1987 300D lack of power :( - Page 2 - PeachParts Mercedes-Benz Forum

gsxr · #16 09-08-2003, 03:49 PM

To see if that makes a different, simply bypass the valve & go for a spin. Either splice the tubes together, or run a small length of hose between the intake fitting and ALDA directly. Make SURE the intake fitting is clean - slide a paper clip or small screwdriver all the way into the hole to clear out crud. You should be able to do a few hard runs without fear of engine damage (due to the overboost protection being disabled), since that safety circuit almost never triggers anyway - it's only there in case the turbo wastegate fails stuck closed. You may be shocked at the power difference, and don't worry if you see black smoke for a few days after it's fixed (that should be reduced the more you drive it).

kashbaugh · #17 09-09-2003, 01:41 AM

gsxr,

I've looked under my hood and at your pix, and call me stupid but I don't see a vac line going to the ALDA. I've looked at your pix again and I'll try again tomorrow.

Thanks!
kma

gsxr · #18 09-09-2003, 10:02 AM

Actually it's a pressure line, but it looks the same - small, light-colored plastic. On your engine it will run from the back of the intake manifold (well hidden) to the switchover valve on the firewall, sort of near the oil filter housing, then to the ALDA. My photos are of a different engine (mine are 87's with the OM603, you have an OM617).

kashbaugh · #19 09-09-2003, 10:58 AM

gsxr,

Ok, I FINALLY found the $%*#( ALDA. Boy, was I blind!!! It was staring me in the face. If it hadn't been for your photos I would _never_ have known what to look for. Thank you!

The lines are harder and more brittle than my arteries after 50 years of fried food! The end at the intake manifold is clogged, too. It appears that the fitting is, also. Can that be cleaned out with q-tips or something similar?

I guess I need to order the line and I'm gonna go ahead and get that bypass as well. Can you tell me exactly what to tell Rusty I want? Or will they know when I tell them where it goes?

Man!!! Thanks for your help and patience on this. If there really is a turbo under all this it will really be great!

kma

kashbaugh · #20 09-09-2003, 11:13 AM

gsxr,

You know, I don't hear any of the usual turbo "noise" during my driving. What is the liklihood that the turbo is not spinning? My previous turbo vehicles always made _some_ kind of noise whether during boost or at spindown or something!

If I correct this ALDA problem and still get no boost - which I am firmly convinced now that is the case after paying close attention to my acceleration and such - is there any way to check it? How much would I have to take apart to check it's spin and such? Any ideas on this?

And if that's true, how hard is it to install a new turbo?

Looks like it may be time to start a new thread!

kma

gsxr · #21 09-09-2003, 11:28 AM

kma,

Glad you found it.

Yeah, the lines are pretty brittle after a long time. If you snap one, you can splice it together with the appropriate size vacuum hose from a local McParts store. You may need to clean the banjo fitting on the back of the manifold, take it apart & use whatever is handy to clean it out. Same with the switchover valve if needed. The "bypass" I mentioned for the s/o valve isn't a special part, just a little piece of small pipe (again, McParts) to connect the two rubber "elbows" that normally connect to the s/o valve, to remove the (possibly blocked) valve from the equation for test purposes.

As to noise, well, most MB turbos are pretty quiet. I almost never hear mine. If you hear a whistle, that's an air leak that needs to be fixed. But lack of noise is NOT a problem.

A simple test is to pull the intake snorkel and spin the impeller with your finger, it should spin pretty easily. If you start the car and look at the impeller, it should be spinning fast. That's the simple test to make sure it's not locked up. To test function, you need a boost gauge plumbed into the ALDA line, check for 10psi or so at full load in 3rd gear, 4000rpm. It would be quite rare that yours has failed, but if so, the turbo R&R isn't hard... takes 3-5 hours plus a few gaskets.

kashbaugh · #22 09-09-2003, 11:36 AM

Actually, the switchover valve is what I was talking about. I suffered brainlock when trying to name it in the message!

If I would get off my butt and charge the battery in my Porsche I would be able to "run for parts" if needed while working on the MB. I'm suffering an almost critical case of newtoyitis!

kma

#23 09-09-2003, 11:42 AM

In the meantime why not just bypass the line from the intake manifold to the ALDA around the switchover valve and see if power returns. The is little danger if you don't push the engine to maximum power levels for very long. The switchover valve is simply to prevent overboost if the wastegate should fail in the closed position and create way too much boost.

Marshall

Marcb · #24 09-09-2003, 12:00 PM

I was going to bypass the switchover valve to see if that would correct my low power problem, but decided to purchase a new valve instead. I'm very curious to see if this will restore "some" power to my 300D. It is very slow at climbing hills right now....

gsxr · #25 09-09-2003, 12:05 PM

I have my s/o valve bypassed permanently on my '84, but I have also confirmed proper wastegate operation (and experimented with disconnecting the wastegate as well!) to see what the results would be. I feel fairly certain that my engine won't overboost itself & cause damage. I don't recommend others do this though. The valve is part number 001-540-86-97, about $25 on online suppliers, if you can't clean yours out (or if it's functionally broken).

Marcb · #26 09-09-2003, 12:21 PM

Thanks Dave....

I went ahead and ordered the part from PartShop and we'll see what happens. I also have some other goodies for you when you're ready for them...

Send me a PM and I will get them ready to ship...

Marcb · #27 09-09-2003, 12:22 PM

One more thought.... does anyone have any good leads on replacement plastic lines? I know you can splice them, but I keep thinking I would like to replace several of them. I also wonder if you can use rubber vac hose?

gsxr · #28 09-09-2003, 12:22 PM

Marc,

Try to blow through your current switch. If you can't, that's the problem. If you can, the problem is elsewhere - check the fitting in the intake manifold also, you should be able to blow into the manifold through the fitting. If not, it's plugged with sooty crud. Easy stuff to check before buying a new valve, which may not fix anything if it's clear!

gsxr · #29 09-09-2003, 12:26 PM

Here's an old post of mine with some info on the tubing for the 124 chassis (this mostly does NOT apply to the 123!)

------------------------------

Date: Sat, 13 Apr 2002 19:49:10 -0700
From: "Dave M."
Subject: [DIESEL] Vacuum line & fitting part numbers

Hi all,

Here's a list of some of the more useful part numbers for rebuilding the
vacuum system on an OM60x, and/or most 85-up MB's. (I think the older cars
used more solid colors, I didn't experiment with ordering those.) I found on
the EPC that the same part number can have a different description depending
on what chassis you look up. Some chassis have more info than others. For a
list, go to the "Intake & Exhaust Manifold" group in the engine section,
then look at the general parts diagram. Try this with several chassis (123,
124, 210 for example). I also found out that the pictures don't always match
up, and some may appear identical but can have widely differing sizes -
which is often NOT mentioned in the EPC! So I've been ordering select items
(1 each) to figure out what's what. Unfortunately some parts have rolled to
generic replacements, so we can never return the car to "original"
condition. For instance, gray pipe was replaced with black, the brown/blue (for I/P shutoff circuit) has also been superceded to generic
stuff, as well as the black w/white stripe to the transmission. The hassle
with this is that the colors actually MEAN something, and when you use plain
items instead it can be confusing. Black is normally a vent line to the
interior, and MB has seen fit to supercede some p/n's to black. OK, enough
rambling, here's the currently available p/n's that I've confirmed:

Vacuum line ("plastic" Tecalan pipe, 4mm OD, 1mm ID)
=====================================================
000-158-14-35 - Transparent (sort of white)
000-158-89-35 - Transparent with red stripe
000-158-91-35 - Transparent with blue stripe
001-997-81-52 - Black
116-276-06-30 - Black with while lettering
123-276-16-30 - Black with red stripe

Rubber stuff (3.5mm ID)
=======================
117-078-02-81 - 90-degree "L" shaped fitting
117-078-05-81 - 45-degree "V" shaped fitting
117-997-09-82 - Rubber hose (order by the meter)

Black "loom" (looks like heat shrink tube)
===========================================
040621-008200 - 8mm ID
040621-010200 - 10mm ID (most useful on my car)
040621-012200 - 12mm ID
040621-014200 - 14mm ID
(notice the pattern here? Larger & smaller are available too...)

601-078-06-45 - "F" shaped 2-port branch fitting - (great to replace the
4-port fitting after you yank the emissions stuff off a 124 diesel!)

Most of the pipe & loom is $1-$2 per meter. The "L" and "V" fittings are
$2-$3 each, the "F" fitting is ~$6. (All prices via Rusty.) If you haven't
replaced them in your car, it's a good idea to just do it. Total cost is
probably less than $20. It's amazing how much of that stuff snaps like twigs
when you start removing it!

===============================================

Marcb · #30 09-09-2003, 01:37 PM

Hey Dave!

Great post on the plastic lines! I have checked the switchover valve and it is plugged! I cannot even blow through the thing! I tried blowing through into the intake and it blows through just fine! I sure hope the S/O valve is the reason for my poor acceleration! Oh, I also noticed I have a small oil leak on the bottom-side of the turbo and I hope this isn't indicative of anything major. Any thoughts?

Thanks again, this forum is wonderful!