300D Tune-up? ( precombustion chamber cleaning - methods?) - Mercedes-Benz Forum
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#1 (permalink) Old 07-31-2010, 08:36 PM
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300D Tune-up? ( precombustion chamber cleaning - methods?)

I just bought a nice 85 300D and was wanting to tuner her up - as of now I have adjusted the valves and put a couple of the smaller cans of Diesel Purge in the tank. I will check the timing of the pump soon and let see what else is good go do? Here are my compression readings - not bad but really not that great either cylinder 1-450, 2-445, 3-395, 4-425, 5-425. The spread difference is 55 so that is up there close to the limits - I think it is at 70 ? is that not correct? Now someone said I would need to clean my precombustion chamber by soaking them in this special acid solution and check or pop test my injectors to see when and how they spray. I was wondering if I could not clean my precombution chambers without taking them off of motor? How hard is it to take these off - I looks like I could notch a socket that size to have it fit into the slotted precombustion chamber and take off - but how tight are these usually to take off? and so was wondering if a person could clean while still on engine by letting some WYNN"S V.I.C. (Valve-Injector-Combustion Chamber Cleaner) soak down through the precombustion chambers and on down onto tops of pistons to seep through the rings and all to loosen up any caked up soot there along ring and piston lands? Is this a good idea or not? What is recommended? I have heard of people using brake fluid but I would think the the V.I.C. would be a bit stouter and do a better job. Does anyone know or have any comments on this idea and procedure? Also someone said that on a tune up there is a pressure valve that needs to be set and I do not know what they were referring to - is there a valve that one needs to set periodically on these 5cyl turbo diesel Benzs?
Thanks for any suggestions!
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#2 (permalink) Old 07-31-2010, 09:23 PM
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Originally Posted by SRHeer View Post
I just bought a nice 85 300D and was wanting to tuner her up - as of now I have adjusted the valves and put a couple of the smaller cans of Diesel Purge in the tank. I will check the timing of the pump soon and let see what else is good go do? Here are my compression readings - not bad but really not that great either cylinder 1-450, 2-445, 3-395, 4-425, 5-425. The spread difference is 55 so that is up there close to the limits - I think it is at 70 ? is that not correct? Now someone said I would need to clean my precombustion chamber by soaking them in this special acid solution and check or pop test my injectors to see when and how they spray. I was wondering if I could not clean my precombution chambers without taking them off of motor? How hard is it to take these off - I looks like I could notch a socket that size to have it fit into the slotted precombustion chamber and take off - but how tight are these usually to take off? and so was wondering if a person could clean while still on engine by letting some WYNN"S V.I.C. (Valve-Injector-Combustion Chamber Cleaner) soak down through the precombustion chambers and on down onto tops of pistons to seep through the rings and all to loosen up any caked up soot there along ring and piston lands? Is this a good idea or not? What is recommended? I have heard of people using brake fluid but I would think the the V.I.C. would be a bit stouter and do a better job. Does anyone know or have any comments on this idea and procedure? Also someone said that on a tune up there is a pressure valve that needs to be set and I do not know what they were referring to - is there a valve that one needs to set periodically on these 5cyl turbo diesel Benzs?
Thanks for any suggestions!
Hi
Likely nothing to be gained by cleaning the prechambers. With normal operation they are sort of self cleaning. It requires special tools to unscrew the coller and a slide hammer puller to remove the chamber - but unless one is broken or completely plugged - why bother?

Its a good idea to pop test the injectors and check the spray pattern. You can build your own pop tester for about $50 using a bottle jack - or some members prefer using a hydraulic manual pump. There are a number of threads on this. An injector shop will test them for something like $10 each - but if they need cleaning, balancing or nozzle replacement, the cost will be quite a bit higher.

A number of us have used Marvel Mystery Oil to soak the pistons with the idea of freeing up carboned up piston rings. Some have experience dramatic improvement in compression by doing so.

Welcome & Good Luck,
Joseph
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#3 (permalink) Old 08-01-2010, 10:43 AM
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If your Engine has a Trap Oxadizer you need to find out if it has been changed or modified by Mercedes; they will do it for free if it is the old one.
Perhaps you can search or other members can give more ditatails on that. If it gets plugged up performance suffers and it can kill your Turbo.

The Factory specs for the compression test are with the Engine hot.

The issue with compression is that if one Cylinder was below the allowable spread of Compression what would you do about it.

You can try the Mentioned Marvel M Oil Soak (this worked for me on my Volvo Diesel that had set for 1 year and was drivein 6 months with a Thermostat that would not allow the Engine temp to be normal and produced hazy gray smoke). If you have sticky Rings due to Carbon it has a good chance of working.
Or, take the Engine apart and find out what is wrong with the bad Cylinder.

I think most people would simply drive the Car as long as it starts OK and does not smoke abnormally and not worry about the out of spec compression on one Cylinder.

My choice would be the Marvel M Oil soak. Cheap, safe, and seems to have worked most of the time. The worst that can happen is there would be no change.

The above assumes it is a Piston/Ring issue.

Presurizing the Cylinder with your Compression Tester Adapter with filtered compressed Air; sort of a 1/2 of a leak back test would tell you if it was a Valve leaking causing the pressure issue.
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#4 (permalink) Old 08-01-2010, 10:54 AM
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If you are dead set on pulling the Prechambers I have made 5 Prechamber Ring Removal tools for the slotted Prechamber Retaining rings.
I will be testing them next week but do not see any reason why they would not work.

I also have made some Prechamber Pullers for 617 engnes not shown in the pic.
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#5 (permalink) Old 08-01-2010, 12:49 PM
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Thanks for the info - I did a search on Trap Oxadizer and came away with you being the only one mentioning it but I am wanting to look into it some more! On the prechamber removal tool(s) - one tool and associated puller would work for all five - correct? but if not I would also be very interested in buying what ever it takes for all five cylinders? - thanks for your time and consideration! It helps a bunch!

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#6 (permalink) Old 08-01-2010, 12:59 PM
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compression testing

Yes I had checked my engine cold so I will need to get it running to bring it up to operating temps and then retest - I have looked for method of compression testing and really have not come across one but here is how I am doing it - I turn engine over with a hand operated starter switch with compression gauge hooked up to cylinder being tested - the gauge is a Sanp On gauge so it should be accurate - now the gauge adaptor that hooks up to the fitting that goes into the engine head has a shreider valve in it to not allow pressures to return back to cylinder and so on the first hit I get around 200 to 250 and then by the time it has hit like 10 times it reads 445 - etc - is that how it is done or does one take out the shreider valve and basically read just what the first stoke will produce? How many times should one turn engine over ? until it quite increasing the gauge reading? - it took about 12 to 15 hit to reach max reading and not add to previous reading as all - is this normal? Thanks for all the advice - life driving a Mercedes is not just sweet it is an adventure! ( :

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#7 (permalink) Old 08-01-2010, 03:25 PM
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Quote:
Originally Posted by SRHeer View Post
I just bought a nice 85 300D and was wanting to tuner her up - as of now I have adjusted the valves and put a couple of the smaller cans of Diesel Purge in the tank. I will check the timing of the pump soon and let see what else is good go do? Here are my compression readings - not bad but really not that great either cylinder 1-450, 2-445, 3-395, 4-425, 5-425.
Not bad?! Those numbers are incredible on an old Benz. I was under the impression anything higher than 400 psi is great.


You can soak the chambers in marvel mystery oil, but my question is why would you want to with compression readings that high?

Try doing both of these and seeing if it helps.:

Diesel Purge Mercedes diesel maintenance tips


Also: Only California emissions cars have a trap oxidizer. It's really easy to figure out of you have it or not by looking at the emissions sticker on the driver's side door. Also a Federal air cleaner housing sits on top of the turbo and the Cali air filter sits off towards the passenger side fender.

Have you checked to make sure the boost line from the intake manifold to the ALDA is clean? Mine was clogged and made the poor car a dog. Cleaning it as well as the overboost protection solenoid will definitely help your 85 speed up.

-Adam

There's something eerily similar about cars and computers.

1985 300D (355,000)

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#8 (permalink) Old 08-01-2010, 03:46 PM
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Adam,
Thanks - and yes my Benz is from California - I know since I replaced the air filter and it was the $65 one that looks like it would work for a Mac truck and sits there off to the front and side of turbo - so now what am I looking for in this Trap Oxidizer? where is it located - and how to I can clean? - I will check my ALDA line - thanks! Adam - when you check your compression do you use a shreider valve inline with testing and do you see what the first reading is or do you crank it until needle stops increasing for reading and call that the compression reading? thanks again
Stephen
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#9 (permalink) Old 08-01-2010, 04:04 PM
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Adam,
Thanks - and yes my Benz is from California - I know since I replaced the air filter and it was the $65 one that looks like it would work for a Mac truck and sits there off to the front and side of turbo - so now what am I looking for in this Trap Oxidizer? where is it located - and how to I can clean? - I will check my ALDA line - thanks! Adam - when you check your compression do you use a shreider valve inline with testing and do you see what the first reading is or do you crank it until needle stops increasing for reading and call that the compression reading? thanks again
Stephen
Well, if you call any Mercedes Benz dealership you can ask for them to do a search with your VIN to see if the recall swap was done. If it wasn't done request to have it done on your vehicle free of charge! But do this quickly because the older catalyst (or was it trap ox?) can damage your turbo.

Since I'm a north eastern I have never seen a California setup before. So I'm sorry I don't know the differences between the two or how to clean them.

If you have access to a Federalized parts you can follow this guide and to get rid of the cali stuff.

PeachPartsWiki: Calf. to Fed. Emissions Conversion

Sadly I have never done a compression test on my vehicle, but from what I've read on this forum and others is any compression reading higher than 300 is good for our vehicles.

Doing some quick and dirty math with a lot of ASSuming, if we all live at sea level (14.7 psi) and the compression ratio from the FSM is 21.5 : 1. I'm guessing any reading over 316 psi is good. I would take this all with a grain of salt, but everything I've picked up from this forum as well as peachparts has been telling me compression numbers higher than 350 are really good.

If the car starts, idles, and runs well than I wouldn't worry much about the health of your car. If your car is slow off the line than check the ALDA boost line and overboost solenoid to make sure they aren't clogged.

Edit:

Here's a pic of the catalyst


Edit 2: Mr. Govert has the best advice on compression readings below.

-Adam

There's something eerily similar about cars and computers.

1985 300D (355,000)

Last edited by areusche; 08-01-2010 at 04:24 PM.
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#10 (permalink) Old 08-01-2010, 04:10 PM
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Normal values for a compression test are 24-30 bar (350-435 psi). Minimum is 15 bar (220 psi). Difference between the cylinders should be no more than 3 bar (44 psi).

I normally let the engine turn over until the highest pressure is reached using a gauge with a schrader valve. The Service Manual says run the engine to 8 revolutions. See also: 01 General Engine Work - OM617 </FONT><I><FONT SIZE="+3">turbo and there 01-110.

A compression test is a comparison test, the results differ depending on how high you are (up in the mountains the air pressure is less), air pressure in general, state of your starter and battery.

The best compression test is whether the engine starts and runs.

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