Breather Tube Questions

[dirtrack49]

Hi all,

My 66 230SL breather set up has a single metal tube with a rubber boot on the valve cover and throttle body fitting.

I decided to replace the boots and clean out the tube. I found the tube to be somewhat heavy in oil residue. After cleaning out the residue, I am now getting some rusty metal flaking.

After several attempts at cleaning up the breather tube, I am wondering if it is possible to just vent the breather to the outside and cap off the fitting at the throttle body? Or, should I just clean up the breather as best as possible and put it back on the car?

I also noticed that the boot at the valve cover had two clamps on each end of the boot. The "L" shaped boot at the throttle body only had one clamp at the housing itself. Should there be two clamps for the throttle body boot?

Thanks for any and all help and suggestions.

[Tyler S]

Tom, Others with excessive blow-by have disconnected the breather from the throttle body and dumped it down the left side of the engine bay. I guess it depends how healthy your motor is and how much of an "Al Gore" you are. Personally, I would leave it connected. The later cars used a plastic tube instead of the metal. I dont know if this is correct but have seen most with only 1 clamp right at the valve cover.

[ja17]

The smell of oil fumes may be  noticed by you when just venting the oil line to the engine bay.

[dirtrack49]

Thanks for the comments. I ended up cleaning the tube out and reinstalling it.

And thank you Benz Dr. (Dan) for your earlier threads that I had read concerning oil coming out of the tachometer drive. Now that I have cleaned up the breather tube, the oil coming out of my tach drive is minimal. Besides wanting to renew the 50 year old rubber boots, I wanted to see if cleaning the breather tube would help with the oil coming out of my tach drive and it did. The tube itself was not plugged, however, there was fifty years of oil residue and some coating of rust within the tube prior to cleaning.

[Benz Dr.]

Did you hook everything back up?

[dirtrack49]

Yes Dan, I hooked everything back up.

I am surprised that I now have only a slight weep of oil coming up around the tach cable where it fits into the engines drive. There was oil residue in the breather along with some minimal rust which I cleaned up as best as possible using some gun cleaning tools. The breather was not clogged from what I could tell. However, it must have been enough residue built up over 50 years to cause some back pressure.

The slight amount of oil coming from the tach drive would probably be cured with new O rings and fittings, although it might not be worth the expense at this point in time.

[Tyler S]

Tom, Also check your tach drive bushing for excessive wear. If it wears too much you will loose your oil pump drive. With only 74k miles, mine was at the end of its life and I caught it before something bad happened. Good thread about it here.
http://www.sl113.org/forums/index.php?topic=3952.msg24189#msg24189

[Benz Dr.]

Good idea about checking the tach drive gears - most are worn when inspected.

  Not that this applies, but you can check how good a MB diesel is working simply by plugging the vent on the top of the the valve cover. Engines with a lot of blow-by will stall quickly while a good engine will run for a minute or longer.

 The negative pressure at the the throttle valve will help to draw blow-by gasses out of your crankcase through the vent tube, which in the overall scheme of things, can't be a bad idea.   
 

[vande17941]

You can use a shotgun cleaning brush with a brass brush tip to clean the loose rust from inside of the pipe. Then once you remove most of the rust, spray it out with carb cleaner. Then apply naval jelly on the brush and get the inside of the pipe coated nicely. Let it sit for about 15 minutes and do that 3 or 4 times. All the rust will be gone and you'll be good to go. You can also use the naval jelly on the outside of the pipe to make her look sweet

[dirtrack49]

Great idea about the naval jelly. I wish I had done that before putting the damn thing back together. However, ever since I cleaned the breather tube out, I now have no noticeable leakage from the tach drive. Thank you Benz Dr. for your previous post I think from 2010. Now that the breather tube is clean, no more blow back through the tach drive.

I went back and checked the endplay in the tach drive since I had not taken a measurement for sometime. I now have approximately 1.0mm endplay at the gear. Don't know if I should shim the tach drive, replace the part, or let it ride? Anyone have a current idea on replacement or shimming?

[Benz Dr.]

That's a fair amount of end play. We have been using a copper seal to shim the end play that's commonly used under a fuel injector. Measure how thick this seal is and you should be able to determine if it will fit. If it's too thick you won't be able to get the grub screw to go back into the sleeve. A thinner seal or a bit of sanding should sort that out.

 

[star63]

  Not that this applies, but you can check how good a MB diesel is working simply by plugging the vent on the top of the the valve cover. Engines with a lot of blow-by will stall quickly while a good engine will run for a minute or longer.

Especially the engines that use a vacuum operated shutoff device. When you plug the vent the engine will start to develop overpressure. This pressure will push the shutoff diaphram from the back side and shut the fuel flow off. I guess...

[Pinder]

The rubber boot I replaced on mine and is actually not an expensive item. I think I paid around $6 for it from Autohous AZ. probably available on Amazon too. the breather pipe on my car is plastic.

[Benz Dr.]

Nice item to have. When they break they make a mess.

[Tyler S]

We have been using a copper seal to shim the end play that's commonly used under a fuel injector. Measure how thick this seal is and you should be able to determine if it will fit.

The injector copper seal rings are 1.0 mm out of the box. Used ones a little smaller. You do need some clearance but I found that the clearance increases with engine temperature.

[Benz Dr.]

The main thing is having a small amount of free play while static. You should be able to move it up and down slightly or it would be too tight.