How to find Vacuum Leaks

My 328 GTS has developed a high pitch whistle. I just rebuilt the engine and that is the only thing holding me up. The engine starts and runs but it's not correct due to the vacuum leak. Below are the responses I've received so far on how to find the leak.

1. Use a heater hose. Hold one end up to your ear and move the other end around the engine.

*** This seems pretty difficult.

2. Spray carburetor cleaner around different connections and seals.... listen for the engine to revive up or down.

*** Also seems pretty difficult if you trying to find a pin hole.

3. Buy a smoke machine and fill the plentum. Where ever you see the smoke come out is the leaks location.

*** I priced one at $1095.00.... just not pratical.

Anyone know of the best way or is sending it to a shop the best thing? I don't have a ferrari mechanic in our area but maybe other dealerships would have the equipment.

Tom

 

During the course of your rebuild, did you remove any emissions related components? Specificly the emulsion tubes that screw into the cylinder heads just above the exhaust ports?

 

Surprisingly, Sears has a very nice stethoscope in the Craftsman tool department. It's pretty cheap, but it works well for finding odd sounds. I hope that helps.

--Matt

 

No I didn't remove any emulsion tubes. My first guess would be the vacuum lines under the Plentum. There are 8 of them that attach from the manifold to an Air Delivery Pipe. Realisticly it could be coming from many different areas so I need something that can pin point the problem.

 

A method often used for very small leaks is to spray water around the suspicious area. The reduced pressure at the leak will evaporate enough water to drop the temperature and form a tiny ice plug. This should change the noise you hear or if using a gauge show an improvement in the vacuum.

 

I'll second that. Its how I found the leaks around the throttle shaft bearings on my carbs...

 

If you rebuilt the engine why not use new vacum hoses? Sorry...I'm not trying to be a smart A

 

I did use new vacuum hoses. A leak like this could be very difficult to find I imagine.

 

I have used the " Spray starting fluid and listen for the increase in RPM's" many times on v-8 gas and diesel engines with pretty good success.

 

I second this method ...... that is if it's a sizeable leak ... you'll hear the difference when it starts sucking starter fluid. Just don't blow yourself up thanks to some sparking plug wires!!!

But I've also had very good success with a stethoscope finding a multitude of issues .... I use the Sears model mentioned .... it's amazing what sounds you can isolate and pinpoint using one of these.

Good luck.

 

There are special foam building additives at cheap prices. Even minor leaks will cause a lot of easy visible foam. I used to use them when I was assembling pneumatic devices in vacation during my time at the University.