clunking sound under hood.... - The 1947 - Present Chevrolet & GMC Truck Message Board Network

GMC Guy · 03-18-2010, 02:04 AM

yesterday i noticed a "clunking" sound when stopped at a light. i was coming back from a friend's house a few miles away. and out on a long open road i was happily cruising at around 70. engine temp was good, oil pressure good. got into town and when i stopped at a light i heard a intermittent clunking noise...
i pulled over, got out and looked, but didn't see any obvious causes. i did find it weird that it was only making the sound when i stopped completely or put it in park. but not when driving down the road.
so i began thinking...water pump? balancer? fan?
i'm really at loss here guys, need some advice...

*seems to be making noise after high speed driving/hard acceleration, then coming to stop (noticed that tonight)

**also, no noticeable loss in power.

Sillyoldman · 03-18-2010, 02:24 AM

Clunk or clatter? My first thought if its clatter would be a nut backed off a rocker stud.

Stepsideride · 03-18-2010, 02:50 AM

how do your motor mounts look?

GMC Guy · 03-18-2010, 03:10 AM

1. i'll check under the valve covers tomorrow

2. motor mounts are probably original, motor was replaced in 1996 (well before i owned it), they look pretty old so i doubt they replaced them

Turbo85GMC · 03-18-2010, 07:53 AM

Does it clunk from Fwd to Rev and back again? Check out the u-joints as well.

GMC Guy · 03-18-2010, 12:29 PM

i haven't noticed it making noise in reverse. but it's doing it all the time either

what should i check for with the u-joints?

slipkorn34 · 03-18-2010, 12:38 PM

mines doin the same thing only itll only do it a few times a week, and completely at randomill check the rockers too since my valve cover gaskets started leaking anyway

GMC Guy · 03-18-2010, 12:59 PM

does it only do it when you're stopped?

jchav62 · 03-18-2010, 01:01 PM

Since you say you are losing power, my guess would be something in the valve train.

GMC Guy · 03-18-2010, 01:16 PM

my bad, i'm not really losing any power. and i don't hear anything abnormal under acceleration. only when coming to a stop

jchav62 · 03-18-2010, 04:21 PM

Make sure the torque converter is tight. I had one come loose on me one time and it made a 'knocking' sound.

GMC Guy · 03-18-2010, 05:20 PM

can i tighten the torque conv. with it in the truck?

Stepsideride · 03-18-2010, 07:01 PM

yes you can its only three bolts.

Hoods69BadBowTie · 03-18-2010, 07:19 PM

Quote:

Originally Posted by jchav62

Make sure the torque converter is tight. I had one come loose on me one time and it made a 'knocking' sound.

x2 That's what I was wondering or maybe bad u-joints as well.

GMC Guy · 03-18-2010, 07:40 PM

the truck was making the noise again today, luckily it did it long enough so i was able to look under it to see where the clanking was coming from......turns out an exhuast pipe hanger worked itself loose and the pipe coming off the driver side header was banging up against the tranny crossmember

thanks for all the advice, fortunately this time the problem was something stupid.

03-18-2010, 02:04 AM	#1
GMC Guy Registered User Join Date: May 2009 Location: Sparks, NV Posts: 913	clunking sound under hood.... yesterday i noticed a "clunking" sound when stopped at a light. i was coming back from a friend's house a few miles away. and out on a long open road i was happily cruising at around 70. engine temp was good, oil pressure good. got into town and when i stopped at a light i heard a intermittent clunking noise... i pulled over, got out and looked, but didn't see any obvious causes. i did find it weird that it was only making the sound when i stopped completely or put it in park. but not when driving down the road. so i began thinking...water pump? balancer? fan? i'm really at loss here guys, need some advice... seems to be making noise after high speed driving/hard acceleration, then coming to stop (noticed that tonight) *also, no noticeable loss in power. __________________ Greg 1974 GMC 1/2 Ton SWB Fleetside L33 5.3/4l65e .................__ ............._____l __\__ ..............l_(O)_ l___(O)]

03-18-2010, 02:24 AM	#2
Sillyoldman #16876 Join Date: Apr 2005 Location: Auburn WA Posts: 12,266	Re: clunking sound under hood.... Clunk or clatter? My first thought if its clatter would be a nut backed off a rocker stud. __________________ Posted via Stationary Device '71 Custom Deluxe C-20 402. '67 Buick Special 455. '49 Plymouth Special Deluxe. *"I love that old car smell"* *Some people are like Slinkies... not really good for anything, but they still bring a smile to your face when you push them down a flight of stairs.*

03-18-2010, 02:50 AM	#3
Stepsideride Registered User Join Date: Feb 2010 Location: Murfreesboro Tennessee Posts: 129	Re: clunking sound under hood.... how do your motor mounts look?

03-18-2010, 03:10 AM	#4
GMC Guy Registered User Join Date: May 2009 Location: Sparks, NV Posts: 913	Re: clunking sound under hood.... 1. i'll check under the valve covers tomorrow 2. motor mounts are probably original, motor was replaced in 1996 (well before i owned it), they look pretty old so i doubt they replaced them __________________ Greg 1974 GMC 1/2 Ton SWB Fleetside L33 5.3/4l65e .................__ ............._____l __\__ ..............l_(O)_ l___(O)]

03-18-2010, 07:53 AM	#5
Turbo85GMC Registered User Join Date: Apr 2005 Location: Medford, MA Posts: 307	Re: clunking sound under hood.... Does it clunk from Fwd to Rev and back again? Check out the u-joints as well. __________________ '85 GMC 1500 "Friends don't let friends drive stock!"

03-18-2010, 12:29 PM	#6
GMC Guy Registered User Join Date: May 2009 Location: Sparks, NV Posts: 913	Re: clunking sound under hood.... i haven't noticed it making noise in reverse. but it's doing it all the time either what should i check for with the u-joints? __________________ Greg 1974 GMC 1/2 Ton SWB Fleetside L33 5.3/4l65e .................__ ............._____l __\__ ..............l_(O)_ l___(O)]

03-18-2010, 12:38 PM	#7
slipkorn34 Registered User Join Date: Dec 2009 Location: Eden Prairie, MN Posts: 73	Re: clunking sound under hood.... mines doin the same thing only itll only do it a few times a week, and completely at randomill check the rockers too since my valve cover gaskets started leaking anyway __________________ 1969 mercury cougar XR-7 - sold 1978 Chevy C-10 Scottsdale - sold 1996 chevy k1500 - sold 1970 mercury monterey - sold 1971 chevy c10 4 speed 4x4 - dd

03-18-2010, 12:59 PM	#8
GMC Guy Registered User Join Date: May 2009 Location: Sparks, NV Posts: 913	Re: clunking sound under hood.... does it only do it when you're stopped? __________________ Greg 1974 GMC 1/2 Ton SWB Fleetside L33 5.3/4l65e .................__ ............._____l __\__ ..............l_(O)_ l___(O)]

03-18-2010, 01:01 PM	#9
jchav62 1962 C-10 Join Date: Apr 2005 Location: Las Vegas, New Mexico Posts: 4,978	Re: clunking sound under hood.... Since you say you are losing power, my guess would be something in the valve train. __________________ Joseph Chavez "See the USA in a Chevrolet!!" ......................_____ .........________//__{\_____ ,,,,,,,/__(O)___//___/__(O)_/ 1962 C10 Shortbed Fleetside 327/th350 GV overdrive 1974 C10 Longbed Fleetside 350/th350 "The Trash Truck" 1999 Chevy 2500 OBS, Longbed 5.7/4L80E 4x4 2015 GMC Sierra SLE 1500 4x4

03-18-2010, 01:16 PM	#10
GMC Guy Registered User Join Date: May 2009 Location: Sparks, NV Posts: 913	Re: clunking sound under hood.... my bad, i'm not really losing any power. and i don't hear anything abnormal under acceleration. only when coming to a stop __________________ Greg 1974 GMC 1/2 Ton SWB Fleetside L33 5.3/4l65e .................__ ............._____l __\__ ..............l_(O)_ l___(O)]

03-18-2010, 04:21 PM	#11
jchav62 1962 C-10 Join Date: Apr 2005 Location: Las Vegas, New Mexico Posts: 4,978	Re: clunking sound under hood.... Make sure the torque converter is tight. I had one come loose on me one time and it made a 'knocking' sound. __________________ Joseph Chavez "See the USA in a Chevrolet!!" ......................_____ .........________//__{\_____ ,,,,,,,/__(O)___//___/__(O)_/ 1962 C10 Shortbed Fleetside 327/th350 GV overdrive 1974 C10 Longbed Fleetside 350/th350 "The Trash Truck" 1999 Chevy 2500 OBS, Longbed 5.7/4L80E 4x4 2015 GMC Sierra SLE 1500 4x4

03-18-2010, 05:20 PM	#12
GMC Guy Registered User Join Date: May 2009 Location: Sparks, NV Posts: 913	Re: clunking sound under hood.... can i tighten the torque conv. with it in the truck? __________________ Greg 1974 GMC 1/2 Ton SWB Fleetside L33 5.3/4l65e .................__ ............._____l __\__ ..............l_(O)_ l___(O)]

03-18-2010, 07:01 PM	#13
Stepsideride Registered User Join Date: Feb 2010 Location: Murfreesboro Tennessee Posts: 129	Re: clunking sound under hood.... yes you can its only three bolts.

03-18-2010, 07:40 PM	#15
GMC Guy Registered User Join Date: May 2009 Location: Sparks, NV Posts: 913	Re: clunking sound under hood.... the truck was making the noise again today, luckily it did it long enough so i was able to look under it to see where the clanking was coming from......turns out an exhuast pipe hanger worked itself loose and the pipe coming off the driver side header was banging up against the tranny crossmember thanks for all the advice, fortunately this time the problem was something stupid. __________________ Greg 1974 GMC 1/2 Ton SWB Fleetside L33 5.3/4l65e .................__ ............._____l __\__ ..............l_(O)_ l___(O)]



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