Boost noise

Don W.

Don W.

Stab it and steer it
I've looked for this before with no luck, I'm gonna try again and need ideas.

I have a noise, best described as a dull or muted whistle or buzz that is directly related to boost. More boost, more noise. No boost, no noise. As boost rises it does not increase in pitch only volume.

Last time I looked I disconnected the vac line in the eng compartment that feeds vac into the cab to eliminate any possibility of that ck valve being bad and boost coming into the heater/ac controls. I also inspected but did not disconnect the line to my boost ga. and found nothing. Noise was still there.

Next step will be to disconnect both lines and see what happens.

Meantime if anyone has any other ideas I'd appreciate it.

TIA
 
dgoodhue

dgoodhue

BuSTeD 4.3
Re: Boost noise

I don't have that noise, but I used to have chirp when got into boost. I cured it by replacing my check valves.
 
G

gmcturbo

Active member
Re: Boost noise

i know this is pretty basic but are you sure you dont have a boost leak at the pipe/intercooler?
 
Don W.

Don W.

Stab it and steer it
Re: Boost noise

kreepinty said:
i know this is pretty basic but are you sure you dont have a boost leak at the pipe/intercooler?
Click to expand...

No prob, yes fairly sure. Thing is it -seems- to be coming from inside the cab, hence the earlier disconnect of the HVAC line. Everytime I've had the IC off in the past (for whatever reason) and reinstalled it, the sound did not change. My boost ga is on the pillar and the noise seems to come from somewhere under the dash. Another way to describe it would be it's like static from the radio (very hard to pinpoint) that's related to boost, only the radio is off.

Still accepting ideas, will be working on it this weekend. If I find it I'll let ya know. I might go so far as to pull the upper intake and check that gasket and while I'm at it pull the inj's and check their o-rings. (#1 inj is very noisy and I have a spare so I'm kinda headed that way eventually anyway.) Then there's always the inner-tube trick.

Thanks again
 
B

Bad Ass Black Trucks

New member
Re: Boost noise

Do you by chance have an amp in your truck? Ground loop usually sounds like a buzzing that varies with RPM. Doubt that is it, but you never know.

Don W. said:
Then there's always the inner-tube trick.
Click to expand...

You have a link to the thread with the inner-tube trick? I was looking for it the other day and couldn't find it.
 
Don W.

Don W.

Stab it and steer it
Re: Boost noise

Nope, no amp. But I have heard ground loops. Interesting Idea though.

The inner-tube trick is basically to get a bicycle tube, cut it in two, tie off one end, slip the other over the inlet to the IC, inflate and listen. Doesn't take much.
 
Flyin Ryan

Flyin Ryan

hated cuz he drives fords
Re: Boost noise

Don W. said:
Nope, no amp. But I have heard ground loops. Interesting Idea though.

The inner-tube trick is basically to get a bicycle tube, cut it in two, tie off one end, slip the other over the inlet to the IC, inflate and listen. Doesn't take much.
Click to expand...


http://www.sytyarchives.com/howto/viewarticle.php?article_name=find_vacuum_leak.php&dir=engine


and could the noise be coming from your speakers Don? like say electrical noise stemming from your MSD box and or plug wires?
 
Don W.

Don W.

Stab it and steer it
Re: Boost noise

Flyin Ryan said:
and could the noise be coming from your speakers Don? like say electrical noise stemming from your MSD box and or plug wires?
Click to expand...

Noise was there before the MSD. It's not speaker noise, I was just trying make an analogy to describe the noise. I've done the hose thing before but thanks for the link. I'm actually gonna start with that. Workin' on my "honey do" list right now to get that out of the way because once I start on the truck... well you know.:rotf:
 
SY2932

SY2932

Administrator
Re: Boost noise

dgoodhue said:
Try the check valve going to the brake booster.
Click to expand...

That's a possibility but, that 's more of a "quack" noise than whistle... Anywho the part number for the brake booster check valve is #18022219. Don't try to get this from the chain stores, the ones that they have won't fit. Make a trip to your favorite "stealership" if you need one.
 
SY2455

SY2455

70's Veteran
Re: Boost noise

Don

A long shot, but to test it i would remove the line going to your boost gage and test the gage. I had a hair line crack in the Bourdon tube section of the gage that show up under 7 psig.
 
Don W.

Don W.

Stab it and steer it
Re: Boost noise

SY2455 said:
A long shot, but to test it i would remove the line going to your boost gage and test the gage. I had a hair line crack in the Bourdon tube section of the gage that show up under 7 psig.
Click to expand...

Wow, I'd have never thought of that one.

Had a little time today and hooked up the bike hose. I can hear some noise. Didn't have time to track it down but it sounded like either the throttle shaft (mine's rebuilt but??) or maybe an inj. Thanks for all the ideas!
 
TYTILIDIE

TYTILIDIE

METH HEAD
Re: Boost noise

I had the exact smae noise you are talking about. It annoyed the hell out of me. I never did figure out what it was though, it just went away on its own.
 
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