Manafold vacume

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May 17, 2011 | 05:09 PM

Huntersbo

Thread Starter

Elder User

Joined: Nov 2004

Posts: 726

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From: So. California

Manafold vacume

I plumed a vacume gague into my cab the other day. I noticed that the vacume drops to between 5 and 10 inch/HG around town. On the interstate at 60-70 mph the vacume is between 15 and 20 inch/HG in 3rd gear. In OD the vacume drops to 10 inch/HG at 60-70 mph. Any time I accelerate even the slightest the vacume drops to about 5 inch/HG. It is idling about 30 inch/HG.

I do have 30.25" tires on 3.55:1 gears. Is this an indication to re-gear.

May 20, 2011 | 06:22 AM

enriched&beyound

Fleet Mechanic

Joined: Aug 2008

Posts: 1,446

Likes: 9

From: NE Iowa JD Country

Quote:

Originally Posted by Huntersbo

check the vacuum lines over for leaks....especially the elbow on back side of the throttle body for the PCV line. 30 inch/HG, seem a bit high, at least to me, make sure that your PCV is working. The vacuum gauge can be a indicator of efficiency....the less you make the gauge drop the more efficient, or the better MPG's you'll get. Tapping the throttle should make the guage drop...depending how hard one taps the GO pedal...that seems normal.

A vacuum gauge also can be a indicator or diagnostic tool ...here is a good reference of vacuum indicators from another web site that I found to be most helpful.
TRS Magazine - Dealing with engine vacuum