On to next problem! Tapping noise.
Thread Starter
Instructor
Joined: May 2011
Posts: 213
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From: Miramar Florida
The bolts on my exhaust manifolds get loose about every six months or so. It's always #7 and #8. All the others stay tight.
The first time I had this happen, I would get a rattling noise when I accelerated up a hill. We finally found the problem when I put the car on a dyno so we could load the engine and listen for the noise. One of the #7 bolts was out more than 1/4".
The first time I had this happen, I would get a rattling noise when I accelerated up a hill. We finally found the problem when I put the car on a dyno so we could load the engine and listen for the noise. One of the #7 bolts was out more than 1/4".
Melting Slicks
Joined: Aug 2008
Posts: 2,082
Likes: 50
From: Palmdale CA
I plan on cheching the bolts at the exhaust manifold again. I wouldn't think that me bolts would have backed off seeing as though I've only driven a few miles since replacing the head gasket. What is the best way of getting to the manifold bolts at the #8. I suspected that I may not have gotten those bolts torqed properly becase they were difficult to get to.
http://www.cncexpo.com/TorqueAdapter.aspx
torque adapters>
http://www.pronto.com/user/search.do...true&obl=false
just a few examples..
Thread Starter
Instructor
Joined: May 2011
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From: Miramar Florida
I may have found the problem. In an effort to eliminate it being an exhaust leak at the manifold collector, I decided to replace the bolts & re-torque them. In the process of installing the new bolts and torqing it down, I noticed that it seemed to get tight before the bolt was all the way in. I pulled the bolt back out & it got stuck but I was finally able to get it removed. Found that there had been a helicoil put in that hole and it had stretched out. I think this may be where the exhaust leak is and the source of the tapping sound. I certiainly hope so.
Melting Slicks
Joined: Aug 2008
Posts: 2,082
Likes: 50
From: Palmdale CA
I may have found the problem. In an effort to eliminate it being an exhaust leak at the manifold collector, I decided to replace the bolts & re-torque them. In the process of installing the new bolts and torqing it down, I noticed that it seemed to get tight before the bolt was all the way in. I pulled the bolt back out & it got stuck but I was finally able to get it removed. Found that there had been a helicoil put in that hole and it had stretched out. I think this may be where the exhaust leak is and the source of the tapping sound. I certiainly hope so.
What do you mean by; streched out?
Thread Starter
Instructor
Joined: May 2011
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From: Miramar Florida
Looks like when the bolt was installed, the helicoil uncoiled as the bolt was tightened, so the flanges never pulled completely together on the manifold. Just my theory at this point, I'm going to finish the repair tomorrow and test it to be sure.
Thread Starter
Instructor
Joined: May 2011
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From: Miramar Florida
I was wrong! Tapping noise was not from exhaust leak. I fixed the helicoil and put everything back together. I drove and I could hear that same sound. So I took to an exhaust shop and they confirmed it was not an exhaust leak. Kinda lost at this point. I played with the timing a little bit today and just as before, when I got the timing too far off, it would make the same sound,like a valve. When I check with the stethoscope, I can't hear it at the valve covers or heads. Kind of sounds like it is coming from the intake area. Also funny thing, thepCV valve seems to be chattering (rapidly opening & closing).
Thread Starter
Instructor
Joined: May 2011
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From: Miramar Florida
I've been on YouTube checking out some corvette videos. There were a few videos with cars idling and I could hear the same ticking sound on the videos as I'm hearing from my engine. So I assume the sound is normal, however the sound seems louder as I'm driving and not as much at idle. I'm lost on what to look for now. My engine is not original for the car. It has the smog system disconnected and there are some electrical connection at the front of the engine, near the throttle body, that are not used, I have no idea where they go, I assume they had something to do with the smog system but not sure. Any suggestions.
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Instructor
Joined: Jun 2000
Posts: 171
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From: Chicago
You sure you are not just hearing normal fuel injector noise or basic old lifter noise, these aren't exactly quiet valvetrains? Not sure if you have roller lifters, I know mine make a sound similair to what might be an exhaust leak but a bit less, but noisy by stock standards they are.
Thread Starter
Instructor
Joined: May 2011
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From: Miramar Florida
Also when I adjust the timing, I can make the tapping noise louder by retarding the timing with the distributor. But when I've got everything set properly the tapping noise is much lower until I start driving. What do you think?
Race Director
Joined: Apr 2002
Posts: 10,036
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From: Anaheim CA
Did you try putting the stethoscope on the PCV valve?
Just for fun, check the EGR solenoid with the stethoscope.
I replied in another thread that those connectors are for the diverter and switch solenoids on the smog pump.
Just for fun, check the EGR solenoid with the stethoscope.
I replied in another thread that those connectors are for the diverter and switch solenoids on the smog pump.
Thread Starter
Instructor
Joined: May 2011
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From: Miramar Florida
I don't think that the EGR is not connected on this engine. From my best guess, the EGR solenoid is under the intake plenum and the valve is on top of the intake. There appears to have been a vacuum hose connected to the EGR valve, but it is now plugged with a screw. If what I'm looking at is the solenoid, it has two vacuum lines, one connected at the front of the plenum and the other is currently plugged with a screw. I'm sure if this isnright or not.
Instructor
Joined: Jun 2000
Posts: 171
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From: Chicago
The solenoid is under the the fuel rail cover on the drivers side. i can't remember right now as I am not looking at it, but Little black box one hose from it should be going to the EGR. I just replaced my EGR.
Thread Starter
Instructor
Joined: May 2011
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From: Miramar Florida
Still no resolution for tapping noise or idle hunting. I most recently replaced the ESM, in addition to all the other items I replaced previously. Still same problem. Is there a schematic or drawing available that shows all the vacuum connections on the L98 engine? There are three vacuum lines that connect to the intake plenum that I'm not sure I have connected correctly.
Race Director
Joined: Feb 2004
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Remove the serpentine belt. Start the car, and run for no more than 20 seconds.
This will confirm or deny that the problem is in the accessories.
If that doesn't isolate it, remove the 3 bolts that hold the torque converter to the flexplate. Slide the converter towards the back of the car to get it away from the flexplate.
Shine a flashlight up there and do a crack inspection on the flexplate, and look very closely between the crank bolts.
If it looks good, start it up and see if the noise went away.
If not, (because you have eliminated the exhaust) you will at the very least confirm it is an internal engine noise.
This will confirm or deny that the problem is in the accessories.
If that doesn't isolate it, remove the 3 bolts that hold the torque converter to the flexplate. Slide the converter towards the back of the car to get it away from the flexplate.
Shine a flashlight up there and do a crack inspection on the flexplate, and look very closely between the crank bolts.
If it looks good, start it up and see if the noise went away.
If not, (because you have eliminated the exhaust) you will at the very least confirm it is an internal engine noise.
