My 2010 Chrysler 300 Touring 3.5 V6 recently had new lifter assembly installed on the drivers side by dealership at 61,000 miles. The car is now making periodic metal expansion clicks until it comes to full temp, about 5 to 6 times. It then makes the same periodic sound when it is cooling down. At first I thought it maybe a heat shield but I have never heard a heat shield on a cat or exhaust manifold make the sound when it is heating up. Is it possible there may have been non-heat treated bolt installed when they did the lifter assembly? Could it be a sticking thermostat? The engine is running as smooth as ever even when it makes the sound.

Any help would be greatly appreciated.

 

You might be able to narrow your search by listening for the noise with a mechanic's stethescope. "Heat treating" bolts has nothing to do with how they sound upon expansion or contraction from heat. Heat treatment is for the purpose of affecting certain qualities of the metal like brittleness, hardness, toughness, etc.

 

Could it possibly be coming from the headers?

 

I tool it back to the Chrysler dealership and they replaced the front drivers side cat. The paperwork said they did not hear the sound. I drove no more then a 1/2 mile and I heard the same noise over and over again until it hit operating temp! I will call them in the morning again. It is a very good dealership and their top mechanic has been working on it, hopefully they can nail it down. I have never heard of a heat expansion noise only when metal is cooling down???

My first experience with a Chrysler is not going too good at this point but it is still way better then the import cars I have had over the years. Still love the big US 70 and 80 cars!

Any suggestions are still appreciated.

 

If they didn't hear the sound then why did they replace the cat? Sounds like they are just throwing parts at it.
You need to ride with the mechanic and point out the sound to him. If it requires a cold engine, then leave it overnight and be there first thing in the morning to take the ride. It could be that they let it warm up while idling, which would cause the car to warm up slowly whereas your driving the car would warm it up more quickly, resulting in uneven expansion.
Sounds don't come from expansion alone, rather they come from uneven expansion, causing one part to slide over another until it jumps. There could be different things going on during warm-up and cool-down producing different movements. If a metal object is going to make a sound on expansion, then there's no real reason it can't make a similar sound on contraction, provided the circumstances that produce the sound are still there.

 

My previous car, S-stype diesel Jag., made this clicking/ticking sound all the time from the exhaust/muffler system when I exited the car. It was never a problem, and I couldn't hear anything inside the car. BTW, the system was stainless steel. It had catalysers and a DPF.

Leedsman.

 

The cars going back in on Tuesday night so they have it cold on Wed morning. It makes the identical sound and time between noises when it warms up at idle or driving. Last weekend, I let it warm up at idle to it's typical coolant temp, 3/8 on the gauge. It made the noise a few times as usual on the way to 3/8. I then ran the engine at higher RPM until the temp gauge went to it's normal max of 1/2 on the gauge and soon as it 1/2 it clicked again. As the temp went back to 3/8 it clicked again.

My DIY thoughts from working on older cars would be a sticking thermostat???, temperature sensor, or a bad hydrolic cam lifter sticking. But I would think the lifter would make the noise at any engine temp and would not click when the engine was off and cooling down. The noise started when the did the drivers side lifter assembly.

I will mention the exhaust manifold when I drop it off, as mentioned in the past advice.

I appreciate everyones comments and ideas.

 

Most probably, it's in the exhaust system somewhere. As previously noted, the most likely cause is uneven heating. That would require something heating up quickly, at least faster than whatever it's next to. The exhaust system heats up faster than anything else. It's all metal (no water or oil) and is exposed to the hot exhaust gases.
I doubt very much that you could ever hear the thermostat do anything as it's pretty small, buried in the engine and heats up and cools down relatively slowly.
A hydraulic lifter would probably make a regular ticking sound with every other engine revolution and would never make a sound with the engine off. Sometimes lifters are noisy until the engine warms up.
If you can, you should try to be there in the morning when they start it up to point out the noise to the technician.

 

When I went to drop the car off at the dealer, the head mechanic said he was going to contact Chrysler. He also mentioned he has heard 3 other cars make the same sounds when warming up and cooling down. Now I wait to see what he hears from other techs.

 

Hi,
I still have the same sounds on warm up and cool down, about 30k miles later. The sound started after the dealer replaced the lifter assembly. When I complained about the sounds, they replaced my driver front cat converter, but the sound is still happens even today. The head mechanic at the dealer said he has heard the same sounds from a few other 300s and the mechanic school has no resolution. I have gotten use to it and have driven the car on x4 13 hour trips and x2 8 hour trips and it still is running perfect (knock on wood) but still has the same sounds that never goes away.
I was a backyard mechanic when I was young, even laying on the snow a few times. I think it is the heads or engine block or maybe a thermostat (that is buried under the intake manifold). I find it to be very relevant with the coolant temperature. I can make the sound by getting it up to normal running temp and then lightly rev the engine, when it hits 50% on the temp gauge it will pop again. Then it will pop again when it comes back to normal running temp. The dealer did not think so and said they would call if they ever found out what the issue is. I think they tossed their hat in after the new cat did not fix the issue.

I gave up worrying about it after running the car straight out on the few long trips with no issue or changes in the sounds.

Good Luck with your car. If you ever figure it out, I would love to know and maybe just maybe tell the dealer.

PS: My boss is an old Fastener/Bolt guy who never heard of metal popping when it is warming up... I still think it is the thermostat but do not have the $250 to try it out...