Valvetrain noise - PeachParts Mercedes-Benz Forum

jfman · #1 06-19-2006, 05:45 PM

I bougth a stetoscope to figure out where the knocking is comingt from on my 300d and I am 99% sure the noise come from the head. More precisely the 4th cylinder counting from the front of the car.

It sounds like a valve tapping, no odd coises comeing from the bottom end.

Think I can save it with a valve adjustment ?

Know where I can find a DIY online for adjusting valves on a 1985 300d ?

pdrayton · #2 06-19-2006, 06:38 PM

I am thinking you have a 123 - the old style. I have a 123 240D and the valves are real easy to adjust. You don't need the funky expensive bent 14 mm spanners, although they would make the job easier.

Read up on valve adjustments at this site - I'm sure you'll find lots of info. If not, let me know at this thread and I'll email you the job from the workshop manual. Haynes actually tells you how to do it too - you could get one of their books.

If it's a 124, it has hydraulic valves - if one of them has failed, you'll have to buy a new one and put it in - a bit of a job. BUt using Mobil 1 synthetic can help.

Hatterasguy · #3 06-19-2006, 06:39 PM

Swap that injecter with another and see if the sound follows it.

jackcmail · #4 06-19-2006, 08:10 PM

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I bought a 1985 300D from a guy who said he ran it low on oil.

The top of the engine has a tapping noise when the engine is running. The valves and lifters look OK when I had the valve cover off.

I have a spare head and spare injectors but haven't had time to do any further troubleshooting.

It seems it would be hard to run the 300D low on oil because there does not need to be much oil in the crankcase to get picked up by the pump.

Could it be a bad injector? Can you elaborate on sound and how they go bad, etc.?

Thanks

barry123400 · #5 06-19-2006, 09:08 PM

At this stage you might just swap in another injector first. When you have the injector out have a look in the prechamber for presence of the ball or too much goop or carbon. If that does not do it you might have visually not picked up a sloppy clearance on an individual valve without measuing it with a feeler gauge. Also at that stage compare the cam lobe profiles on the affected cylinder for wear. I personally would just read the milli volt output from the glow plug harness first. If #4 was higher voltage than the others it would be the injector or too much fuel on that cylinder. If lower voltage the injector or problems with the prechamber. If the same voltage as the other cylinders a sloppy valve, worn cam,bad valve spring or something mechanical. Divide and conquer is usually the best stratagy with most problems rather than guessing. Just my opinion.

Hatterasguy · #6 06-19-2006, 09:53 PM

No don't install another injector. Take the one out of the suspect cylinder and swap it with say cylinder no 1. What you are trying to do is see if the sound follows the injector. This is the quick 5 minute way to save yourself a lot of work if it is a bad injector.

Nailing sounds like someone is smacking the cylinder head with a hammer.

Unfortunitly over the net I cannot listen to the sound, but it could be a bad valve. It isn't a glow plug either, just forget about them for now. But it could be a bad pre chamber, maybe the ball is rolling around inside.

You should adjust the valves and inspect the valve train anyway. Every 617 owner should do this when they purchase their car.

jfman · #7 06-19-2006, 10:42 PM

Thatnk you guyz for the tips.

The taping noise is almost if not non existent when the motor is cold AND only does it if the engine is reved up. As the motor gets warmed up, it itensifies.

Another thing I should mention is that throttle response is pretty darn bad, power is down if I compare it to my organ donor 300d.

I will do the injector swap tomorrow and see what happens.

I also bougth a Haynes manual last night and if the sounds persist after the injector swap, I will adjust the valves afterwards. hell I will do it anyway, it cant usrt on a 22 year old car.

barry123400 · #8 06-20-2006, 12:19 AM

With these older engines we have to have a more comprehensive way to repair/tune them. Some engines I have seen reciently are in horrible general condition. This thread starter is starting to describe problems like low power as well. When you read the voltages from the glow plugs you start to get some real idea of whats is really going on in there. In reality the same method used to service really large diesel engines. All you are really reading is the heat level in each individual cylinder converted to milli volts. It is not rocket science. They should be simular in a good running engine. When they are not you have problems and their location and probable cause indicated. For engines with single problems you usually will catch it but if say you have four overlapping problems how do you differentiate them? Without a lot of experience or a fat wallet to throw money at them you just do not. Unless there is a usable system for amateurs like myself that will work. That is the thrust behind reading the glow plugs or otherwise known as the milli volt method. . Even the possible restoration of a good power balance is in sight now at a very reasonable cost unless your engine compression is all over the place. These cars are getting older and older. Things are aging at the same time other things are becoming truly defective. There are already too many 123s out there with less power and fuel milage than they should be getting plus a lot with rough idles and noises. For example lets say he changes the injector out and adjusts the valves. Where do you go after that without a workable system if the problem is still there? What about his low power? Sure it could be as simple as filters. But as these cars get older and older it will not be them in far too many cases. As I see it we either develop a workable system usable by the majority of members. Or there are going to be a lot of cars around with problems unresolved but just lived with. Yet in reality so easy to rectify if we have a workable system that is used. We do have the system. It is getting people to apply it and think about it that is going to be the problem. I would drop this approach if there was any other system in sight for indirect non computorised diesels like the 616 and 617 series. It has always exceeded expectations when used so far.

jfman · #9 06-20-2006, 02:37 AM

I'm doing these experiments because they are free and not too time consuming.

I have a perfectly running motor siting in my organ donor but if i can save myslef from yet another engine swap job, better that way.

That being said: I love this site and the tips you guyz gave me.

if the problem perssits after the injector swap and the valave adjustment, I will most likely swap the motor out with my organ donor.

aklim · #10 06-20-2006, 02:42 AM

With a long pry bar or screwdriver where you head isn't next to the engine, can't that be just as good or better than a stethoscope? I wouldn't buy one except I inherited my wife's professional grade when she got her Master Cardiological unit. Of course i got to try it out when we lived in the apartments and can tell you that the MC one is much better than the regular professional one, both being made by Littmann. The MC one is better for listening to softer voices and/or sounds, but I digress.

jfman · #11 06-20-2006, 02:46 AM

Quote:

Originally Posted by aklim

With a long pry bar or screwdriver where you head isn't next to the engine, can't that be just as good or better than a stethoscope?

Can I make a confession ? ..... I lied

I used an antenna off a 1997 ford escort. The round ball end is perfect.

I didn't wat you guyz to think I was the backyard mechanic that I am.

aklim · #12 06-20-2006, 02:56 AM

Quote:

Originally Posted by jfman

Can I make a confession ? ..... I lied

I used an antenna off a 1997 ford escort. The round ball end is perfect.

I didn't wat you guyz to think I was the backyard mechanic that I am.

Screwdriver is better since the antenna, if it is sectioned has hollows while the driver is solid.

Also, you will not be able to listen in to the neighbours when they are..... er, listen to the valvetrain noise.

jfman · #13 06-20-2006, 03:57 AM

Escorts have solid antennas and the end ball is solid as well.

anolley · #14 06-20-2006, 10:26 AM

Quote:

Originally posted by Hatterasguy

Nailing sounds like someone is smacking the cylinder head with a hammer.

Excuse me if this is an ignorant question, but what is the cause of "nailing". My 85 300SD is making that very lovely sound you described. It runs for a little while making the nailing sound, then dies.

jfman · #15 06-20-2006, 12:20 PM

what size wrench do I need to remove the injector ?

My comb wrench set stops at 19mm and I'd like to buy the right size, the first time.

ALSO: THE TUBES that connect the inmjectors to each other. Do it juts yank them off ?