[Red 78']

My motor is making a "whistling" sound. It is a 1978 Mercury Zephyr with a 6 cylinder.
I have removed all the belts and checked to see if it is a pulley or accessory. There was no change. I have removed and capped every vacuum hose from the carburetor and the manifold (one at a time) There was no change. I have removed the EGR valve and checked its operation, all is good. Ditto with the PCV valve. I have pushed down on the carburetor to see if possibly the threads to the manifold have come loose. (I repaired them several years ago) The sound and pitch did not change.

The only thing I see left to do is take the carburetor apart. Am I correct? Or did I miss something?

The car had been running really good (as usual) I had just checked the timing, vacuum, and rpm's 2 days prior and was ready to take it to the smog station when this set-back occured.
The car still runs good without any change in performance. There is just that noise!!

By clicking the picture you can see the vacuum gauge and hear the sound.


Thanks for your help!

[MichaelJennnings]

From your video it looks like the vacuum gauge is reading about 15" of vac at idle. This definitely sounds like a vacuum leak. Try taking some carb cleaner, just be very careful about safety it is flammable, and spray it around the base of the carb, intake gaskets, PCV hose, to see if there is a change. Or you can use water from the garden hose running slowly. When you hit the leak, it will sound like a milk shake cup when you get the bottom as water is drawn into the leak. Doing this while the car is running, you should also notice the gauge jump up as the leak is plugged momentarily. You can also take a short length of garden hose, about 14-16" for ease of use, and use it like a stethoscope to isolate where the noise is coming from.
I noticed when you rev the engine, the vacuum increases, this also points to a leak. Also, disconnect and plug the vac hose going to the brake booster. You could have a blown diaphragm in the booster causing the noise.
One other item is if this has the metal "coffee can" type of vacuum reservoir on the car, they were notorious for breaking around the rim causing similar noises.
It is going to take some troubleshooting and time, but it is loud enough that you should be able to locate the leak.

[Poppy]

Wow, that noise is certainly loud enough that you should be able to locate it easily with the garden hose trick mentioned above.

[Zephyrman]

Could be maybe your base gasket on the carb may have blown out just enough to not be seen easily and the carb will still be on tight. Happened to me with my old 81 F150. Drove me nuts.

[Red 78']

Today I sprayed carb cleaner at the base and the engine sped up. Did this a few times.
So I take off the carb, and EGR assembly and replace the gaskets. Try it again, same sound.
Spray at the base and the engine speeds up. Spray anywhere in the engine compartment (just about) and the engine speeds up.
So I try the stethoscope again, did this last week. Still hear nothing thru that, try a 16" piece of hose, nothing.
Remove the brake booster hose and plug it, no change.

My friend thinks its mechanical. So I watch the balancer while revving it to see if the bearing is bad. No change.

Took one of the many carbs I have and rebuilt it. Now the TNA PPV is on so thats it for today. Should not have taken the lunch break.
We will see what happens tomorrow. Thanks for your help!

[Poppy]

Just throwing this out there... is there any possibility that it might be an exhaust leak? I had one once that sounded like a valve tap.

[Canuck623]

Take the PCV valve out and put your thumb over it.

[Zephyrman]

^^^^ This was gonna be my next suggestion^^^

[Kruser]

Originally Posted by Canuck623

Take the PCV valve out and put your thumb over it.

On a related note, it was a long time ago and it was on a Chevy, but I'm just throwing out ideas.
On a lot of older vehicles, there was a PCV valve on one valve cover and a PCV fresh air intake hose somewhere else on the engine, either on an opposite valve cover on a V8, or on the opposite side of the valve cover on an I6 or I4. I knew a guy that took the PCV fresh air hose off and replaced it with a spark plug. (He thought a spark plug looked COOL sticking out of the valve cover) The engine vacuum from the PCV valve sucked so hard that the front and rear main seals were deforming and making a funny noise on the crankshaft. Removing the spark plug and hooking up this hose restored the function of the PCV and stopped the noise.
So in the case of your Zephyr, make sure that the fresh air intake of your PCV system is open as well as the PCV itself.
Like I said, just throwing out ideas....

[MichaelJennnings]

Originally Posted by Red 78'

Today I sprayed carb cleaner at the base and the engine sped up. Did this a few times. So I take off the carb, and EGR assembly and replace the gaskets. Try it again, same sound. Spray at the base and the engine speeds up. Spray anywhere in the engine compartment (just about) and the engine speeds up. So I try the stethoscope again, did this last week. Still hear nothing thru that, try a 16" piece of hose, nothing. Remove the brake booster hose and plug it, no change. My friend thinks its mechanical. So I watch the balancer while revving it to see if the bearing is bad. No change. Took one of the many carbs I have and rebuilt it. Now the TNA PPV is on so thats it for today. Should not have taken the lunch break. We will see what happens tomorrow. Thanks for your help!

Be aware that if you are using carb cleaner and spraying it all over the place, it can actually get sucked into the intake of the carb causing the idle to speed up because you are countering the lean condition of the leak. This is definitely a vacuum leak if it is speeding up when you use cleaner. Try the water instead. It won't affect the idle until you hit the leak. As mentioned, this could actually be a plugged PCV inlet and had caused a valve cover gasket to get sucked in or something along that line. There is a lot of vacuum on the PCV system and it is a major source of leaks. Also, the valve itself can be defective causing the noise. I've seen numerous valves lose the entire inside and cause a pretty good whistle. Try replacing the PCV Valve. I personally would have done more diags before jumping into the carb. I don't think this is going to fix the problem. You are chasing the symptom not the problem. I may be wrong and am willing to admit that because I haven't personally seen the car, but based on experience with this kind of problem, I have seen very few carb overhauls fix this unless it is either the base gasket or the main body gasket that is blown. But since you have indicated that the carb is tight, it is hard to say.

[Red 78']

I did not spray the carb cleaner all over the place, it was just anywhere or direction near the motor I sprayed resulted in the engine speeding up. The air cleaner was on and all hoses were connected when I did this.

I removed the heat shield from the exhaust manifold. There is no sign of leakage and the sound is not coming from there. It seem to be coming from the carb throat. But removing the air cleaner lid does not make it louder.

The valve cover shows no signs of oil leakage so I doubt it has shifted.
While I had the carb off, I checked bottom and top body bolts and they were tight. Also checked carb for blown out body plugs (had this happen once, was hard to track down).

I removed the main vacuum junction and brake vacuum connection from the manifold and checked its fitness, was OK.

With the motor off, PCV rattles like it should. With new gaskets again, I put the old carb back on. I pulled the PCV valve and put my thumb over the end. The suction stuck it to my thumb.
It does seem to be coming from this area, or the front of the motor but stethoscope found nothing.

Tomorrow I will replace the 200 mile old PCV, remove the spark plug from the other end of the valve cover, I mean check the fresh air inlet and hose for obstructions and try the water in looking for a vacuum leak.

Thanks for all your help! I appreciate all the help and ideas you have given me. I have heard and solved lots of noise problems in the 34 years of owning this car, but this sound I have never heard.

Here is a vid I posted elsewhere. Click the picture.

[dyngrngalaxie]

You've had some good advice from some sharp guys. Just throwing a thought out there. Any possibility it's an exhaust restriction? For what it's worth, ran into a collapsed inner jacket just ahead of muffler. Only showed up on acceleration, under load, jabbing throttle.

[diyfordguy]

Is there any oil showing near the valley seals under the intake? When you plugged all the vac hoses did that include the pcv valve one too? Since you say that it increases idle when you just spray around the motor, it kind of makes me wonder about the valley seals giving a shortcut for the pcv system to suck it in there instead of the opposite valve cover!

[dyngrngalaxie]

Never caught that before. Original owner - that's awesome.
Car looks drop dead gorgeous, under the hood too! It's an accomplishment just to keep it around for all those years, let alone for it to look like that. Very very nice! Hats off to you!

[Red 78']

Sorry I have not replied in awhile.

The 4-door is the one I've owned since 1978. The coupe I bought for $200 in 2007. No motor, wheels, seats, or paint.

Have not messed with it since February. Like I said, it sounds like it's coming from the carb throat. The exhaust system I put on new in 2008, It has a metal donut so it will not leak. I did take the shield off and check anyway. The sound happens in idle. You cannot hear it while driving, or under load. I will check the compression of the cylinders in a couple weeks, and try looking at some other things I've been thinking about since I stopped working on it.

I don't have the money to get it smog checked so I'm not going to worry about it right now. The 4-door needs smogged in May and I can't afford that either. Work has been non-existent.

Thanks for everyone's help!


I'm going to take my 4-door to the big car show this Sunday.
It has not been there in awhile. Just have detail the engine since I have not taken it to any show in a year and a half, and fix the damage my ex gardener did to both rear quarter panels, and replace the tail light he broke.


If your in Southern California make sure to go. There will be around 2000 Ford's and Mercury's there.