Technical Glasspack ting noises after engine off or at a stoplight

Hi All,

On my C-10 with a SBC 350 I had 18" hearthrob glasspacks and all new pipes from the engine to exit point installed at an exhaust shop. I noticed a ting (sounds just like taking a wrench and tapping a metal fence post) when it's been running for a while and I'm at a stoplight or if I parked somewhere and turned the engine off. I installed them in August 2020 and first noticed this noise maybe a year ago or so but then again maybe it was doing it right when I installed them and didn't notice. Now that I know it's doing this it's so annoying to hear it especially when parked and engine off!

I spoke with Hearthrob and they mentioned that's just noise from expansion and contraction of the metal inside. I read in some other forums of someone having this issue and using screws driven from the exterior to secure the baffle inside (in the places shown with the arrows in the photo below). Hearthrob said that may make the problem worse and the only way to get rid of the noise is to have a shop take the glasspacks off and weld a bead on both sides of the core and expansion joint and this would last a limited amount of time if it were a daily driver. I only drive this truck maybe 150 miles a year but when I do that noise drives me crazy.

Before I consider having a shop do something has anyone else had these noises with their glasspacks? I wonder if I'd be better off with a different brand or altogether going to something else. I had brockman mellowtone glasspacks with a SBC 350 on my 53' Chevy (that I sold) and never heard that type of noise ever.

 

Most cars including late models will make that noise due to expansion and contraction, my daily Subie has various noises as it cools down. My old daily Ranger had a relay under that dash that you could hear click off about 4 minutes after shutting off even.

 

Yeah on my 2009 daily driver I hear all the exhaust creaking noises after I park it and turn the engine off but this glasspack ting is loud and sounds like someone hitting a fence post with a wrench and it drives me crazy!

 

If it's clamped together, might pull it apart and smear a bit of high temp anti seize compound on the joints. It may be you are hearing the tubing pop when moving (expansion/contraction), under the pressure of the clamp...?

 

My new car does that every once in awhile... No biggie!

 

The glasspacks are welded in when installed by the exhaust shop.

 

I've run packs all my life on everything (muscle car in high school that had Blue Streaks to older cars now) and some have had the same sound. Currently I have 3 cars with generic packs and 1 with Porters....all don't make noise. I would get new packs put on, also make sure the hangers are on right and letting the exhaust expand and contract also.

 

Thanks, yea I'm guessing I need to go with something different like you suggested.

 

After a number of heat and cool cycles plus contamination of carbon and other exhaust byproducts to "grease the skids", it should quiet down. The mufflers are already in there so it won't cost you anything but time and some jangled nerves for a few weeks. Then if you judge it to have failed the "no ping" test, you can replace them with something else.

 

That may work but I may be gone from this earth by the time it has any contamination build up.. I drive this truck maybe 6 times or 150 miles per year (I know kind of pathetic)..

 

When it is cooled down, can you bump it with the palm of you hand and make it rattle, if so the baffle is broke loose.

 

Thanks no rattle at all I just checked both of them. Here is what Hearthrob had told me a while ago when I asked why I'm having this issue:


"You are hearing the heat expansion joints. The core inside the muffler is welded solid on one end, but the other end is slip fit. This allows the internal core of the muffler, which gets hotter than the shell of the muffler, to expand during heating, and contract during cooling. It should be most prevalent after a long trip, if you sit in the vehicle in the garage, in my car I hear some popping/pinging as the core cools and the core contracts. In my car, I don’t hear it as it heats as my exhaust is rather loud.



Without the expansion joints, the core of the mufflers would get stress fractures and crack and break prematurely.



To get rid of the noise, if you can remove the mufflers, and if you could get a welding gun tip inside to where the muffler core and expansion joint meet, if you can get the tip in there, run a weld bead on it to have it welded on both ends. But, this weld will likely break on a daily driven vehicle after about a year from our experience."

 

Have you ever paid attention to a Harley after it shuts off. Tink tink tink in different rhythm and octaves tink tink tink as it cool and things are contracting back.
It probably tinks like crazy heating up to but I’ve never heard it

 

If the glass packs are welded on, about your only option is to be sure the entire exhaust system can expand towards the rear as it heats up, and can contract towards the front as it cools off. That growth and shrinkage could add up to as much as 2" of movement.

The easiest way to assure you have that movement is in the way the exhaust system is set on the hangers. Many muffler shops pay very little attention to exhaust hangers. They throw them on and tighten the clamps and call it good. Then the hangers bind the exhaust as it tries to expand and then shrink as it heats up and cools off. The pings, snaps, and pops is the system trying to work bet the hangers are not allowing it to.

Exhaust hangers with a strap that bolts to the body at the top and has a rubber loop on the bottom that a "Z" shaped rod passes through are the best kind. The strap part is bolted to the body and has a rubber loop on the bottom that is strong enough to support the weight of the exhaust. Then a round (or flat) "Z" shaped piece of steel with a top leg at least 2" longer then the rubber loop it passes through and the bottom of the "Z" is clamped to the pipe.
The best set up with them is to have the the "Z" positioned so the vertical part of the "Z" is against the rear side of the rubber loop with the long end facing forward (about 2" past the front edge of the rubber) when the exhaust is cold. As the exhaust heats up and expands, the top of the "Z" that slides through the hole in the rubber is free to move towards the rear as the exhaust heats up and expands. Then when the exhaust cools and contracts, the top part of the "Z" can move through the loop towards the front
Those rubber and "Z" shaped rubber and steel hangers need to be at the rear of the glass pack (or muffler) and also at the end of the tail pipe.
Hopefully the picture helps this make sence.

 

Awesome thanks for that advice! I'm going to get underneath and identify how my exhaust was installed by the muffler shop and will take a look at your diagram and compare. I'll report back with some photos tomorrow.

 

Exhaust hangers that can swing a few inches can also allow the exhaust to expand and shrink, but swinging hangers often can put the exhaust into a bind. Most shops hang exhaust so the hangers are hanging centered when the exhaust is cold and that usually doesn't allow enough space to expand when hot.

Just keep in mind that as the exhaust gets hot, it gets longer (long is the only direction it can expand very much), and the closer to the rear end you get, the longer it grows when it gets hot. The single 2 1/2" diameter exhaust on my truck tailpipe will be 2 1/2" - 3" longer at the same point on the rear bumper after a 20 mile run then it was when I first started it.

 

I’ve heard the “thinking “ on modern cars, which have hangers on the exhaust, when shut down, but never heard the tinking when stopped.
I’ll be interested in what you find out.

 

I just have 1 question... Can an engine that runs real lean cause the exhaust system to expand as much as 2"????....
Maybe we should look into it..

 

Not a clue, but I’d question the two inches of growth.

 

Turn the radio up.
Seriously, many have given interesting info here, about mounting and expansion. Thanks to all. Seems the manufacturer has fielded the question about the product issue before. You're young! Buy different mufflers if that's what it takes.

 

Gonna hafta tink about dis ting.

 

Yeah, I was thinking more like 5/16s to 3/8s inches longer....

 

It sounds like the manufacture of the mufflers is saying that it is the insides of the muffler that is making the noise not the length of the complete system. The even said something about running screws into the shell to hold the internal parts still. I would say, if you can't live with the noise try drilling 1/4" holes where they say to put the screws but just through the outer shell. Then weld up the hole, welding the inner parts to the outer shell. If you don't want to do that, a simple fix that may work would be to just dent that area with a ball peen hammer. From what the manufacture is saying, it sounds like the inner parts are moving as they cool down, making the sound as the pressed together parts move on each other. Denting the outer shell would make these parts fit differently, tighter, looser or in a smaller area (just where the dent is) and this may stop or lessen the noise. Look at it this way, if you are thinking about changing the mufflers, what would it hurt to just dent them in the suspected areas a little?

 

Hearthrob suggests not to put any screws in like I showed in the diagram. I was just trying to show what I read someone else did (actually might have been in a HAMB forum) some years ago driving screws into it from exterior. It's true that if I am thinking about changing mufflers it wouldn't hurt to try but I still need to price in what a muffler shop will charge to change them out and what new mufflers will cost. I believe I spent $780 or so on this in 2020 running new pipes from the engine to where they exit just in front of the front wheels and with the two 18" hearthrob. I'm hesistant to spend much more on this but wanted to learn if others have seen this same issue with other glasspacks as well before I try another brand or move to something else non-glasspack.

 

Here are some photos of what I have:

 

Those exhaust hangers are good hangers, but it sure looks to me like all the rods are welded to the pipe facing the wrong direction (unless what I think is the front of the car isn't). Also, the short amount sticking out past the rubber isn't long enough (if it really was letting the exhaust expand, the rod could fall out of the rubber and the exhaust would fall to the ground).

This set up looks to me like as the exhaust gets hot, all the hangers are bind it up and are trying to keep it from expanding, causing the noise you are hearing. That noise is very likely the rods at the point they are welded to the pipes twisting, or it is stressing the bolts holding the rubber bracket on the body. At some point the rods will fail and break off the pipes, or the bolts will break or pull out of the body. Those rods and bolts do not have the capacity to restrain the exhaust expansion for very long.

Good pictures by the way. Gene

 

Thanks! Interesting a muffler shop installs exhaust without considering how things would contract/expand. In the photos you will see a white door towards the floor that would be towards the front of the vehicle or you may notice the washer/dryer. Otherwise in other photos where its a side view looking left would be front and right would be rear. The exhaust exits in front of the rear wheels.

To me it looks like the front hanger would let it move forward.

 

Yes, the hanger like installed would let the exhaust move forward, I am assuming this exhaust is cold, or near cold.
As the exhaust gets hot, it expands towards the rear because its bolted to the motor at the front, and hanging in space at the rear. The exhaust has to expand towards the rear when it gets hot.

Now if that exhaust was hot and hung like it is, it might be OK (other then the rod is still too short). As the hot exhaust cools, it contracts and moves forward towards the motor. The difference between the exhaust being cold and the exhaust being hot can easily be at least an inch and could be two inches difference in length in front of the rear axle, and another extra inch in length at the rear bumper (if the exhaust hangs back that far).
There is no place on the hangers on the car pictured that can accommodate 2" of exhaust expansion and contraction.

Most muffler shops are not concerned with any noises an exhaust would make involving pipe expansion and contraction. If the vehicle gets out the door and is gone for 6 months, they don't care. They will just charge you to fix it again and blame you for somehow breaking the hangers. Until someone points it out, they probably have no idea, and even if its pointed out, they would probably be suspect to the information.

 

The exhaust was totally cold in the photo. I wonder if I can do a test by removing all the bolts and using bailing wire to suspend while parked in my driveway to let it get hot and then let it cool off to see if the noise is the same or not.

 

As long as you can support the exhaust close to where it usually runs, removing the bolted on hanger and wiring the exhaust up should work to see if that is what is causing the noise. Run the motor through the full range of getting completely hot to cooling back down enough to touch the pipes.

You may have to remove the entire bracket bolted to the frame, if it can interfere with the exhaust expansion. You can probably remove the bolted on part of the hanger and slide it off the rod, then screw the bolt back into the hole, and use the bolt as the body support to wire the exhaust up with. Just be sure the wire is loose enough to allow the pipes to expand and that the rod doesn't bind against anything.

I'll be awaiting the results of your test.