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1976 Eldorado Convertible knocking noise

Started by Mihai Tarţa, April 30, 2014, 09:02:15 AM

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Mihai Tarţa

I wonder if any of you have experienced something similar.
The car makes a knocking noise (one knock every 150 feet or so) coming from the front right side.
It doesn't seem to depend on speed (the frequency doesn't increase or decrease with speed), it isn't affected by steering, breaking, accelerating (or accelerating while steering) or bumps in the road.
Also, the following parts have been replaced on both front sides with new ones: tie rod ends (inner and outer), stabiliser bar links, idler arm, lower and upper ball joints, wheel bearings and seals, and the steering gear was rebuilt.
The only thing that is in worse shape is the upper bushing of the front shock absorber on the right side, but being that the noise doesn't necessarily come about on bumpier roads, it may not be the cause.

Any input would be greatly appreciated.

Thanks,
Mihai
1969 Coupe DeVille
1976 Eldorado Convertible

Oradea, Romania

The Tassie Devil(le)

Boy, a knock every 150 feet.   That is a new one.

Make sure there is no pedestrian trying to alert you to his plight. ;) ;) ;)

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe

Mihai Tarţa

#2
It's driving me insane.
I should get new front shocks and have them replaced by next week.
If that doesn't fix it, I 'm out of ideas, because most suspension and steering related parts are brand new.
The mechanic suggested that it might be coming from the CV, but I think that if it were the case, the frequency of the knock would increase with speed and it would be more likely to occur when cornering.
1969 Coupe DeVille
1976 Eldorado Convertible

Oradea, Romania

"Cadillac Kid" Greg Surfas 15364

Mihai,
First things first. Pull the right hub cap and check for loose lug nuts. Jack the car up and support both sides under the lower control arms. With the car in Neutral rotate  (by hand) the whels (right first) and see if the noise repeats every 7 to 8 revolutions.  Rotate the wheel foreward and backward and see if the noise or any looseness when going from forward to backward occurs.
Try that for starters and see what you find.
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

Jeff Rosansky CLC #28373

Need to isolate it from the engine/drivetrain.  Would like to know if it happens in reverse.  Then, going down hill, see if it happens in neutral and then, see if it will do it with the engine off (remember, no power brakes so it will take longer to stop).  Could be something in the rear but the sound is transmitted thru the driveshaft and/or exhaust
Jeff Rosansky
CLC #28373
1970 Coupe DeVille (Big Red)
1955 Series 62 (Baby Blue)
Dad's new 1979 Coupe DeVille

bcroe

I suggest, if its not a loose lug nut, the wheel bearing may be going.  It turns a few
times till the innards get cranked into a particular position, then it slips into another
spot.  If the wheel bearing hasn't been greased on some kind of basis, I'd have no
confidence in it.  Swap in a different one and see what happens.  Bruce Roe

Mihai Tarţa

#6
I'm going to try what you guys suggested.
The wheel bearings are brand new and installed correctly with the wheel hub machined on CNC about a month and no more than 50 miles ago, so I guess them being the cause is out of the question.
I'll check the lug nuts, but the guys in the shop always use a compressed air impact wrench to remove and install the lug nuts, so I'd be really surprised if they would be loose.
1969 Coupe DeVille
1976 Eldorado Convertible

Oradea, Romania

Scot Minesinger

Did this noise begin after some recent work on the car was performed?  If so that is a place to start.  It would be more convenient for me to write a check rather than work on my Cadillac myself.  Out of necessity for work done the way I want it, had to resort to performing it all myself.  Checking the work of others, such as lug nuts is the first place to start, as the mechanic could have been interrupted and not finished tightening all of them.

Many of the posts in this column read along the lines of "my mechanic removed the engine and re-built it but does not know how to hook up the vacuum lines, does anyone have a diagram?"  Really, a professional took apart something without noting along the way how it goes back together - just crazy stupid.  Many of the posts do highlight mechanic errors.  Last year needed an inspection done, which I can't do, and had the oil changed - how can you mess that up?  They overfilled, put in 6 quarts total in 472 RWD that takes 5 with filter.  Ran the car 500 miles before noticing that.  It is a business and it is difficult to earn a profit working on the se cars.

Things like this noise drive me crazy.  Hope you get this resolved soon and get to enjoy your Cadillac! 
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

Mihai Tarţa

I took the car out for a drive today, checked the lug nuts before and they were all tightened, drove around for about 15-20 miles and it didn't make the knocking sound.
I'll drive it every day to see if I can identify the circumstances in which this noise occurs. Next week i'll take it to the shop to change the front shocks and the parking brake cables and to install a set of anti-rattle clips for the brake pads. I'll have them double check everything they've done.

1969 Coupe DeVille
1976 Eldorado Convertible

Oradea, Romania

mgbeda

It might be (or have been) a loose hubcap.  They can make a surprising amount of noise.  And when you took them off to check the lug nuts you may have fixed the problem.

-mB
-Mike Beda
CLC #24610
1976 Sedan DeVille (Bessie)

Mihai Tarţa

Actually I took the hubcaps off when it started making the noise just to eliminate them as the cause, but it made the noise with the hubcaps off as well.
I'm hoping it's the upper bushing of the front right shock absorber, but at this point it's just wishful thinking.
I was planing to replace the front shocks anyway because the bushings are fairly dry rotted, the upper one on the front right shock has some play in it and they're among the few front suspension parts left to replace.

I'll keep you posted.
1969 Coupe DeVille
1976 Eldorado Convertible

Oradea, Romania

bcroe

1.  I would NEVER assume a new part can't have a fault; most of my problems
these days are defective parts, new but inferior to the original. 

2.  I have had wheels on crooked because the (idiot) torqued them wrong.  Also had to replace
otherwise perfectly good rims, because the impact wrench had gouged out the tapered holes. 
Now I use the impact wrench for taking things apart, or maybe putting them LOOSELY
together.  All  final tightening is carefully done (in proper sequence) by my calibrated right arm. 

3.  I originally had cars repaired, but I spent too much time repairing their repairs. I decided to
just do it myself.  Dozens of stories led me to this.  Nobody has touched my cars for decades,
I even bring in wheels for tires, then put them back on the car myself.  Bruce Roe

Scot Minesinger

I don't think I have ever read a post that I more agree with than yours.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

dplotkin

Quote from: Mihai Tarţa on April 30, 2014, 09:15:41 AM
The mechanic suggested that it might be coming from the CV, but I think that if it were the case, the frequency of the knock would increase with speed and it would be more likely to occur when cornering.

Not necessarily. Bad CV joints can pop and click just like that, no rhythm required.   Problem with noises such as these is it could be almost anything. I once had a knock coming from under the dash on the far right side that turned out to be a non-tightened fender bolt.

I think you should view your CV joints with suspicion, if you do not otherwise know them to have been recently replaced.

Dan
56 Fleetwood Sixty Special (Starlight silver over Dawn Grey)
60 Buick Electra six window
60 Chrysler 300 F Coupe
61 Plymouth Savoy Ram Inducted 413 Superstock
62 Pontiac Bonneville Vista
63 Chevy Impala convertable
63 Ford Galaxie XL fastback
65 Corvette convertable 396
68 Chrysler New Yorker

Mihai Tarţa

It is a possibility, because the CV's haven't been replaced and I bought the car with torn CV boots.
I was kinda hoping they're not it, because they cost around $450 shipped to Romania.
1969 Coupe DeVille
1976 Eldorado Convertible

Oradea, Romania

Julien Abrahams

I have to agree with bcroe > I also have had work done to my classic cars, or ask other people (who work on regular cars) for advice, but usually (not all the time luckily) found that I was better off doing stuff myself. At least when you screw it up, you can learn from it, and it usually costs less money to fix it.
1954 Cadillac series 62
1967 Cadillac Sedan De Ville HT
1969 Austin Healey Sprite
1979 Opel Kadett

Mihai Tarţa

#16
Eventually it started making the same noise from the left side as well.
We've determined that it comes from the outer joint of the CV and it comes about on Wavy roads when the front wheel tends to move up and down a lot.
I've ordered two remanufactured (A1 cardone) CV's and had them both replaced.
Now the right side is ok, but the left keeps making that noise and it seems to be louder than it was with the old CV.
I've read here that A1 Cardone has a good reputation, but from a total of 4 remanufactured parts I've purchased from them so far (two steering pumps and these two CV's), two were broken (one steering pump and this one CV).
I don't know about you, but in my book that doesn't make for a good reputation.
There's really no point in sending it back, as the shipping alone is $100/piece, so I might as well spring for another one, hopefully with more luck.
On Rockauto.com I have three options: cardone, Empire and Surtrack at roughly the same price. I've only noticed now that Empire and Surtrack are new, not reman. I'm an idiot like that....

From your experience, which would you recommend?
1969 Coupe DeVille
1976 Eldorado Convertible

Oradea, Romania

TJ Hopland

Last time I had to deal with them there were no such thing as new ones.  Only issues I had were the boots being cracked right out of the box from sitting on the shelf so long.   I did have one that had the threads slightly damaged at the end so I had to take it apart again to clean up the threads so I could get the nut on.    Now I have learned to always check the but before I assemble things.
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

Mihai Tarţa

#18
I got a new Surtrack CV and installed it. It's made in China, but at least it's new.
So far so good... I'll let you know how it holds up over time.
On the down side, more bad news: the other A1 Cardone CV is defective as well. How about that? Two "remanufactured" CV's, both defective and $460 plus labour down the drain.
Man, this is like a never ending nightmare...

I strongly suspect that their remanufacturing process consists of no more than replacing boots and lubricant...
No more remanufactured parts for me, that's for sure.
1969 Coupe DeVille
1976 Eldorado Convertible

Oradea, Romania

Scot Minesinger

Bad parts is such a huge problem in our hobby, including remanufactured and new.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty