Front end noise and thermostat question

JDaPP · **Posted:** Wed Mar 28, 2012 1:05 am

I have noticed a noise coming from the front end. When I am at slower speeds I notice a sound that is like heavy rain/marbles hitting a tin roof or coffee perculating/heavy popcorn. When I come to a complete stop it goes away. Vehicle is running fine other than that.

Second issue I notice the thermostat only goes to slightly higher than between a third and a half. I haven't driven it in ~8 months due to a deployment, but I thought it almost always went to halfway. Not a big deal but I am just curious with the sound if this is an issue.

kapalczynski · **Posted:** Wed Mar 28, 2012 5:15 am

"a sound that is like heavy rain/marbles hitting a tin roof or coffee perculating/heavy popcorn"

- sounds like a fun guessing game. Any more clues? What have you done to narrow it down?

Have you looked under the hood while revving the engine a bit or tried putting it in neutral or park and revving a bit? does it make the same noise then or only while driving?

In other words, narrow it down to drive-train noise or engine noise.

It could be differential/drivetrain related. On the engine side something on the accessory drive system? Its common the alternator pulley/dampener goes out. What about the fan clutch, if it was completely gone and falling appart inside itself it might sound like :POPCORN:

Just some thoughts.

On the thermostat issue, its normal to run below half mark a bit, but not way lower.

- Mark

papaindigo · **Posted:** Wed Mar 28, 2012 8:20 am

When warmed up the temp gauge should sit between 1 tick left of dead vertical and dead vertical. Any location significantly colder than that is a sure indication of a failed or failing thermostat. Of course this assumes the temp sensor and the gauge are accurate. The sensor rarely goes bad and you can check the gauge by invoking the cluster test per the FSM.

A quick check on the alternator pulley is to set the vehicle at idle in park, pop the hood, remove engine cover, look down the serp belt to the serp belt tensioner. If the tensioner is bouncing around (mine barely moves) chances are the alternator pulley clutch is bad.

JDaPP · **Posted:** Wed Mar 28, 2012 4:44 pm

I have looked under the hood, but I did not remove the cover, I will try that and see what I can find. It does not make the sound when reving it only makes the sound when moving. I can take my foot of the brake at the light and the sound will start as I roll. There is also some squeaking but that has been there awhile and I think is more attributable to the suspension. I would say it is worse at slower speeds but that might just because I can hear it better. My inital thoughts were brakes (vehicle has ~80,000), CVs, ball joints or engine mounts. I am going to take it into a shop in the next couple of days but I am hoping someone has seen this before to help the process. Thanks to help.

camo · **Posted:** Wed Mar 28, 2012 11:42 pm

Marbles like sound from the front end at low RPM = one or both motor mounts bad... easy fix!!!
And do not worry about looking at them. They will look OK, as our libby mounts are also isolators and the isolation part of it is the one that goes bad not the mount itself.

camo · **Posted:** Wed Mar 28, 2012 11:47 pm

OOOO also, the temp gauge thing, you need a new thermostat, not a big deal either. total both mounts $80 plus about one hour labor, and the thermostat will be $112 plus about another hour of labor. Those are prices ordering from http://www.partswebsite.com/dcjpartsdep ... rt=1&type=
Order both motor mounts for the right. They are both the same but the right one is 10 bucks cheaper because of the heat shield which you will be able to reuse from the old one.
Hope that helps.

JDaPP · **Posted:** Thu Mar 29, 2012 11:18 am

Thanks! Now I just need to find a good mechanic in San Diego

Front end noise and thermostat question

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