How to track down a vacuum leak?

bug buggy · Nov 7, 2016

5.9L. After a couple minutes at start up in these colder morning temps is when it starts to whistle. I try to home in just by listening , but it sounds like its coming from the whole engine bay. Its a very loud whistle? I can drive it to the office, about 6 miles, still doing it, pull in park and turn it off let its set for a few minutes start it back up and not doing it. Cant notice any change in idle or going down the road?

RonJon '06 · Nov 7, 2016

On the carbureted engines I'd test for a vacuum leak by spraying starter fluid around the base of the carb listening for a change in idle speed. Making noise after sitting overnight suggests a leaking intake manifold gasket however I'd think that it would have a rough idle. I've heard an exhaust manifold leak sound like a whistle too.

Bullitt5339 · Nov 7, 2016

RonJon '06 said:
On the carbureted engines I'd test for a vacuum leak by spraying starter fluid around the base of the carb listening for a change in idle speed. Making noise after sitting overnight suggests a leaking intake manifold gasket however I'd think that it would have a rough idle. I've heard an exhaust manifold leak sound like a whistle too.

Ether was going to be my recommendation as well.

crash_eco · Nov 7, 2016

I like propane. Using a small tank with a nozzle for soldering. When the engine revs. You're close to the leak.

justin13703 · Nov 7, 2016

I like using propane too just because spraying chemicals around on plastic and rubber parts can damage stuff and may leave residue. Propane won't damage anything or leave any signs that it was even there.

Keep in mind, only use a SMALL amount of propane.

bug buggy · Nov 8, 2016

I have worked on my vehicles some over the years, mostly the basic things. Is this something that would be time consuming, but not to difficult? I have not checked any thing out yet , but what is the consequences of NOT fixing right away if this is my problem? I really want to Thank you all for your input. I know i'll be back with more questions soon.

justin13703 · Nov 8, 2016

There really aren't many major consequences of a small vacuum leak. May just cause the engine to run a little strangely and negatively impact your gas mileage. You might wanna check your plugs after you get the issue fixed. You want to get it fixed regardless, but a small vac leak isn't a catastrophic thing.

Reddragonjodi · Feb 8, 2018

I am burning gas and it’s making my broke ass cry! It’s been -29 here so I haven’t found a warm place to check for leaks. I have been told to use carb cleaner, ether, dish soap, propane .... all say to spray around vac lines, intake etc... hopefully it will warm up some this weekend and I can tinker with my beast... I think my right side manifold has a broken bolt too, I just did them in July! What pain!

How to track down a vacuum leak?

bug buggy

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Bullitt5339

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justin13703

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bug buggy

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