All you smart diesel benz guys, help!!! 300CD runs like crap!!!! - Page 2 - PeachParts Mercedes-Benz Forum

rcounts · #16 02-24-2010, 07:17 PM

Quote:

Originally Posted by MattBelliveau

Has anyone mentioned whether or not it runs better once at the proper temp.?

Yes, in the original post the OP said
"Idle smooths out and smoke subsides once it has warmed up"

And I quoted him and highlighted the statement in bold lettering in my first post in this thread...

beena77 · #17 02-24-2010, 08:02 PM

Well, the glow plugs are all like new.
Did a compression test... I think this is the problem- here are the results

320
320
290
240
280

What are they supposed to be? Over 300 right? Is my engine toast... nice...

NoSparkNeeded · #18 02-24-2010, 08:20 PM

Yep at bit low, however, you might just need a good valve job. I have a Snap-on
leakdown tester I found at a garage sale, many years ago. If you have
a compressor, you can test to see if the problem is with the valves or the piston rings. You could get a shop to do this, just make sure they REALLY know what a "leakdown " test is. Amazingly some do not. If you "just" need a valve job, then somewhat easy-peasy, if rings, then start looking for a motor at the junkyards.

JEBalles · #19 02-24-2010, 08:22 PM

Although those aren't good numbers, don't think you're engine is toast. Bad injectors could also be a culprit, and with low blow-by, that low compression indicates a head issue, much more manageable than a ring issue. Could just be valve stem seals. Get the injectors pop tested.

beena77 · #20 02-24-2010, 08:46 PM

Swapped the injectors of our 300D. Didn't make a difference.... there is blowby

Skippy · #21 02-24-2010, 09:18 PM

Quote:

Originally Posted by beena77

there is blowby

How much?

vstech · #22 02-24-2010, 09:33 PM

ouch. 240 on one pot is not good. how many miles have been driven since it was in storage? it's possible you have some stuck rings that need to loosen up. try a little marvel mystery oil in the low pot, and let it soak a few days with the block heater plugged in. then crank the motor over with the glow plug or injector out to blow leftover oil out and re do the compression test on the motor.
did you crank em cold for the test or warm?
I'd check the valve clearance and if tight re adjust and re test.

beena77 · #23 02-24-2010, 09:39 PM

Quote:

Originally Posted by Skippy

How much?

a lot more than we originally realized.... picture a small campfire... lol. I am a girl , don't know how to properly describe it... maybe as much as the smoke that comes out the exhaust of my clean running 82 300d.

beena77 · #24 02-24-2010, 09:44 PM

Quote:

Originally Posted by vstech

ouch. 240 on one pot is not good. how many miles have been driven since it was in storage? it's possible you have some stuck rings that need to loosen up. try a little marvel mystery oil in the low pot, and let it soak a few days with the block heater plugged in. then crank the motor over with the glow plug or injector out to blow leftover oil out and re do the compression test on the motor.
did you crank em cold for the test or warm?
I'd check the valve clearance and if tight re adjust and re test.

It was not in storage... I bought it sight unseen from a liar. The minute it came off the flatbed it was screwed. The valve clearance is within spec. We swapped the valves from our 300D, made no difference.
The dry compression test was done when the engine was cold.

vstech · #25 02-24-2010, 09:45 PM

Quote:

Originally Posted by beena77

a lot more than we originally realized.... picture a small campfire... lol. I am a girl , don't know how to properly describe it... maybe as much as the smoke that comes out the exhaust of my clean running 82 300d.

um, yeah... that's bad.
search for tea kettle test.
you might even look on youtube for videos of it.
basically, you start the car, take off the oil cap, and set it loosely in the hole and see if it's weight can hold it on the car, or if the blowby pushes it off.
another test involves a 30 gallon trash bag, and time how long it takes to fill it from the plastic tube connected to the valve cover.
I think a good tight motor takes 3 minutes or so to fill the bag.

vstech · #26 02-24-2010, 09:47 PM

Quote:

Originally Posted by beena77

It was not in storage... I bought it sight unseen from a liar. The minute it came off the flatbed it was screwed. The valve clearance is within spec. We swapped the valves from our 300D, made no difference.
The dry compression test was done when the engine was cold.

I am sure you meant injectors...
were the valves within spec when you checked, or did you just adjust them?
ok, cold dry compression test. fine, squirt a smidge of motor oil in each pot, and redo the test.
if the numbers climb you have ring problems, if they do not, you have valve problems.

beena77 · #27 02-24-2010, 09:55 PM

Quote:

Originally Posted by vstech

I am sure you meant injectors...
were the valves within spec when you checked, or did you just adjust them?
ok, cold dry compression test. fine, squirt a smidge of motor oil in each pot, and redo the test.
if the numbers climb you have ring problems, if they do not, you have valve problems.

Yes, I meant injectors!!!
The valves were within spec when we got the car. It was the first thing my husband checked. the glow plugs are new. The ALDA looks like it has been screwed with.... the screw that you turn to adjust it is all stripped out.

vstech · #28 02-24-2010, 10:01 PM

ok, it's not a total loss. if they were in spec when you got it, the PO may have just adjusted them to try and make the car run right... they take a few miles to reseat themselves, and so they MIGHT settle in and seal. if you can stand the smoke a few days, try driving the car around hard a while and then recheck the valve clearance. hopefully it'll tighten up more and give you something else to adjust!
of course, if the oil brings the compression up... it's not the valves.
then it's back to the marvel mystery oil soak, and hope you have some stuck rings.

bbboomer · #29 02-24-2010, 10:09 PM

Smoking and rough idle when cold that clears up when warm points to glow plugs.
Cold compression tests can be misleading.
Low compression can be from bad rings, leaking valves or leaking head gasket, not much else. Having one cylinder low is not good but without running the engine enough to at least reach operating temp before doing a compression test can give misleading information.
Valve stem seals can cause smoke, particularly at start up, but they will not reduce compression. In fact they may actually increase compression due to the sealing effect the additional oil has on the rings.
I would suggest you recheck the valve adjustment then take the car for a good drive at highway speeds, let it cool for a while and then do the compression test.
If the compression is acceptable or substantially improved, change the glow plugs.
If you still have rough idle check for air leaks at the primer pump or fuel line connections.

neumann · #30 02-26-2010, 08:42 AM

I've read you've stated.the following for the gps...like new and then later as new. Were they just visually looked at or actually tested with a meter? I've had nice looking bosch gps test bad...