Grinding/Screech from Block
 

Hey all, back once again but this time the truck is street...street...well.... uh, street-somewhat. It runs and can get from A to B. With that being said!

I have this interesting issue where there's a grinding/screeching noise, like an old belt noise coming somewhere from around the block/behind the block. I've taken the belts off to ensure it's not something that's being turned, or the belts themselves. Still screeching.

I have no idea how to relate the noise to anything except possibly a loose bearing. It sounds like a wheel turning and grinding against something else? I don't have a video right now to showcase it, but imagine the noise that a loose fan with a bad bearing would make, until I can get a video.

The noise does not increase with RPMs/Acceleration.
The noise is constant.
Gear selection does not change anything. Noise occurs in P/N/D.
Engine Temp/Oil Temp doesn't affect it - Hot or Cold, noise occurs.
Noise occurs immediately after startup.
Noise does not exist when turning over.

1969 GMC Custom 1/2 ton
Chevy 350 small block, new plugs, new belts
Edelbrock Carb (1406?) - 500CFM (New)
Truck drives with no noticeable issues.

[EDIT]
SOLVED
Power brake plug in the back side of the Edelbrock was open. Once plugged, the sound stopped completely.
Will be hooking the brake booster hose to it appropriately soon.

Re: Grinding/Screech from Block
 

Disconnect your heater or A/C blower motor electric wire and see if that's it.

Re: Grinding/Screech from Block
 

Fairly certain it's disconnected; Tried to follow a wiring diagram with no luck. I disconnected an orange wire from the back of the wiper motor, and the heater assembly next to it has no wires attached to it.

I'll get a video when it's daylight outside and I'm off work.

Re: Grinding/Screech from Block
 

Check your transmission bellhousing and torque converter bolts. I know you said it's not RPM-dependent, but still...

Re: Grinding/Screech from Block
 

Check your starter. If it doesn’t disengage once the engine is started it can make a squealing noise.

Re: Grinding/Screech from Block
 

An electric motor with bad bearings that is not directly attached to the engine would squeal or grind but not change with engine RPMs/Acceleration, and it would also normally come on with the engine started or key on. So that would be my top suspect, a bad electric motor. The only electric motor like that on a stock truck is the blower motor. But some folks have put in accessories, such as electric fans on the radiator.

Re: Grinding/Screech from Block
 

I have had an exhaust leak make a noise like you describe. Very weird, but it had me chasing engine noises for a bit.

Re: Grinding/Screech from Block
 

The constant in all RPMs has me stumped, unless it's the heater motor. Just pull the fuse. There is the wiper motor, too, and that is above the back of the engine, so pull that fuse, too. How about a radio, is one in it? IIRC, they don't play while cranking, only before and after?

Re: Grinding/Screech from Block
 

If you put the key to the on position but don't crank the engine and there is no noise then
It's not a blower motor or wipers etc. simple way to rule those items out.

Take about a 36" piece of broom stick and hold it to your ear. Hold other end to starter, trans, back of engine etc.
you be amazed how much you can hear.
That may help you pinpoint the location.
Mark

Re: Grinding/Screech from Block
 

"Poor mans stethoscope" for sure. I've used a piece of 1/2" pvc for years.

Re: Grinding/Screech from Block
 

Or a long piece of hose. Great for exhaust leak diagnosis, you won’t hear that type of noise thru something solid.

Re: Grinding/Screech from Block
 

OP
Please post back when you figure it out.
Help the next guy.

Re: Grinding/Screech from Block
 

x2! And those who offered their help would like to know if they in fact did help you.

Re: Grinding/Screech from Block
 

Sorry everyone that it took so long to reply. We work 24 hours on the ambulance and I got busy.

I dropped my stethoscope into the engine, and isolated where the noise is coming from but it makes no sense - Noise is coming from the back side of the Eddy. When I lower the steth towards the block, the noise disappears. When I turn it around to the distributor, it disappears. The noise is loudest towards the bottom half of the eddy on the back side of the block.

I'll read through your responses right now.

[EDIT]
I had the starter tested at O'Reillys, no noises or issues.
Stethoscope located the noise to be the back lower half of the Eddy.
No changes with the blower motor/heater.

Re: Grinding/Screech from Block
 

I know that you said it doesn't change with RPM but pull the engine oil dipstick to make sure it is not hitting the crank.

Re: Grinding/Screech from Block
 

No change.

VIDEO
https://www.youtube.com/watch?v=nmnGATsI4ZU

Re: Grinding/Screech from Block
 

Spray the back side of the carb with carb cleaner to see if you have a vacuum leak.

Re: Grinding/Screech from Block
 

Carb gaskets leaking?

Re: Grinding/Screech from Block
 

What the hell is an "Eddy"??

Re: Grinding/Screech from Block
 

Edlebrock carb

Re: Grinding/Screech from Block
 

Yup, that is sure what it sounds like!

Re: Grinding/Screech from Block
 

I was thinking a little "man" named Ed, you know that special option that did not show up on the SPID...lol, I'm too funny...sorry.

Now we know, short for the carb.

Re: Grinding/Screech from Block
 

>>the eddy on the back side of the block.<<

What's a carb doing on the back of the block.


>>>... dropped my stethoscope into the engine.... When I lower the steth towards the block....When I turn it around to the distributor...<<

What kind of stethoscope do you drop, lower and turn around?

Re: Grinding/Screech from Block
 

Look at the video at 7 seconds and it looks like the "Eddy" is missing a plug that would normally be used for power brakes. And, again at 29 seconds. AND at 32 seconds...this one is the money shot...I don't see a plug. I hope that's it...easy fix!

Re: Grinding/Screech from Block
 

The noise is coming from the back of the Eddy, towards the end of the block. I can get more technical if necessary. I figured it wasn't that hard to understand.

The kind that you stick in your ears and listen to **** with.

Didn't think anything of that threaded hole, I'll run in and grab a plug for it, and cap anything else I find on it before I go. I have to run to O'Reilly's to grab line for the transmission cooler, I'll grab these while I'm out.