Tips, tricks or techniques to test for an exhaust leak.

[nurse]

Not sure if this is in the right place so feel free to re-locate it if needed.  This thread is meant to seek out different ideas and techniques more than anything!!

Have installed a new delkevic exhaust from collector back.  Had a few alignment issues but think they are mostly ironed out now.

I am happy with individual joints but need to check for leaks of gases where the headers meet the exhaust port

I spoke to my dad (a prototype drive train engineer for Ford MC - with access to a tonne of technical equipment and specialists bt given he is150 miles away the help is limited to phone calls!!) who suggested covering one of the collector outlets with a pressurised seal then using a valve to pressurise the system, he described having to manually turn the motor over to find the point where exhaust valves are shut also, after twenty minutes of him describing 'how easy it was' my head was spinning!!
I chatted to mechanic friend of mine who said he would just hold a lit cigarette up to the areas you want to check and look to see if the smoke is moved! 

From the sublime to the ridiculous!!

You guys got a better, simpler, more reliable or any other ideas!!  Preferably one that doesn't involve me having to start smoking!!

[aviationfred]

I chatted to mechanic friend of mine who said he would just hold a lit cigarette up to the areas you want to check and look to see if the smoke is moved! 

From the sublime to the ridiculous!!

You guys got a better, simpler, more reliable or any other ideas!!  Preferably one that doesn't involve me having to start smoking!!

Not really that ridiculous.

In the late 90's, I worked for Learjet and performed Functional tests of the aircraft. One of the tests was pressurization of the cabin. Specifically to detect leaks at the cabin door. We would send a person inside, close the door, pressurize the cabin. The person inside would have a Cigar and he would light the Cigar. The test ran for 20 minutes. After we de-pressurized the cabin and opened the cabin door. We were able to detect where the leaks were by brown smoke streaks left by the air escaping on the airframe around the door.


Fred

[markmartin]

Would it be possible to pressurize the exhaust system by removing the little bolt that is on the bottom of the header pipe, blocking off the mufflers with a cork, and then using an air hose & nozzle at the removed screw? Then use soapy water at all unions to check for bubbles / leaks?  

[ribbert]

With the way the headers fit into the head it is difficult for them not to naturally want to seal, unless one of the pipes is seriously out of alignment. The collector box makes this unlikely by locating the pipes one end and the amount the pipe goes into the head locates the other.

As long as the nuts are moderately tight and have pulled up evenly, there should be no need to check.

Professional exhaust fitters do no more than hold their hand around the joins to check for leaks on a newly installed system. Any leak worth worrying about can be felt with your hand.

Exhaust leaks at the head (of anything) have a distinctive "tic" that is louder under load.

Unless you have some reason to believe it is leaking, I would assume it is not.

When fitting an exhaust, you mount everything up loose, front to back, jiggle everything around to make sure nothing is under too much stress then progressively and evenly tighten everything up starting at the front and working towards the back.

All of the above assumes the gaskets are in good condition.

Noel

[X-Ray]

Exhaust leaks at the head (of anything) have a distinctive "tic" that is louder under load.

It sure does. I decided to reuse an exhaust header gasket a few months back and went for a quick spin. Tic Tic Tic Tic, sounded like a valve going off, lol. Replaced the gasket and all good.
I reckon if you can't hear anything it should sealed as good as it can be.

[ribbert]

Exhaust leaks at the head (of anything) have a distinctive "tic" that is louder under load.

It sure does. I decided to reuse an exhaust header gasket a few months back and went for a quick spin. Tic Tic Tic Tic, sounded like a valve going off, lol. Replaced the gasket and all good.
I reckon if you can't hear anything it should sealed as good as it can be.

It 'aint necessarily so (hmmm, sounds like a line from a song, Kev?) when you get further back on the system, leaks get a "fluffy" sound to them, which can be difficult to distinguish on a bike because of all the other noise going on.
A better check would be if you can't feel it with your hand it's good enough. It is an effective means of checking for leaks that I don't believe has ever been, nor needs to be, improved on.

As a bit of general advice, I will re post the following because it is important and something I have seen a lot of.

When fitting an exhaust, you mount everything up loose, front to back, jiggle everything around to make sure nothing is under too much stress then progressively and evenly tighten everything up starting at the front and working towards the back.

Noel

Exhausts vibrate and one that ends up with a join or hanger or mounting point that is under stress does two things. It transmits vibration to the body or frame and it eventually cracks.

Noel

[airheadPete]

One technique I've heard of is hooking up your shop vac's nozzle to it's exhaust, then jamming it into the exhaust pipe's end. Look for leaks with soapy water.
But I agree with everyone else, if you can't feel it with the back of your hand, I wouldn't worry about it.

[racerrad8]

One technique I've heard of is hooking up your shop vac's nozzle to it's exhaust, then jamming it into the exhaust pipe's end. Look for leaks with soapy water.

I would not do that...

At least one cylinder is going to have the exhaust valves open and you are just going to blow crap back into the cylinder which could damage rings or valves & valve seats.

Randy - RPM