Hi, I'm looking for some help interpreting my '00obw exhaust pipe paper towel test results.

 

I saw in some other thread about holding paper towel near the exhaust pipe. If the paper towel seems to get sucked into the exhaust, what does that mean?

 

I happened to have a paper towel at hand today and tried it on '00obw when I got home. It does seem like the paper towel gets sucked into the exhaust.

Here is video: Please select format: Apple Quicktime .MOV (download free player - sorry that's what my camera uses)

.MOV medium-res (1.3 MB) .MOV hi-rs (8.8 MB) .MOV low-res (0.5 MB)

or for Windows Media Player --> MPEG4 (0.4 MB) or .AVI (3.5 MB)

 

Then I did this test on '94 Legacy for comparison. It was a little harder to do the test since '94 Legacy has that dual tip muffler. However '94 Legacy did not seem to suck the paper towel onto the exhaust. Here is video:

Please select format: Apple Quicktime .MOV (download free player - sorry that's what my camera uses)

.MOV medium-res (1.4 MB)

or for Windows Media Player --> MPEG4 (1.4 MB) or .AVI (3.5 MB)

 

So what do you think? If you watch the video for both the '00obw and the '94 Legacy I think the difference is readily noticeable. I could try this test on '96 Legacy too for comparison if needed. Thanks!

Hi, I'm looking for some help interpreting my '00obw exhaust pipe paper towel test results.

 

I saw in some other thread about holding paper towel near the exhaust pipe. If the paper towel seems to get sucked into the exhaust, what does that mean?[...]

Sorry, but my computer doesn't have the necessary codec(s) to view your video. However, when I did that sort of paper test, I'd hold the paper so that it hung vertically, just at the end of the tailpipe.

 

At idle, the "puffs" of exhaust from each cylinder normally happen often enough to keep the paper away from the tailpipe. If there's a misfire, the paper will typically "fall back" to the end of the pipe. Sometimes an exhaust valve that's burned or sticking open can cause the paper to be sucked in.

 

Is there a particular reason you're concerned about the '00? Are there any other symptoms? Is the "sucking" rhythmic, or sporadic? Testing with a vacuum gauge can help determine if there's a significant problem, followed by a compression test, and perhaps a leak-down test if merited.

Well I'm not sure. The '00obw seems to be running fine. I just recalled the paper towel test today and decided to try it. On the '00obw the paper is definitely sucked slightly back onto the tailpipe, whereas on the '94 as a control it did not exhibit that behavior.

 

Did you try the .avi videos? Even older windows media players should be able to play that I believe.

[...]On the '00obw the paper is definitely sucked slightly back onto the tailpipe, whereas on the '94 as a control it did not exhibit that behavior.[...]

If it's minor, it could just have to do with differences in the cams (valve overlap).

Not to be rude or anything, but is there a point to this?

If it's minor, it could just have to do with differences in the cams (valve overlap).

Hm...that sounds good. Has anyone else tried this test on a 2.5L sohc to see if it behaves this way? The 2.2L did not. I guess I am nervous since I adjusted the valve lash about 10k miles ago...

Not to be rude or anything, but is there a point to this?

I'm not sure. I thought I remembered seeing this test in another post. It said something about if the paper gets sucked onto/into the exhaust it could mean an exhaust valve is not closing all the way or is sticking or something...can't remember for sure...

BAck in the day, way back in the day, this test was used to see if there was a burnt or stuck exhaust valve. The same thing could (DO NOT ATTEMPT) be done at the intake using your palm of your hand. Your hand should be pulled into the intake and not pushed out.

 

The proper way to do this is with a vacum gauge (and they are dirt cheap). The vacum gauge will tell you whats going on much better. The paper towel test may no longer be valid on the exhaust, as that was back before multiple or variable cam timing and emissions.

 

 

nipper