are you Whistling at me?

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Serg911

Well-known member
Jan 21, 2006
72
0
After replacing the plenum heater plate, spark plugs and wires; my truck has developed a whistling noise that is relative to acceleration/deceleration, and it?s idling just not as smooth as it was. The noise is more noticeable when driving in town at no more than 40mph, and it is audible only when I release the accelerator. It goes away as soon as I accelerate. I assume ?perhaps incorrectly- that the culprit is a vacuum line, but I can?t see any obvious sign of a vacuum line being disconnected or torn. Any ideas what line I could check?

Ps. I did sprayed starter fluid around the visible vacuum line connectors and didn?t notice a change.
thank you

I searched before posting, but the posts I found seemed to not describe what I'm experiencing.
 
jafir

jafir

Well-known member
May 4, 2011
1,628
0
Northwest Arkansas
I'm going to vote for the hard line that goes from the intake to the brake booster.... or actually the little piece that everyone breaks when disconnecting the line. But I'm just guessing.
 
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Serg911

Well-known member
Jan 21, 2006
72
0
yes it is a 99 DII with 109K, checked both turbos and they are just fine :)rofl: ). Will check the vacuum line that connects to the break booster. thanx guys...any more ideas?
 
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ddavis

Well-known member
Feb 5, 2006
80
0
My 04 did the same thing. Used an electronic stethoscope and it ended up being the lower intake gasket.

But like others have pointed out, there are several areas (ones easier to fix) where the vacuum leak may be occurring.
 
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Serg911

Well-known member
Jan 21, 2006
72
0
well, just checked -retraced- my work and what I could possibly had moved around the spark plug coil packs, around the heater plate, and around each spark plug. Frustratingly I don't see anything obvious that might be causing the vacuum leak. Now, I removed the throttle body in order to remove and replace the heater plate and did not use a gasket where the throttle connects to the other part of the intake.
also, could the vacuum noise come from a loosely installed spark plug?


As for the lower intake possibility, how would I check that? also, prior to me replacing the plugs, wires and heater plate; the truck ran very smooth. As soon as I did the work and ran the engine I noticed the rough idle, so it is a safer assumption that there is a direct correlation between what I did and the rough idle, than to consider the possibility that while I had my truck in the garage with the engine turned off, the lower intake gasket failed in the 3-4 hours that took me to do the job.
 
Hugh166

Hugh166

Well-known member
Mar 1, 2009
80
3
NYC
I had this exact same issue about 2 years ago and chased it for a good while, i ended up replacing the lower intake manifold gasket along with the upper plenum intake gasket and the 2 little gaskets on the upper intake itself as it is really 2 pieces, the noise finally went away. I cant tell u which was the cumprit unfortunatly but i know that job fixed it
 
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Serg911

Well-known member
Jan 21, 2006
72
0
thanx...i have other pressing issues now, and will look into the gaskets suggested as soon as I take care of the major hose failure now.
I'm getting really frustrated with the car, I love it, but come on! can't I get a full week of use without having a hose or gasket fail?

since replacing the TB heater plate and gasket, one of the coolant lines that connect from the heater plate to the expansion tank broke (fixed), then less than 2 hundred miles later the thermostat failed for the second time in less than five months (fixed), about a week later, the upper thermostat hose just started leaking and had to replace it (fixed); and this evening, after feeling kind of good about the truck, as soon as I pull into the gas station after a 40 mile drive....the other hose that connects to the thermostat (upper) and looks like it is a complex design hose just split..it now has a gash that is almost as long as the hose itself.

I've been wanting to sell it but I'd be embarrassed to sell such an unreliable ride. I guess I have to spend more money on it that it's worth...again.

ps. I had all hoses, water pump and thermostat when I bought the truck 8 years ago as a preventative measure, despite that, I've been dealing with coolant issues since day one.

sorry...just ranting.
 
p m

p m

Administrator
Staff member
Apr 19, 2004
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La Jolla, CA
www.3rj.org
ptschram said:
Year?

The Lucas trucks will whistle at some throttle positions.
Click to expand...
My 95 LWB drives me nuts with this. It has been doing it since I bought it 10 years ago, and it didn't change after I did a head gasket job. Funny that should have come up now - I planned to take a closer look at it today.
For comparison, 95 SWB is dead quiet.

Edit: fail, at trying to locate the vacuum leak. Ended up re-plumbing the cruise control, which is in no way related to what I was looking for, and, most likely, won't make it work. To pacify myself, brought out Lexol leather conditioner and Armor-all shit, and made some leather and some outside plastic parts temporarily look less neglected.
 
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BTALBERT

BTALBERT

Well-known member
Jul 6, 2008
258
0
41
fayetteville
i know its ghetto but you can spray a lil starter fluid around the top of the motor and listen to hear if the idle goes up then you know its vac lines.
 
Injuhneer

Injuhneer

Well-known member
Nov 9, 2011
399
0
Southeastern Arizona (near Tombstone)
www.ootfab.com
BTALBERT said:
i know its ghetto but you can spray a lil starter fluid around the top of the motor and listen to hear if the idle goes up then you know its vac lines.
Click to expand...
It is simpler if you use a propane torch. Turn it on very low, unlit of course :p, and wave the tip around the suspect areas. This works well and doesn't have the flash potential of spraying starter fluid at a running engine.

Another way to find it is a stethoscope. A piece of small diameter vinyl tubing placed close to your ear then moving the other end around the engine will help you pinpoint the sound. If you have a mechanics stethoscope you can remove the transducer (the probe) and just use the tubing. Same effect.
 
PFS

PFS

Member
Oct 20, 2010
20
0
Manitowoc, WI
I'm gonna dig this thread up again because I'm having the same exact issue with my '99 D1. We hooked up a smoke machine to the intake and, with the motor off, pushed smoke in. Smoke came out of the throttle body pivots and I figured that air was leaking into there when vacuum pressure was highest--at idle. That's why the noise gets louder as RPMs drop. I replaced the plenum/throttle body with a used one, and took it for a drive. As it warmed up, dammit if the noise was still there! I sprayed WD-40 at it and the noise didn't change.

I'll check the gaskets Little Green Giant replaced, but the only other thing I can think of is that the used plenum I put on has the exact same problem. I'm gonna drive it this weekend and probably put the smoke machine on it again next week. arrrrgh.
 
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