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Continuing saga of the noise

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drooartz

drooartz

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So I spent a bit more time this weekend working on the Tunebug. I dove into my recurring noise issue (sort of a ticking, pffft-ing, heard under load). The car seems to be running fine otherwise -- though I don't have much of a frame of reference to know as I've never driven anything like the Tunebug before.

Here's what I've done over the last month or so:

* Tuneup (points, timing, carb sync). Car is running well as far as I know.
* Timing is set to 28*BTDC at high RPM (with all advance in), as checked with vacuum advance plugged and engine revved. This is conservative for this motor, but should rule out pinging.
* Drove the car with the vacuum advance plugged (both sides) to see if that was having a strange effect. No change at all.
* Wondered about the header hitting the car where it passes through the frame. Wrapped the edges of the frame with a bit of cut-off fuel line, figuring the rubber line would muffle the sound if that was the culprit. No change in the sound at all.
* Thought it was an exhaust/intake leak issue, had a LBC mechanic install new gaskets (Payen) and check everything. Made no difference.

I'm running out of things to check. I may call the mechanic back and get the car back to him. It wasn't running when I brought it down last time (I had pulled the carbs already) so I couldn't make the noise for him. A quick test ride with more experienced ears might help.

I've had a few others listen to the noise, and so far there have been no insights.
 
And you're pretty sure it's coming from the motor or something connected to it?

I had the strangest noise for a long time after I first got my Midget.
I could not locate it, no matter what I did or what I tried.
I pretty much had given up ever finding it.
Then I got a random orbital polisher on sale and wanted to try it out, so I went to work on the Midget.
Strangely enough whenever I would pass it over one area of the hood that confounding noise would appear.
So I closed in on the noise with the polisher vibrations and found the rubber hood buffer on that side was missing. When I would drive at certain times that area would vibrate just right and the noise would happen.
When I would rev up the engine the noise would happen and rise and fall with the revs.

I spent $3 and fixed the problem with a replacement rubber buffer.
 
RickB said:
And you're pretty sure it's coming from the motor or something connected to it?
Click to expand...
I am sure of nothing, just that it occurs under load and seems, as best as I can tell, to be coming from the front half of the car.

One other thing I did try:

I tied the accelerator and clutch cables down so that they wouldn't rub on the bonnet. Didn't help.

I do have all the rubber buffers in place.
 
Big speakers and a nice amp, then play your favorite driving music while zipping around?

OK - that was the only smart-axed remark I have.

:wink:
 
I'm sure you've done this already - place your hand or some other obstruction over the tail pipe and listen for sounds from places there shouldn't be sounds?

You only hear the noises under load, meaning in motion? Make a check list of what components are effected when the drive train is under load. Work your way from front to back - clutch, trans, driveshaft, differential, springs, shocks, brakes, etc. Would a universal joint make those sorts of sounds if it was dry or low on grease? Have you checked the tires? A rock or nail, etc. wedged in the tread could cause a ticking noise and the pffft-ing sound maybe a belt going/gone bad?

I know you've been very thorough with the more obvious probable causes. Maybe a bit of advice from Sherlock Holmes may help: “...eliminate the impossible, whatever remains, no matter how improbable, must be the truth.”
 
Under load, but not speed related. I could get the noise to happen with the parking brake on -- brake on, start to release clutch, engine loads up and makes sound.

Haven't tried the tail pipe blocking -- will give that a go tonight.
 
Drew do you have a gear reduction starter? How about a few pictures of underhood the tune-bug? (plus I haven't seen the pics of it completely installed yet!)
 
Standard starter.

I'll post a few new underhood pictures tonight.
 
Try this: start the engine, then get behind the car and hold a rag on the end of the tail pipe. Listen carefully, you might hear increased puffing or sounds of rushing exhaust gas from the system.

There may be a loose exhaust connection somewhere, or maybe a loose or cracked manifold.

Strange, please keep us informed. :yesnod:
 
Drew,
Have you tried the parking brake on and partial release of the clutch with the bonnet raised. Have your helper be at the controls and you try to listen from the engine compartment. Make sure you stand on the side. If you can hear it, then get a long listening hose to help you find the location of the sound. Once you can reproduce it, it can be found. My mechanic friend has microphones that he places at various spots and then has the noise repeated. Have you tried taking off the fan belt? Loose motor mount? Clutch slave cylinder hard line noise. Fan hitting the radiator? Crank pulley comming apart? Take the end of the exhaust pipe and try to wiggle it hard. Then try to wiggle the down pipe between the header and the muffler (don't burn yourself). You can also put it on a lift and listen from underneath with an partner in crime at the controls.
Good luck
Scott in CA
 
The way you have described the sound and the fact it only happens under load sure sounds like a very small exhaust leak. No matter what I think of, I just keep coming back to this.
 
Drew,
I have what sounds to be a noise very similar to yours. It turned out to be a tiny exhaust leak in the joint between the exhaust manifold and pipe at the clamp. Still haven't fixed it....
 
Drew, I know you did before but can you post (or repost) some video with the sound?
 
I still think it is an intake/exhaust leak, but I'm trying to rule out any other possibilities. A couple weeks ago I had a local mechanic work on the intake and header, and that was supposed to have cleaned up the exhaust problem. Obviously, it didn't. I just want to make sure I've checked through the other options before I take the car back down there (it's a bit of a hassle to get down there). Besides, the weather has been so nice that I don't want to miss the nice driving days while I have them. Not too many left at this time of year.

I haven't ruled out a bad engine mount (though they are new). It's not the fan/radiator, and the crank pulley is new as well.

I did try the parking brake/load the engine trick, with a mechanically adept friend under the bonnet to listen. He also thought exhaust/intake leak, but couldn't nail it down.

Here's a sound file of the noise (you can really hear it at about 19 seconds in):

https://www.drooartz.com/public/tunebug_noises.mp3

We've got fantastic weather this week, so I'm mostly just going to drive the car.

And here's some quick photos of the engine bay from tonight. Sorry about the quality, all I have handy these days is an iPhone.

enginebay2.jpg


enginebay1.jpg
 
And you haven't used an inspection mirror and light to look for black streaks around the flanges?
 
TOC said:
And you haven't used an inspection mirror and light to look for black streaks around the flanges?
Click to expand...
I have, and couldn't see anything when I looked. I'm going to try and look again tonight when I get home -- I've been driving the car for the last few days, so that should give any leak a chance to make some marks. :smile:
 
Still sounds like a small exhaust leak to me as well, Drew get the car on lift with it running at idle, and put your hands near all the joints in the exhaust and see if you feel air rushing form anywhere, if you have a smoker around, have him hold his cigarette near the joints in the exhaust if there is a leak you will see in the smoke coming off the cigartette. When I owned my Goddyear store, we had one fo the best exhaust guys in the area, and this is excatly how he checked for leaks. Oh and some shops will have those AC leak detectors, that would work just like the cigarette.
 
+1 on the exhaust leak.

Silly idea alert:

Would removing a spark plug wire one at a time help identify the leak?

I know there would still be compression, but just wondering...
 
I hear it right off the bat. I'm with them; exhaust leak.

Drew, you say you have a header, it may have a bad weld or cracked pipe.

I put headers on my Grand Wagoneer a while back. The factory welds were bad and covered up a good bit of the ports. I cleaned the up only to have them crack once they got hot. Same little pfft pfft pfft noise driving me nuts. I strongly suspect the header quality. Possibly warped flanges too. I couldn't see my leak till I pulled them all the way off and inspected. I was only ably to tell by the carbon track. The crack closed up when cold.


Mine 1500 sounded the same way, but it was because of a bad gasket. On the 1500, you have to cut out the bridge b/w 2 and 3 if you use the stock manifold or the heat pulls up the bottom part of the gasket and makes it leak. It's not aplicable to you, and you say the gasket has been addressed already.


The car has been down too long to worry about this right now. It's time to drive that thing, plus, you need to leave a good carbon trace where ever the leak is, so driving it is fixing it. :driving:

BTW, it sounds great. (other than the leak)
 
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