Shake Rattle and Roll

[Patton]

I had the car out Saturday and everything was pretty good. I had the car up to 70 for a while and the motor sounded nice. It ran a little warmer than I wanted it to ~195, so I will have to address that.

The car did have fair amount of what I am assuming was scuttle shake starting just over 60. I will check balance on the wheels and drums as soon as I can find a place to do the work. It shook off my rear tag and bracket /ubbthreads/images/graemlins/frown.gif. Something else to buy. The thing I really hate is that I lost the Penn. antique tag that I got with the car.

The concerning thing is it developed a rattle sound when I let off of the gas. If the clutch is depressed it goes away. Does that point to anything? I could easily have been something in the boot or the exhaust, but going away when the clutch was in seemed "significant"

I posted this over on the team.net list, and the answers are all over the board. The only one that I got more than once was that it was exhaust related. Maybe....

It was not doing this the first 15 miles of driving, I did hear a sudden noise, then it started the next time let off the gas. Unfortunatlly, I remember hearing that nosie, but I can't remember what it sounded like.

Still, a good day driving the car. I got a couple of complements on the car's appearance and am feeling more confident about putting it on the road. That's why they call them shakedown runs!

Thanks
Patton

Patton

 

[Dave Russell]

[ QUOTE ]

The concerning thing is it developed a rattle sound when I let off of the gas. If the clutch is depressed it goes away. Does that point to anything? I could easily have been something in the boot or the exhaust, but going away when the clutch was in seemed "significant"

I posted this over on the team.net list, and the answers are all over the board. The only one that I got more than once was that it was exhaust related. Maybe.... Patton

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When you depress the clutch are you keeping the engine rpm the same, letting it drop, or speed up? What I'm getting at is whether the noise is related to engine speed, or car speed, or engine load.
D

 

[Patton]

When I am driving down the road at speed (say 65 MPH) the sound is not there. When I take my foot off of the gas the sound starts. If I then push in the clutch it stops. /ubbthreads/images/graemlins/confused.gif

Patton

 

[Dave Russell]

Patton,

So - If I read you right, the noise is there only when the engine is decelerating under compression. Releasing the clutch stops the noise.
Possibilities;
1 - The engine is torqued the opposite direction in it's mounts during deceleration. Some part of the engine is touching a body part & causing a noise under this condition. Could be some part of the exhaust system is touching the frame or body under this condition. Since the engine is flex mounted there needs to be some room around the exhaust parts to prevent contact when the engine is twisted over to the right (CW) as viewed from the front. The original Healey flex connection in the exhaust down pipe or pipes, was intended to minimize this problem. Also true for any other engine parts that are close to the frame or body. You could loosen the exhaust clamps & hanger connections & make sure that everything is centered in it's limited travel range, & retighten. This is a common procedure for dealer mechanics to deal with when new cars are brought in with this complaint. In factory jargon it is known as "normalizing" the exhaust mounting system.

2- There is a loose baffle in the muffler which vibrates when subjected to the different exhaust flow pulses which occur under deceleration conditions.

I would be inclined to check these things first before pulling the clutch.

3- A less likely, but it has happened, problem is that the anti vibration/cushion springs in the center of the clutch hub are bad. I once built an engine with a dual disc clutch that had purposely solid clutch hubs, no springs, I it always did just as you describe. Vibrated the car very annoyingly when decelerating unless the clutch was released. So much for race car clutches in a street car.

As already noted, the throwout bearing could be having a problem also. Another test would be to slip it into neutral instead of depressing the clutch. If the noise quits it pretty well eliminates the throw out bearing. If you have to pull the clutch as a last resort careful checking of the parts should show the cause of the problem.

To recap, check the easy things before taking the clutch apart.

Good luck, this kind of thing can be a real puzzle.

I think that the scuttle shake is another problem. Enough vibration to shake off parts is not likely caused by clutch or drive train problems.
D

 

[ThomP]

Your scuttel shake sounds pretty severe if it shook the tag lamp and tag off! I would carefully check the tyres to see that they are round. If you have a ply separating, it will definately shake enough to shake the whole car. Tyres that are more than 5 years old are highly suspect.

To add to your collection of possibilities for the noise when slowing with the engine engaged; I would check the universal joints. They are loaded differently when slowing and may be the source of the noise. Come to think of it, they may also be causing the vibration you mention.

If the vibration is high speed; check the U-joints, if it is slower, sometimes bouncy, check the tyres.

 

[Patton]

Actually the shake is not that bad, I don't think that the tag bracket tightened down. Most of the trim on the car wasn't when I got the car, and I don't remember checking that.

Patton

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I think that the scuttle shake is another problem. Enough vibration to shake off parts is not likely caused by clutch or drive train problems.

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Your scuttel shake sounds pretty severe if it shook the tag lamp and tag off!

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[Patton]

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the noise is there only when the engine is decelerating under compression. Releasing the clutch stops the noise.

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Exactlly!

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In factory jargon it is known as "normalizing" the exhaust mounting system.

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This is very possible since I replaced the downpipes and all of the exhaust hangers. Something very well could have moved.

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There is a loose baffle in the muffler which vibrates when subjected to the different exhaust flow pulses which occur under deceleration conditions.

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Also possible, as I have the Stainless Steel exhaust, and I have heard of problems from that.

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A less likely, but it has happened, problem is that the anti vibration/cushion springs in the center of the clutch hub are bad.

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Lets just say I hope not. I don't think this will be is as the sound happened while the clutch was engaged. I would think that something like that would only break as it was being used.

Thanks for the help, it will be next weekend before I can isolate it.

Patton

 

[Dave Russell]

Quote:
A less likely, but it has happened, problem is that the anti vibration/cushion springs in the center of the clutch hub are bad.
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Lets just say I hope not. I don't think this will be is as the sound happened while the clutch was engaged. I would think that something like that would only break as it was being used.
Thanks for the help, it will be next weekend before I can isolate it.
Patton
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Clutch engaged condition is exactly when the springs come into play. The disc is a two piece affair. The hub can rotate a small amount, separately from the outer lining section. This rotation is cushioned by six strong coil compression springs. There is also a flat type compression spring between the friction facings which is intended to reduce abruptness of clutch engagement. I was refering to the former.
D

 

[Patton]

Re: Shake Rattle and Roll [HAPPY UPDATE]

I figured out what the rattle was.... The hood prop rod popped out of the rubber clip. The sound appeared to come from behind me, but I put the rod back and the sound is gone. I like free and easy solutions.

Overall the car ran great today, pushed it up to 75 again, the shake is not that bad, but I will start looking for a place to balance the wheels.

I still need to address the heat issue, in today's 89 degree Houston heat, the gauge was reading just over 190 again (of course may gauge could be wrong). I learned the lesson not to wear sandals while driving or you will get the hot foot.

Also, I am still looking for the license tag brackets to replace the ones I lost.

Thanks
Patton (sorry for posting this to both lists, but I got respomces from both) /ubbthreads/images/graemlins/cheers.gif