vacuum leak

[broker-len]

any suggestions on how to find a possible vacuum leak on a older 4 cylinder motor        I could squirt oil over and see if it is sucked in by it make a mess       tried to use torch gas bet it did not make any difference in motor even when in the air intake

[Larry Schramm]

One way to use wd40 and just a little bit at a time until the rpm's speed up.  That will be where the leak is.

[cahartley]

Or carburetor cleaner.

[joe_padavano]

5 minutes ago, cahartley said:

Or carburetor cleaner.

^^^THIS!

[keiser31]

Look between the manifold and block.

[sfair]

Want to save the mess?

A little dish soap mixed with water in a spritz bottle, spray around the suspect areas and watch for the bubbles to disappear.

Edited May 5, 2017 by sfair (see edit history)

[37_Roadmaster_C]

Carb cleaner  or  brake cleaner.  Just make sure it is flamable, some are not.  I just did this with brake cleaner two days ago.  When I  hit the spot the rpm jumped up.  I like the brake cleaner as it evaporates much faster with no residue.

[Curti]

11 hours ago, sfair said:

Want to save the mess?

A little dish soap mixed with water in a spritz bottle, spray around the suspect areas and watch for the bubbles to disappear.

The OP is looking for a vacuum leak . In this case bubbles will not appear.  If there is a pressure leak such as a head gasket bubbles will appear.

[sfair]

1 hour ago, Curti said:

The OP is looking for a vacuum leak . In this case bubbles will not appear.  If there is a pressure leak such as a head gasket bubbles will appear.

You set the spritzer to spray bubbles and watch for them to get sucked in.

Very easy to spot.

 

Edited May 5, 2017 by sfair (see edit history)

[lump]

Technicians at various shops I worked at used spray ether....(fast-start spray). It works beautifully, but is WAY flammable, and can be dangerous. You have to be very careful to keep your head back out of the way, and with ANY of the above methods, keep a fire extinguisher nearby. Be very careful to spray out only a tiny amount. Engine will instantly rev up noticeably. 

[keiser31]

Some early Chrysler products have a vacuum line or hole on the engine side of the manifold and can only be seen with a small mirror.

[huptoy]

Try checking the vacuum line from the fuel pump to the windshield wiper.  

My car has a 5 inch rubber hose under the dash connecting the two metal lines.  

The hose was hard and cracked, replacing it cured my problem.  

I was tipped off by an 85 plus year old mechanic. 

[Ltc4748]

I have seen flash fires over the years when people use a flammable spray to check for vacuum leaks. The only way I check for vacuum leaks is just water in a spray bottle. When you spray an area that has a leak you will hear the slurping sound of the water being drawn into the manifold. If the leaks are big enough to let enough water in to damage an engine they are also large enough to hear the leak and to not allow the engine to have a low idle. Be carful that you don't spray water directly on a hot exhaust manifold or you can suffer a steam burn.