Found this Ingenious VACUUM LEAK Testing Trick

OK,

I came across this thread for a 1998 740i but you can virtually use this technique for any car:
http://www.bimmerboard.com/forums/posts/559025
One thing I'd do different is:
- Block the Inlet to Air Mass Meter with a Plastic Lid and Duct tape.
- Use the Brake Booster Hose Inlet as sucking point
NOTE that you need:
1. Stethoscope
2. Leave the vacuum machine outdoor to keep noise out of the garage.

Here is a repost of this thread:
Please don't laugh, but here's a technique that I found to be quite effective to diagnose the dreaded "fuel trim" errors in a 1998 740i (pre-9/98). First, many thanks to "Phil in Philadelphia" for his suggestions. I considered a few other possibilities, but it seems the most common cause of the fuel trim errors is an intake manifold vacuum leak, after the MAF.

I took out my stethoscope with the engine idling, but even at idle there are too many legitimate noises in the engine compartment to hear a leak.

I tried spraying starter fluid, jetting propane, and spraying water at suspected leak locations. None of these affect the idle, I found, enough to be useful. Other articles say use propane and monitor the O2 sensors, but that seemed like a pain. So I had an inspiration:

I parked my car in front of the garage and hooked a garden hose to my vacuum cleaner inside the garage:



Then I made an adapter for the other end of the hose to go into the MAF. This was from a new MAF cover but one could use anything with some gray tape:



Then I closed the garage door to muffle the sound of the vacuum and took out the stethoscope and listened in the usual places, on a quiet afternoon, engine off!! If one of the cylinders is near TDC with the intake and exhaust valves open you may have to graytape the exhaust pipes to get a better vacuum, but I didn't need to. I first checked the vacuum by removing one of the black plastic tubes at the top of the OCV -- clear vacuum just like with the engine running -- loud hissing in the steth. Then I replaced that and I checked all around the throttle assembly, the rear OCV area, even down by the intake manifold gaskets. Found a HUGE hissing sound from underneath the throttle body-manifold gasket. Very clear leak.

I got a new gasket and six new torx bolts and removed the throttle body. Believe the earlier posts and my earlier cussing that those ten-year old torx will strip! My technique is to remove everything to get some room, then clean the torx heads three times with carb cleaner and a toothbrush (need a mirror to do that for the one in the middle underneath), then with a good T30 on a 3/8 ratchet, push with all your might and crack them loose.

Here's what I saw. The gasket on the left bottom clearly lost its seal:



I cleaned everything, put in the new gasket, and reset the light. Fuel trim looks good and no light!!

Cheers......Will
-------------------

Having said that, if you have more than 100K miles, it is a good idea to refresh all rubber parts in the Air Intake System (Intake Manifold Seal, all gaskets at Throttle, Vacuum Elbows, Vacuum Hoses etc.). Info is here for 1998 528i:
http://www.bimmerfest.com/forums/sho...d.php?t=379225

Cn90--Thats the same as I posted back a month or so ago--I use a large vacuum machine that you pump by hand--some here use this same devise to remove the oil from the sump--while doing this I use suran wrap
over the throttle body boot and also cover the tail pipe--I found that this sealed off the entire system--a few pumps on the vacuum machine and there's 20 inches of vacuum and then you start to listen for leaks--to my surprise I didn't have any---I use large rubber bands over the suran wrap to hold it on the ares that are to be sealed--it sealed so well the the ribbed sections of the throttle body boot would start to deform and compress in on themselves.
Great catch--this is a lot cheaper way to check for leaks than going to a shop with a smoke detector--and you can do it at home on the cheap--my machine cost me around 60 bucks from harbor freight--you can also be assured that this method will find leaks that the smoke machine doesn't find sometimes.

Cool.

Poolman,

Actually this costs nothing (the stethoscope can be had for $10, you can even use a cheap nursing stethoscope).
As I mentioned before, I'd do the following:
1. Remove the Air Filter Housing.
2. Using a large Yogourt Container CAP, cap the Air Mass Inlet and duct tape it.
3. Then fashion some tubing and suck through the Brake Booster Vacuum Hose, labeled as "Cut this Clamp" in my DIY:



PS: #1. If one is "lazy", one can remove ONLY the Air Filter itself and wrap it in a Large Ziploc bag, tape it and reinsert, this should block airflow enough for diagnosis. So no need to remove the A.F. Housing itself.

I need to do this!
Thanks CN and Poolman!

I tried to make a homemade smoke machine, but failed. These cars are plagued with vacuum leaks, so any method to find them is always welcome. Great idea!

This original post was based on vacuum machine at home.

I just came across another DIY trick by a tech in Volvo forum but this one uses very low air pressure (like 3-5 psi) and a soapy spray bottle. In this pic, he attached a pressure regulator to the white plumbing cap but if your air compressor already has a regulator, then you simply make a cap with the 1/4" NPT air adaptor and that is all:
http://volvoforums.com/forum/showthread.php?t=18125

*** Once the air compressor reaches 5 psi, shut it off so it does not make noise and you can go for troubleshooting of air leak:

Originally Posted by cn90

This original post was based on vacuum machine at home.

I just came across another DIY trick by a tech in Volvo forum but this one uses very low air pressure (like 3-5 psi) and a soapy spray bottle. In this pic, he attached a pressure regulator to the white plumbing cap but if your air compressor already has a regulator, then you simply make a cap with the 1/4" NPT air adaptor and that is all:
http://volvoforums.com/forum/showthread.php?t=18125

*** Once the air compressor reaches 5 psi, shut it off so it does not make noise and you can go for troubleshooting of air leak:

Great idea: find a vacuum leak by using pressure instead of vacuum.

I finally ended up using something similar to this:
How-test-boost-leaks-s-cd-s62

I was able to find several leaks around the ICV, supercharger outlet piping, and around the BOV. Although I had a 12v air pump, I used a hand pump with a gauge on it instead. The 12v air pump made too much noise, but the hand pump requires someone to help you.

Either way, testing for vacuum/boost leaks should be the first thing you try when diagnosing engine problems. With all the fittings, hoses, clamps and gaskets there is bound to be a leak somewhere.

Just wondering if anyone has ever done this:
- Install this adaptor thingy to the intake rubber boot and duck tape it shut.
- Attach a clear vinyl tubing to the adaptor to a garden spray tank.
- Light a cigarette and place it inside a metal cup to prevent damage to the garden spray tank (itself is $9 at hardware store).
- Now the garden spray tank is filled with smoke, now you pump the tank to pressurize it.
- Now it is time to watch smoke coming out of the intake hoses/seals.

Good idea or bad idea?

you're going to give your car cancer...

Originally Posted by cn90

Just wondering if anyone has ever done this:
- Install this adaptor thingy to the intake rubber boot and duck tape it shut.
- Attach a clear vinyl tubing to the adaptor to a garden spray tank.
- Light a cigarette and place it inside a metal cup to prevent damage to the garden spray tank (itself is $9 at hardware store).
- Now the garden spray tank is filled with smoke, now you pump the tank to pressurize it.
- Now it is time to watch smoke coming out of the intake hoses/seals.

Good idea or bad idea?

You are on the right track. You could use a small metal cup that could screw into metal piping the same size as your intake piping - my piping 3.5 inches ID. The you could use smoke machine oil (it's baby oil). I saw someone use an inverted diesel glow plug and applied 12v to the glow plug to heat up the baby oil. The glow plug would have to screw into the inverted metal reservoir holding the oil and the metal reservoir would have to screw into your metal piping. Then you could apply 12v to the glow plug and pressurize the system and that should get you a poor mans smoke machine.

Not sure if I describe it so you can get a visual, but I think something like that could work. Now we just need some to build it...

On some other forums, some people use dry ice!

Basically:
- Remove the Air Filter Housing
- Place a small cube of dry ice in a small flat cup of water inside the rubber elbow.
- Now duct tape the rubber elbow shut.
- Dry ice expands (basically CO2) when it undergoes sublimation.

Originally Posted by cn90

Good idea or bad idea?

Well, the next obvious question would be..

Menthol or regular?

It does not matter menthol or regular, the car gets cancer anyway from the smoke, LMAO.

Originally Posted by cn90

One thing I'd do different is:
- Block the Inlet to Air Mass Meter with a Plastic Lid and Duct tape.
- Use the Brake Booster Hose Inlet as sucking point

Sorry to dig up the old thread. I am trying to diagnose engine misfire on Cyl #4 and #8.

I have a oil sucker.

Where is the "Brake Booster Hose Inlet" on M62 (12/97)?
http://www.realoem.com/bmw/showparts...02&hg=11&fg=45

If I use the vacuum cleaner method on Air intake, do I have to block off any hoses or exhaust to perform the test?

Thanks.

thanks you all make me feel dumb im going to buy a vacume this weekend. i have learnt heaps on me first page beem me up im going to fix the sucker yet

Going to try this out on an E46 im working on.

Removing the Torx screws the easy way. Buy the IRWIN 10mm Bolt out for $8. and take them all off front and back in 20 seconds replace with stainless steel hex screws.

This older thread popped up today and I wasn't aware of it so I'll add a reference to the misfire diagnostic thread (since many trouble codes are vacuum related):
- How to diagnose a BMW E39 engine misfire (1)

It seems apropos to link it to this nascent thread in addition:
- Might we be able to list, with pics (realoem diagrams ok) of ALL E39 vacuum lines?

I like the approach of fighting fire with fire (only in this case, it's fighting vacuum with both vacuum and with, strangely enough, pressure!).

I don't know if anyone's tried the cigarette method yet, but I don't think it's a great idea. If you place a cigarette in a vessel that contains regular air (78% N2, 20% O2, 0.9% Ar, 0.03% CO2, etc) under pressure, it probably will burn faster than expected; how fast I'm not sure, but it might just combust efficiently (i.e. completely, yielding steam and CO2) in no time, producing little smoke.

Originally Posted by cn90

Just wondering if anyone has ever done this:
- Install this adaptor thingy to the intake rubber boot and duck tape it shut.
- Attach a clear vinyl tubing to the adaptor to a garden spray tank.
- Light a cigarette and place it inside a metal cup to prevent damage to the garden spray tank (itself is $9 at hardware store).
- Now the garden spray tank is filled with smoke, now you pump the tank to pressurize it.
- Now it is time to watch smoke coming out of the intake hoses/seals.

Good idea or bad idea?

Good Idea.

Old thread, but hey! I read it while battling my lean codes and associated issues, so just thought would share experience in case somebody else runs into it.
Some time ago I paid $80 to a mechanic to do the smoke test. Then read posts on the net about complicated things people make to DIY. Cigarette work just fine.
I didn't use garden tank though. I had clear tygon tubing with chamber in the middle (there I put a cigarette). One end of the tubing goes to a unused capped port (cap removed obviously) on the back of the manifold. Remove air box, put latex glove onto the rubbed duct. Light a cigarette stick into the chamber, close the chamber, blow into the open end of the tubing. Glove inflates, and BAM smoke comes from a poor connection between lowen intake duct and TB (well that was my experience). Fixed connection, repeat smoking -> no leak.
Doubt the car will have any adverse health effects (cancer) from two cigarettes, but residue I've seen left in the chamber will keep me from smoking.

Note: when I blow into the tubing the air doesn't go past cigarette!!!, it all goes through it, I burns quickly and makes enough smoke for one test. Cigarette over -> pinch tubing and squeeze glove to make smoke come out from where it comes out (if it comes out).

Originally Posted by chemist

pinch tubing and squeeze glove to make smoke come out from where it comes out (if it comes out).

I found the hardest part of a home built smoke machine was getting the smoke to move under pressure ...
- How to make your own smoke machine (1)

Or you can use a cigar!!

Nice. Here's another for an M54 engine:

Originally Posted by RainyRider

Hi all, here is my version of a M54 vacuum system smoke tester.
Built it today with stuff laying around. I could never have come
up with this if it were not for this forum. Thanks all to contributors!

Tools:
Glue gun.
Something to cut hose.
Something to make holes in plastic.
A source of compressed air.
Parts:
Plastic jar with screw on lid.
5/8 plastic elbow (i used a tee).
5/8 rubber hose.
1/4 rubber hose.
Cheap cigar.
3/8 drive socket that fits cigar.

Assembly instructions:
Drill hole in center of lid.
Drill hole in side of jar, at top.
Glue together. Lol

How to use:
First remove air filter box and put a rubber glove over MAF.
Remove hose from brake booster (be careful, the connector is plastic).
Put cigar in socket, light it, screw on jar, shoot air (low pressure)
into 1/4 hose at top of jar to get it really smoking good.

Insert smoking end into brake booster hose. Look for leaks.

And I got the famous CCV hose to dip stick leak.

A video of using it.