Find exhaust leak with shop vac?

[stuartrubin]

I suspect I have an exhaust leak for a variety of reasons, mostly the smell (plus bad idle, the engine was pulled apart, etc.) I stumbled across this method for finding the leak:
http://www.instructables.com/id/Find-an ... /?ALLSTEPS

Basically you connect a vacuum cleaner (I would use a shop vac) to the tail pipe and listen for the leak.

The appeal is that you can do it with the car cool, not running, etc.

Is this crazy? Can I damage anything by sucking on the tailpipe like this (with a vacuum cleaner, you pervs...) ?

Thanks

[lglade]

I can't think of anything that could be damaged in that scenario.

[RRoller123]

You could do it with the reverse flow, blowing air into the exhaust system, and it might be easier to find that way too. Maybe somehow get cigarette smoke in there and make it visible (?)

[stuartrubin]

Thanks everyone for the help. For reverse, what about this method:
<Ooops! I had the wrong link here. I'll find it!>

He uses a shop vac (looks like a small one) to blow back into the exhaust pipe through the muffler and sprays soapy water around the exhaust system.

Looks easier to find bubbles than listen for hissing.

Can that much force damage the system?

[aj81spider]

Wouldn't blowing soapy water back up your exhaust pipe run the risk of putting soapy water into one or more of the cylinders through any exhaust valves that were open?

[AriK]

Wouldn't blowing soapy water back up your exhaust pipe run the risk of putting soapy water into one or more of the cylinders through any exhaust valves that were open?

What he meant was blowing air through the tailpipe and spraying soapy water anywhere on the exhaust system where he'd expect a possible leak.
I don't see any problem either with reverse air flow.
If the weather is cool enough and it's the first start of the day you may briefly see exhaust condensation flowing out of any cracks.

[RRoller123]

Or rent one of those disco fog machines and run it up the tail pipe.......

[stuartrubin]

Here are the results. I used my small (lower flow) "bucket head" shop vac in reverse. The tube is taped into the tailpipe. I ran the vac and sprayed soapy water around the exhaust manifold. Here is a video of the bubbling which pretty clearly shows the leaks.
http://vid1167.photobucket.com/albums/q ... zvulvf.mp4

I marked up a photo to show the leaky spots. For some reason it looks like a smiley face, but I'm not smiling (much)! I may have the terms wrong, but it looks like I have a leak between the exhaust pipe and exhaust manifod, small hole(s) in the manifold, and two (or more) leaks between the manifold and engine.


I think there may be some bolts and/or nuts missing between the pipe and manifold. I only saw one nut! Photos from the Internet look like there should be four...

And if anyone is interested in the setup, here's the vac connected:


Should I take this to a muffler shop or does anyone have suggestions on fixing these. I have not had much luck fixing things...

[124JOE]

yes if you are not good at fixing things take it to a muff shop that will braze the crack better
but if you can pull the manafold yourself you will save money
ether way you need a exhaust gasket and one for the bottom of the manafold

[stuartrubin]

Joe, thanks for the reply. I ordered the gasket, but I think I'll take it to a shop to do the work. (I hope this https://www.midwest-bayless.com/Fiat-12 ... a-new.aspx is the right one!) There may be more leaks lurking, and I'm just as likely to cause more when I "fix" the ones I have.

Speaking of gaskets, is there one between the manifold and engine?

Do you or anyone know the size(s) of the bolts connecting the pipe to the manifold?

Thanks again to everyone for their help.

Stuart

[ORFORD2004]

Speaking of gaskets, is there one between the manifold and engine?

Yes
https://www.midwest-bayless.com/p-7152- ... 0-new.aspx
or something like this.

[124JOE]

10mm x 1.25 pitch it should have a 13 mm head