Main IndexAuto Repair Home Search Posts SEARCH
POSTS
Who's Online WHO'S
ONLINE
Log in LOG
IN









Search Auto Parts

thumping noise in rear


  Email This Post



parker831
Novice

Nov 17, 2012, 12:20 PM

Post #1 of 9 (1583 views)
thumping noise in rear Sign In

I'm hearing a muffled thump in the center rear of my '97 Chevy Lumina (72,000 miles; 3.1 engine) about 2 minutes after I turn off the engine. It comes in a series of 2 thumps. This started about a week ago and now the thumping is occurring when I'm in a slow idle--just a series of two thumps. Maybe it's releasing pressure? Any ideas what this could be?


Racer 51
User

Nov 17, 2012, 1:24 PM

Post #2 of 9 (1551 views)
Re: thumping noise in rear Sign In

Make sure that one or more components of the exhaust sytem are not loose and viberating aganist the floorboards.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Nov 17, 2012, 2:20 PM

Post #3 of 9 (1533 views)
Re: thumping noise in rear Sign In

Racer, please don't respond to anything if you are not experienced in the subject and at least read the question.


Quote
about 2 minutes after I turn off the engine.




Parker831 ............. Does your van have rear A/C?

I ask because you could be hearing one of the air doors thumping shut.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



parker831
Novice

Nov 17, 2012, 2:52 PM

Post #4 of 9 (1528 views)
post icon Re: thumping noise in rear Sign In

Thanks guys. A friend's husband was able to diagnose it for me. He said the trouble is that my gas cap is not releasing gas fumes properly. So the noise I'm hearing is the release of the built-up gas fumes. Whew! Seems like it'll be an easy fix! Smile


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Nov 17, 2012, 3:00 PM

Post #5 of 9 (1521 views)
Re: thumping noise in rear Sign In

The gas cap is not supposed to release fumes. They spend a lot of money to prevent that.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



parker831
Novice

Nov 17, 2012, 4:41 PM

Post #6 of 9 (1512 views)
Re: thumping noise in rear Sign In

Hmmmm. Maybe I misunderstood. He said I need a specific type of gas cap. Maybe it's something else about the gas cap??


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Nov 17, 2012, 4:43 PM

Post #7 of 9 (1505 views)
Re: thumping noise in rear Sign In

If he's telling you to get a vented cap, do not listen to him. It's not even legal to do that. That system has to remain air tight by law.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Discretesignals
Ultimate Carjunky / Moderator
Discretesignals profile image

Nov 17, 2012, 5:21 PM

Post #8 of 9 (1499 views)
Re: thumping noise in rear Sign In

You sure the thumping noise is from the fuel tank? The tank is vented through the normally open EVAP vent valve, not the gas cap. If the EVAP vent valve is stuck closed or there is a restriction in the canister or lines and the EVAP system is purging the canister, that will put the tank under too much vacuum. The gas cap has a safety valve in it to relieve excess vacuum to prevent the tank for collapsing. Usually an EVAP problem such as stuck closed vent valve will set a trouble code.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

(This post was edited by Discretesignals on Nov 17, 2012, 5:22 PM)


parker831
Novice

Nov 18, 2012, 11:34 AM

Post #9 of 9 (1475 views)
Re: thumping noise in rear Sign In

Well, he made a hole in the gas cap to vent it and the thumping noise is gone. So maybe as you say, the EVAP vent valve is stuck closed? Is that an easy fix (I hope)? I'll consult a mechanic and see. I did get an error code, but now I can't find it. Thanks for the advice!






  Email This Post
 
 


Feed Button




Search for (options) Privacy Sitemap