sorry for the stupid question

[Roman Tasel]

I know a lot about my l18, but what is a vacuum leak and how can you fix them?

[ggzilla]

Vacuum is what is inside the intake manifold when the engine is idling. A leak lets air in, but that air is not going through the carburetor so it messes up the idle. It can cause rough running (a tiny bit rough, or so rough it won't idle) or an above-normal idle speed -- or both. Also the same thing affects EFI engines.

 

These leaks are tough to track down because you can't see them. 20-year old cars tend to have more than one leak. Yet often they still run OK. When it gets bad enough to require fixing, it is a chore to find them all.

 

Read through these, they may give you more understanding:

* http://wiki.datsun1200.com/index.php/Carburettor_Diagnosis

* http://wiki.datsun1200.com/index.php/Carburetor_Adjustment, section "Check for Vacuum Leaks"

Edited January 13, 2009 by ggzilla

[hang_510]

These leaks are tough to track down because you can't see them.

 

vacuum leaks suck! :mellow:

[moparvwfreak]

the only stupid questions are the ones not asked. good question for begining mechanics though. vac leaks are absically "unmetered air entering the engine through gaskets that have gone bad at the carb base, or intake to head mating surfaces." if you have one, thenyour running WAY lean and it could do damaget o the motor.

 

to check for one, carb cleaner on ALL gasket surfaces dealing with the intake is the best way. it will either smooth out or bog and try to die when the leak is found. i cant remember which. its been a while since i checked for one.

[racerx]

I know a lot about my l18, but what is a vacuum leak and how can you fix them?

 

 

1. You have to know where the vacuum leak is coming from.

 

2). Spray carb cleaner around intake area and carb area, if RPM goes up there's vacuum leak where you spreayed.

 

3). If it's around carb area, like the adapter or the bolts that hold down the carb, DO NOT over tigthen the bolts since this can cause your carb to warp and have more vacuum leak.

[ggzilla]

Good advice.

 

> Spray carb cleaner

If idle speeds goes up OR down, it indicates a leak. The fluid is temporary plugging it and/or changing the mixture. I use WD40 cause it's usually handy.

[Cuts metal like mad]

Many times unless you have done this before you won't "hear" the engine idle up or down because it may be very slight in it's change... Listen very carefully!