommend we use to spray?  Figure that some things, like starting fluid is too aggressive/dangerous, but maybe only a little would be ok.

Any other ideas?

Re: Find air intake system leaks

Reply #1 –
W-D 40
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Find air intake system leaks

Reply #2 –
Yup, wd-40 is also sometimes used to start diesels that have air in the fuel lines, less harsh than ether but not recommend also. May bump the rpms enough to detect. Safety first, so maybe wise to do internal white glove or swab inspection starting out at the air cleaner.
Old Phart Phred, EIEIO
89 GV ored 36' #3405 300 hp cat 3208 ATAAC side radiator, mountain tamer exhaust brake

Re: Find air intake system leaks

Reply #3 –
Or, you can do it the backward way. Shut engine off, put a leaf blower into the air intake and bubble test the air intake piping joints. Probably only be a couple of pounds pressure but  should produce enough to make some bubbles on the  leaks.
Jim C.
coachfree, previous 1997, 1999, 2000, and 2003 Foretravels.

Re: Find air intake system leaks

Reply #4 –

How about using smoke?  I've heard of this technique being used in the HVAC industry, to detect air duct leaks.  Fill the intake with smoke, seal it off, and pressurize with air from air tank.  Smoke comes out the holes?

Smoke Emitter, 3 Minutes, PK5 - Security And Surveillance Products - Amazon.com

As an Amazon Associate Foretravel Owners' Forum earns from qualifying purchases.
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Find air intake system leaks

Reply #5 –
As long as these "air leaks" are not letting dirt in its a moot point, its not the same as a vacuum leak on a car.Make sure all the clamps are in good working order and if you really want to put double clamps on where possible.
96 U270 BUILD 4810
85 380SL
Drummonds TN.

Re: Find air intake system leaks

Reply #6 –
I can see using WD-40 would make an oily mess everywhere, so that doesn't sound like the best approach.  I figure some kind of spray, like starting fluid that evaporates and does not leave a residual, just being sprayed along the whole air intake system. 

Be nice to find pin holes, cracks that are not visible, but wait, air cleaner to turbo is vacuum, but everything after turbo is under pressure, so leaks would not be sucking in unfiltered air. 

The pressurized parts would affect performance, but not letting in dirt.  So I just reduced the potential location to the big pipes from filter housing to turbo.  Nice...

I did not pick up on what John was saying about if not letting  dirt in. . .  But now see he was referring to the pressurized  parts..

Re: Find air intake system leaks

Reply #7 –
Was referring to the side between air filter and turbo, if it just letting some air squeeze by no harm done, the clamps more than seal
a "leak".
96 U270 BUILD 4810
85 380SL
Drummonds TN.

Re: Find air intake system leaks

Reply #8 –
The air filter is sized so that it won't be a restriction to the engine so it won't show vacuum between the filter and the turbo ever. Maybe full load wide open throttle and peak torque but even then it shouldn't. The only way you could create vacuum especially at idle would be to cover the air intake opening gradually while watching a vacuum gauge and you wouldn't want to do it for long or with fingers between the block off apparatus and the housing you are blocking.

After the turbo you need real pressure, at least 20 psi and soapy water. You want to check how much boost your engine is exposed to and check it there. This is where you will find the small leaks at clamps and porous charge air coolers that are robbing power on those long uphill climbs.

I used to have access to some aluminum pucks some one had machines on a lathe to mimick the shoulder of the turbo and of the intake where the rubber hoses go on so you would just install them with the stock clamps. One pick was drilled and tapped end we fed it with an old spike valve and a gauge but any air regulator and a gauge would work.
Toby a 94 u280
Cummins 8.3
6 speed Allison
Exhaust brake


Adopted by Derek and Annabelle

Re: Find air intake system leaks

Reply #9 –
Maybe carburetor cleaner, but id ask a diesel mechanic first.
The selected media item is not currently available.
Lynn & Marilyn Sickel
Tollville, AR
1997  U320  40'
2021 Chevrolet Silverado pickup
Motorcader  17257

Re: Find air intake system leaks

Reply #10 –
Quote from: its toby –
The air filter is sized so that it won't be a restriction to the engine so it won't show vacuum between the filter and the turbo ever. Maybe full load wide open throttle and peak torque but even then it shouldn't. The only way you could create vacuum especially at idle would be to cover the air intake opening gradually while watching a vacuum gauge and you wouldn't want to do it for long or with fingers between the block off apparatus and the housing you are blocking.

After the turbo you need real pressure, at least 20 psi and soapy water. You want to check how much boost your engine is exposed to and check it there. This is where you will find the small leaks at clamps and porous charge air coolers that are robbing power on those long uphill climbs.

I used to have access to some aluminum pucks some one had machines on a lathe to mimick the shoulder of the turbo and of the intake where the rubber hoses go on so you would just install them with the stock clamps. One pick was drilled and tapped end we fed it with an old spike valve and a gauge but any air regulator and a gauge would work.
Say what? A restrictionless air filter, I need one of those. The only time there is not a vacuum between the air filter and the intake is at zero flow, aka engine not running. You need a manometer to measure the vacuum. I would bet you will see -2 to 3" even with a new filter at idle.
Old Phart Phred, EIEIO
89 GV ored 36' #3405 300 hp cat 3208 ATAAC side radiator, mountain tamer exhaust brake

Re: Find air intake system leaks

Reply #11 –
I have a Dwyer electronic manometer, will measure in a few days, engine full of old insulation now.
96 U270 BUILD 4810
85 380SL
Drummonds TN.

Re: Find air intake system leaks

Reply #12 –

Think he was referring to a new/clean air filter. The dirtier

they get the more vacuum there would be  post filter to

the turbo. One important thing he said was if you put a

board over an intake DO NOT get fingers under it between

the board and the intake pipe. There is tremendous force there

and can cut fingers off.

Carter-
   

Re: Find air intake system leaks

Reply #13 –
Yes dirty air filter would lead to some vacuum. Of course there will be some losses related to friction and turbulence and such. The point is unless you try something it without some how falsely creating vacuum you won't get enough suction to suck in the accelerant reliably also if you do create the vacuum with an aid you will still have to go slow as there can be some lag time for it to go through the turbo and piping to reach the engine.

Bottom line diesel shops pressurize the charged side to check for leaks and for the suction side visual inspect and check clamp torque. Have yet to see a diesel shop use an accelerant to check for the leak as the diesels don't have throttle plates to create the vacuum required.
Toby a 94 u280
Cummins 8.3
6 speed Allison
Exhaust brake


Adopted by Derek and Annabelle

Re: Find air intake system leaks

Reply #14 –
Restricting  the air intake port will create additional vacuum to enhance leak detection with accellerant.
"Not so  long ago we were a nation of risk takers, riding five million pounds of  thrust straight into space."  Joe Gresh
Chuck Pearson
1996 U295
2018 Can Am X3 TurboRS

Re: Find air intake system leaks

Reply #15 –
Our 1st MH, an SOB, had an 8.3. After driving it for a year and having everything on the road pass us on the slightest grade, we took it to a Cuimmin's shop in Charlotte. Dyno showed we were getting 60 to 80 hp to the rear wheels. Should have been 220 or so! Tech immediately looked for fuel problems. While sitting on the engine moving fuel pressure gauges from here to there he just happened to feel an air leak. There was a short rubber elbow between the CAC and intake manifold. The factory seam on the bottom of it had opened, dumping turbocharged air into the engine compartment. Back then it was about a $17 part. Seemed like a totally new coach after that!
Air leaks can can cause big problems....

Dick
Dick, '03 U320 40' Tag, 2 slides, Coach #6075
Full Timers
2009 Honda CR-V

Re: Find air intake system leaks

Reply #16 –
Feeling/looking for pressure leaks in the CAC should be part of what we do as routine maintenance checks, is very easy to do.
I for one would rather do it myself then pay a shop $100 an hour.Was he sitting on the turbo?
96 U270 BUILD 4810
85 380SL
Drummonds TN.

Re: Find air intake system leaks

Reply #17 –
No, he was sitting on the other side. Just happened to feel the leak.
Dick, '03 U320 40' Tag, 2 slides, Coach #6075
Full Timers
2009 Honda CR-V