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  #1  
Old 03-09-2019, 03:08 PM
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New guy with questions

I'm new to the forum. A week ago I bought an 82 300SD that is complete but in rather poor condition. It shows 242k on the odometer, but I don't think that's still working. I'm attempting to turn it into a reasonable driver.

My main concern is a noise that comes from the engine. It's a loud tapping, it sounds for all the world like tapping sheet metal stop sign with a tack hammer. It is in time with engine rotation--it gets faster when the engine turns faster. The engine also has remarkably little power, and the amount of power seems to vary rather wildly. Sometimes it barely has the power to reach 5 mph with the gas pedal hard to the floor, other times it seems kind of weak but capable of reaching 40 mph. The noise is loud enough that I haven't had the courage to take it up above 40 yet.

I have already changed the oil (but not the filter; had to order one), the air filter, and changed both of the fuel filters that are under the bonnet, and I have done a diesel purge. During the first few seconds of diesel purge, the engines shaking stopped and it started running much more smoothly. After a couple of minutes the tapping noise went away--and then came back. Since then I've not been able to get the tapping noise to go away again. Loosening the fuel lines at the injector to the point of creating a cylinder miss does not make the tapping noise go away. I can't really tell where the noise is coming from, except that it seems louder on the left (injection pump) side of the engine.

The oil pressure gauge tops out when the engine is cold, but shows rather low pressure when the engine is fully warmed up.

I'm guessing the next thing to do is pull the valve cover, inspect for timing chain stretch and set the valve lash--which I'm certain has not been done in years. And I guess, look for anything under the valve cover that might be making noise. Anybody know what a broken valve spring sounds like?

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  #2  
Old 03-09-2019, 03:12 PM
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Post a video with good audio quality and your chances of getting a correct diagnosis on the first try increases dramatically.
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Old 03-09-2019, 03:13 PM
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Additionally, it’s completely against form rules to announce a purchase and not provide pictures.
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Old 03-09-2019, 03:30 PM
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As mentioned a video will help. Also a mechanics stethoscope Harbor fraught sells them very cheap can help pin point it. With my bad hearing I had been worried about serious engine problems but then discovered it came from a loud vacuum pump, rattling air filter housing to loose exhaust component. On the oil pressure issue, quite normal 3 bar at start dropping after warm-up, but should go back up to 3 once off idle driving.
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  #5  
Old 03-09-2019, 03:36 PM
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It is common for the Air Filter Bracket to break or the little rubber isolators to strip out or fall apart. Mine was only loose and when it vibrated it sounded like something was boing to fall off of the Car.

If you hear the sound mentioned and it was not the Air Filter Housing/Bracket take a Mechanics Stethoscope or my favorite a 3-4 foot section of Broom Stick and place either on different parts of the Engine and see where the sound is coming from. Pay particular attention to the Vacuum Pump. If it falls a part the pieces fall into the timing chain and gears and can ruin an engine.

Look at the Motor Mounts to see if they are squashed.

Concerning the low speed. It could be the Fuel Tank Screen plugged up or the Fuel Filters plugged.

See if you problem is similar. When I got my Car it was scary slow during acceleration. Once it got up to speed it drove normally (notice it being able to obtain good speed later is not a symptom of a plugged fuel system). It turned out that my Throttle Linkages were all mal adjusted and when I stepped on the Pedal the throttle arm on the Fuel Injection pump was not moving as far as it should.

One way to tell is engine cold and stopped reach in and hold the throttle arm on the Fuel Injection Pump and have someone slowly depress the Pedal and view how much play is in the linkages.

Another issue is on the fire wall where the pedal linkages and throttle linkages connect can fall apart.
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Old 03-09-2019, 03:37 PM
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Have you adjusted the valves? Also, with your power issue, check that the throttle linkage is moving all the way to the store when the accelerator is floored, and that the turbo turns easially and smoothly by hand (engine off of course)
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  #7  
Old 03-09-2019, 03:38 PM
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There is a lot of rubber parts that deteriorate. The mentioned Motor Mounts, Transmission Mount and on the Drive Shaft has a Flex Disc on each end.

If you are having abnormal tire wear the upper or lower control Arms are mounted on rubber bushing that can rot out.


There is also a fuel tank vent that when covered with Mud and so on can restrict fuel delivery. With 1/2 Tank of Fuel drive without the fuel fill cap (the fill pipe now becomes the fuel tank vent) on and see if your acceleration improves.
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Old 03-09-2019, 03:59 PM
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Quote:
Originally Posted by R.Diesel View Post
Additionally, it’s completely against form rules to announce a purchase and not provide pictures.
Whoops, sorry. Don't want to break the rules on my first day! Took some pics, I think I have them attached. If I'm working the forum interface correctly.
Attached Thumbnails
New guy with questions-benz-1.jpg   New guy with questions-benz-2.jpg   New guy with questions-benz-3.jpg   New guy with questions-benz-4.jpg  
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  #9  
Old 03-09-2019, 04:12 PM
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Quote:
Originally Posted by R.Diesel View Post
Post a video with good audio quality and your chances of getting a correct diagnosis on the first try increases dramatically.
Ok, here's a video of what it's doing.

https://www.youtube.com/watch?v=XIHD15ImfV8&feature=youtu.be
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  #10  
Old 03-09-2019, 04:27 PM
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It could be simple or serious. Injector dripping or rod knock. I would do the simple things first.

1) loosen one injector at a time and see whether the noise go away.

2) if you have an injector tester, pressure test them for spraying pattern. A dripping injector would give tapping or knocking noise. Btdt. It happened to my 617 and 603 engines.

3) do a compression test.

I would not worry about the timing chain stretch or valve for now. Good luck.
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  #11  
Old 03-09-2019, 04:34 PM
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Quote:
Originally Posted by Diesel911 View Post
It is common for the Air Filter Bracket to break or the little rubber isolators to strip out or fall apart. Mine was only loose and when it vibrated it sounded like something was boing to fall off of the Car.

If you hear the sound mentioned and it was not the Air Filter Housing/Bracket take a Mechanics Stethoscope or my favorite a 3-4 foot section of Broom Stick and place either on different parts of the Engine and see where the sound is coming from. Pay particular attention to the Vacuum Pump. If it falls a part the pieces fall into the timing chain and gears and can ruin an engine.

Look at the Motor Mounts to see if they are squashed.

Concerning the low speed. It could be the Fuel Tank Screen plugged up or the Fuel Filters plugged.

See if you problem is similar. When I got my Car it was scary slow during acceleration. Once it got up to speed it drove normally (notice it being able to obtain good speed later is not a symptom of a plugged fuel system). It turned out that my Throttle Linkages were all mal adjusted and when I stepped on the Pedal the throttle arm on the Fuel Injection pump was not moving as far as it should.

One way to tell is engine cold and stopped reach in and hold the throttle arm on the Fuel Injection Pump and have someone slowly depress the Pedal and view how much play is in the linkages.

Another issue is on the fire wall where the pedal linkages and throttle linkages connect can fall apart.
It's not the air filter housing rattling, though one of the rubber isolator brackets is bad and all of the nuts that hold the air cleaner on are missing. When it misses and the engine shakes, the air filter housing makes it's own racket, which goes away if I put my hand on the air cleaner. Replacement isolator brackets should have arrived in the mail yesterday, I'll get that tightened down.

The fuel filters are new and they seem to be flowing fine. I will probably go ahead and replace the fuel tank screen, but I just put 16 gallons in the tank today--that job probably needs to wait until there's less fuel in the tank.

Will check motor mounts and will check for play in the linkage.
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Old 03-09-2019, 04:47 PM
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Quote:
Originally Posted by ah-kay View Post
It could be simple or serious. Injector dripping or rod knock. I would do the simple things first.

1) loosen one injector at a time and see whether the noise go away.

2) if you have an injector tester, pressure test them for spraying pattern. A dripping injector would give tapping or knocking noise. Btdt. It happened to my 617 and 603 engines.

3) do a compression test.

I would not worry about the timing chain stretch or valve for now. Good luck.
1. Did that, loosened far enough to create miss in each cylinder. Noise remained unchanged. Do I need to loosen the injectors further than that, to be able to tell?

2. I don't have an injector tester, but I wouldn't be at all surprised if one or more injectors was leaking. But I thought the test I did--loosening the injectors--would make the noise go away if it's caused by injectors.

3. I thought compression testing before setting valve lash would be a waste of time. Surely incorrect valve lash would somewhat reduce compression. Judging by the condition of the clear fuel filter, I honestly doubt if any maintenance has been done on this car in years. And also, I own feeler gauges, but don't own a diesel compression tester.
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  #13  
Old 03-09-2019, 05:32 PM
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Check those air filter rubber mounts first. It is free and they are a common failure and a source of expensive sounding noises that are actually minor.

By all means adjust the valves. It is a 15k miles service item on the OM617 engine. After adjustment do a quick blowby test by loosening the oil cap. If it just does a little dance, your compression is probably o.k. If it releases a lot of pressure, check your compression.

I agree that throttle linkage problems are a common source of apparent power problems but again, not serious. DO NOT jump into adjusting the linkage rods. The lengths are factory adjusted and should never need readjusting (unless the P.O. messed with them. The most common linkage problem is the pivot mechanism at the engine side of the firewall. It is a wear point and also has a critical rubber component that deteriorates over time from heat and oil exposure. Look it over carefully. It is an inexpensive item to replace.
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  #14  
Old 03-09-2019, 09:42 PM
dkr dkr is offline
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I would check everything under the hood for wobble ... air filter enclosure, alternator, AC compressor, power steering reservoir, etc. Diesels generate a lot of vibration and can knock bolts loose. It could be literally anything bolted under the hood...

Dkr.
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  #15  
Old 03-10-2019, 11:32 AM
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Quote:
Originally Posted by R.Diesel View Post
Post a video with good audio quality and your chances of getting a correct diagnosis on the first try increases dramatically.
I made a video yesterday, uploaded to youtube and made a post with a link. I got a message that said it's waiting for moderator approval, which makes sense 'cause I'm a new guy and posted a link. I just don't want anyone to think I'm ignoring the video request.

Concerning location of the noise, it seems loudest in the cylinder 2-3 region on the injection pump side of the engine. My best guess is it's under the valve cover OR coming directly from the injection pump (all of the delivery valves are in that region). But it could be from deeper in the engine--rod knock, piston slap, or even coming from one of the injectors.

When the video posts, you'll see--it's loud enough that I really need to make sure the noise isn't something catastrophic, before I really address the lack of power.

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