I have aftermarket headers and a cold air intake on my '06 Charger. It sounds like it’s got an exhaust leak, but I’ve taken it to three different mechanics who say it doesn’t. It seems improbable that the aftermarket airflow components could add enough airflow to make it sound like there’s an exhaust leak when there’s not.
When I use premium instead of midgrade fuel (the manual recommends mid for the 5.7L), the sound is quieter, but doesn’t go away. It doesn’t sound at all like knocking, though, it sounds more like the “tic” of an exhaust leak.
Lifter noise?
An exhaust leak/tick can be one of the hardest sounds to eliminate when you can’t exactly pinpoint the source. Are you certain this sound did not exist before the mods? And have you checked for bent or mis-adjusted valves?
Trust me, if it’s a valve, you don’t want the piston swallowing it.
Also, is it a hard or soft sounding leak and does it seem to coincide with the firing of a particular cylinder?
The car had 6k on it when I bought it, and it already had headers. It started sometime after I added the intake, but at the time, I didn’t associate them. It was a gradual increase, getting a bit louder, but has since plateaued.
How does one check for bent or mis-adjusted valves?
I’m not sure exactly what you mean by hard or soft, but I’d guess soft. I wouldn’t know how to pinpoint it to a specific cylinder, but it does tic at a regular interval that coincides with the RPMs. It gets louder when the engine is under more of a load, and also seems to be dependent on engine and ambient temperature (louder when it’s cold, which seems counterintuitive to the mechanics not finding a leak, since they’re probably looking at a relatively cold engine).
Headers are famous for not sealing properly. If the sound goes away/lessens when the car warms up, I would guess exhaust leak. The gasket often seals when it heats up and expands.
Typically a ticking or clacking sound coming from a) hydraulic lifters that aren’t holding oil properly [which gives them some slack] or b) solid lifters that have too much clearance [from misadjustment or wear].
A bent valve would cause a miss. Check the repair manual to see if the valves are adjustable, and if so how to measure the lash (it would require removing the valve cover).
Why counterintuitive? Lifter noise is typically louder in a cold engine.
If you want to set your mind at ease about an exhaust leak, have a shop with a smoke machine (normally used for testing evaporative control systems) test the exhaust system with that. It’s unlikely that three mechanics would miss it, but anything’s possible.
Work with a patient mechanic who has an emissions detector. Have him move the probe around the exhaust gaskets. Any leak will show up as unburned hydrocarbons on the meter.
To expound a bit on the smoke machine - it would be used with the engine not running. This can be a big advantage for leaks that diminish as the engine warms up. You start with a cold engine, when leakage is at its maximum level, and don’t have to worry about the leak going away from things getting hotter. It will indicate leakage from places that are not accessible to the eye or ear (pinpointing such a leak may require some disassembly, but verifying its existence would not). It’s hard to beat for finding air-type leaks (e.g. vacuum and exhaust) that are small and/or obscure.
Manufactures go to great lengths to quiet intake and exhaust noise. Some cars – yes even high performance car – have restrictive intakes and/or exhausts that actually rob power for the sake of keeping noise levels down. Imagine that they steal 10 hp to keep people from complaining.
I am not surprised that an intake and exhaust upgrade doesn’t sound right, but you throw in another variable that is hard to control for: ticking noise.
I just read the Wiki article on lifters. Am I understanding correctly that they’re a cushion between the valve and the cam? (And that they’d be a PITA to fix?)
I’ll check this out tomorrow on my work computer, as it’s nearly impossible to read on my laptop.
It seemed counterintuitive to me because it really, really sounds like an exhaust leak, even though there’s an equal chance it’s the lifters you guys are talking about. However, after reading the Wiki article, that talks about rattle on startup from a worn lifter, I’m thinking you guys are right. I didn’t mention that, upon startup, it goes, “BVBVRROOOOOMMMM rattlerattlerattle bvbvrooommm bvbvroom…”, and it also rattles just enough to bug me when I’m completely stopped. The only time I notice that one, though, is at an underground parking garage or between the guard shacks at work.*
It’s not that I mind that it has an exhaust leak, it’s more that it sounds like crap when I accelerate. Most people riding with me don’t even notice, but I do, and the ones who know more about cars than I do, do, also.
This makes sense, too, especially considering that’s about the amount of power each component is likely to add. I’m starting to wonder if the extra air may be amplifying the existing sound somehow. The exhaust sure is louder as a whole.
Living in New Mexico, I sometimes forget that mechanics with emissions detectors exist. :smack:
No, not what I would call a cushion. A lifter (tappet/cam follower) has a couple of jobs. First off it transfers the sideways motion imparted by the camshaft to the cylinder head or cylinder block (depending on where the cam and lifter are located). secondly it allows for adjustment of the clearance between the valve stem and the camshaft lobe. This second function is what you should be concerned with if you have a lifter noise.
Hydraulic lifters are supplied with oil under pressure that allows them to pump up to remove any and all clearances in the valve train. Sometimes when they get old, the can lose their oil overnight and they make a noticeable rattle in the morning when the car is started. This will subside as the car warms up. They can also fail where they don’t pump up enough and they tick all the time. One failed lifter will tick at exactly 1/2 engine speed.
Mechanical lifter can also wear, and cause noise. With a mechanical lifter, the noise would be fairly constant cold or warm. Again for each loose lifter the tick will be at 1/2 engine speed.
I don’t know which engine you have or how it is constructed, so I can’t comment on how difficult it would be to change the lifters on your particular engine.
Depending on the design of the engine some lifters are a snap to swap, other are truly a pain in the ass.
A couple of other things. First off, to me anyway, a lifter noise doesn’t sound like an exhaust leak. I guess if you lack the experience they might sound the same, but they really don’t. A lifter is a metallic click or tap, an exhaust leak is not metallic sounding at all.
I would think that an experienced mechanic would know if he heard an exhaust leak. Disclaimer: some exhaust leaks get louder when warm, others get quieter. In general I would not expect an exhaust leak to get much louder during acceleration.
Do you still have functioning oxygen sensors on the car? If you have an exhaust leak before the O2 sensors I would expect that the ECM would set a code for adaptivity, too lean at idle due to air being drawn into the exhaust after each exhaust pulse.
I will throw in one other item for your consideration. if the mixture in the cylinders is too lean, you could be getting a lean misfire, also known as piston ping or knock. Ping will get louder during acceleration. It can sound like a coffee can full of marbles being shaken.
Modifying the intake, might be allowing enough air into the cylinders that the mixture is lean causing a misfire. Or it could be caused by using too low an octane gas causing pre-ignition.
A couple of things you might try.
Open the hood, and with the engine stone cold, start it. Working quickly move your hands around the the joint where the headers meet the cylinder head. If there is an exhaust leak you fill feel the leak on your hand.
Next try to localize the noise. Take a long metal rod (a long screwdriver for instance) and place it on the valve cover. Holding it there, put you ear to the end of the handle. Move the screwdriver to various parts of the valve covers and headers. See if you can localize where the tick is coming from. Warning: stay way from the spark plug wires! They are no fun to listen to.
Good luck
Does this mean you don’t have to take your car for routine emission tests? In which case, I have to ask: When the aftermarket parts were added, did the mechanics remove the catalytic convertor(s)? This is not exactly legal, and could be causing part of your problem, if they did, in fact, remove the convertor(s). Emission controls are tightly integrated into modern cars and if you remove them, it can not only screw up your engine performance, but also damage it as well. (Read big $$$$ to fix.) If things like the cat(s) have been removed and the mechanics who looked at your car didn’t point this out to you as a potential source for your problem, then you need to find better mechanics.
Rick, right, a lifter will sound different from an exhaust leak to someone who has dealt with both.
I had a bent intake valve which was allowing some of the explosion to go into the intake and it sometimes sounded like a tick (lifter) and sometimes sounded like an exhaust leak. I took it to several shops, friends, and gear heads and no-one was able to diagnose it correctly.
I took everything off that engine-, intake, headers, any gasket that had anything to do with exhaust and I couldn’t eliminate the sound. I never removed the heads though. I would have seen the valve. I also didn’t do a compression test. It was a new motor, how would I have bent a valve?
8,000 rpms finally diagnosed it.
I bought my car in Albuquerque, so it had to have emissions done at that time. I live in Santa Fe, so I won’t have to do it when I reregister. It already had the headers on it, so it had to have had both catalytic converters. Carmax did say it was a pain in the ass to get it to pass emissions, and they said they had to run it for an unusually long time to get it to pass (at the time, I thought they just wanted to put a few miles on it :D)
I put the cold air intake on myself, and it came with a CARB sticker, so I’d venture to guess I’d still be able to pass emissions. What damage can be caused by taking off the cats, though?
To answer Rick’s question about the 0[sub]2[/sub] sensor, the only sensor I messed with on the intake was the probe right before the intake tube goes into the engine. I forget what it’s called, but I think it’s a thermocouple, so the engine can match the amount of fuel to the temperature of the air, but I’m not sure.
Rick, thanks for the tips, I’ll see what I can do with them this weekend. It really doesn’t sound like the type of knock I used to get on my '79 Chevy, though. Also, it’s more of a “pfft” than a “ting”, which is why I was just sure it was exhaust.
It has the 5.7L Hemi in it. Any idea how much of a pain in the ass changing lifters is?
I don’t think I’ll be able to move my hands around the gasket, though, I can barely see the headers, much less put my hands next to them. :eek:
The “tic” your describing sounds like lifter noise to me. I have had many customers complain about it on the 5.7 and 6.1 hemi. It’s normal and is inherent due to the geometry of the valve train. Both of the vehicles I have owned with hemis have had it and it’s most noticable when idling next to a wall or confined space.