When I first start the suburban I can back out of the carport without hearing the noise but as soon as I go forward I hear a loud metal on metal noise that sounds like someone hitting a hammer on a piece of metal. Trying to locate it I have narrowed it down to underneath and behind the engine. It will do this for a few minutes until the vehicle is warmed up. Here lately even warming up is not stopping it. Camshaft? Lifters? Oil circulation issue (I am going to replace the oil screen o-ring and clean the oil screen this weekend). Anybody had this same issue?
Is it a continues noise, even while standing still, or only driving? I doubt it is the lifters, they make more of a ticking noise then the sound a hammer makes and in rhythm with the engine turning.
The most common source of this symptom is a heat shield for the exhaust system, typically around the cat converter, that’s broken loose. The easiest and most affordable solution it to overwrap it with a long worm-gear hose clamp. You can attach two together if you need the length.
But… to verify this and fix it someone will need to get under the car. Other things like exhaust hangers & clamps can also rust to breaking.
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It is only when pressing the gas pedal. I didn’t think it was the lifters based on what I was reading. One forum recommended cleaning the oil pump screen and putting in a new o-ring and oil pan gasket.
On another forum something similar was identified. They said that the bolts tend to rust and break off for the exhaust manifold. It should be continuous if that was the case though, right? It only does it when the gas pedal is pressed.
Get underneath the truck and pull on the metal parts to see if anything is loose. You will probably have to put it on jack stands and do it when the engine and exhaust are cold.
I will basically attempt all this on Saturday. My steps are 1) check for loose parts and missing bolts around the exhaust manifold and transmission/engine flywheel area; 2) drop the oil pan and clean the oil pump screen and replace the o-ring and gasket; 3) perform an oil change and filter change while everything is off. If I still get it after that then I will take it to a local guy next week that I called today. If anyone has any suggestions aside from these then please let me know.
All I can add is a request that you stop back here after your look-see and let us know what you find. It looks like you are on top of the problem.
I wouldn’t bother with dropping the pan and cleaning the screen. If that was the problem…if would make the sound in reverse also. The heat shields would be my guess or an exhaust hanger that has broken. Once it’s warmed up and the heat expands parts… this repositions things and the two fighting parts are farther apart and stop hitting each other.
Yosemite
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Will do. I am an amateur DIY who uses YouTube like it’s crack cocaine because I cannot afford the repairs normally. @Yosemite, I really hope you are right!
You have an exhaust manifold leak, look for broken/missing manifold bolts. You hear the leak when there is a load on the engine because there is more exhaust gas and pressure in the manifolds. When the manifolds get hot they generally leak less and the there is less noise.
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@Nevada_545 makes a good point. Manifold leaks can be pretty loud until the metal expands and closes the gap that is causing the leak. That’s about how long it would take you to start the engine and back out into the street. Then the noise is gone because the parts have expanded.
Yosemite
I got under the burb this morning before work. Keep in mind that I am not a seasoned mechanic. So on this model engine it looks like there are two sets of exhaust manifolds. I am missing a bolt on the end on one side. Then on the other side where it connects to the muffler pipe there is bolt broken there. But…
I have had a slow oil leak since we bought it used back in January. I figured it was just a worn out seal. But looking underneath I think it is leaking by the starter. This engine has the starter going into the oil pan? Ever seen that? Or am I looking at it wrong? Could it be that the starter is not retracting and that is why I am getting that noise? We can take the vehicle out somewhere, park for thirty minutes then get back in and get the noise again, especially going up hills. I wonder if it isn’t able to keep it pulled back so going up a hill causes the starter to drop the engagement arm?
It doesn’t stay gone though. See my response to Nevada_545. I personally think it is the starter.
The starter does not go into the oil pan. It is attached to the bell housing between the tranny and the engine.
I cannot imagine how it could be the starter and that it would make more noise going uphill.
A starter can bind up and not retract the gear that contacts the flywheel, but in the first post you said that you could back out of your carport and not hear the noise until you went forward. If it were that starter, it would have had to reengage when you placed the shifter into “Drive”. This would eliminate the starter as the problem.
I know that the noise has become constant, but the starter would still be eliminated.
My understanding is that this noise is not present if you start the engine and leave it in “Park”.
Because the noise is continuous now…while driving…, have you checked the drive shaft U-Joints.
Yosemite
I recall a problem where the starter pinion return spring broke and the pinion hit the flywheel going uphill. Pull the starter for a quick confirm.
So I replaced the starter this afternoon. I am going to attach a couple of pictures (I can’t figure out how to attach pics - anybody know how?). The spring wasn’t shot completely but it definitely is not 100%. There was damage to the flywheel and to the pinion on the starter. I forgot to take pics of the flywheel. The new starter made the noise a lot better but it is still there. I am going to have to pay someone to do the flywheel. I don’t think I can do that myself.
To fix damaged flywheel teeth, there’s usually a separate part that’s pressed onto the flywheel, that part contains the little teeth you see when looking through the starter’s window to the flywheel when the starter is removed. I think they call that part the flywheel “ring gear”. I doubt the part costs much but the transmission has to come out to replace it. Anyway, sounds like you got things under control there OP. Good for you. ,
hmmm … trying to think what a discarded ring gear could be used for ?
Is it terribly difficult to drop a transmission at my house without special tools? I have a couple of jack stands, and a basic tool set. No pneumatic or power type tools. All manual sockets and wrenches. If I pay someone else to do this then I am expecting about $500 in labor (6 to 8 hrs labor right?)?
They experts who’ve done it before will chime in too, but if you had a Civic or Corolla, it is probably something you could do in your driveway. Wouldn’t be a simple job, but doable. On a Suburban tho, that transmission is going to be one heavy beast. Transmission removal/installation is a tricky maneuver b/c it has to be precisely aligned to the engine as it is coming out and going in, and that’s going to be hard to do in a driveway with that heavy of a transmission. Still I’ll bet there’s folks here who have done this exact job in their driveway on a suburban. Beyond basic tools you’d need some kind of transmission jack, but you can probably rent that.