Vetter86

Hi all,

I just purchased my first corvette, when I bought it, it didn't run. The guy I purchased it from had it for a year and couldn't get it started. Thanks to the help from posts I've read and guys here on the forum, i got it running.

Other than the oil thats been on the exhaust manifold for at least the last year that pretty much smoked me out of the garage, I noticed a tapping noise that sounds like its coming from the top end of the engine. I think its a loose rocker, but I'm not 100% sure.

The tapping is not a constant tap but an intermittent one and I didn't rev the engine to see if it would get worse. I'll check the rockers when I replace the valve cover gaskets. What else should I be looking for? What else would cause an intermittent tapping from the top end? and how can I pin point this problem?

It has the L98 Engine and as far as I know everything is stock.
Thanks


Edited - Video Added
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Tell me what you think? through-out the video if you listen closely you can here a random click ...click ...click click or kind of an intermittent clattering. I notice it more at 41, 57 and 107 seconds ...you may here it more at other times ...but as I said, its through out the whole clip.

I don't think the video is true to the real sound the car is making.

walter schweigert

I know you are going to if you haven't already changed the oil.

That being said, it may be a collapsed or sticky lifter that is causing the noise. It may also be the noise which the injectors make.

Try a stethoscope on the injectors.

If it is a lifter, it MAY remedy itself after an oil change and a bit of running.

My 2 cents.

CorvetteMike2024

100 %. I guess that makes it 4 cents now

Corvette Mike

Pete K

When you change your oil, dump in a quart of Marvel Mystery Oil and fill the rest with 5w30. That stuff works wonders regarding cleaning out sticky lifters.
Some guys substitute auto trans fluid for the qt of Marvell Mystery oil.

Vetter86

Changing the oil was the first thing I done to the car. I thought that would be best considering theres at least 1 year of sludge in it. I wanted to get as much of it out before I even attempted to start it, just incase it did start. I think I had it running for for a total of 2 minutes because of the noise. I wanted to figure out where the noise was coming from and fix the problem before letting it run for a longer period of time. I didn't want to cause any more damage than may already be done.

I'm going to put some 93 or 94 octane in it tomorrow. I'm just concerned that if its not a sticky lifter It may end up causing more problems and costing more money in the long run. I'm kind of stuck, because I need to replace the valve cover gaskets, which would be perfect opportunity for me to adjust the valves, or at least take a look at what may be going on. I don't think it is a fuel injector, but I could be wrong. Its more of a clicking metal noise than a tapping.

JrRifleCoach

I suggest that you add a pint of SeaFoam to the fresh tank of fuel.
This should help the injectors loosen up some.
Although a good cleaning by "FIC Injectors" should really be accomplished ASAP.
Sometimes a noisy injector can sound like a lifter.

The suggestion by PeteK of using a light weight oil and MMO is really a good idea.

pletzvet

I agree with the previous responses and might suggest one other step...although your oil pressure read out might be showing that you have oil pressure, you might consider starting the engine with the rocker covers removed just to see what oil is getting to the top end, if any....

walter schweigert

Injectors tend to make a clicking ticking noise. Dry lifters usually tap, or clatter, depending if just one or perhaps more have decided to make noise, and sometimes they click. Its a bit subjective.

However, if you hear a heavy knocking, clunking or a slapping noise. THIS, tends to be more serious.

You might want to hook up a mechanical oil pressure gauge and confirm the oil pressure is where it should be. Just to be on the safe side.

How many miles??

Running it for two minutes, for having sat so long, is probably not enough for the lifters to get totally lubricated, filled with fresh oil and pumped up to the point where they would take up all the lash in the valve train. They are gonna be a wee bit noisy until they do.
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If you do decide to add Marvel , atf or some other type of crankcase flush, make sure you change the oil and filter again after you have let it do it work. Don't leave it in and run it for months that way.

86PACER

Just go ahead and do the valve lash from scratch since you're going to replace the valve cover gaskets anyway. If you still hear it afterwards, just let the car idle and let it come up to operating temps if oil pressure is fine on the guage. The car hasn't been started in a long time and 2 mintues isn't enough to let everything get warmed up, lubed up, and settled in.

What PSI did your oil pressure guage read when it was running?

A sound clip would help.

Vetter86

OK, I went out and let it run for a while longer ...about 5 minutes and decided to take a video of it. I think its hard to hear. If you need a better sound clip I'll get another video of it, I'll try to stand back farther or something. Video is in initial post. It didn't improve anything letting it run for a while, I think it sounds the same.

walter schweigert

I have viewed and listened to your video several times.

Given the constraints and limitations of the sound of an internet video:

I hear two distinct noises. When you rev the engine the tapping/clattering I hear is IMHO the lifters. You probably have at least two to three per side that is really sounding off.

The second noise is when you are not revving, but just letting it idle down. I perceive a knock.

You never did mention, unless I missed it, HOW MANY MILES ARE ON THE ENGINE?? I'll bet lots.

Do the lash adjustment and do a 'look & see' while the valve covers are off, as mentioned previously. Verify the presence of oil at every rocker arm pivot, and double check oil pressure.

Report back.

Vetter86

I'm not sure off had how many miles are on the car. I remember looking at it, but can not think of what it is right now. I'll post that tomorrow. As for any oil pressure reading, if its on the instrument panel, I can't tell. The instrument panel needs worked on and I don't have a mechanical oil pressure gauge (how much do they run?)

I don't hear a knock myself, in person. I just had a chevy van go out on me because of a bad knock, I still haven't pulled that engine, but I'm pretty sure the main bearings went out on the van but, I'm not hearing a knock like that. If its there perhaps it will be more prevalent after the valve noise is gone.

I'll start on the valve adjustment tomorrow and report back if I get it finished tomorrow or just report back with the miles, I'm thinking they are high.

walter schweigert

If your dash gauges are not working you have no way of knowing how much IF ANY oil pressure you have.

I would NOT continue to run the engine unless and until you first get yourself a mechanical oil pressure gauge, probably less than $60, hook it up to the place where the oil pressure sensor is installed and VERIFY that you have sufficient oil pressure while the engine is running.

You are asking for problems if you do not.

If your oil pressure is grossly insufficient or, heaven forbid, nonexistent, that would be the A number one reason your lifters are tapping.

pletzvet

Admittedly, listening to the video recording - it is hard to tell exactly what is extraneous noise and what is engine noise. A few thoughts...if you have a decent exhaust system on the car then I think I heard a pretty definitive knock especially when you were on the right hand side of the engine. It does look like a pretty high mileage engine. What I'm wondering is...if all the noise that I hear on the recording is coming from the engine, it does sound like a dry engine (i.e. no oil) but what has me hoping for your sake that this is not the case is the fact that the engine actually turns over and runs. Also, is there any blue smoke coming from the exhaust? Is it firing on all 8 cylinders...kinda hard to tell?

Pop those rocker covers off and see what's going on under both sides...there are so many possibilities...bent push rod(s), collapsed lifter(s), loose rockers, damaged piston/con rod, bearings, camshaft, oil pump failure, noise from the serpentine belt system...WP bearing, AC bearing, Idler bearing, alternator, etc. I wouldn't run it anymore until you are certain you have adequate oil pressure and oil is getting to the top of the engine. Then start eliminating other sources of the noise....I am concerned that there might be a good reason why the car has not been running for a while, but don't want to discourage you until you know for sure what's happening.

Vetter86

I'll start by saying, the car has 202,496 miles on it. I began tearing down the top end to get a better look at whats going on. I spent a good while getting the grease and gunk away from in between the top of the valve cover gasket and the intake manifold. The intake is so filthy I decided to remove it totally, that will be tomorrow though.

I removed the intake runners and the plenum, the fuel rails and the fuel injectors, egr valve and the distributor (by the way I brought the number 1 cylinder to TDC before doing any of this, by lining the crankshaft timing mark up to 0 BTDC and the rotor on the no.1 spark plug wire terminal on the distributor), I removed the valve covers, removed the rockers/nut and pushrods (inserting them in the bottom of a box marked front and in order of removal.) Removed the air pump. I did find a bare wire exposed on the engine coolant temperature sensor (or one of the sensors going the the front of the intake manifold) also when I removed the distributor cap I found a few pieces of plastic laying in there that was broke off of the plastic wire casings inside the distributor.

There were at least 4 or 5 push rods I could spin easily with my fingers, so I'm sure I was getting some rocker noise. The heads have some thick oil/dirt deposits in them. It seems like everything plastic near the engine has become brittle, I had some of the clips that hold the wire connectors to the sensors break off on me. When I removed the fuel rail with the injectors, some of the injector tips stayed in the intake manifold, almost like the tip broke off on a couple injectors (so now I really have to remove the manifold) The plenum was hard to get off, like the gaskets fused to the aluminum.

I'm trying to think of anything else I failed to mention. The pushrods looked like they were in pretty good shape. I haven't tested them to see if they are bowed or bent yet (they dont look like it to the naked eye, but I'll roll them on a piece of glass). Oh yeah had two of those plastic tubes for vacuum lines snap on me, on was to the egr valve. Thats just how brittle all the plastic is next to the engine.

I did want to mention that oil is getting up into the heads.

I'm definatley going to pull the intake manifold off tomorrow to see how bad it looks under there, like I said I have to take it off anyway because of a couple injector tips fused to the metal. I guess I'll decide what to do next then. I'd love to pull the whole engine and rebuild it. I don't have the money for that at the moment.

86PACER

Looks like you're on your way, and you're paying attention to the details. You should not be able to spin them like that, you're correct. 0:58-1:00 of the video definately sounds like valve noise. Keep the valve train parts organized exactly as you're doing. If you reuse them, you want them back in their original locations due to their unique wear patters. If you mix things up, they will wear faster. If any of the rocker arm nuts came out real easy (like they did not feel like a nylon nut does), you should replace them with new ones. These are supposed to go in tight, so they don't come loose and start making chattering noises again later on. New ones have the top end slightly ovaled in, creating a tight fit on the stud as they screw in, preventing them from backing out later. I get mine at Napa for a dollar something each.

About those little sections of hard vacuum line, Napa carries straight sections of them. You can heat them with a lighter and bend them to the needed shape. Or splice sections of them with pieces of rubber hose in the middle.

Replace the pair of rubber o-rings at the front end of the fuel rail, where the car lines screw in. These o-rings get trashed, and you might need to fish them out with a hooked pick. Make sure they are for fuel.

Use Fel-Pro intake gaskets, and don't use the supplied cork ends that come in the box. They are unreliable, and cause the intake to sit too high, making it difficult or damn near impossible to align all the intake bolt holes. Instead lay a good bead of sealant down each "china wall" on the front and back of the block. Slightly overlap the gasket. Also put a ring of sealant around each coolant and air port on both sides of both intake gaskets. Let everything set overnight after the intake is torqued down. This ensures you won't end up with an oil leak and the front or back of the intake, that only redoing it all over again would fix. I use Permatex "Right Stuff" sealer for this task.

You need to lay the intake base straight down on the first shot. If you lay it down, then move it around to alight the bolt holes, you'll shift the gaskets and smear around the tacky sealant. I straddle over the entire motor, one foot on each tire, and lower the intake straight down so I can see the bolt holes on both sides as I'm lowering it down.

This is also a good time to degrease the engine. The first time I did this, I dropped off my aluminum intake parts at a local machine shop for cleaning. They came back looking like new.

Vetter86

I did buy the fel-pro valve cover gaskets, I like the quality of them. Do you use any sealer at all on the valve cover gaskets? Looking for the fel-pro intake manifold gaskets at auto zone and advance auto, I only saw them for the aluminum heads, but not the iron heads, so I don't know if they make them for the iron heads.

As for the bottom end, without a full rebuild i guess there is really nothing I can do about that. I'm just concerned about all the sludge buildup that may be in there. Is there something I can do to help clean as much out as possible? Will that marvel mystery oil help clean everything out (I thought that was for the fuel system), or is there something better out there on the market that will do the job?



I did find the fel-pro intake manifold gasket for cast iron. autozone part #MS93316. I think it includes everything I need.

walter schweigert

The Fel-pro intake gasket kit does not include the fuel rail o-rings for the crossover tubes, CSV, etc. Those come in a separate fuel rail oring kit for about $3.50.

Vetter86

I pulled the intake manifold (dripped a little antifreeze in there which I immediately sopped up everything with a rag, hope none got down in the camshaft part) although I did see a little speck of dirt on the camshaft, how would I make sure none of that hurts anything? run it for a little while and change the oil again? I have to clean off all the old gasket and build up gunk inside and outside the area (although it really doesn't look that bad), I'm just afraid some of it may fall down in where the camshaft is and distributor goes (not big chunks or anything but some debris).

After checking everything out visually, it actually looks pretty good, although i noticed something when I shined the light in towards the front where the camshaft timing gear and timing chain is. The camshaft sprocket looks a little chewed up. I guess thats where the small, almost metal flake size pieces of metal came from that I saw when I drained my oil. I think I need to look into this, although I hate thinking about pulling the harmonic balancer. I was thinking if the timing chain tensioners are shot and the timing chain is slapping around in there, perhaps that was some of the noise also.

Right now I'm waiting on my fuel injectors to get here from FIC, and my fel-pro intake gaskets to get here from autozone. I did get rocker arm nuts also. I just hope I got the correct permatex "the right stuff" can it was part number 25223 from autozone 1 minute gasket 4 oz., so I hope thats right.

How much would a machine shop charge for degreasing the plenum, runners and manifold? I might call around tomorrow and get some prices. Are there any ways I can degrease things myself at home with engine bright or something?

86PACER

Yes, it's the same sealant. I've used both. You got the right one. Even though it's a quick set sealer, I leave intake gaskets to sit overnight for good measure, cause this isn't something you want to redo twice due to leaks.

This is a supreme opportunity to see if your oil pressure switch is leaking oil, and fix while it's staring at you in the face. When they leak, oil runs down the back of the block. It's very hard to get to it when the intake and distributor are on. Located on the back of the engine block near firewall, by where the base of the distributor was.

http://forums.corvetteforum.com/c4-t...questions.html

I took my parts to a shop because I couldn't get them looking brand new myself. I don't know what they use to be honest. They probably bead blasted them in a cabinet. Engine Brite, some cleaning brushes from harbor freight, and rags really cleans up the engine bay though.



If that's the original chain in there, that a lot of miles on it. Your call.

I'll tell you ahead of time though, this WILL require you to drop the oil pan. Reason is, you will NOT be able to reinstall the bottom edge of the timing cover if you don't. You'll be able to remove it, but you ain't getting it back on right unless you remove or just loosen and lower the front of the oil pan. But at that point, you might as well just drop it all the way to put a new 1 piece Fel-Pro rubber Perma-Dry gasket in there and wipe the inner sump clean. Fel-Pro Perma-Dry (usually blue) go on dry, no sealant. And then you'll also have the old water pump sitting on the bench by that time. Water pumps and timing chain sets are dirt cheap for these motors.

The balancer is easy to replace, but do you need to?

You should take a look at it closely to see if there is any signs of ring slippage. If there is, you'll be setting your timing to a false mark when you reassemble and time the car again without knowing it, and the car might not run right. When they slip, the timing mark moves, and the balancer ring walks back wards and begins to grind on the timing cover if left unnoticed. If you don't know how to tell if it's slipped, I show how here:

http://forums.corvetteforum.com/c4-t...rk-on-harmonic

The hardest part will be holding the motor stationary while you break loose the center crank bolt. I wedged a wrench in between the flywheel and my exhaust pipe to remove and retighten. It worked great!



The Balancer Puller is Part#27019

If you have ever used a steering wheel puller, it works the exact same way.
Use a deep socket to turn the puller tool. The threads of the tool will be very close if not on the steering rack body. A deep socket acts like a protective cup to keep the tool's threads from getting trashed against the steering rack as you turn and back out the balancer.


Balancer Installer Part# 27144


Do NOT try to press a balancer on using the crank bolt. You'll strip out the crank snout threads. Beating it on ain't going to happe either.This tool is a little more complex.

For the installer, you need to loosen the upper steering rack oil line and move it aside because it's right in the spot that the tool will need to be for a straight shot at the crank bolt hole. There is no o-ring on this fitting. Use a crowfoot socket with long extensions from above for an easy removal of this fitting.



How to use:
Orientate the tool as follows.
Arrow toward engine.
Out of the kit, select adapter A that threads into your crank bolt hole.
A threads into crank bolt hole hand tight only.
Back side of A threads into front of bolt D faily tight (threads hidden in pic).
Hold shaft C stationary with crescent wrench by it's flattened end, while you turn nut B with large wrench.
Allow your crescent wrench holding C to wedge itself againt the frame, which will free up your hand. Turning Nut B presses roller washer against balancer while head of bolt D stops rearward movement and forces balancer on. Roller side of washer goes against balancer. Lube tool threads.



I bought Autozone's Dorman brand balancer part# 594-012 for $50

This is the EST plug that you must disconnect before setting the timing with a timing gun. Tan or brown wire. It will throw a code 42 which is normal. Disconnect the battery for 10 minutes to clear. Reconnect before staring the car again.