Help with sluggish 1984 300cd - PeachParts Mercedes-Benz Forum

drmathieu · #1 05-04-2006, 11:31 AM

My 1984 300cd has been garage kept since last fall. I have 303,000K miles on the car. I needed to replace the two rear axles. I was hearing a noise in the rear but the car was also very slow off the start and would be very slow going up hills. I would lose 10+ mph (up hills) with the gas pedal push to the floor. I was thinking that the noise was due to the CV joints and the sluggish driving was a result of the CV's also. After having the CV joints replaced, the noise has stopped but the performance of the vehicle is still the same.

I have also replaced both the primary and in line fuel filters.

I was just wondering if anyone would help to point me in a new direction?
Could it be wheel bearings? transmission? turbo?

Thank you in advance for your time.

t walgamuth · #2 05-04-2006, 11:28 PM

i would treat it for fungus in the fuel, also clean the alda banjo fitting. this is located at the back of the valve cover.

good luck

tom w

Brian Carlton · #3 05-04-2006, 11:31 PM

What's the grade on the hill?

What's the speed at the bottom of the grade??

The SD can hold about 65 on a 4.5% grade in high gear with a 2.88 axle.......not more......

The CV joints won't affect the performance unless they fail completely. Then, there will be a noticeable loss............

Veloce300DT · #4 05-05-2006, 12:14 AM

In addition to treating the fuel system for fungus, and cleaning the banjo bolt, check your tank screen.

Tired injectors can also dramatically decrease engine performance- fuel delivery is hampered with poor injectors- often times leading to rough idle, poor acceleration, and keeping speed up grades.

mespe · #5 05-05-2006, 09:17 AM

Quote:

Originally Posted by t walgamuth

i would treat it for fungus in the fuel, also clean the alda banjo fitting. this is located at the back of the valve cover.

good luck

tom w

I don't think all 300CD's have turbo's. and the banjo fitting is in the intake manifold not the valve cover.

Have the valves been adjusted lately? Is the car hard to start?

Marty

Diesel Giant · #6 05-05-2006, 03:49 PM

Man there are lots of things that can cause it to be sluggish. Check out the ALDA cleaning pictorial and then look at adjusting the valves and doing some general maintenance.

http://dieselgiant.com/mercedesaldaboostsystemservi.htm

drmathieu · #7 05-05-2006, 08:04 PM

Thanks for all the help seems that this is a great forum.

t walgamuth · #8 05-05-2006, 09:52 PM

i should have said near the back of the valve cover.

actually this is one task i have never done, i am just repeating what i hear here all the time.

so it is in the intake, huh?

tom w

drmathieu · #9 05-10-2006, 10:05 AM

Thank you for the suggestions. I had the valves adjusted when I had the rear axles replaced.

I have cleaned the tank for fungus and I also checked the alda banjo bolt. I followed the directons as per the diesel giants web page(thanks!)

. The Banjo bolt was not that dirty or the line. But it did seem to give me a little more power(+1-3 mph).

I started reading a little about the injector cleaning method on the webpage(diesel giant) and that seemd to be the next course of action. What do you think?

85chedeng300D · #10 05-10-2006, 10:12 AM

[QUOTE=t walgamuth]i would treat it for fungus in the fuel, also clean the alda banjo fitting. this is located at the back of the valve cover.

how do you treat fuel for fungus??? is there an additive to pour directly into the tank to treat it or do i have to drain the tank and flush it with fresh diesel???

SD Blue · #11 05-10-2006, 10:26 AM

drmathieu,
Another point that has not been brought up, how is the fluid level in the transmission? These cars seem to be very sensitive to this and I definitely notice this behavior on mine. Be sure and check it hot.

85chedeng300D,
Do a search for Biobar and you will be up late reading all of the threads. It is a fungicide, any will do, that you just pour in the tank. Be sure and have spare filters on hand. Are you seeing black particles in the in-line filter?

83-240D · #12 05-10-2006, 10:34 AM

[QUOTE=85chedeng300D]

Quote:

Originally Posted by t walgamuth

i would treat it for fungus in the fuel, also clean the alda banjo fitting. this is located at the back of the valve cover.

how do you treat fuel for fungus??? is there an additive to pour directly into the tank to treat it or do i have to drain the tank and flush it with fresh diesel???

biobor is good. available at west marine(yeah boat shop) check with your autoparts store.

some folks use seafoam. i saw it at a station that sells diesel. just pour in the prescribed amount........or more to shock it good. then when the tank is low on fuel plan on draining the tank and take out the fuel strainer to clean it. gunk accumulates on it.

1983/300CD · #13 05-10-2006, 10:49 AM

I believe the Startron treatment eats it, so all the crud just "goes away".
But as mentioned, you should be seeing black bits if this is your problem.

85chedeng300D · #14 05-11-2006, 12:18 AM

83-240D; 1983/300CD,
thanks for the knowledge guys! the last time i changed my in-line fuel filter was last january of 2006 and even if my old filter was not transparent, i can tell that the element was black but i have no clue that it is fungus. i will definitely try biobar/biobor or startron or seafoam whichever is available.

83-240D · #15 05-11-2006, 10:29 AM

having done all this now maybe you want to diesel purge the engine also. diesel purge available from fastlane or performance products or diesel giant. check the websites for price. dg has a tutorial for the process.