The following page is a backup which was originally created by Richard Easley and Stu Ritter, all credit should be given as such. Most links on these pages are unfunctional.

Turbocharger Wastegate Valve
Spring Tension Adjustment for 617 Engines

Introduction

The technical material for this FAQ (Frequently Asked Question) was provided by Stu Ritter of Stu Ritter Mercedes-Benz Technician, Inc. of Denver, Colorado, was edited by Richard Easley of Baylor University, and is provided as a service to the subscribers of the Mercedes-Benz Discussion List.

To receive similar quality tips as described below on a daily basis, consider subscribing to the Mercedes-Benz Discussion List, which is located at the following site:

http://hsb.baylor.edu/html/easley/mercedes/welcome.html


Assumptions

Using the categories of mechanical ability from the Mercedes-Benz Discussion List <http://hsb.baylor.edu/html/easley/mercedes/subscribe.html>, you need to be at the level of "Medium Do-It-Yourselfer" at minimum, to check the boost pressure. If you are below that level, you may want to provide these instructions for someone who is at the medium level or beyond.

Introduction

Garrett Turbochargers

If you have a Garrett turbocharger (w/ wastegate adjustment inside cover), removing the cover takes some time and perserverance. It is not particularly difficult, just tedious. Make sure that the turbo area is cool (use a fan between adjustments) and when re-installing the spring, "squeeze" it to reduce its diameter before inserting. Then, with a screwdriver push on the flat part of the spring until it seats.

 

KKK Turbocharger

If you have a KKK turbo, the adjusting screw sticks right out of the top (sideways on engine) of the wastegate chamber and does not require removal of a cap.

Caveats

Remember both of these turbos are capable of over 40 pounds per square inch of boost and they run against an open wastegate all the time so these adjustments are really critical. Don't get carried away or you are going to buy a motor. However, please note that it is hard to get a tremendous amount of boost (i.e., well beyond safe ranges) from an original 617 turbo now that the cars have a few years on them now and the springs are fatigued somewhat. Still, confidently proceed with caution.

If you have an exhaust temp gauge in-line you can carry the boost procedure a little further, but even at 0.9 bar (upper limit of factory specifications) they just fly.

Preliminary steps necessary before adjusting wastegate valve spring tension

Prior to adjusting the wastegate valve spring tension, there are two necessary preliminary steps that need to be taken, each of which is provided at this web site: http://hsb.baylor.edu/html/easley/mercedes/mercedes.html and is referenced below:

  1. The first step is to ensure that the injection pump is timed correctly. This procedure is described on the following web page: http://hsb.baylor.edu/html/easley/iptiming.htm
  2. Checking the boost sensing lines and overboost sensing switch is the next step in this process and is described on the following webpage: http://hsb.baylor.edu/html/easley/boostchk.htm
  3. After successful completion of the above two steps, you are now ready to adjust the wastegate valve spring tension (i.e., boost adjustment).

Tools needed for adjusting wastegate valve spring tension on turbocharger

  1. High quality vacuum/pressure gauge (needed for checking boost pressure only)
  2. "T" fitting for vacuum gauge and 6 - 8 foot length of vacuum hose for monitoring boost pressure while driving vehicle (needed for checking boost pressure only)
  3. Phillips screwdriver
  4. 10 mm socket and 1/4" drive ratchet and extension for removing air horn
  5. Pliers for removing sensor hose clamps at turbocharger
  6. Small mirror for clarity during cover removal
  7. High powered flashlight or shoplight

Instructions

  1. Remove the u-shaped air intake and the intake to the air cleaner. Make sure to re-install before testing boost pressure.
  2. Cool the turbo area with fan.
  3. Spray the cap cover "spring" area with Liquid Wrench or other similar solvent.
  4. Using a couple of small screwdrivers (a very thin bladed 5-8" shafted one is great), "spin" the spring around until it starts popping out.
  5. Pull out the spring with needlenose pliers or fingers.
  6. Remove wastegate valve cover. Be careful not to damage the rubber seal behind cap (but attached to body of turbocharger) when removing. There will likely be a small quantity of oil that will leak out when the cover is removed; this is normal – not a problem.
  7. Completely remove locknut on wastegate valve.
  8. Make a note of measured length of exposed threads on valve.
  9. Turn spring assembly (it has flat, thin edges for wrench) clockwise. Begin with 3 full turns - it sounds like too much, but it isn't! If our approximations are
    correct, for every 1/8" of threads exposed (by screwing spring assembly in),
    this equates to 0.15-0.20 bar of boost.
  10. Reverse disassembly procedure. To reinstall spring as easy as possible:
  1. Make sure that you've thoroughly cleaned the groove where the spring
    resides.
  2. Make sure that the spring is thoroughly clean.
  3. Lightly file or grind the flat side of the spring at each end so that it's
    shiny. This enables you to manuever better when inserting 'cause shiny end
    shows.
  4. Make sure that rubber gasket is firmly seated before replacing cover.
  5. Compress spring with fingers to reduce diameter when placing in groove.
    And, push cover hard simultaneously.
  6. Then, push spring with biggest screwdriver that you can use. Tap
    screwdriver with rubber hammer. You should "feel" spring seat.
  7. Do this only on fan-cooled turbo area.
  1. Road test using Stu's guidelines: having the boost gauge in the car, start driving a fully warmed up motor and engage "S" and go up to 4,000 rpm and full throttle, read the boost. Good luck and hold on to your hat.
  2. If further adjustment is needed, cool turbo area with fan.

Finally

    Please let me know if you complete this procedure successfully; it took a while to type this, and I'd appreciate knowing when each person has completed the repair! Please e-mail me at richard_easley@baylor.edu

     

    ©1998
    Richard Easley, Waco, Texas and Stu Ritter, Denver, Colorado.
    The Mercedes-Benz Discussion List is not affiliated with any other Mercedes-Benz electronic discussion lists nor is it affiliated with Mercedes-Benz of North America or any of its subsidiaries.