New to the Benz world - PeachParts Mercedes-Benz Forum

Scottr · #1 06-17-2012, 02:01 PM

Brought home a 85 300SD yesterday. Has 129K on it. Paid 1500 bucks. Starting to go throught it, been sitting for 3 years. Changed fuel filters and doing oil/ air today. Major lack of power and hard shifts. Will start looking at vac lines. This looks to be a CA car as it has the trap filter below the turbo ??
Can I "gut" the trap so it's just a wide spot in the system?
Any pointers are sure welcome. As this is all new to me. Lots of good info and talant here on this site. Thanks everyone. Will order service CD's or books soon.
And what's the little micro switch on top of the valve cover do?

junqueyardjim · #2 06-17-2012, 03:11 PM

Hi Scott, Welcome to the Forum. I could be off the boat on this, but if you have a "trap oxidizer", I think I have heard that the factory is still taking that junk off and replacing it with good junk. Do "search" top of this page and see what has been said about that. Go to search and type in trap oxidizer. If you can't find out, just call your nearest dealer.

junqueyardjim · #3 06-17-2012, 03:19 PM

We need a better description on hard starts? Could you tell us more? Hard starts have a lot of variables like fuel, glow plugs, battery, starter motor. These cars run nice when all is well, but they are not hot rods. You have a large heavy car there with about the same hp as a 53 Mercury giving you a zero to 60 time of about 17, (really good) to about 19/20 seconds about normal. That is not fast, hardly brisk but very a very luxurious ride.

t walgamuth · #4 06-17-2012, 03:26 PM

That would be a 617 motor in 85. I don't know about california but the rest of the country did not have trap oxidizers.

I agree with Jim, its a pretty heavy car with a very tall rear end ratio so they were never quick off the line. A common problem with them was taking off in second which makes them unbearably slow.

shadetree77 · #5 06-17-2012, 05:28 PM

don't attempt to gut the trap ox; it is very dangerous as the material inside the trap ox will react with water and burn. there's a thread on here somewhere listing the dangers. the dealer should replace the oxidizer under the recall free of charge

shadetree77 · #6 06-17-2012, 05:31 PM

here it is:
http://www.peachparts.com/shopforum/diesel-discussion/299897-how-do-i-work-safely-trap-oxidizer.html

vstech · #7 06-17-2012, 06:23 PM

I think the ca SD has a 0-60 time of around 12 seconds, not 18ish...
if you are having vacuum problems, be SURE you look over the pump!!! I trashed my engine, by not investigating the pump until too late...
you've been warned!

the 150K miles could EASILY be wrong, as could future mileage, as the odometers are extremely easy to hack, and swap with others. you should take a pic of your cluster, and have the members on here check to see if it looks hacked, or if the part numbers of the speedo match what the 85 is supposed to have!

Welcome to the forum!

junqueyardjim · #8 06-17-2012, 07:08 PM

Well I would have to see that, a 12 second 0 to 60 with a 617T but I guess one could make one go that fast - in Norway. Anyway the pump VSTECH is talking about is the vacuum pump. Get a vacuum gauge, can't hardly get along without it and check the vacuum right out of the pump. The vacuum pump is on the left front of the engine and the big plastic line goes right from the vacuum pump to the power brake vacuum booster. You can't miss it.

Diesel911 · #9 06-17-2012, 09:31 PM

Gutting the Trap Oxdizer would turn it into an expansion chamber and would slow down the velocity of the Exhaust Gas going to the Turbo and it would not work as well.

As they said if the Trap Ox has not been updated yet Mercedes is supposed to do that for free. I think I also read that if the Trap Ox has damaged the Turbo someone got a Free Turbo out of it.
If you just don't want the Trap Ox there is a so called "Test Pipe" that can either be bought or made to replace it.
For details on a lot of projects:
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charmalu · #10 06-18-2012, 01:14 AM

Might be hard to find MB parts in Fairbanks, Ak., compared to here in Calif.

You don`t need the Trap Oxidizer living where you do. was a calif requirement, and was/is a factory replacement item done at the dealer. It is part of the smog warranty.
Some have added a coustom made pipe to relace the Trap.

I changed my 85 cali 300D several years ago, by changing to they had them in 83. picked up all the parts for the Trapendectimy.

If you can find a 78 or 79 300SD, those 2 yrs didn`t have the EGR, so nothing to close off in the manifolds, and looks much cleaner.

The 85 300SD & 300D use the 2:88 differential. a one year thing.

Here is a DIY from the Resources Tab at the top of the page.

PeachPartsWiki: Calf. to Fed. Emissions Conversion

At the rear of the intake manifold is a Banjo Bolt with a pressure line, remove the bolt and make sure it is clean, and not plugged with black goop from the EGR and blow by oil.
The pressure line goes to a switch over valve and then to the ALDA, the square thing on the Injection pump. make sure this line is also open.
I blow it out with Brake cleaner and blow it out with compressed air.

If this pressure line is plugged, it will cause your engine to become doggy and gutless.

Charlie

Scottr · #11 06-19-2012, 05:03 PM

Thanks for all the advise everyone, found some vac leaks, car shifts much better now. Havent decided weather to remove the trap ox or not yet. Fabracating a new tube to go into it's place looks very easy and wouldnt take long. I called MB, they told me the origional trap was replaced in 1990. Not sure if they put the same thing in or a newer replacement? I did disconnect the vac. lines to the EGR and fresh air valve (plugged lines) I cleaned the banjo fittings, then hooked a vac gage to the intake man. tapped the gage to the windshild (see pic) and pulled a good hill at WOT. The best boost I saw on the gage was 2.5 psi.
I still have to ajust the valves (tonight) and look into the adla, I isolated it and pulled vac but it wouldn't hold, leaked off prety quick.
Can anyone tell me how much boost I should see? ( 85 300sd )
Couple other questions:
I found a parts car for very cheep, thinking about getting it, it's a 89,300SE, how much trim & body parts will cross over to my 85? It has 15" wheels, will they fit my 85?
Does the kick down switch under the fuel peddle go directly to the trans? or whats the lodgic of this switch, where does it go?
Thanks again for all the help, just been into this call for a weekend now, so much to learn.

ROLLGUY · #12 06-19-2012, 05:37 PM

Quote:

Originally Posted by Scottr

I cleaned the banjo fittings, then hooked a vac gage to the intake man. tapped the gage to the windshild (see pic) and pulled a good hill at WOT. The best boost I saw on the gage was 2.5 psi.
I still have to ajust the valves (tonight) and look into the adla, I isolated it and pulled vac but it wouldn't hold, leaked off prety quick.

The boost line is supposed to have PRESSURE not vacuum. If you disconnect the line from the ALDA and place the openings between two fingers, you should feel pressure when the engine is revved. If no pressure, then the banjo fitting is clogged, or the overboost valve is bad. Most folks just bypass the valve, and have the line going directly from the manifold to the ALDA. On the '85 there should also be another hose that goes to a flying saucer looking unit on the driver side wheelhouse. Plug the line, or replace the banjo bolt with one without the extra line (non CA emissions).

ROLLGUY · #13 06-19-2012, 05:43 PM

Edit: I just remembered that the CA cars don't have an overboost valve! The valve on the side of the turbo (ARV) releases boost pressure. If it was my car, I would remove every vac line and hose except the hose for the trans and VCV. Everything else is for CA emissions, and is not needed. You asked about the switch on top of the valve cover, that is the compressor cut-out switch (de-clutches the A/C compressor at WOT for a BURST of power!).

vstech · #14 06-19-2012, 06:47 PM

... should be around 9 to 12 psi max boost. some have modified the assembly to net 14psi boost.

car should not accelerate from a stop in 2nd. it should pull away from stop in 1st.

your alda may be damaged. see if the cover has been removed. also, if the vacuum lines on the bottom of the blue "flying saucer" have rotted, you will loose boost signal, and the pressure gauge will read lower than actual boost!

Scottr · #15 06-19-2012, 07:39 PM

Thanks for the help, I was not clear in my previous post, the gage I hooked up is a combo, vac / psi gage so I was reading 2.5 psi tee'd into the line off the back of the intake.
Will dive into the lines you have mentioned tonight.
The idea of removing all the vac line sounds wonderful. I will need to continue to understand this system before I do that. Don't want to go into it blind.
thanks again