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Well the old Seville has me puzzled again.

I have a consistent tapping noise or rattle that is coming from the rear ed of the engine somewhere above or around the transmission or intake. I tried isolating the noise by taking the serp belt and water pump belts off but the sound was still there. The car has a rough idle and now and gas mileage is pretty lame these days too.

Oil is fresh and the pressure seems OK too. The thing about this noise however, is that if I rev the engine up past 3000rpm it disappears in the noise the engine produces. If I rev it to 5000 - 5500rpm whether sitting or during WOT, the sound goes away for a few seconds and then slowly comes back. There are a few occasions where the car won't even make the noise until driven, or after a high rev it will disappear and not come back until the next time I start the thing. I've had my stethoscope all over the place, heads, valve covers, water pump crossover, block, oil pan, etc. but the engine through the scope sounds like a beautiful mechanical symphony. The only place I did detect a portion of the noise was on the steel flex tube that comes off the back of the egr valve.

Keep in mind however, that this noise is a consistent tap and has no breaks in-between each tap,

it is relatively rapid at idle (faster than the valves making a full reciprocation when looking at them through the oil cap), and way too fast to be a rod bearing. This thing gets its regular exercise and I even sea foamed it the other day but to no avail. The seafoam did restore a lot of power but the sound remains and so I have my doubts its a chunk of carbon.

Has anyone heard of this or experienced this before?

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Well first I would never use Seafoam, see this

http://caddyinfo.ipbhost.com/index.php?showtopic=10036

and this

http://caddyinfo.ipbhost.com/index.php?showtopic=11113

Have you done the WOT procedure in the proper way?, not just WOTs, the WOT procedure

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Use the stethoscope and listen to the EGR valve. Maybe try unplugging it and see if that makes any difference.

EGR valve seems quiet through the scope, I unplugged it too, but the sound remains... I have the one off my old motor so maybe I'll try swapping it just in case.

Would a cracked manifold produce a loud tap? Or quite possibly this be coming from the tranny somehow?

It's loud when the engine is cold and quiets down a bit when it is at operating temp and it can be heard in the car very well with the blower and stereo off. I'm wondering if when revving it, it just heats whatever it is up and somehow silences it until it cools back down.

It's been making this noise for about a week now and hasn't gotten any louder, and I've driven it about 220miles in that time.

The thing that has me scratching my head is the rough idle and poor gas mileage. If I'm waiting at a red with the car in Drive, the car will idle around 600rpm and then drop just below 500rpm for a split second as if it is about to stall, so I just throw it in neutral to keep it alive although it hasn't actually stalled yet.

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Just throwing out ideas....

Do you have any DTC codes...

If so...what are they?

Did the rough idle and bad fuel mileage start about the same time as the TAPPING noise?

If so...they are "PROBABLY" related...but not "NECESSARILY" related.

If your car has the rubber plenum at the throttle body...be sure to check that.

A plug wire that is jumping fire to a ground can make a pretty loud sound that could sound like a TAPPING sound.

A bad wire would also cause rough idle and poor gas mileage...but the sound from a bad wire probably would "NOT" go away after revving the engine.

Pull the DTC codes and post any codes here to give us a place to start diagnosing the issue.

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I was thinking the same thing last night that its probably that the noise and rough idle are not related

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Yes I do regularly do the WOT procedure that many people have posted here and on Cadillacforums.

I replaced the EGR valve with the one from the old motor for shits and giggles I guess and nothing changed.

This sound is actually a lot louder than I originally thought... The last motor went out after 6 months of owning the car because the oil pump PRV was clogged and didn't throw a code. The only way I knew something was up was after a 6 1/2 hour drive and some heavy acceleration down the highway I had a quiet knock. It was very inconsistent sound and I thought it was just carbon. I followed the WOT procedure a couple times and all of sudden it could be heard throughout the neighborhood.

After the tear down we had found that two rod bearings were shot and the crank was no good and the oil pressure sensor was shot and not giving an accurate reading.

This sound I have now is a lot quieter than what I had then, but yet this sound is very consistent and never skips a beat like the rod knock I had.

I have no codes except for the ones after disconnecting my battery a couple weeks ago and the rough idle and gas mileage came in with the sound like clockwork.

Here is a soundclip, I had the camera underneath the car to get away from the accessory noises and the car is warm at this point. Car was idling at around 800rpm and I revved it to 2500. This sound clip is painful to the ears!

http://www.box.net/shared/kf5c8tz9he :unsure:

I'm beginning to think that this is mechanical and I just may not have been able to get my scope seated properly on the block when under the car through all the wires and hoses etc.

I'm going to raise it up and try listening again today... But I'm just a 2nd year apprentice plumber in the middle of my 2nd year school and I need a vehicle for the 45min commute to and from the city twice a day for the next 2 months until I get my work truck back.

I don't have much time nor money to put in this car and so I am already just considering a 1999 Regal GS down the road from an older gentleman who doesn't need it anymore and has maintained and garaged it since new. He's asking $1500 and has it 150k miles on it and is loaded to the teeth, he even put seat covers over the front seats so the leather looks not even a day old from the factory.

My old 86' HT4100 was 10 times more reliable than this Northstar ironically, and it still purrs minus the transmission needing replacement.

I love this old caddy, but maybe after these couple months of school I can get a newer one even though buying them used requires you to kick all four tires and to consult a psychic.

And it seems if you get one that was properly cared for "Cadillac Style", then it might be a good day to go buy a lotto ticket :lol:

One thing is for sure though... Once a caddy lover, always a caddy lover.

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Well first I would never use Seafoam, see this

http://caddyinfo.ipbhost.com/index.php?showtopic=10036

and this

http://caddyinfo.ipbhost.com/index.php?showtopic=11113

Have you done the WOT procedure in the proper way?, not just WOTs, the WOT procedure

In a last resort act I poured the 4 oz. of seafoam in the cylinders over night and drove it for 20 mins and changed the oil again. But I never have put the stuff in the crankcase directly as I know it is basically like driving around with a can of engine flush in your oil. I have also been leery of sucking it through the vacuum lines... Just something wrong with the whole idea there in my opinion lol.

I've heard a lot of guys pouring ATF in the crank case however, and at this point I have accepted there is a good chance that it may blow up anyway, so I'm willing to try that out too.

However, the 8L of oil does get pretty pricey if purchased 2 times in one week, let alone 3...

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There is no oil pressure sensor, its an oil pressure switch, its on or off at about 5 PSI. So your are saying you had NO oil pressure and the light did not come on?

You are VERY smart learning a trade and being an apprentice plumber, that is a great thing to do, I am glad to see that apprenticeships are still done.

Its interesting that you had two bad rod bearings, I have a knock also, and I am thinking rod or main bearing problem, what do you suppose caused the rod bearing problem oil pressure?

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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There is no oil pressure sensor, its an oil pressure switch, its on or off at about 5 PSI. So your are saying you had NO oil pressure and the light did not come on?

You are VERY smart learning a trade and being an apprentice plumber, that is a great thing to do, I am glad to see that apprenticeships are still done.

Its interesting that you had two bad rod bearings, I have a knock also, and I am thinking rod or main bearing problem, what do you suppose caused the rod bearing problem oil pressure?

Yes it never set a code or a light. When my mechanic and I pulled the engine apart he pointed out that the electrical connection was damaged and didn't look like it was making contact. He was surprised the pcm didn't pick up on that, let alone that it had looked like someone put some sort of snake oil in at some time because all the components felt greasy and not oily like you would normally find. He questioned if the additive may have screwed up the oil pressure switch somehow but we really didn't investigate as we had another engine to throw back in the car. The mains and the rest of the engine looked fine to his eyes except for the cams, sprockets, and chains were worn down and showed the true age of the car.

He's a retired heavy duty mechanic and was shop manager at an Olds dealer for a number of years and had worked on a lot 4.0L V8's and a couple 4.6's so I figured he knew his stuff.

And thank you, trades are a very good thing to be in I suppose because all in all we'll always have some time of work (everybody poops).

The Canadian provincial and federal governments take apprenticeship trades seriously which is good for me with all the grants that are available upon each year of completion and the broad experience I gain in the field and through school.

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Well I decided to go for a relaxed half hour drive to my parents place with a 1/2 quart of ATF in the crank case.

Got out of the vehicle and noticed the darn thing is just louder now.

Dissected the oil filter from a few days back and noticed a few sparkles here and there but I had to look hard for them.

So now with the loud tapping + the metal filings in the oil filter = Time to say goodbye to this car.

When listening around underneath the car I found the rattle only barely in the exhaust pipe. The block, heads, valve covers, and the oil pan revealed nothing out of the ordinary... So long story short I'm putting the thing up for sale for parts while its still mobile and in the meantime get to borrow my step-dad's S-10 until I get another set of wheels.

I know I'm kind of jumping to one conclusion here, but I just don't have the time or $$$$ to gamble and play with this car anymore especially in my current situation.

I would like to thank all you gentlemen for your help and general concern with me on this car lately.

It is incomprehensible how much information I've absorbed off this one site alone, and it is really nice having access to such a vast pool of knowledge in a community with good people who enjoy helping other folks more than they enjoy their cars it seems.

Cheers

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I just listened to your MP3, that is a solid metal on metal knock. Since you had rod bearings go, do you have any idea as to what you think this noise is?

Good luck and sorry about the demise of your engine

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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I just listened to your MP3, that is a solid metal on metal knock. Since you had rod bearings go, do you have any idea as to what you think this noise is?

Good luck and sorry about the demise of your engine

No idea what it is. When the rod bearings went, they tapped a little louder and slower than this and could be heard over the blower motor and at all RPM's... And that was before I followed the WOT procedure which made the car echo through the neighborhood and sound like guy with a ball pein hammer going wild inside the crankcase lol.

This noise can't be heard over the blower and disappears into the music of the engine around 2500RPM.

This last summer I thought I heard a similar but quiet noise that sounded like the rod knock I had on the original motor, but was in the top end and very intermittent unlike what this is. I only noticed the noise because I was waiting in a drive-thru one day and the sound echoed. I hadn't done a WOT run in a while and gave it a couple treatments during a 4 hour drive to the mountains. When I got to the campsite we got out while it was running and could no longer hear the noise.

All was quiet until now.

This car sounds like it has a giant roulette wheel connected to the crankshaft.

Could these oil pumps make such a noise??? I never once thought of that. <_<

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KHE is familiar with the oil pump, but I dont think that it can make that kind of noise, it is located behind the crank pulley.

That you found metal filings in the oil filter does not bode well. It is possible that you have a bad cam lobe or valve lifter problem, but you said you thought the knock was too slow for that.

This is a shame, I am sorry that it happened

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Engine Knock Diagnosis

Knocks Cold and Continues for 2 to 3 Minutes

Engine flywheel contacting the splash shield. Reposition the splash shield.

Loose or broken crankshaft balancer or drive pulleys. Tighten or replace as necessary.

Excessive piston to bore clearance. Replace the piston.

Cold engine knock usually disappears when the specific cylinder secondary ignition circuit is grounded out. Cold engine piston knock which disappears in 1.5 minutes should be considered acceptable.

Bent connecting rod.

Heavy Knock with Torque Applied

Broken Balancer or pulley hub. Replace parts as necessary.

Loose torque converter bolts.

Accessory belts too tight or nicked. Replace and/or tension to specifications as necessary.

Flywheel cracked.

Excessive main bearing clearance. Replace as necessary.

Excessive rod bearing clearance. Replace as necessary.

Light Knock Hot

Detonation or spark knock. Check operation of EST or ESC. Refer to Engine Controls.

Loose torque converter bolts.

Exhaust leak at the manifold. Tighten the bolts and/or replace the gasket.

Excessive rod bearing clearance. Replace bearings as necessary.

Knocks on Start-Up but Only Lasts a Few Seconds

The following conditions may produce engine knocks on initial start-up, but only last a few seconds:

Improper oil viscosity.

Install proper oil viscosity for expected temperatures.

Refer to SECTION 0B.

Hydraulic lifter bleed down

Clean, test and replace hydraulic lifter, as necessary.

When the engine is off, some valves will open. Spring pressure against the lifters will tend to bleed the lifter down. Repair the lifter only if the problem is consistent.

Engines operated for only short periods between start-ups may have lifter noise that lasts for a few minutes. This is a normal condition.

Excessive crankshaft end clearance; Replace the crankshaft thrust bearing.

Excessive front main bearing clearance; Replace the worn parts.

Timing chain tensioner malfunction; Clean, inspect and replace the timing chain tensioner, if required.

Knocks at Idle Hot

Inspect the drive belt for wear. Check the tension and/or replace as necessary.

Inspect the A/C compressor or generator bearing. Replace or repair as necessary.

Inspect the valve train. Replace the parts as necessary.

Inspect for improper oil viscosity. Install proper viscosity oil for expected temperature. Refer to SECTION 0B for engine oil specifications.

Inspect for excessive piston pin clearance. Replace the piston and pin as necessary.

Inspect the connecting rod alignment. Check and replace the rods as necessary.

Inspect for insufficient piston to bore clearance. Hone the bore and fit the new piston.

Inspect the crankshaft balancer for looseness. Torque and/or replace the worn parts.

Ensure that the piston pin is not offset to the wrong side. Install the correct piston.

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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For the hell of it, check your torque converter bolts before you trash it

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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I'll check them out tomorrow when I get time. I remember my friend had a sunfire that made a knocking noise that was his TC, but sounded more harsh. I guess this is a Cadillac and not a sunflower though.

I was just thinking that the flywheel could be cracked too. Guess we'll see.

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This may sound stupid...(wouldn't be the first time)... :D:D:D

It almost sounds like the starter bendix is hitting the flywheel.

If not that...maybe 2 or 3 lifters clicking at the same time...which could indicate a bad cam.

In my opinion...It is way too fast to be a rod bearing or a crankshaft pulley.

After you drove it today with the ATF in it...you said it was louder.

That could lean towards bad lifters.

Have you tried using a "HEAVIER" oil and see if that makes any difference?

Just a couple of thoughts...for what ever it might be worth.

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the purpose of the sea foam is to clean everything out right? i'm just wondering if maybe the sea foam treatment had something to do with the appearance of metal in the oil filter because you said you had to look really hard to see it.

big4870885.jpg

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This may sound stupid...(wouldn't be the first time)... :D:D:D

It almost sounds like the starter bendix is hitting the flywheel.

If not that...maybe 2 or 3 lifters clicking at the same time...which could indicate a bad cam.

In my opinion...It is way too fast to be a rod bearing or a crankshaft pulley.

After you drove it today with the ATF in it...you said it was louder.

That could lean towards bad lifters.

Have you tried using a "HEAVIER" oil and see if that makes any difference?

Just a couple of thoughts...for what ever it might be worth.

I have a couple 5 gallon 10W-40 pales kicking around and I should change the oil (again) to get that ATF out so I'll try that.

One thing I noticed today is that when under the car, the sound is LOUD! but yet the stethoscope isn't giving me anything back except for the regular sound of movement of a healthy motor which I can hear clear as bell (silence and small vibrations).

The flywheel shroud is in the way and I don't want to wreck it taking a peak. Wouldn't it be a lot louder on the top of the engine if it was either the starter bendix or lifters/camshaft(s) then? I also took the front wheel off and checked all the TC bolts as BodybyFisher had mentioned and they were all tight.

It was really mild here the past week or so and a few degrees above freezing. Every time I would fire up the car it would be quiet for about 15 secs and then start knocking away.

Now that it has cooled off about 10 degrees on average, the car takes about 30secs to start getting noisy which would indicate that it could very well have something to do with the oil warming and thinning? But then last night after running it and then sitting for 20 minutes on the lift with warm oil in the pan, I started it up and I had a good 15 seconds until I heard the sound. Coolant temp was around 190 at that start-up.

A few months ago I got a knock sensor circuit fault code only once. The SES light came on while it was idling at a light and then when I started accelerating it went away and I pulled the code when I got home.

Not sure if that would have anything to do with this though but figured I'd throw it out there...

I've never been more than a 1000kms late for an oil change, and have always ran 91-94 octane (no exceptions), but I do agree that this sound is not rods or mains... I would have seized the thing up by now if it were.

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the purpose of the sea foam is to clean everything out right? i'm just wondering if maybe the sea foam treatment had something to do with the appearance of metal in the oil filter because you said you had to look really hard to see it.

It really is only meant to clean out carbon deposits and sludge depending on how it is used.

I had to look hard to find the 1 or 2 specs every couple of square inches in the filter element.

I've done this before with the same car and I've never seen metal in the filters which is why I'm leery now.

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I just listened to the sound clip - It didn't sound like bearing knock - it was too rapid and not a low enough pitch. Jim said to check the flywheel bolts. Check the exhaust for leaks just to rule it out. Bottom line, I wouldn't give up on the car just yet.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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Well after having the dust plate off and noticing the sound increase in decibels I think I have located the problem.

All 4 of the TC nuts and I used a snake camera to inspect the bell housing and it looked clear of any sparkly metal filings.

So at this point I'm assuming the torque converter is biting the dust.

At this point I'll keep the old girl until I can get some time to have "fun" and pull the tranny and figure this all out once and for all...

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