Boost Gauge Noise question

[jjohn]

I Installed DiPricol gauges, love them but I have this high pitched whirling sound at 16 PSI and up. when it first appeared it was at 10 PSI, I then sealed the threads on the 1/8 NPT base in the aluminum air intake. Then the sound appeared at 16 PSI.



I assume this is escaping air around the capillary tubing fitting , they seem tight enough if I tighten any tighter I feel like I will distort the brass cap. Any of you guys have a solution or idea?



Thanks JJ

 

[01smokinram]

Noise

Check the tubing all the way from the intake. Sounds like you may have a crimped line or it my be the gauge leaking. Use soapy water to find any leaks.

 

[jjohn]

01smokinram

After I try the soapy water or windex maybe, I may just pull a new piece of tubing, I installed the capillary line in a flexible nylon rubber coated conduit. Actually its spark plug wire heat shield. so checking it in place isn't going to happen.

Thanks for the Idea

JJ

 

[illflem]

Overtightening the brass cap will cause leaks, finger tight plus half a turn with a wrench is plenty. You may have to replace the ferrules if they are too distorted. If you have the boost tubing inside a protective sheath I doubt if it is kinked or leaking. If you replace the tubing use new ferrules anyways, they don't take well to more than one tightening.

 

[John]

I was told some years ago by a VDO tech. (I was the first TDR member on the BB to use VDO Vision series gauges), that since I had a turbocharged engine, he recommended NOT TO use their nylon tubing installation kit to install my new (then) boost gauge. I was instructed to acquire the appropriate fittings and utilize vacuum hose (thicker walled hose) to supply the boost gauge.



He was right! I NEVER heard any turbo whine backfeed through my rubber supply line/boost gauge. The reason I say he was right was because sometime afterward I installed a BD exhaust brake. As I had to set (or at least check) the idle pressure as well as the max. back pressure, I hooked up a second VDO pressure gauge using the original nylon supply tubing kit I had intended to use with my VDO boost gauge. After carefully routing the hose out of the engine compartment and into the cab where I had my pressure gauge temporarily mounted, I drove off to test max. back pressure. What I discovered on the very fist hill was the turbo whine backfeed through the nylon tubing!



:--)



Personally JJ, I think that is your problem. Your problem is no more difficult to understand than a childs makeshift toy telephone... i. e. , two soup cans with a string tied between them! Remember how well that worked?

 

[wsmalley]

I had the same problem with my autometer, and it may be a simple solution:



Go to your local Auto Zone/Advance/etc and by some teflon sealing tape. Unscrew the fitting and wrap the threads with the tape and reattach the fitting. I would recommend hitting the fitting on the intake fitting as well just to eliminate the leak there. Now take it for a test drive and run up the pressure. My guess is this may stop the hiss.



Just a recommendation

 

[jjohn]

Thanks Guys

I already tried the Teflon tape, I replaced the ferrules or "compression sleeves" as Mr NAPA informed me the are called... that worked, "some what" because now the noise is reduced in level and intermittent.



I'm thinking maybe the seat in the intake fitting may not be true and in need of replacement? The sound is louder with the window down so I sure it's under the hood I wouldn't think it is the tubing.

I may pull in a new boost tube just because its easily replaced and eliminates one more variable before I try replacing the intake fitting, it is sealed in pretty tight.



If that does't do it I may try the vacuum hose idea.



Thanks again guys

 

[jjohn]

Noise is gone

Hey guys Thanks again for all the suggestions.



I couldn't find a air leak with the windex, new fittings just changed the sound and made it intermittent.



I bought a 16 foot role of boost tube, routed it the same way but left a nice slack loop out of the firewall, cut to length, covered the tube with split wire loom, a couple of cable tie's, half a turn after finger tight with new hardware "and" no boost line noise... . none!



There was no damage to the old line but it was fairly snug the way I routed it. John was probably right with soup cans and string idea.

 

[jjohn]

I thought I would fess up

When I said the noise was gone… well it was… for a while and then back again.



I replaced the nylon boost tubing with thick walled fuel line and 1/8th NPT barbed hose fittings. Still had the noise. I then ordered a taped boost bolt and relocated the boost source to the manifold from the intake horn…. Still had the noise!



I then checked every connection I touched from installing the gauges again for the 4th or 5th time…. Still had the noise.



This time I took off the band clamps and rubber hose that connects the aluminum intake -to- the piping from the intercooler output, looked at it and put it back on… Noise is gone and has stayed gone!



I didn’t really want to admit this and look like a dumb @$$… but oh well at least I was a diligent dumb @$$!

 

[jmeehan]

Thanks for sharing your find. This may save someone else the run-around you had to go through.

 

[jjohn]

I hope that is the case 85CJ

Sure had me fooled. The Sound transmitted up to the gauge very efficiently. I was sure the noise was gauge, boost tube and fitting related.