[img]/forums/images/icons/tongue.gif[/img] Yep.....that's a squeezer-locker nut with a flange; very job-specific and costly. [img]/forums/images/icons/crazy.gif[/img]
<font color="blue"> Yep.....that's a squeezer-locker nut with a flange; very job-specific and costly. </font color>
The ones on there now are just like these, except they were not squeezed or they would not have backed off. [img]/forums/images/icons/confused.gif[/img]
In order to pass inspection this last time, the dealer had to replace the down pipe, the one held on by these 2 nuts. The mechanic must not have known to squeeze them either. Sigh.
This weekend I will put on these new ones and be sure to squeeze them. [img]/forums/images/icons/grin.gif[/img] I assume using slip joint pliers will do the trick?
[img]/forums/images/icons/tongue.gif[/img] Actually, the nut is designed such that the tightening of the nut itself is supposed to actuate the clamping action of the top end. I've never really placed much credence in that theory, however, and usually go for a double nut arrangement if it is a "must hold" kind of thing. I've questioned whether those type of lock nuts can be effective, given the thermal-cycling that takes place day after day. Chev-Lay pickups used to be real bad about dropping header pipes off and I've owned NINE of them. The double nut arrangement was the fix in each case. [img]/forums/images/icons/tongue.gif[/img]
Well, this was a lesson in not assuming. [img]/forums/images/icons/tongue.gif[/img]
This problem started a few months ago with a sound I heard coming from the engine compartment. It sounded like a slipping belt. However, it only happened when the car was moving and I only heard it as the engine rpms decreased from about 2,200 to 1,500. No other time. So, I concluded it was not a belt, rather it was something loose in the exhaust system. Since the dealer had recently replaced the down pipe (end of exhaust header to beginning of exhaust system - shaped like the letter 'L'), I started there.
I removed the exhaust header shield which runs from the engine down to the collector. It was held on by 5 small bolts, one of which was broken off. Hmm...
I also removed all the plastic shielding under the engine and started trying to move the exhaust system by hand. Sure enough, I noticed that the these 2 nuts were loose. I tightened them up, put all the shielding back and thought everything was fixed.
After a few weeks the sound comes back, so I assumed the nuts had loosened again and I posted this original message, then bought four new nuts so I could double nut the ehaust pipe. This past weekend, when I checked the 2 nuts, one was as tight as I could get it and I could only move the other one about 1/8 of a turn. So, what was making the sound?
I removed the exhaust header shield and when I did I noticed a small crack. The shield has some louvers cut in it and one of the 'rungs' in the louvers was cracked through. This got me to thinking that maybe where the shield could not be attached to the header because of the broken bolt (see earlier paragraph) was also a source of vibration.
So, I took the exhaust shield off. No noises driving into work this morning!
<font color="blue"> My guess is that the shield keeps something nearby from FRYING from the radiating heat off the manifold. </font color>
Very good point, Dave! I'll put the shield back on. The item in front of the headers is the radiator.
I always paint the heat shields with high temp silver (1200F) paint. to try and reflect as much radiant heat as possible. If you are careful you can usually use a spray can to paint the shield after it's on the car.
Heat shields are there to protect something from frying.
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