Find an exhaust leak without burning your hands!

I have had an exhaust leak on my trusty Skoda for a while, I can hear it coming from miles away!

My problem was that to find the leak with the engine running was too difficult as the manifold and downpipe heated so quickly that I didn't have time to find the leak before everything was too hot to touch.

My solution, the mighty power of the humble vacuum!

WORDS OF WISDOM
1) Make sure the whole exhaust system is completely cold before starting work - I ended up quite ill after burning my hand on my friends exhaust many years ago.
2) Don't forget to disconnect the vacuum before starting the engine

(Photos by my 3 year old daughter Sennen)

Step 1 Connect the vaccum cleaner

This step is easy, just duck tape the pipe of the vacuum to the tail pipe of the exhaust and switch on.

I have used a Dyson cleaner which has an effective bypass valve to stop the motor overheating when the machine gets blocked. If you use a vacuum which does not have a good bypass, then you might need to make a deliberately leaky connection to the exhaust to stop the motor in the vacuum overheating.

Comments

[chekespeare]

i think you can also use a manual air pump to blow in , of course with the use of the washing up liquid. i wonder if just by obstructing the exhaust, it can create a pressure to obtain a good clue where to concentrate your attention.

[DIY Dave]

Now how do you patch the hole?

[PeterTheUnGreat]

New downpipe for most of the holes, but a little bit of welding on the manifold.
(I do the welding with the engine hot (not running because you need to disconnect the electrics) and this helps to avoid heat stress cracking around the weld)

[DIY Dave]

I never would have thought to weld with the engine hot.

[kill-a-watt]

IIRC cast iron is tough to weld. They usually do a pre-heat with torches and hammer on the weld while it cools. Also, there's a special type of arc electrode for cast iron that is expensive because of a high nickel content.

[PeterTheUnGreat]

Yes the main trick with cast iron is to pre-heat (blow-lamp or bake - this is what getting the exhaust up to temperature does) and then cool slowly - often burying in sand or wrapping up. I have done a bit of cast iron welding, repairing an old wood-burning stove and the manifold and it seems to work OK.
I don't have a special electrode - I just use my MIG welder with standard steel wire
Pete

[kill-a-watt]

Using the engine to preheat is an outstanding idea, BTW.  This way there is residue heat throughout the entire casting which should allow it to cool slowly.

I'm sure the special rod is more critical when fixing a large crack or split.

For a hole, I wonder if drilling, and then tapping a hole might work?

[PeterTheUnGreat]

I don't see why it shouldn't - you sometimes see plugged holes on manifolds anyway as part of the design - you could lubricate the threads with a bit of exhaust assembly paste

[classtopher]

Great post. Would it be a bad idea to use a shop vac and blow air into the tailpipe? I dont know if this would be bad for the catalytic converter or not. But if you did that then you could simple feel the leaks with your hand and probably wouldn't need the funnel contraption.

[PeterTheUnGreat]

You could try blowing - I couldn't do that because the Dyson doesn’t have a blowing attachment.
I don't think you would be able to find the tiny leaks just by feeling, but you could try a bit of washing up liquid and look for bubbles

[Chrislee]

Thank you for your genius. I'm gonna use Mighty Putty. They won't have this
noisy 'ol lady to kick around anymore!

[JuCo]

cool idea. and i love everything about the "car doctor" picture.

[aaahotdog]

Very good idea

[jeff-o]

Great tip! Thanks very much.

[pfred2]

Pretty good idea. I use welding gloves, when I am over the leak it gets muffled so to speak.

[Babyshoes]

I must admit I was skeptical when I read your title, but this is a clever way for someone to check for leaks at home.

[zazenergy]

Awesome! This is so handy!