w124 smoking like crazy - PeachParts Mercedes-Benz Forum

blan · #1 10-12-2008, 04:09 PM

I've been reading alot of "smoking" diesel threads in hopes to figure out what's going on with my 92 300D 2.5 turbo diesel. I recently purchased the car as a mechanic special and towed it home. It always starts immediately but the idle lopes right away. It smokes whitish grey and sometimes a little black mixed in and seems to load up if I let it idle too long. I DON'T smell any sweet antifreeze burning and there is no excessive pressure coming from the reservoir cap. It has a hesitation on lower rpms but seems to run pretty well from the mid to upper rpm range. After you rev it up, the smoke diminishes a little but quickly worsens again when returned to idle (loads up). It knocks a little louder as it loads up.

I showed it to my buddy who owns 3 turbo diesel 300 Merc's and he was convinced that it was my injector nozzles. I replaced and balanced all 5 nozzles only to get the same results.

I decided to start my own thread so that I'm not confusing w123 or w126 solutions with my w124. There's a bit of oil in the turbo and the crossover tube and some thick sludging inside the intake side (if that's what you call it) where the turbo crossover piece connects. I have yet to do a compression test, although that's probably what you all will suggest first.

Being my first Mercedes, I don't want to just start replacing parts randomly and would like to follow a logical routine knowing what to check first, second and so on. I think that my nozzles may have been fine now that the car's symptoms are unchanged. I am experienced with gas engines, but diesels are new to me.

I'm amazed at how good it sounds when you hold the gas pedal just above the hesitation point...it even smokes slightly less.

Should I begin with a compression test at the glow plugs? If it's low on one or more cylinders should I pull the head off next? Could it be timing (like I have read about on the older models). If I start the car without the turbo crossover connected (to see if smoke goes away) will I hurt the engine or the turbo?

Thanks in advance for your help...this place is great!

johnathan1 · #2 10-12-2008, 04:15 PM

Sounds like the problem I'm having...I'll be keeping an eye on this thread...

C Sean Watts · #3 10-12-2008, 04:30 PM

How is the blowby (teapot test)?

sixto · #4 10-12-2008, 04:45 PM

Check cam and IP timing.

Also do a balance test - with the engine loping at idle, crack each injector line one by one to see if any doesn't make the engine idle worse. If you find such a cylinder, swap injectors with another cylinder to see if the problem moves with the injector or stays in the cylinder. If the problem is with #1, it could be a blown head gasket. The good news is a new gasket will put things in order.

Sixto
87 300D

Cervan · #5 10-12-2008, 04:50 PM

timing chain stretch maybie, Also try advancing your Injection pump timing see if that cures it.

blan · #6 10-12-2008, 06:28 PM

I haven't done a teapot test because I've never heard of it before. I searched on this forum for "teapot test" and "blowby" but nothing really came up describing the test. I did open up my oil cap to see if I noticed any excessive blowby into the valve cover...I'm not sure what normal is though. Seemed similar to a gasser. Please let me how to do teapot test or if you could point me to a link that would be great.

Sixto, When you do the balance test and crack each injector line open, is fuel going to squirt everywhere? Can I stick a fuel hose on there and direct it into a bucket or something? Won't it hurt the cylinder, valves or injector being tested by running too lean for the test?

I'm beginning to think that it sounds more and more like a blown head gasket on #1. I will start with a compression test and balance test.

I'm a little chicken to mess with my injector pump timing at first in fear that I won't be able to get it back to the same place if that isn't the problem. Do you check timing with a timing light on these cars?

How about testing to see if the oil is from the turbo by removing the crossover piece? Nobody mentioned if that's a bad idea or OK to do.

sixto · #7 10-12-2008, 07:10 PM

Crack the line, don't disconnect it completely. A half turn is usually enough for fuel to dribble out of the fitting. Nothing you can't quickly wipe clean. If fuel doesn't leak out with a full turn, the line is probably dry.

There are many ways to check IP timing in a 60x. All involve checking crank position when the timing lug visible/accessible through a port on the driver side of the IP is centered in the port. You can do this as simply as looking in the port, a mirror helps, and turning the crank CW until the lug is centered to the best of your visual acuity(sp?). A little more precise is to use an IP locking tool. The lug is centered when the locking tool engages. Read IP timing off the crank. More sophisticated is to use an A-B timing tool or light. A sensor fits into the port to detect the position of the lug. You watch a couple of LEDs. When the lug is close, one LED will illuminate. When the lug is centered, both LEDs will illuminate. As the lug moves away, the first LED will go off then the second LED will go off. This tool costs $3-400. Maybe more now. The most sophisticated method is a tool which consists of a sensor and a timing light. You use it as you would a gasser timing light. You should be able to rent an IP locking tool and an A-B light in the tool forum. You don't need both.

The timing access port is covered by a bolt that takes a 17mm wrench. You'll do no damage by removing the bolt and turning the crank (CW only!). You'll lose a teaspoon of engine oil.

Pulling the crossover pipe is inconclusive because oil could be coming from the turbo or the valve cover. Remove the hose from the valve cover where it connects to the turbo air inlet hose. Cap the fitting in the air inlet hose and direct the valve cover hose into a vented or unsealed collection bottle. Drive around for a while to see how much oil collects in the bottle. You can clean and/or dry the crossover pipe as well as you can. Any oil in the crossover pipe will come from the turbo... assuming there isn't a pool of blowby oil sitting in the turbo.

Sixto
87 300D

oldiesel · #8 10-12-2008, 07:43 PM

Start with simple stuff,loosening injector lines is just like grounding out spark plugs,when/if you find one that dosnt make a difference or makes less difference than the others you have located the cylinder that is weak,you then have to determine the reason.You dont have to worry about a cylinder running lean,no fuel,no fire no heat! Did the tree rats build a nest in the air cleaner inlet? Does it have only diesel fuel in the tank,no gas mixed in? You can easily hook up a bottle of fuel to the fuel line to see if it runs better on good fuel. change both fuel filters,does not sound like a fuel restriction but inexpensive to do and a good idea on a car you just got even if it was running good.
Teapot test is nothing more than undoing the oil filler cap and letting sit on the opening,if you have alot of blowby it will dance around with the engine idling,if the engine is idling poorly it may shake too much for you to tell much by that test anyway.

blan · #9 10-13-2008, 01:47 AM

This is alot of great advice. It still baffles me that this much thick smoke could possibly come from injection pump timing being off but you guys are the pros. On a gas car, I'd swear it was burning a ton of motor oil because it is thick lighter smoke but not white like burning antifreeze. I did see a little of the black smoke today which I thought was probably unburned diesel but there is much more of the lighter colored, thick smoke.

I keep thinking it's a head gasket leak on number 1 cylinder but I'll start with the simple stuff that you guys have mentioned. I also noticed that my oil pressure gauge was pinned when the car was running...that kind of makes me think it is blowing compression into the oil return raising the oil pressure reading to the gauge. It almost runs like it has a "miss" and I know that is a term usually used for spark ignition cars.

I wish I knew the car's history. 179k on the odometer. It looks like the valve cover gasket was recently changed out. I found a long bolt (maybe a head bolt) lying in the bottom radiator shroud caught between the shroud and the radiator. I'll freak out if I take off the valve cover and see that a bolt is missing...lol. Anything is possible I guess. The mechanic on Doc Hollywood always has a box of extra parts....remember? Maybe he worked on it last.

2.5Turbo · #10 10-13-2008, 11:26 AM

Does the light smoke smell like fuel? As has been stated, check the injection timing and chain stretch as well as filters and fuel. Also check and make sure the EGR and flapper valve in the intake are working properly. If for some reason the flapper gets stuck closed it will starve the engine of air and it will run very rough with lots of light smoke (fuel) out the pipe.

Oil pressure should be pegged at 3 bar when the engine is cold. A fully warmed up engine should idle between 1 and 2 bar; anything over about 1500rpm should peg it on a warm engine as well.

blan · #11 10-13-2008, 11:45 AM

No, it doesn't smell like fuel to me. More like burning motor oil. I will try all of your suggestions and post my results.

Maxbumpo · #12 10-13-2008, 12:33 PM

I'll second the injector-line loosening test. Once you ID a weak cylinder, move the injector to see if the problem follows. If it doesn't, rebuild that delivery valve (new spring, copper washer and o-ring, need special socket and torque wrench for 30-30-35 Nm torque sequence).

I also like the idea of checking the injection pump timing.

I'd also recommend disconnecting or blocking-off the EGR valve; if it has failed in open position, it will cause lots of smoking.

What is your oil consumption like? The failed head gasket problem will cause oil consumption to increase, rough/smokey idle like you've got, and usually some lifter noise as well (the oil passage that ruptures feeds the hydraulic lifters).

Oil pressure is normally pegged at 3 bar when engine is cold or when RPM is over 1500 or so. When it is not is when you need to worry!

More thoughts: if you had a bad injector (did the shop tell you anything about their state?) and you have a lot of carbon built up in a pre-chamber or two, it may take hundreds or thousands of miles of driving to burn off the carbon so that fuel ignition becomes normal and the noise and smoking goes away.

Even the smallest disruption inside the pre-chamber can cause the combustion process to be incomplete and smokey and noisey. Italian tune-ups are your friend! If you get a lot of smoke under full throttle, you may need to perform an "Italian Tune-up". The idea is to increase engine temp to 100 or 110, at high speed and using lots of fuel. The elevated temperatures at high RPM with lots of fuel burning will quickly get rid of any carbon deposits. The best way to do this is to drive up a long steep grade (mountains) carrying plenty of weight and with the AC on high. Put a BIG load on the engine and keep it on, so that temps climb to 100 or 110, and stay there for several minutes. If you don't have a long steep grade, then repeated runs from 0-70 at full throttle can also do the trick. Find a lonely stretch of highway that will allow this and repeat until engine temps are up there and no more smoke is visible under full throttle.

pmari · #13 10-14-2008, 08:32 PM

I sound like a broken record but...... Make sure the ALDA lines are clean from the manifold back.... IIRC it's a 10mm socket to pull (nope now I think it's a 14mm

) the nipple out of the manifold that the ALDA's rubber hose connects to. A large pipe cleaner and solvent work well. There is a green plastic connector(after the manifold before the ALDA) that has a very small orifice that clogs eaisly. All the small hoses and that green connector need to be cleaned. I used brake parts cleaner and compressed air. If the ALDA doesn't get vac it won't do it's job. Kinda like cleaning the banjo bolt on a OM617

If that's all clean, then it's over to other side and the dreaded "rats nest"

Which I always kept clean and working

Quote:

I'd also recommend disconnecting or blocking-off the EGR valve; if it has failed in open position, it will cause lots of smoking. Even the smallest disruption inside the pre-chamber can cause the combustion process to be incomplete and smokey and noisey.

I concur....

sixto · #14 10-14-2008, 08:34 PM

Quote:

Originally Posted by pmari

If the ALDA doesn't get vac it won't do it's job.

Boost.

Sixto
87 300D

pmari · #15 10-14-2008, 09:05 PM

Will also cause excessive smoking at idle.