|
|
|
|
|
#1
08-26-2004, 03:06 PM
|
||||
|
||||
OM617 turbo - ALDA boost pressure signal Banjo Bolt and fitting
This is to help people new to Mercedes Benz diesels.
Banjo bolt location on the 1985 W126 300SD. Rear of intake manifold. What is it = a hollow bolt with a hole in the side to give passage. What does it do = pass intake manifold pressure to the ALDA. Why does it need cleaning = oil sludge, carbon and other gunk builds up and plug’s the bolt and line. What happens if the bolt or line are plugged or broken = massive power loss. Warning: Do NOT over tighten the Banjo bolt; you will strip the threads from the manifold. Note: Follow the line to the ALDA, and remove the Hex banjo bolt from the ALDA, you should clean this bolt and banjo fitting at the same time.
__________________
ASE Master Mechanic asemastermechanic@juno.com Prototype R&D/testing: Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician. Noise Vibration and Harshness (NVH). Dynamometer. Heat exchanger durability. HV-A/C Climate Control. Vehicle build. Fleet Durability Technical Quality Auditor. Automotive Technical Writer 1985 300SD 1983 300D 1984 190D 2003 Volvo V70 2002 Honda Civic https://www.boldegoist.com/ Last edited by whunter; 03-08-2014 at 07:08 PM. 
|
|
#2
08-26-2004, 07:40 PM
|
|||
|
|||
|
Would drilling out the cross hole in the bolt (Where the tube goes around) to a larger diameter help airflow in/out of the fitting?
|
|
#3
08-26-2004, 08:49 PM
|
||||
|
||||
|
No
the flow is limited by the tube.
BTW, I lock the banjo bolt in a vice and use a low speed wood drill in a hand mandrel to clean the banjo bolt, and then throttle cleaner, use safety glasses. The hose is cleaned with throttle cleaner then compressed air. Lock the banjo fitting in a vice and use throttle cleaner then compressed air, in that order, repeat as needed, and use safety glasses. Years back, I tried enlarging the side hole, at customer request, result = no change in performance and a slightly weaker banjo bolt. Last edited by whunter; 08-28-2004 at 10:45 AM.
|
|
#4
09-08-2004, 06:51 PM
|
||||
|
||||
Oops
Repaired someone else’s oops.
1985 300SD (not mine). Encountered at the fuel station. We talked and showed off our cars. His car lacked power and smoked bad.   Looking around, found the intake line to ALDA was trapped and broken under the valve cover. You could watch the engine oil being blown through the tube to the ALDA. He had the valves adjusted the day he bought the car.  I cut the tube off the banjo and attached a rubber hose, jerked the broken stubs out of the valve cover gasket, started the car and no more smoke.  We drove around the block, he was happy! How could I know?  He stuffed a $100.00 in my pocket and would not allow me to say no.. When you or anyone adjusts your valves, PLEASE look too see that this line is not trapped. Last edited by whunter; 02-27-2005 at 03:46 PM.
|
|
#5
10-28-2004, 01:53 AM
|
|||
|
|||
|
The next item downstream would be the valve on the firewall that has an electrical and an air pressure component to it. What controls the electrical part of that valve? Does that valve pass the manifold pressure to the ALDA or is there vacuum somehow involved?
Is that called the crossover valve? Is it controlled by the overboost sensor? Is the overboost sensor on the intake manifold? I have read a lot of threads on this but different views are expressed and I am not sure how this system really works. I promise to read about it in the manual someday.
|
|
#6
10-28-2004, 01:59 AM
|
||||
|
||||
|
Time for one answer.
Quote:
Good night.
|
|
#7
10-28-2004, 09:36 AM
|
|||
|
|||
|
The crossover valve is normally closed, allowing manifold pressure to be "transmitted" to the ALDA. If the manifold pressure is excessive, the overboost sensor switch (on intake manifold) closes, electrically opening the crossover valve, venting the pressure that would otherwise go to the ALDA. Without the pressure, the ALDA reduces fuel flow, thereby reducing manifold pressure and preventing an overboost condition. There is no vacuum involved. Pressure is either maintained or relieved by the crossover valve.
|
|
#8
10-28-2004, 10:57 AM
|
|||
|
|||
|
Thanks, I have been putting this off for too long, this thread is answering questions I have been wondering about.
More questions in the form of assumptions: So, I can test the overboost switch with a Mityvac and an ohmmeter. At what pressure should it switch? I can test the crossover valve with a Mityvac and battery voltage? 12V won't hurt it? I can test the ALDA with the Mityvac and engine running. Engine should speed up with pressure applied? The no vacuum involved rule really helps. With all of those vacuum lines around there I thought there must be a tie to the vacuum system somewhere.
|
|
#9
10-28-2004, 12:17 PM
|
|||
|
|||
|
You can test the crossover valve by grounding the wire that connects to the overboost sensor. The valve should open and vent pressure with the wire grounded. The overboost sensor switch should close at 1.2 bar (approx 18 psi.) Check the markings on the overboost sensor to verify operating pressure for your particular sensor. Mine says 1.2 bar. To do a primitive check on the ALDA, just drive the car with the pressure line disconnected. If it feels like you are dragging an anchor, as compared to driving with the line connected, then things are generally working.
|
|
#10
12-18-2005, 12:21 PM
|
|||
|
|||
|
Does anyone have a part number for the pressure hose from the banjo bolt to the alda in an '85 300DT? Mine was replaced with soft rubber vacuum line and I'd like to go back to the hard plastic hose designed for pressure rather than vacuum...
A FastLane reference would be great.
__________________
1985 MBZ 300DT 1969 MBZ 220d 1984 MBZ 300TDT 1981 VW Vanagon
|
|
#11
12-18-2005, 08:04 PM
|
||||
|
||||
|
My 85 300D has been running with that line on the back of the intake manifold broken. It's pretty darn slow now... am I getting no boost now or what? The banjo bolt with the line fitted is a special order thing and costs 40 dollars...............................................................
 Anyone know the part number?
__________________
1985 CA 300D Turbo , 213K mi
|
|
#12
12-19-2005, 12:08 AM
|
||||
|
||||
|
You're still getting the same amount of boost but the IP doesn't know it so it doesn't send any more fuel in. Just adding extra air with no extra fuel won't do any good. Sorry don't know the part number.
__________________
Seth 1984 300D 225K 1985 300D Donor body 1985 300D Turbo 165K. Totaled. Donor Engine. It runs!!! 1980 300SD 311K My New Baby. 1979 BMW 633csi 62K+++? Dead odo
|
|
#14
12-19-2005, 12:35 AM
|
||||
|
||||
|
Mine ran like that for I don't know how long. The first time I changed the air filter I saw that the wastegate hose was disconnected = no boost. A couple of months ago I noticed that my hose from the banjo bolt to the alda was broken = also no boost. I don't think it hurts the engine but I could be wrong. Its just an inconvenience IMHO because its not running like it should.
__________________
Seth 1984 300D 225K 1985 300D Donor body 1985 300D Turbo 165K. Totaled. Donor Engine. It runs!!! 1980 300SD 311K My New Baby. 1979 BMW 633csi 62K+++? Dead odo
|
|
#15
12-19-2005, 01:04 AM
|
||||
|
||||
|
Answer:
Quote:
Ask for the white semitransparent plastic tube, typically you can buy a roll cheap. #1. Cut the tube to length. #2. Put the fitting in a vice with the barb up. #3. Warm the barb with a lighter. #4. Quickly slide tube on warm barb. This repair should last five or more years.
|
 |
| Bookmarks |
|
|
Linear Mode
