Inoperable Vacuum/Presure Gauge

[Red63R3]

Folks - am now getting around to addressing the inoperable Boost/Vacuum/Presure gauge on the R-3. Any experience on most likely faults? As always many thanks - Steve

[brad]

Folks - am now getting around to addressing the inoperable Boost/Vacuum/Presure gauge on the R-3. Any experience on most likely faults? As always many thanks - Steve

Most of the time, it's just years of sitting, and dirt, and dried lube. Rarely the bourdan tube inside gets cracked, or the link connecting to the needle gets dislodged. All easy fixes. Also, check for an obstruction in the end fitting, it is a very small hole which helps dampen vacuum pulses from the engine.

[ernier]

On my '64 the hole in the hose fitting on back of the gage was never punched out! Opened it up and the gage worked perfectly.

ErnieR

[Red63R3]

Thanks gents - it comes out next weekend - will let you know what i find - hoping it's simple dirt/sludge....Steve

[PackardV8]

Best way I've found to exercise the gauge is a MityVac tool. The good ones will provide both vacuum and pressure. Pump it alternately to max vacuum and max pressure readings while watching TV. A couple of dozen full cycles will usually free up the gauge. Of course, watch the gauge on the vac tool and don't exceed the capacity of the S-W gauge.

jack vines

Thanks gents - it comes out next weekend - will let you know what i find - hoping it's simple dirt/sludge....Steve

[Stan Gundry]

Best way I've found to exercise the gauge is a MityVac tool. The good ones will provide both vacuum and pressure. Pump it alternately to max vacuum and max pressure readings while watching TV. A couple of dozen full cycles will usually free up the gauge. Of course, watch the gauge on the vac tool and don't exceed the capacity of the S-W gauge.

jack vines

[Stan Gundry]

My vacuum pressure gauge was sluggish. What I did to cure it was to drip Teflin Tri-Flow lubricant into it and let it soak for a couple of weeks. I then repeatedly blew compressed air across the opening (not into it, but rather across it to produce the venturi effect).

Ever since it has been very responsive.

[brad]

My vacuum pressure gauge was sluggish. What I did to cure it was to drip Teflin Tri-Flow lubricant into it and let it soak for a couple of weeks. I then repeatedly blew compressed air across the opening (not into it, but rather across it to produce the venturi effect).

Ever since it has been very responsive.

I don't see how this would make it into the mechanism of the gauge. The hole in the back just goes into the bourdon tube, which is sealed off from the rest of the gauge mechanism.

I don't doubt it worked for you, and I'm glad it did. I googled how to spell bourdan (tube) and it shows a good shot of how pressure gauges are made.

[Stan Gundry]

I checked out the online sources of information about bourdan tubes. Very interesting. I never realized before how vacuum and pressure gauges worked. When I applied my "cure" of TriFlow teflon lubricant, I had no idea of how the vacuum gauge worked. I now understand that there is apparently no way that the lubricant could have reached the mechanical moving parts of the gauge. Nevertheless, allowing the libricant to soak in the tube for several weeks did make a dramatic difference in its responsiveness to changes in vacuum. What accounts for that? Perhaps it was this. The TriFlow lubricant has a solvent base. Perhaps this solvent dissolved deposits in the tube or at the access entrance to the tube. This deposits could have slowed down the tubes responsiveness to changes in pressure. Then when the solvent and the loosened deposits were sucked out of the tube when compressed air was blown over the small opening (the venturi priniciple), the obstructing deposits were removed and the gauge was as responsive as when new.

Just a theory that is trying to account for the dramatic change this procedure made in the functioning of my vacuum gauge.