How do I determine if engine mounts are shot?

[LFrank]

Can it be done visually? A suddenly-developed vibration (at speed, but not idle) has me wondering if my mounts are gone....

LFrank
Washington DC
65 230 sl - auto
DB334/Hellblau

[ja17]

Hello Frank,

Yes, you can visually check the mounts. If the center metal part of the of the mount is punched down into the rubber or the mount is noticeably collapsed, then it is most likely bad.  Below the mount is a engine torque plate and bolt which will be contacting the frame and causing vibration if the mount is bad.

Be sure to  check the drive shaft for a bad flex disc or loose bolts (this is more likely).

Joe Alexander
Blacklick, Ohio

[LFrank]

<<Be sure to check the drive shaft for a bad flex disc or loose bolts (this is more likely).>> Thank you Joe; that's the first thing I will check!

LFrank
Washington DC
65 230 sl - auto
DB334/Hellblau

[waltklatt]

Hello Frank,
The vibration at speed is the clue.  Something is off on your driveline.  Check the usual rubbers and tightness of bolts, etc.
Suspect as Joe says, the flex disc or the center carrier(not sure what it's called), but the holder in the middle of the driveshaft from the tranny to the diffrential on the axle.
Do you have a stick or auto?  I've got a stick driveshaft in my parts collection.
Maybe one of your tires is out of round or has a bulge/flat spot.
Walter
1967 220SL-diesel

[66andBlue]

quote:Originally posted by ja17
 ... Be sure to  check the drive shaft for a bad flex disc or loose bolts (this is more likely)...

Joe,
how do you check for a bad flex disk, or how do you decide that it is "bad"?

Alfred
1966 blue 230SL automatic

[ja17]

Hello Alfred,

The rubber flex discs can deteriorate from age and/or use. Examine them closely for cracks in the rubber with cord showing. In advance cases, the cords will be frayed and sticking out from the disc. The danger is that after complete failure, the drive shaft, centering bushing or transmission can be seriously damaged.

Often times these are not installed correctly and they don't stay fixed. Make sure to study the installation diagram and use all the correct hardware in the correct places. Notice three of the drive shaft bolts are longer than the other three. The washers are always next to the rubber (one under each short bolt head and one under each long bolt nut, total of six).  The flex disc kit comes with all new hardware.
Download Attachment: BPossel flex disc.jpg
17.51 KB

Joe Alexander
Blacklick, Ohio

[LFrank]

Update: yes, new mounts were in order but that was not the cause of the vibration at speed.  Wouldn't you think I might notice that a blade had broken off of the radiator fan?

LFrank
Washington DC
65 230 sl - auto
DB334/Hellblau

[waltklatt]

Wow that must've caused some racket when it broke off.  Guess it hung on till you parked the car and shut the engine off.  
Do you have a new hood ornament propped up on the hood?  How about the hoses and all the lines around the path of the fan.
Again, wow!  That is an unusual cause of the vibration.
Walter
1967 220SL-diesel

quote:Originally posted by LFrank

Update: Wouldn't you think I might notice that a blade had broken off of the radiator fan?

[al_lieffring]

quote:Originally posted by LFrank

Update: yes, new mounts were in order but that was not the cause of the vibration at speed.  Wouldn't you think I might notice that a blade had broken off of the radiator fan?

LFrank
Washington DC
65 230 sl - auto
DB334/Hellblau

The service manuals all warn to never turn the motor by using the fan blades. I don't want to say that you may have done this, but this is the result that they are warning of.

Al



66 230sl
113-042-10-014715
904/396 blue, Ivory Tex
condition: not-as-rusty-as-before-bucket

[ja17]

Hello LFrank,

A fan blade will not usually fail unless it is damaged. The blades are magnesium and very strong and light but very brittle.  If a blade is cracked, bent or badly nicked it should be replaced. A damaged blade can be dangerous.  I once saw the steel hood of a Mercedes sedan where the fan blade left a nice 3 inch slot in the steel as it exited. I often think of this when I am leaning over an engine to set the ignition timing!

Joe Alexander
Blacklick, Ohio

[LFrank]

Who else out there has plastic fan blades? C'mon, I can't be the only one!

LFrank
Washington DC
65 230 sl - auto
DB334/Hellblau

[waqas]

I think the early cars had plastic fan blades (like my '65 230sl) and later cars with fan clutches had metal fan blades (like my '66 250se and '72 280se). I'm not sure if they made metal fan blades for use without a fan clutch... but I'm sure someone else here can clarify.

WAQAS in Austin, Texas

[J. Huber]

Hi Lfrank, Mine are plastic. Only 4 blades too. The later ones have six I believe.

James
63 230SL

[gnj588d]

Hello  everyone My 65 230 has a plastic fan with 4 blades       Cheers Mike Rutledge

[jacovdw]

Hello all,

The original fan on the earlier cars were made of metal and had 4 blades (no fan clutch). The current replacement is made of plastic with 4 blades.

I still have the original dull grey metal fan on my early 64 230sl.

Regards,


Jaco van der Walt
1964 230sl
1975 230.6