Just bought my first f150... a '98 4.2l 5sp. Nice truck… no problems. I read about someone installing a vacuum gauge and I'm wondering how that could be done. I’m not sure where I should tap the vacuum from the engine. Should I cut into a vacuum line and tee off of it? Which line should I tap into? Is there an unused tap somewhere on the intake that would be better to use? Would installing this gauge cause any problems with how the engine would run? Thanks.. Rick

 

Just for curiousity, why do you want to run a vacuum gage?

 

I used to have a vacuum gauge installed in my '69 Ford Galaxie. I think it helped me save gas. It was also useful to spot engine troubles such as a leaky manifold gasket which I understand may be a problem for a 97-98 f150 4.2l engine. So I'd like to keep a close watch on what is happening to my engine. Since I'm not a mechanic I'm not sure where to make the connection. I thought that before I spent my cash to have a pro install the gauge someone might help me figure out how to attach the vacuum line myself. So - that's my story about adding a vacuum gauge.

 

Makes sense to me.

It is my understanding you should connect the vacuum gauge directly to the intake manifold vacuum, not to ported throttle body vacuum.

I am just new to these 4.2L f150 split port set ups and have not checked out to closely where the intake manifold vacuum line is located. I know on my T-bird it is located right behind the upper intake, sandwiched between the intake manifold and the fire wall. A real pain in the *** to get at. So my guess, and this is just a guess, is that it is also located behind the intake manifold between the fire wall.

However, I am sure someone else here probably knows exactly where the intake manifold vacuum line is located on our trucks, for sure. If I have time tomorrow I will snoop around my truck and see if I can locate it for you. Hope I helped a bit.

 

Look on the passenger side of the engine compartment, back near the firewall. On my 2001, there is a white 'T' in a vacuum line comming off the vacuum reservoir. The reservoir is behind the battery, but the 'T' I'm talking about is in plain view.
It has one of the ports capped off. I removed the cap and plugged my vacuum gauge line into that.

 

F150Forever,

Is this a dedicated vacuum gauge or did you just hook it up to check???

There are 2 other sources come to mind for me.

• PCV hose
• Brake booster vacuum hose

The Ford manual simply says to hook up a vacuum gauge to the intake manifold to check vacuum levels. It doesn't state where to hook it up though.

The PCV hose runs into the intake manifold behind the throttle body. The brake booster is on the driver's side of the engine.

Although I don't have experience with this, I'd think the brake booster would be a more reliable source than PCV because the combustion gases won't be flowing through it then.

 

Thanks for your ideas about the brake booster vacuum line and the 'T' next to the battery. If it ever stops raining I'll go out and take a look. The weather guy says its supposed to rain right through the weekend... anyway... thanks again for your advice...

 

AjRagno,

Yes, I installed my vac. gauge in the dash. The line to the reservoir was easy to get to and like I said it already had a spare port that was capped off. Works good - I read about 25" Hg at idle with no load, 20" Hg at idle in drive, 15 - 18" Hg at 65 mi/hr.