I got Gerbels in my Engine

[SteveCZ]

I've just recently started hearing this noise from the engine coming from the right side (passenger side inside truck).

 

After the truck is sufficiently warmed up, and I accelerate away from a stop (hard or soft acceleration, doesn't matter) I get what sounds like plastic or something rolling around under the hood. It is engine speed related, as I rev the engine it will do it, and if it idles, it won't do it.

 

At cruising speed of 60-65 it won't do it unless under load (up a hill).

 

I've read on here about a few guys using the "De carbonizer" for the top end of their engines, but I'm not sure if thats the issue here.

 

Heres my info:

 

99 Silverado Z71

5.3 Auto, Autotrac 4x4.

just over 50 grand on the odo.

 

It seems to lessen after I change the oil but its still there. All my levels are good and oil pressure is normal. Its not a knock or ping from octane or like the dreaded CSK..... just an annoying sound of marbles rolling around....

 

Thanks for any help

 

SteveCZ

[77ddt]

Glad to hear I'm not the only one with this problem. I just started noticing it a few months ago. The symptoms are exactly like you described. My truck is pretty similar to yours, 99 Z71, 5.3, Autotrac, and about 75K miles. I couldn't find anything loose under the hood or under the dash. Maybe it's something in the HVAC? It will probably be alot more noticeable after I get the steering knock fixed. Just got my parts today If you figure anything out, please post the solution.

 

Thanks,

Dave

[SteveCZ]

Another way to describe this is something along the lines of what Dave is saying.

 

It sounds like some kind of little candies rolling around in the HVAC Fan, but its not related to the HVAC fan speed at all, its purely engine RPM related.....probably most noticable around 1800-2200 rpm.... right before each shift.

 

Just some additional info....

[motobrett]

sounds like the coolant system has an air bubble..check the announcements at the top of the light duty forum for a fix

 

mine did this and i did the fix and it is nice and quiet now...

 

one thing the 'fix' doesn't say is in between cycles is to let the engine cool down again

[SteveCZ]

Well,

 

I think MotoBrett was right on this one.....

 

After I got home on Thursday from work, I went and bought a gallon of DexCool..... mixed it about 60/40 with water....

 

First thing I noticed when I popped the hood was that the coolant was about a half an inch below the Full Cold mark.

 

I topped it off (more than I should have), but I then let it run per the instructions.

 

I was bummed at first because it didn't get rid of the noise right away, but I let the truck sit all day Saturday after work on Friday night, and got in it this morning (Sunday), and low and behold, no more noise.... I proceeded to open up the over flow tank cap and heard a big bubble of air work its way out of the tank.

 

I know the system is pressurized, but it never made that much of an "air escaping" noise before..... I'm hoping that was my air bubble....

 

Good to know, thanks again MotoBrett

 

SteveCZ