Odd High-Pitched Whine

[Redskinsjbs]

I have a very odd high pitched whine coming from my engine bay. At first I thought that it was a water pump, but I changed that and the whine did not go away. Thomas and I tried to locate the source of the sound and we *think* that it is coming from around the carburetor, but we aren't completely sure. We were able to change its pitch one time by wiggling the carb.

So here are the symptoms described as best as I can:

The pitch does not change with the speed of the engine or car, nor does it change with the amount of load on the engine (fast acceleration, slow acceleration, deceleration down a hill without and added gas . . . I would call this 'engine braking' for lack of a better term)

The sound can be intermittent; not in a rhythmic way, but in a comes and goes way. And as far as I can tell, it does not matter how cold the air temperature is, how cold or warm the engine is or the load on the engine.

The pitch of the sound can also be variable, but it tends to stay at the pitch that is primarily heard in the video below.

I am going to replace both the thick and thin gaskets on the carburetor, but I just wanted to see if someone out there has had a problem like this before and if they had a solution.

TIA,

Jay


And here is the video:

Mysterious Engine Whine on Vimeo

Mysterious Engine Whine on Vimeo

[Aardvaark]

Alternator brush whine maybe?

[Aardvaark]

Also, I've heard vacuum hose leaks create a whistle.

[Redskinsjbs]

Originally Posted by Aardvaark Alternator brush whine maybe?

I thought about this, so I removed the belt (for less than 5 seconds of actual run time) and the sound still was there.

Originally Posted by Aardvaark Also, I've heard vacuum hose leaks create a whistle.

Yeah, once this video loads, I think that you may be amazed at the volume of the noise, but I will take thing suggestion as something to look for.

[Aardvaark]

Wow! That is a strange sound.

Suggest you get yourself a length of heater hose and use it as a stethoscope
holding one end to your ear and search for the source if you haven't already.
I can always pinpoit the source of noises eventually using this old mechanics method.

[Redskinsjbs]

Yea, Thomas and I did this and we think that we located it to around the carb. That is how we located it. BUT, I will give it another go in the morning and see what I get.

[Aardvaark]

It'll make a mess, but sometimes squirting some light oil around
the carb base will change the sound enough to verify that as the source.
Or even packing the area with rags to muffle the sound if that's the source.

[Redskinsjbs]

Ok, a few more things that I can try tomorrow while I try to diagnose this problem further. I will let you know what I come up with.

[CDN OpelNut]

Could be timing chain rub. How worn are the tensioners? Noise can travel down the head and sound like its coming from the intake/exhaust area.

[SpringGT]

Jay, on the video it really sounds like a metallic noise to me more than a vacuum leak. Check to see that something isn't rubbing on the flwheel or an accessory pulley isn't rubbing on something.
Bob

[tomking]

I made the mistake when fitting weber carbs in place of the original Solex of not using the right gasket and base. You need a different gasket and base for the weber vs. the solex as the flat bases are different. JM2CW

[MICAH1]

As I recall...... Like Jay stated in his post, and video, that sound is coming from the base of the carb (had to be there to hear it). It is not metallic, does not come from the alternator (bran spanking new), plus the vac hose from the brake booster is new and very secure. The sound did change when we rocked the carb from side to side. We also noticed that all four nuts used to hold down the weber to the intake were very loose. We did re-tighten them. One other thing of notice... as the engine warmed up the sound cleared. I am thinking that the gasket(s) expanded and sealed the vac leak and sound. Jay is ordering new gaskets so we hope that will satisfy this issue.

Also a re torque of the intake/exhaust bolts won't hurt!!!!!

[hrcollinsjr]

Did you remove the valve cover cap to see if the sound got louder? I would think it would IF it were internal.

Simple process of elimination. You've removed the belt with no change in sound. If it isn't internal then you're left with vacuum leak or looking at whatever else that might be rotating at idle. Flywheel? A friend's GT, years ago, was making a terrible sound and it turned out that the wrong bolts had been used in the flex plate of his AT and they had backed out rubbing the dust cover.

When I can hear it on a low quality video, it's BAD!

Harold

[Redskinsjbs]

Well, something that I don't understand is that it has no rotational cues to it whatsoever. and if I rev the engine, through its entire rev range, the pitch will not change at all! BUT, the pitch of the sound will change randomly when I am not even touching the car!

Gosh! Frustrating, frustrating, frustrating!

[ghcoe]

Does not sound like a vacuum leak to me. Sounds like what you would hear at a saw mill. I would look at the flywheel/flex plate for something stuck or rubbing against it. Sounds like reverberation which is very hard to track down. Reverberation transfers well through different densities of metal and seem to appear someplace else because of the metal density response.

George

[Aardvaark]

On my stone age pc it sounds like a vacuum leak and not metallic
like a timing chain or tensioner.
It could be, but just recently I helped correctly diagnose a worn
timing chain on a 1971 Chevy Monte Carlo with a small block 350
and it sounded nothing like Jay's noise. it also changed pitch with engine rpm at idle as would be expected. Plus it was obviously comming from inside the timing chain cover and sounded like a dragging component and lower in pitch. I've heard other worn TC's and never have thet sounded or behaved like this noise. It could be a first though, since it's an Opel.

I going with a blown carb base gasket too.
I'd try wrapping that rag around the base and see if that changes the tone.

[OriginalOpelGTOwner]

Sounds like an air pressure leak to me like a wind instrument. I would look for an air pressure leak somewhere in the exhaust system. In this case the leak just happens to be through a very small hole tuned to that frequency. No matter how much air pressure is behind the leak the frequency will not change just like a wind instrument.

[Redskinsjbs]

Alright. So I spent the day tinkering with the car and I am just about sure that it is a leaky carb gasket. I sprayed starting fluid onto the gasket and the whistle would stop about 3 to 5 seconds afterward and come back around 15 to 20 seconds later. I have to say, if that isn't a result, I don't know what is!

So, I have ordered both the thick and the thin gaskets for a Weber 32/36 from OGTS and I am just awaiting their arrival.

A neighbor of mine who works on old VWs and Mercedes said that with a vacuum leak that large, I could be in danger of burning some valves. Is this true? Would a compression test tell me if I did any damage?

TIA,

Jay

[guyopel]

I would not expect that with what you have been running but you can do a compression test but why have you not done a vacuum test with a good vacuum gauge ? This would be helpful to diag. leaks and show you what your normal readings are when you fix the leak . HTH
John

[markandson]

Originally Posted by Redskinsjbs Alright. So I spent the day tinkering with the car and I am just about sure that it is a leaky carb gasket. I sprayed starting fluid onto the gasket and the whistle would stop about 3 to 5 seconds afterward and come back around 15 to 20 seconds later. I have to say, if that isn't a result, I don't know what is! So, I have ordered both the thick and the thin gaskets for a Weber 32/36 from OGTS and I am just awaiting their arrival. A neighbor of mine who works on old VWs and Mercedes said that with a vacuum leak that large, I could be in danger of burning some valves. Is this true? Would a compression test tell me if I did any damage? TIA, Jay

IDK but seems to me that the only way you could burn valves/pistons would be to have it out on the road under load and be pulling sooooo much air in at the base of the carb that you lean out the mixture.

[wrench459]

Originally Posted by Redskinsjbs So, I have ordered both the thick and the thin gaskets for a Weber 32/36 from OGTS and I am just awaiting their arrival. Jay

Jay
I've found that the 32/36 is a little to much carb for the 1.9-2.0L engines.
Theres more power to be found by dropping the carb. closer to the intake.
Make sure you dress the intake and carb. flanges to get the best sealing you can. BTW I only use the thin gasket without a heat shield.

Originally Posted by markandson IDK but seems to me that the only way you could burn valves/pistons would be to have it out on the road under load and be pulling sooooo much air in at the base of the carb that you lean out the mixture.

Theres other factors...
cooling system or should I say lack of
Ignition timing
and A/F ratio
Anything that raises the cylinder combustion temps over 1800 degrees or so can lead to trouble. Don't get the EGT's confused with the cylinder temps.

[MICAH1]

Guys,
I think we just might be getting ahead of ourselves with this run-a-way train of burnt valves/pistons. MarkandSon makes more logical sense about the air leaning out the mixture from the carb to the cylinders. But that does not fit this problem..... remember that Jay very recently got his title, and temp tags, so he has not had the opportunity to run his beast under serious load around town/highway. The leak as we hear it now only came to light last week!! My bet is on the thick gasket between the carb base, and heat shield.

[Redskinsjbs]

We will have to wait and see what the new gaskets do.

@ John (GuyOpel) - Good idea, I will run a vacuum test tomorrow to see what I have right now. Where is a good place to tap in to the system?

@ Jeff (markandson) - That is good to hear. I really wouldn't want to have done all of this work, only to have to do a whole lot more because of my incompetence.

@ Dan (wrench459) - I am going to run with what is normal before I start experimenting. That said, when you say dress the intake, what specifically are you saying to use?

[wrench459]

Originally Posted by Redskinsjbs @ Dan (wrench459) - I am going to run with what is normal before I start experimenting. That said, when you say dress the intake, what specifically are you saying to use?

The PO's tend to over tighten the carb thereby warping the mounting surfaces of both the carb flange and the intake.
Make sure both are flat.

[Redskinsjbs]

Originally Posted by wrench459 The PO's tend to over tighten the carb thereby warping the mounting surfaces of both the carb flange and the intake. Make sure both are flat.

Gotcha, I will be sure to do that.