Testing For An Air Leak

[Grim.Badger 15]

I'm fairly certain after swapping engines that my inlet manifold is leaking as I get a misfire/kangaroo at medium throttle. The car idles okay and is like a scalded cat when accelerating so I'm thniking that a leak is the cause.

The question is how do I check? I've read that spraying WD40 around the area is a good way but I've also heard that this can catch on fire Is this only on a hot engine? Am I fine doing it on a cold engine?

 

Cheers

[jim21070 2]

Here is one method...

 

On a cold engine, disconnect the AFM to TB hose and disconnect the hose going to the SAD. Place the palm of your hand over the TB and blow with all your might down the SAD hose. This will pressurise everything south of the TB. You can prove how much pressure you can develop by allowing a leak out of the TB by moving the palm of your hand.

 

You may have a false leak if any of the valves are on overlap. If you have this, just turn the engine a few degrees until all inlet valves are closed.

 

If all is good, you'll turn purple in the face

 

On a hot engine, you can also check your SAD is fully closing by leaving your hand off the TB and still meeting considerable resistance when blowing.

 

Not a perfect test but OK for a quick one. You could refine it by pressurising the inlet tract via an air-line but don't use too much pressure!

[matt1900 0]

i believe you can get a proper leak detection fluid that you spray on the manifold area while running.

[t16ryan 1]

brake cleaner is a good one and it evaportes after anyway, and will increase the revs when you spray near the air leak

[pugrallye 0]

a little word of warning for people leak detection fluid, its highly volotile, and can cause major probs if used over enthuiastically, ie blowing manifolds up is quite common, so use sparingly

[boombang 2]

I take off the air filter and put a metal plate over the end - if it doesn't stall you have an air leak.