How to find a Vacuum leak.

[hurron]

I've read/printed the tech library description, any other tips to find a leak. I am currently loosing vacuum whenever I push down the gas, to the point of the vent louvers closing.

Thanks...Eric

 

[Dave R]

Well, you normally loose vacuum when you depress the accelerator. Are you finding that you really have to put your foot into the get the truck to move? The vent door closing is a fairly common problem but it should only occur when your at or near WOT.

 

[hurron]

I lose the vacuum even when I lightly press the accellerator.

 

[kunar]

then it may not be a leak. could it be plugged exhaust? check out this link. use a hand vac pump (sold as 'one man brake bleeding kit') to check actual values

 

[hurron]

I hope its not a plugged exhaust, I just had it replaced last year. No, I don't think it is.

Any other ideas?

 

[hurron]

Any Ideas? Responses?

Any more ideas or responses would be greatly appreciated.

 

[kunar]

what year/engine? pull codes and see if it comes up with anything. if its not running right it could show the same signs...

 

[hurron]

its a '97 XLT extended with a 2.3 and 5spd manual. No codes showing up that I can tell.

The vacuum gauge is definitley dropping at the slightest accelleration.

 

[hurron]

Did some more snooping and found that the vacuum is close to normal , at idle, where the black vacuum tube enters through the firewall.

If I measure at the white tube (for the air recycle vent), it measure between 15 and 20 (midway).

This tells me I am losing vacuum within the dash (krap). Anyone have an idea of a common place?

 

[Rocky Ranger]

losing it

it could be the vacuum control switch, but most likely it is the check valve between the manifold and the vacuum tee, or the line to the hvac. You can pick up a generic check valve at most auto parts stores for less than $5, just make sure you connect it to the hvac line only. and make sure you install it in the correct direction as it allows vacuum only one way. On one side of the valve it might say engine, source, manifold etc... that side goes to the engine.