|
|
|
#1
|
|||
|
|||
76 300D W115 engine vibration
I have a mid RPM engine vibration in my 76 300D that has me completely baffled. It is like a harmonic vibration that happens going up to speed and then back down through the RPM range coming to a stop. I have read every post I could find for clues. This is what I have done so far.
Replaced engine mounts with new original MB parts. Replaced tranny mount. Replaced fan clutch (old one had a lot of play in it) When it hits that certain RPM range the vibration can be heard throughout the car and felt in the gear shift lever. When sitting still the vibration is still there when you rev the engine which tells me it is not in the drive line or transmission. Any clues to what I am missing? Thanks for your help.
__________________
Western NC 1987 300SDL W126 Turbo Diesel 335,000 + miles 1976 300D W115 275,000 miles+ |
#2
|
|||
|
|||
Has anything ever been done to the fuel system? New injectors, filters, primer pump, tank cleaned, fuel pressure relief valve stretched...
Ever seen a valve adjustment? New air filter?
__________________
|
#3
|
|||
|
|||
Has the driveshaft ever been off the car? The drive lines are sensitive to miss alignment causing vibration...
|
#4
|
||||
|
||||
OK
Quote:
Please note the stiffening bracket and bolt in the following picture. This bracket and bolt are critical, as they reduce movement and add strength to the transmission mount. If the front sub-frame mounts have failed, it will shift around making random (mild to horrible extreme noise is possible) body contact and exaggerating any engine movement. Some of the W115 chassis have at least one engine shock absorbor, if it or the bushings fail, expect excess engine movement and noise. I understand you replaced the injector nozzles. However I will note that the injectors in my daughters 1976 300D have been removed for cleaning (body and nozzle) several times, this has been due to sludge apparently trapped in the injection pump from previous infestation. My repeated use of Diesel Purge, BioBor, StarTron, and vigorous manual fuel system cleaning has at this point eliminated the contamination. Here is the thread about my daughters car, with many links to procedures done. Welcome to the fleet 1976 W115.114 "300D" dark Green .
__________________
ASE Master Mechanic asemastermechanic@juno.com Prototype R&D/testing: Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician. Noise Vibration and Harshness (NVH). Dynamometer. Heat exchanger durability. HV-A/C Climate Control. Vehicle build. Fleet Durability Technical Quality Auditor. Automotive Technical Writer 1985 300SD 1983 300D 1984 190D 2003 Volvo V70 2002 Honda Civic https://www.boldegoist.com/ |
#5
|
|||
|
|||
Quote:
everything done except valve adjustment. Very smooth except for those mid range rpm's. Good suggestion though. Thanks
__________________
Western NC 1987 300SDL W126 Turbo Diesel 335,000 + miles 1976 300D W115 275,000 miles+ |
#6
|
|||
|
|||
Quote:
I have not replaced the sub frame mounts. They are pretty sad looking but I didn't think this would isolate an engine vibration. The single engine shock is shot but I thought this was only for idle shaking. The car idles very smooth. Thanks for the suggestions.
__________________
Western NC 1987 300SDL W126 Turbo Diesel 335,000 + miles 1976 300D W115 275,000 miles+ |
#7
|
||||
|
||||
^^^If I were you I would listen to whunter's advice. If you don't have a copy of the W115 FSM there is mention of this early extra stiffening bracket and the procedure for the adjustment of the transmission mount in the W123 FSM (which is more widely available).
__________________
1992 W201 190E 1.8 171,000 km - Daily driver 1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone 1965 Land Rover Series 2a Station Wagon CIS recovery therapy! 1961 Volvo PV544 Bare metal rat rod-ish thing I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior Don't leave that there - I'll take it to bits! |
#8
|
||||
|
||||
Have you checked the front vibration damper,AKA the harmonic balancer. That dampener is capable of a lot of problems if the primary or big bolt gets a tad loose. Also the smaller studs holding the pulleys to the dampener can get loose and or crack off. I would recommend that with the engine running you really watch the motion down there at the very lower part of the front of the engine to see if any side motion is evident. You just don't want that assembly to get loose or it will cost you an engine.
__________________
Junqueyardjim Christianity, if false, is of no importance, and if true, of infinite importance. The only thing it cannot be is moderately important. C.S. Lewis 1983 Mercedes W123 240D 4 Speed 285,000 on the road with a 617 turbo, beautiful butter yellow, license plate # 83 240D INDIANA 2003 Jaguar Type X, AWD. beautiful, good mileage, Mom's car, but I won't let her drive it! |
#9
|
||||
|
||||
Answer
Quote:
Sub frame mounts on the W115 are important. The single engine shock is important for more reasons, due in part to the odd Sub frame mounts on the W115. .
__________________
ASE Master Mechanic asemastermechanic@juno.com Prototype R&D/testing: Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician. Noise Vibration and Harshness (NVH). Dynamometer. Heat exchanger durability. HV-A/C Climate Control. Vehicle build. Fleet Durability Technical Quality Auditor. Automotive Technical Writer 1985 300SD 1983 300D 1984 190D 2003 Volvo V70 2002 Honda Civic https://www.boldegoist.com/ |
#10
|
|||
|
|||
Quote:
I am leaning to think that it is the subframe mounts causing the resonating vibration noise. I see that the motor mounts are connected to the subframe and that could cause a metal to metal connection to the body. I do feel the vibration through the steering wheel as well. At certain rpms the car is extremely smooth and quiet and then as you accelerate or decelerate you suddenly feel and hear that low bear grumbling sound. My engine shock mount seems to be ok but the shock itself has no resistance so if I can find a new one I will replace. Thanks again for the help! John
__________________
Western NC 1987 300SDL W126 Turbo Diesel 335,000 + miles 1976 300D W115 275,000 miles+ |
Bookmarks |
|
|