# Strange Car Problem **URL:** \ **Category:** Factual Questions\ **Created:** [January 17, 2007, 4:50pm UTC](https://boards.straightdope.com/t/strange-car-problem/388334 "2007-01-17T16:50:27Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![Evil\_Joe](https://avatars.discourse-cdn.com/v4/letter/e/a9a28c/32.png) [@Evil\_Joe](https://boards.straightdope.com/u/Evil_Joe)\ **Post date:** [January 17, 2007, 4:50pm UTC](https://boards.straightdope.com/t/strange-car-problem/388334/1 "2007-01-17T16:50:27Z")
I have a 2001 Hyundai Sonata and when I am going slow or stopped something is making a pulsing type thump. At first I thought it might be the transmission slipping in and out then I thought it might be the power brakes slipping any ideas? ---
**Author:** ![Leaffan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leaffan/32/299_2.png) [@Leaffan](https://boards.straightdope.com/u/Leaffan)\ **Post date:** [January 17, 2007, 4:53pm UTC](https://boards.straightdope.com/t/strange-car-problem/388334/2 "2007-01-17T16:53:00Z")
[QUOTE=Evil Joe] I have a 2001 Hyundai Sonata and when I am going slow or stopped something is making a pulsing type thump. At first I thought it might be the transmission slipping in and out then I thought it might be the power brakes slipping any ideas? [/QUOTE] Leaky exhaust? I think we need more to go on. ---
**Author:** ![A.R.Cane](https://avatars.discourse-cdn.com/v4/letter/a/ee7513/32.png) [@A.R.Cane](https://boards.straightdope.com/u/A.R.Cane)\ **Post date:** [January 17, 2007, 4:54pm UTC](https://boards.straightdope.com/t/strange-car-problem/388334/3 "2007-01-17T16:54:34Z")
Could the sound be from somthing loose under the car, exhaust system, splash shield, etc. ? ---
**Author:** ![Evil\_Joe](https://avatars.discourse-cdn.com/v4/letter/e/a9a28c/32.png) [@Evil\_Joe](https://boards.straightdope.com/u/Evil_Joe)\ **Post date:** [January 17, 2007, 4:58pm UTC](https://boards.straightdope.com/t/strange-car-problem/388334/4 "2007-01-17T16:58:23Z")
[QUOTE=Leaffan] Leaky exhaust? I think we need more to go on. [/QUOTE] Sorry I wish I could give more info 🙂 Hmmm it is definitely more like noiseless thumps, very similar to when I have had transmission slipping. It doesn’t rev high or jump durring these events though which is why I thought it might be a belt slipping. ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [January 17, 2007, 7:39pm UTC](https://boards.straightdope.com/t/strange-car-problem/388334/5 "2007-01-17T19:39:35Z")
When you put it in park does it still thump? If so, does the thump go away when you rev the engine? I’m thinking maybe the engine is running rough. You might also want to check the fluid level in the transmission. ---
**Author:** ![Evil\_Joe](https://avatars.discourse-cdn.com/v4/letter/e/a9a28c/32.png) [@Evil\_Joe](https://boards.straightdope.com/u/Evil_Joe)\ **Post date:** [January 18, 2007, 3:06am UTC](https://boards.straightdope.com/t/strange-car-problem/388334/6 "2007-01-18T03:06:49Z")
[QUOTE=engineer\_comp\_geek] When you put it in park does it still thump? If so, does the thump go away when you rev the engine? I’m thinking maybe the engine is running rough. You might also want to check the fluid level in the transmission. [/QUOTE] I will check to see if it does it in park. Trans fluid level is good. The engine is running smoothly - I’m pretty sure its ok. If it is the transmission what will have to be done? Any ideas? ---
**Author:** ![Evil\_Joe](https://avatars.discourse-cdn.com/v4/letter/e/a9a28c/32.png) [@Evil\_Joe](https://boards.straightdope.com/u/Evil_Joe)\ **Post date:** [January 18, 2007, 3:15am UTC](https://boards.straightdope.com/t/strange-car-problem/388334/7 "2007-01-18T03:15:00Z")
I will check to see if it stops when I rev also - I don’t know what running a bit rough would sound like in this car so I shouldn’t dismiss that idea so quickly… 🙂 Any other ways to diagnose this? ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [January 18, 2007, 5:19am UTC](https://boards.straightdope.com/t/strange-car-problem/388334/8 "2007-01-18T05:19:57Z")
If I understand correctly, you feel this when going slow and while idling in gear. Do you feel it while going slowly while slowing down? While going at a steady speed? While speeding up? What’s the approximate speed under which you feel it, over which you do not? If you feel it while taking off from a stop, does the symptom go away when the transmission shifts into the next gear? When stopped and idling, do you feel it any gear positions besides D? Which ones? ---
**Author:** ![Evil\_Joe](https://avatars.discourse-cdn.com/v4/letter/e/a9a28c/32.png) [@Evil\_Joe](https://boards.straightdope.com/u/Evil_Joe)\ **Post date:** [January 18, 2007, 10:03pm UTC](https://boards.straightdope.com/t/strange-car-problem/388334/9 "2007-01-18T22:03:56Z")
[QUOTE=Gary T] If I understand correctly, you feel this when going slow and while idling in gear. Do you feel it while going slowly while slowing down? While going at a steady speed? While speeding up? What’s the approximate speed under which you feel it, over which you do not? If you feel it while taking off from a stop, does the symptom go away when the transmission shifts into the next gear? When stopped and idling, do you feel it any gear positions besides D? Which ones? [/QUOTE] I check that too! ( It is my wife’s car ) :smack: ---
**Author:** ![Evil\_Joe](https://avatars.discourse-cdn.com/v4/letter/e/a9a28c/32.png) [@Evil\_Joe](https://boards.straightdope.com/u/Evil_Joe)\ **Post date:** [January 18, 2007, 10:06pm UTC](https://boards.straightdope.com/t/strange-car-problem/388334/10 "2007-01-18T22:06:53Z")
I’ll check that too! ( It is my wife’s car ) :smack: ---
**Author:** ![Evil\_Joe](https://avatars.discourse-cdn.com/v4/letter/e/a9a28c/32.png) [@Evil\_Joe](https://boards.straightdope.com/u/Evil_Joe)\ **Post date:** [January 19, 2007, 5:26am UTC](https://boards.straightdope.com/t/strange-car-problem/388334/11 "2007-01-19T05:26:05Z")
Ok it seems to only do it when stopped or almost stopped in gear - Rev and Drive - it doesn’t do it in neutral. Looking at the tach it idles at about 1000rpms and when I put it in gear it drops to about 600rpms. These lower ( 600 ) rpms seem to be when the thumping starts. Over about 600 it doesn’t do it anymore.