Connecting rod big end bearings noise

[lgr]

Hello!

I have a 1970 280 SL  and it has a noise on the engine like a "sewing machine", bigger when engine is cold and, following the diagnostic of the mecanic, is from a connecting rod end bearing
As the noise as been allways there since I bought  it 10 years ago,  and to avoid spend a huge ammount of money on a engine overall, I would like to know if I can use an adititive like STP  to protect the engine to bigger damages and slow down a bit this noise.
I look forward your valuable comments

Kind regards

Luis Gama Rocha

[J. Huber]

Hello Luis,

It's not uncommon for the rev. counter (or tachometer) to eventually need some service. The howl is usually the primary symptom. In some cases, only the tach cable needs to be changed. Really not difficult and about $40 or so US? In most other cases, the unit needs to be serviced by experts. Again, in the US -- a couple places are Palo Alto Speedometer and No. Hollywood Speedometer. There are others I am sure. In this case, you pull it out and send it. I think this runs about $125 and takes a week or so.

And now for the fun part -- how to get it out! It's not difficult (really) but you do need to learn the technique. Please do a search for "tach removal" or similar words. You'll get lots of stuff. Good luck! Again, a fairly common malady. But very fixable.

James
63 230SL

[glennard]

Discover the joy of the 'under the dash' exploration.  Disconnect the speedo cable.  Lubricate the cable. Reinstall.  Should work.  If the noise is still there, might be the odometer or the lube didn't work on the cable.

[al_lieffring]

The tachometer drive cable can be removed from the flexible housing and lubricated by disconecting the housing from the engine and puling the cable out from the housing, I usualy soak the cable in automatic transmission fluid wipe off the excess and reinstall the cable in the housing.

If this doesn't help, then I remove the tach from the dash, and use a rubber bulb from an antifreeze tester. I remove the bulb from the top of the tester and fill it with ATF, press the open end of the bulb over the shaft bushin on the tach where the cable attaches and gently squeese the bulb to force some lube into the tachometer drive shaft. getting some lube into the bushing here is usualy all that is needed to get rid of the squeal.

If you have the tach out you might as well lube up the speedo too using the same procedure, but the speedo cable does not come out of the housing for lubrication like the tach cable will.

Al Lieffring
66 230SL

[glennard]

Hey, Your '70 SL--mechanical or electronic tach?  Speedo mechanical?  You never know what 'upgrades' you might have!

[ja17]

Hello Luis,

Remove the under dash padding (three screws). Next remove the two screws holding the metal bracket with the two large electrical plugs. Move the bracket out of the way. You should be able to get your hand up to the rev counter cable now. Unscrew it then remove the knurled thumb screw holding the instrument in place. Notice the ground cable (earth) witch attaches under the knurled thumbscrew. The rev counter can now be pushed out from behind. The light sockets with bulbs just pull out of the back of the instrument.

Joe Alexander
Blacklick, Ohio

[glennard]

Question--  Did all 113s have mechanical tachs?  Later 111 coupes had electrics.

[al_lieffring]

quote:Originally posted by glennard

Question--  Did all 113s have mechanical tachs?  Later 111 coupes had electrics.

Yes
They all (113s) had a mechanical tachometer.

Al Lieffring
66 230SL

[Raymond]

Joe knows!  It helps to have skinny hands and some patience.  You'll spend some time on your back under the dash but I've done it without removing the seat.  Watch your scalp on the heater and pedals.

While you have it out, you might want to replace the light bulbs as a preventive measure.  If you can get LEDs, even better.

Ray
'68 280SL 4-spd Coupe

[waqas]

Jim Villers' excellent presentation on making our cars more drivable at Blacklick this year included some good LED replacement bulb candidates for those dim dash light blues... (for example, check out http://www.superbrightleds.com/mini-wedge.html)

Waqas in Austin, Texas

[paulr]

These sound very interesting. Which one do you think should replace our lamps and is it a straight swap?

thanks a lot

quote:Originally posted by waqas

Jim Villers' excellent presentation on making our cars more drivable at Blacklick this year included some good LED replacement bulb candidates for those dim dash light blues... (for example, check out http://www.superbrightleds.com/mini-wedge.html)

Waqas in Austin, Texas

paulr
lovely 1970 280 SL

[Cees Klumper]

Hello Luis - I had that problem and a new cable solved it.  Al Lieffring's lubrication tips appear very useful (and innovative!) and could solve the problem as well; I've taken the tach several times and, once you get the routine, is not really difficult - although it helps to have skinny hands.

Paul: I believe that Daniel Stern Lighting in the US can also help with advice on replacement lighting and sells the bulbs. If I recall correcty, Jim Villers had a hand-out at the tech session with details on the replacement (LED) bulbs.

Good luck,

Cees ("Case") Klumper in Amsterdam
'69 white 280 SL automatic

[lgr]

God bless you all!

I'll give you soon my "under-the-dash" fantastic week-end.

Rgds

Luis

[waqas]

Paul,
Not sure if there's a drop-in replacement (haven't done it myself yet). I imagine the bulb with a bayonet-style base and having the same diameter should work just fine. This winter, I plan to do a complete dash-board and tail-light replacement with LEDs (there's a few that need replacement anyhow), so I'll let you know how it goes.

quote:Originally posted by paulr

These sound very interesting. Which one do you think should replace our lamps and is it a straight swap?

thanks a lot

quote:Originally posted by waqas

Jim Villers' excellent presentation on making our cars more drivable at Blacklick this year included some good LED replacement bulb candidates for those dim dash light blues... (for example, check out http://www.superbrightleds.com/mini-wedge.html)

Waqas in Austin, Texas

paulr
lovely 1970 280 SL

[lgr]

Hello again!

As promised here I am to described my fantastic “under the dash tacho removal experience”

In one word: I DID IT!! And I did it with your help, otherwise I was still looking to find out the screw to release the tacho, but I had to remove the seat and the steering wheel!

Now the question is: I remove the tacho, lubricate the cable (it seam to have some traces of rust) but the noise and the vibration still there. I hope the problem is with the cable and  not with the cable (I removed the rubber protection of the tacho and it seams to be ok), so I’ll replace the cable and see what happens.
The funny thing is that the noise and the vibration only appear from 2500 rpm on.
Anyone as a clue for this?

Luis

[J. Huber]

Good job Luis! Despite advice from the pros, I never removed my steering wheel (or seat) to tackle the tach -- but I can see how that would really help out. Give the cable a try -- can't hurt. In my case, the noise also began at a certain RPM. It also seemed to occur more when it was cold outside. Eventually, the noise became a buzzing howl and the little silver center piece even fell off! I tried cable -- but it took a rebuild from PAS. Thanks for the update...

James
63 230SL

[ja17]

Hello Luis,

I always remove the steering wheel also. It makes the job so much easier. Most of the time the problem is some minor wear in the instrument itself. Some very fine watch oil in the instrument can temporarily cure the problem.

Joe Alexander
Blacklick, Ohio

[J. Huber]

Hey Joe. A slight diversion: when I remove my horn pad to take off the wheel, I don't see the large nut which one removes to take it off. Instead, there is a plastic cover plate -- and I don't really know what to do next...are the earlier columns different in some way?

James
63 230SL

[Naj ✝︎]

quote:Originally posted by J. Huber

Hey Joe. A slight diversion: when I remove my horn pad to take off the wheel, I don't see the large nut which one removes to take it off. Instead, there is a plastic cover plate -- and I don't really know what to do next...are the earlier columns different in some way?

James
63 230SL

James,

This plastic plate may have detatched itself from the 'horn pad'.
Just pry it off with a screw driver or similar implement. Its held by three plastic 'press on' type studs.

naj

68 280SL

[CraigD]

Any suggestions for unscrewing the cable nut on the back of the tach? I took out the seat, the steering wheel, and moved the wiring harness to get good access.  Now I can't get the tach cable nut off the back of the tach.  Finding a good hand position for leverage is hard, for sure.  Any suggestions?  Thanks in advance...


Craig
'70 280SL Euro, Manual,  Leather
Silver/Black

 

[CraigD]

Tried again and got the cable nut off, so the tach is out.  

I have 2 questions:

1.  The second photo below is the back of my tach.  I noticed the bulb sockets are different... one has the black plastic holder and one doesn't.  Is this correct?
2) In the third photo, what is the bracket centered beneath the front seat?

Thanks for the help,

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Craig
'70 280SL Euro, Manual,  Leather
Silver/Black

 

[ja17]

Hello Craig,

Your light sockets are correct. The one that sticks out has an insulator around it. I am not sure what the bracket is. It may be a seat stop?

James, I think Naj is correct. You removed the upholstery part of the pad without the backing.

Joe Alexander
Blacklick, Ohio

[hands_aus]

quote:Originally posted by CraigD


2) In the third photo, what is the bracket centered beneath the front seat?

Thanks for the help,

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Craig
'70 280SL Euro, Manual,  Leather
Silver/Black

 

Is it a fire extinguisher mounting bracket?

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[J. Huber]

quote:Originally posted by naj


James,

This plastic plate may have detatched itself from the 'horn pad'.
Just pry it off with a screw driver or similar implement. Its held by three plastic 'press on' type studs.

naj

68 280SL

Hi Naj, sorry, I must have missed your response! Thanks, and thanks Joe for reminding me... I bet you all are right, the upholstered part has lost its stick -- and comes off fairly easily. Actually bugs me as it goes cock-eyed once in a while. Time to glue it back on!

James
63 230SL

[Douglas]

Is it a fire extinguisher mounting bracket?

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

In fact, Bob is exactly correct. That little bracket in front of the driver's seat is for the fire extinguisher.

This post was made a little over 2 years ago.... I'll try to reply faster next time. :-)