Thud sound feel while idling

nbenjamin

Original poster
Member
Dec 7, 2011
76
Third time now I have felt / head this while sitting waiting for wife shopping. Sound like someone kicked under the truck somewhere around the middle I think closer to passenger side. Idling for a while. I felt the fan kick on. Some time soon after I felt / heard it
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
I'm just not getting a "feel" for your problem yet to guess the cause. Electric fans can "kick on", but our engine fan is electroviscous and spins up slowly . A "thud" usually means a one-time mechanical impulse, not a "vibration". Could you describe it with more verbosity?

Are you familiar with the 10 Hz rotational vibration caused by collapsed motor mounts? The one that gets better in PARK compared to DRIVE?
 

nbenjamin

Original poster
Member
Dec 7, 2011
76
the roadie said:
I'm just not getting a "feel" for your problem yet to guess the cause. Electric fans can "kick on", but our engine fan is electroviscous and spins up slowly . A "thud" usually means a one-time mechanical impulse, not a "vibration". Could you describe it with more verbosity?

Are you familiar with the 10 Hz rotational vibration caused by collapsed motor mounts? The one that gets better in PARK compared to DRIVE?

i have been chasing this vibrating issue since we were in the other forum . I thought it was my harmonic balancer but GM said i would prob have thrown a code if it was ( 6 months still waiting for a answer back ) I did notice my water pump has minimal vertical play but there is play . purchased a new pump think this is my 3rd now haven't installed it yet ( Canadian cold weather ) , thought it was my fan clutch , did test unplug etc and took fan off as per your instructions no difference . so my last guess was water pump .

now you said motor mount hmmmm . the thud is a new thing now . feels like someone kicked under the truck a very heavy thud i actually looked around cause i thought someone backed into me . i took spare off thought it was that .it happens only when sitting idle . almost like something sprang into or out of place . alomost lke if you were sitting on a old couch and a spring pops .

" Are you familiar with the 10 Hz rotational vibration caused by collapsed motor mounts? The one that gets better in PARK compared to DRIVE? " no i am not familiar with . but when i do get that weird vibrating feel i tried changing trough all gears including neutral and no change . that's why i thought could be water pump

would a failing fan throw a code ? also do the fan fails intermittently or wither they fail or don't ?
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
We had a thread on the OS - "Feeling of being bumped when stopped". If it's a one-time only impulse after you drive to a stop and then leave the brakes on instead of putting it in park, it might be a driveshaft slip joint that needs grease. GM went to a nickel-plated design later, and I even heard of some folks getting a free replacement.
 

nbenjamin

Original poster
Member
Dec 7, 2011
76
the roadie said:
We had a thread on the OS - "Feeling of being bumped when stopped". If it's a one-time only impulse after you drive to a stop and then leave the brakes on instead of putting it in park, it might be a driveshaft slip joint that needs grease. GM went to a nickel-plated design later, and I even heard of some folks getting a free replacement.

Could be , I saw that one but I was in park for about 10 mins when it happens.
 

Forum Statistics

Threads
23,429
Posts
639,198
Members
18,647
Latest member
Lortigemt

Members Online