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Thumping, knocking noise?


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KHE Posted on Aug 22 2004, 09:38 AM

The 4.9 is a reliable engine. At higher mileage, they may exhibit the main bearing thump noise but that is totally harmless and easily fixed by replacing the #1 main bearing with the service replacement bearing.

I hear a mild thumping, knocking, or clunking noise...usually after it's warm...coming from the engine I think. It's hard to hear sometimes and as far as I can tell the noise seems to cut out around 20 mph. Maybe the other noises (road) drown it out at 20 mph, not sure. I hear it though when I pull up the driveway. I dont hear it in Park...idling or when reving it. This is the same noise I thought I was only getting while turning right (earlier post). How do you think I can isolate where it's coming from. Could the tranny make a thumping noise like that, CV's or motor?

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I had the number one main bearing knock in my 91 4.9. I may be wrong, but I think they may have fixed the knock by 94. BUT, the knock may be due to the serp belt design that could not be helped and you may also have the knock. I can say this however, the knock way much more pronounced when the engine was very hot, say after bumper to bumper traffic. It was much more pronounced with Mobil 1. I do not recall it going away however at 20 mph, it never went away, it was most pronounced on acceleration and when the engine labored. It occurs because the serp belt pulls up on the crank at the number one bearing and combustion pushes down creating an up and down motion that causes the noise as the bearing clearance increases. There is a service bearing that is suppose to aleviate this problem. I have minimized the knock in the summer by using 10W40 (I used 10W30 in the winter), but ask others their opinion about using 10W40, it worked for me.

Our resident expert bbobynski said this problem could be diagnosed by warming the engine up, and take the belt off and drive it a short distance that would normally cause the noise (we are talking about short distance here meaning a few blocks). Obviously you will not have power steering, alternator, AC or water pump, so be careful. If the knock is gone, you found the culprit... Quite honestly, my knock never got worse except in the summer and I began to ignore it. Mike

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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Thanks Mike! So was your noise noticeable at all speeds? Mine too seems more pronounced when the engine is labored...going up the drive. But it also does it at 0 grade...going from a standstill to 20 mph, at 20 it seems to go away. Do you recall the cost to have the service bearing put in?

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Thanks Mike!  So was your noise noticeable at all speeds?  Mine too seems more pronounced when the engine is labored...going up the drive.  But it also does it at 0 grade...going from a standstill to 20 mph, at 20 it seems to go away.  Do you recall the cost to have the service bearing put in?

Originally I was going to have Caddy do the job for me, my memory tells me that it was about $500 to do the job, the pan comes right down on the 91, I believe. I originally inquired to have the job done by them about 65,000 miles and they were receptive. When I went back at 95,000 miles they were not receptive and did not want to do the job, they said they could not warranty it. I told them I did not care if they warrantied it, but they were also concerned that the number one crank journal might be scored. I was going to do it myself but decided that it was not worth it as the noise was only really bad when the engine was really hot, I was putting mileage on it very quickly and 10W40 and a new AC DELCO radiator helped. You and adallak may be correct that the noise lowers over 20 mph, I can't recall. However, if that was the case, it would reappear as you accelerated laboring the engine, does yours reappear when you accelerate over 20 mph? It should if its the main bearing knock unless yours is in the early stages, maybe it stabilizes from rotation who knows... Mike

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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does yours reappear when you accelerate over 20 mph?

I have never noticed it over 20 mph. I'm not sure though. I'll drive it tomorrow and report back. I was primarily concerned that maybe something was going wrong and would get worse. As it is now, and if it's just an annoyance, I can deal with it. I just hate hearing something that's not right and not know what's causing it. Could it be something else besides the main bearing? Has anyone else had this problem? Adallak, have you determined where your noise is coming from for sure?

I have a small oil leak in the front of the motor also. I can't determine exactly where it's coming from though...thinking maybe the main seal possibly. I've been under her I bet 50 times with a rag trying to find that leak...atleast my motor's clean now though! It appears to come from the front (passenger side), above the oil pan gasket area. There's a remote chance it's the oil pan gasket though, but I doubt it. I torgued the bolts down to see if that would help...not. I was thinking of getting the dye test done possibly, as I hate oil leaks. :angry:

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Turn side to side like a Nascar driver warming up his tires while the noise is happening and see if it changes pitch or goes away. A bad CV with or without a torn boot could cause a low speed noise. I don't think it could be detonation (mistakenly called pre-ignition at times) a rattling, tappeting noise that occurs when the car is hot and and not necessarily laboring. Detonation is not typically speed sensitive. Let me know what you find out... I still believe that your ears are too good, hey...I have a set of BOSE noise cancelling headphones, they are excellent, when I wear them in the car its like being in SPACE!!! Warp Factor 10 Sulu! Mike :lol:

Click Link for headphones, if you buy 2 and give me one, you will save 10%, I have the old style noise cancelling... :lol: All kidding aside, the BOSE noise cancelling headphones are outstanding... It is not often that you hear 'silence' but with these headphones when you flick the on switch its like you are enveloped in silence.

http://www.bose.com/controller;jsessionid=...dsets/index.jsp

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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Mike you are too funny! :lol::lol: $299.00 ea....I better get my car fixed 1st. We'll see, maybe later Santa will get you a pair if you're good! ;) You're right though, ears too good for my own good probably. My pet peave: Noises when I don't know what's causing them! :angry: I won't be as concerned a year from, no doubt...but I just got her and I gotta know! :D

I just had to move the car, engine cold,...NO noise for sure. Definately temp. related. Tomorrow I'll see if speed related over 20.

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I won't be as concerned a year from, no doubt...but I just got her and I gotta know! :D

Its a hobby for me. I have always been mechanically inclined, since about 6 years old. I used to take apart Big Ben and Baby Ben clocks, spread them out all over the table, clean up all the gears re-oil it and put it back together, my parents told me they were stunned by this. When I was growing up, my parents had:

54 Packard Carabean Conv (wire wheels all hydraulic)

55 Fleetwood, 59 Sedan (but an ugly green one with the wrap around rear window),

62 Cad Calais (no power windows, my least favorite, had cloth seats),

64 Coupe (426 ci Rocket had old style tranny with reverse all the way right),

65 Sedan de Ville (426 cu Turbo-Hyrdomatic w/variable stator it was quick),

66 Coupe Conv (felt heavy but nimble, power vent windows),

68 Coupe Conv (472 OMG rocket),

70 Sedan, 74 (Eldo - 500 ci torsion bar suspension hit bumps like Model-T, TITANIC, ENTERPRISE come to mind)

They were used cars always babied, low mileage trade-ins that were in mint condition from General Sales Cadillac, West Chester, PA. We had the 64 when I was learning to drive in high school. We never took the cars to the dealer for service, I was the service tech. By the time we got the 64 I was rebuilding the AFB Carb and loved rebuilding the venerable QUADRAJET. In college I worked as a mechanic at Sun Ship Building, Chester, Pa, in the yard's mechanical maintenence department responsible for the maintenance of all machinery (cranes, pumps, shotblast machines, the assembly of new machines, along with some not so exotic handy man type repairs like installing door closers, AC units through the wall, etc). I am also a computer nut and have built a few hundred high performance computers since 1990, when I built my first, a 386-33 that was once considered a screamer and I sold for $3,000 :blink: The machine I am working on is a screamer starting with its Seagate Cheetah X15 15,000 rpm, Ultra 160 SCSI drive, WOWIE. Anyway all of what I said above is the reason why I LOVE my Cadillacs these days. The on-board diagnostics are incredible, which excites the computer lover in me, imagine, a machine as sophisticated it is... that can also HELP you to fix it!! Do you think its a lifeform? Its genious if you ask me. The diagnostic feature combined with my love of mechanics is the reason why I love the Cadillac. Bbobynski once said, if he were to build a car he could build it like GM does and I couldn't agree more. If you have ever worked on a Ford or Chrysler you know what I mean, each has distinctive ways to deal with the same issues, some of which have always irked me, like a FORD starter for example. I think its amazing that GM somehow has retained the Cadillac look (Deville look), feel and smell from the 1957 period on, while improving fuel efficiency, safety, comfort and emissions (except for that period in the 80s where they were on LSD, thank God that they righted the ship, they were in a flat spin).

You have a new toy there, my gut tells me that if you still have the car a year from now, you WILL still be concerned and tinkering, these cars are outrageous if you ask me. Nothing else on the road gives me this feeling..

Marika is this you and your MINI next to a 59? :P

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Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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Thanks Steve! Mike, I see now why you know as much as you do about these caddies and what not. I grew up around Fords myself...so I know what you mean. My father was an engineer at the Indpls. Ford plant so all my parents ever bought were Fords. They had:

56 Lincoln Premiere Convertible (still in the garage needing to be restored badly)

67 Corvair Convertible...sold before it became a collectible

64 Ford Falcoln Sprint Convertible...also sold before it became a collectible

68 Mustang Convertible - My 1st driveshaft I ever put on was on this car. He sold that for $1500 in '76 I believe...before the rage hit.

Then many LTD's, Tauruses, Sables, F150s, E150 Vans, Explorers and so on.

Vehicles I've personally owned:

67 Dodge Coronet 440 - Fun, Fast High School Ride

60's really small Japanese Datsun that wasn't made for export...before Datsun was exported to the U.S. I can't remember what model it was...very rare though...and very unsafe I remember! I remember taking an exit and thought it was going to flip over. Sold it quick after that. Very short wheelbase and extremely narrow. Looked like a minature Rolls Royce. Probably a high dollar collectible now.

73 Pinto - Learned to drive w/ that piece of crap

75 VW rabbitt - College car...had some times with that one

78 Sleekcraft 23' Executive Cuddy Jet boat...I hopped up that Ford 460 to the extreme

81 Camaro...bought that instead of inheriting my dad's 68 Mustang Conv...DUMB in hindsight...had no idea then...besides I wanted a newer car then (high school) to impress the girlies!

85 Mustang GT

86 Ford F150 supercab...still have, selling soon

87 Ford Ranger Supercab

88 Toyota 4Runner...newly acquired winter beater

89 Chevy full size custom van

92 Honda Accord

93 Dodge Grand caravan SE 3.6L...still have, has been very dependable transportation

94 Cadillac Sedan Deville 4.9L...my new baby!

96 Impala SS...miss that car, that was my baby, then my wife wrecked it...had to sell it since I knew it would never be the same.

That was fun to look back and remember those cars...have never done that...forgetting some I'm sure. I too was the mechanic when I grew up. That's how I made my spending money when I was a kid...fixing all my dad's cars. Slave wages I was paid most likely. But I enjoyed it and I have always loved challenges & learning new things. I never got heavy into motor rebuilds per se, simply because no one ever taught me. When I graduated from College in 85 with a BS in Business, I said to heck with working on cars as I was burned out on it, and began buying new...No worries w/ the warranty. Then later on I learned that cars were a liability and not an asset, so I now buy used and pay cash. No more car payments for me! I grew up in the Drycleaning business as my father started our family business in 1954. I then bought my 1st drycleaners in '87 and have been doing that ever since. When it comes to pipe fitting, boiler mechanics, and all aspects of drycleaning equipment repair, I'm your guy, as I have set up and maintained many plants. I dibble and dabble buying & selling on ebay when I have time and have been an out-of-state fireworks dealer for the past 6 years. My wife calls me a geek sometimes as I love computers. No where near your level of expertise though Mike. Since having 2 kids, my priorities have also changed...for the better may I add...my kids and 2 nice vacations every year!

I always heard that Caddies were expensive to work on, so I had no intentions of buying one until I saw this one in my mechanics drive. I expressed to him how clean it was, and that's when he sealed my fate; by asking me if I wanted to buy it. He shot me the price ($3000) the owner wanted for it, so I couldn't turn it down. He said he just replaced the fuel pump and the kid that inherited it two months ago from his grandfather who passed away was having trouble coming up with the money, so I then replied "Sold"! So I figured after buying this Caddy, I'd better roll my sleeves up again, knowing that repairs were gonna cost me dearly if I were to send it off. In turn I decided to do some research on Caddies via the net, which is how I found this board. And man has it been a Godsend to have found this site, to meet the incredible people I've met, and to learn what I've learned by reading the post and getting all my questions answered. And what a great bunch of guys that have gone way out of their way to help. I can't thank you all enough! And Mike and adallak, I owe you guys dearly and hopefully can pay you back somehow, someway, someday! And Mike, you're probably right, I will probably always want to tinker with this car. It's become my new found obsession. I had no idea how sophisticated Cadallacs were. It is such a marvelevous car, and quite the challenge might I add. And to know with your and everyone else's help, I can do what before I thought was impossible, inspires me even more. I lOVE MY NEW CADDY! B)

Sorry to bore you with my life story...literally!

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I just read the past post on thumping, Thanks Steve! Q: Can I get one of you guys to come over and loosen my tensioner w/ a breaker bar while I sit inside & power brake it. :D I will see today if power braking brings on the noise. I don't think it does though???

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There is a summary of the thump problem in the old FAQ section:

http://www.caddyinfo.com/howto4pt9bearingthump.htm

I have found that if I put in one qt of 30 wt oil and the rest 10-30 it quiets considerably.

That is also a good idea...and not as radical as putting 10W40 I was doing

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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"Sorry to bore you with my life story...literally!"

Not boring at all quite interesting. I am impressed with the diversified list of cars you have owned so you more than I can speak to how different manufacturers deal with the same issues. What engine was in the 67 Dodge Coronet 440 my friend had one with a 426 hemi that scared the hell out of me.

I graduated in 76 with a BS in Finance and currently am an MAI commercial real estate appraiser. Your mechanical experience is also diversified. If you don't have the service manual yet, you may be able to pick it up on ebay or www.helminc.com Glad you enjoy the Caddy... Mike

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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I just won a set of factory manuals on ebay over the weekend. Can't wait to get them. My Dodge had the 426 hemi. It really screamed too. That car was so light, it would almost fly. I wish I had it now. :( I gave it to my grandmother as a present when I got my Camaro. Not even a year later, lightning struck a huge tree that was above it and the tree came down on the hood and totalled it...wasn't meant to be her car I guess. :rolleyes:

Commercial real estate appraiser...WOW! BTW, I have a piece of commercial property I've been thinking of selling maybe next year. I might lease it out though. It's a hot corner property that I've been selling fireworks out of the last 6 July 4ths. Used to be my 1st drycleaners. It's had contamination issues the last 4 yrs. due to being a former Shell gas station. They're flippin the bill though. But they are taking their time with remediation and clean up. I'm sure you know what I mean. I talked w/ IDEM (IN Dept. Environmental Mgmt.) a little while ago and they said it could take yeeeeaaaars. Shell is fighting Amoco oil, who is across the street, as to who's responsible for contamination on my neighbors property...it's a real mess! Good for the attorneys I imagine.

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I also won Book 1 of the 2 volume set last week also and I am negotiating with the person that won book 2.

I am actually taking a seminar in September called Appraising Environmentally Contaminated Properties: Understanding and Evaluating Stigma... Good Luck with that property those proceedings last for years, it would be nice if Shell would buy it back from you.

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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I paid too much for my manuals, bid closed at $86 + $10 shipping. But I needed those manuals...oh well. They're supposedly like new, but I would have paid the $111 including shipping for a new set if I would of known of helminc.com before yesterday. I had no idea what they sold for new. I did a google search before eBay, and came up with nothing. A set sold yesterday on eBay for $51.99 :angry:

I don't think Shell would offer me FMV if they were so inclined. I paid 55k for it in '87 and had it sold this spring for 325k, but I didn't like their terms. They approached me, as it was not on the market, & wanted to lease it for 2+1 years w/ option to purchase. They buyers appeared real shady, as well as their realtor. I felt I couldn't trust them to be in my building for 3 years. At the time, I wanted from under it completely w/ no lease. I'd probably accept that offer now though. I've been waiting for this huge commercial development 1/8 mile away to get under way. Fortunately they started putting buildings up this summer. :) So that should hopefully spike the property value nicely. I was also hoping to get the contamination issue cleared up beforehand...but just found out that won't be happenning anytime soon. So I think I'll use it for fireworks again next summer, then put it up for lease, as I want to take a break from the fireworks for awhile anyways.

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how far is Shelbyville from you, I appraised the 750,000 SF LOF plant there in the late 80's, it was 15 below 0, froze my butt off, they made windows for GM, it was the biggest building I was ever in...

If the manual is in good shape you saved money, dont worry about it, you need it, Mike

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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BTW, took the caddy on a road trip yesterday and no thumping noises noticed at all...go figure! <_< Drove 350 miles roundtrip and averaged on the highway 29.2 mpg. Hard to believe that big of a car can get that kind of mileage. Drove mostly with the cruise set at 74mph w/ the AC on. That also included a few WOT's to get around the idiots. :)

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Shelbyville is around 50 miles or so from my house. Have you heard that Shell has bought back contaminated properties from the current owners in the past?

No I have not. Since they are liable anyway it kind of makes sense for them to have control over the property.

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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BTW, took the caddy on a road trip yesterday and no thumping noises noticed at all...go figure! <_< Drove 350 miles roundtrip and averaged on the highway 29.2 mpg. Hard to believe that big of a car can get that kind of mileage. Drove mostly with the cruise set at 74mph w/ the AC on. That also included a few WOT's to get around the idiots. :)

Thats incredible gas mileage!

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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Heh.. I doubt it got 29mpg... unless i cruise at 60 I don't ever get anything over 25.. I cruise at 80 and i get 23-24 max no matter how long of a drive I go.. at 60 or 65 it goes up to 26-28

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Yeh, I'm lying. :D That's what the DIC said. I reset the mpg calculator once I got up to speed on the highway (which is 1.5 miles from my house), drove 350 miles roundtrip, and when I pulled in my driveway, it said 29.2 MPG. Rountrip was just about all highway, hardly no city driving at all, windows up, AC on. Lot of hills too!

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