Thump, Thump noise from driver side inside engine compartment

[gmhowe]

My 96 CE has developed a thumping noise sometimes after turning the engine off. Doesn't do it all the time and averages 4-6 thumps. Seems to be coming from around the computer area but cannot isolate it. Any thoughts ?
Thanx
Gordon

 

[Hib Halverson]

These thumps---

They occur after the engine has stopped running or they occur as it stops running?

 

[gmhowe]

It occurs after turning the engine off, but not every time. Today went to the store and it did it, when I got home not thumps at all.

 

[LLC5]

It occurs after turning the engine off, but not every time. Today went to the store and it did it, when I got home not thumps at all.

It could be an air pocket in the cooling system. Did you have any cooling system service done, and is the coolant level at the full mark?

 

[hcbph]

It could be an air pocket in the cooling system. Did you have any cooling system service done, and is the coolant level at the full mark?

That's one I've not seen or heard before. Really hope it's true as that should be a relative easy fix. I don't know what it would be other than something like bearings but then again I'd expect that to happen every time.

 

[gmhowe]

Got to check it out, am thinking maybe the master brake cylinder. I know its not coming from the engine itself but from the firewall.

 

[hcbph]

Got to check it out, am thinking maybe the master brake cylinder. I know its not coming from the engine itself but from the firewall.

I didn't realize from your comments it wasn't originating in the engine. Might be the check valve on the power brake booster. Maybe have someone assist you, using a long handled screwdriver, use it like a stethoscope while turning off the engine and see if you can narrow the point of origin down.

 

[gmhowe]

Well figured out where it's coming from, Its the Headlight gear when I turn off the parking lights, Its like the headlight is trying to close more ( even though they are close ). Tried turning off the parking lights with hood up and you can see the Headlight motor trying to keep closing even though I didn't turn on the headlights, and can see shavings from the gear falling out. I don't know if that can be adjusted or what to adjust since when I turn on the headlights and close them things work fine?

 

[Hot Rod Roy]

Try this:

http://www.corvetteactioncenter.com...ns-headlight-motor-gear-replacement-1222.html

 

[gmhowe]

Thanx Hot Rod for the info, but still curious as why all of a sudden did it start this and how could things get out of whack and trying to keep on closing after turning the parking lights off which don't even have anything to do with the headlights

 

[Hot Rod Roy]

Surprise, surprise! Things do eventually wear out! This is a normal wear item on our beautiful '88-'96 C4's!

Your '85 headlight motors won't have this problem, but they would appreciate a good cleaning of the limit switches and lubrication (Lubriplate or CRC Sta-Lube) of the motor bearings. The '84 - '87 headlight motors are a different design. (Maybe you already knew that.)

 

[LLC5]

Thanx Hot Rod for the info, but still curious as why all of a sudden did it start this and how could things get out of whack and trying to keep on closing after turning the parking lights off which don't even have anything to do with the headlights

That's not exactly the firewall, but noise transfer can be a bitch, believe me I know. Sometimes chassis ears are your best friend. Glad you found the problem.

I don't think your park lights are related to the problem, what most likely happened is that while driving vibration moved the headlight out of the limit range because of the worn gears, and when you turned the key off the headlight motor cycled until it got back into range. Good luck with the repairs.

 

[gmhowe]

Gears on order should be here by Wed this week, figured I might as well replace both.
Thanx for all your help guys, as always help is here when I need it.
Now to figure out why my 85 driver side sometimes needs a smack on the headlight to get to open:L
Gordon

 

[gmjunkie]

Gears on order should be here by Wed this week, figured I might as well replace both.
Thanx for all your help guys, as always help is here when I need it.
Now to figure out why my 85 driver side sometimes needs a smack on the headlight to get to open:L
Gordon

The brushes in the H/L motor are getting worn out,I usually take them apart and go down to the hardware store and match up a set out of their vacuum cleaner motor brush assortment!:L

 

[Hot Rod Roy]

Now to figure out why my 85 driver side sometimes needs a smack on the headlight to get to open.

See post #11 before you resort to any new parts. Easy and cheap. Inspect the brushes while you're in there. I've got 240,000 on my '84, and I'm quite sure my headlight motor brushes are original. gmjunkie knows his stuff, but I like to try the easy way first.