"Grind/groaning" on start-up - PeachParts Mercedes-Benz Forum

Radioarch · #1 10-01-2002, 09:04 PM

Symptom - My 300TD has 150K on the odometer. Beginning at 130K I have occasionally experienced a noise on the first start-up of the day. The engine fires up, but a second later there is a grinding or groaning noise that lasts about half a second, building to scraping 'crescendo' before abruptly ceasing. The time lag before the noise stops appears to coincide with a delay in the oil pressure gauge going up. Most noticeable on cold mornings last winter and shortly before an oil change, this noise has recently begun to feature (almost) every time I start.

Location - seems to be emanating from the lower right of the engine

Current suspects - Timing chain, but tension would indicate this is _not_ loose or maladjusted. Alternator, but this would discount any connection with oil flow/pressure. Oil pump/chain?

Anyone else had this problem? Know a fix?

Many thanks for any and all advices.

leathermang · #2 10-02-2002, 12:33 PM

Maybe the pads are wearing off timing chain tensioner.. ? Initial position , before oil pressure hits it... could make a noise.. and not when held in position with oil pressure.. I am just guessing ....the rachet mechanism only keeps it from retracting TOO much.. does not place in running position... ??????????

surfblau · #3 10-02-2002, 12:45 PM

So, are the belts tight enough and in good condition?

kerry · #4 10-02-2002, 01:21 PM

Could it be the starter slow in disengaging?

franklyspeaking · #5 10-02-2002, 01:39 PM

Is it a belt slipping? Can't think of anything else.

Good luck.

#6 10-02-2002, 02:30 PM

I just had a similar issue which everyone is pointing at--the belts. Even after tightening them, the noise didn't go away until I sprayed some belt dressing on the pulley with the engine running.

Radioarch · #7 10-03-2002, 12:25 PM

Thanks for all the responses. I have lubricated the belts and it hasn't made a difference. I am going to look again at the timing belt adjustment/tensioner and at the starter disengagement. In the meantime, can anyone positively discount the oil pump/chain theory?

surfblau · #8 10-03-2002, 01:25 PM

That might help.

I am guessing that it is an 87....

Radioarch · #9 10-03-2002, 02:51 PM

My apologies, it's an 85.

surfblau · #10 10-03-2002, 02:57 PM

So you have a 5cyl engine, and no "belt" tensioner (that is a feature of the 603 engines).

Instead of one serpentine belt, you should have four other regular v-belts. My guess is that one of them is loose. Push on each with a thumb and see how much deflection.

That is about all I can offer.

dieseldaddy · #11 10-03-2002, 11:03 PM

No belt tensioner?
I have a 1981 300TDT and...if it is what I think it is...I have TWO belt tensioners:
1. at Alternator
2. at A/C compressor

Maybe I am mistaking the names.(?)

surfblau · #12 10-04-2002, 11:43 AM

I guess you could call the pivoting mount that the alternator or the compressor is on a "belt tensioner", but generally, when people say "belt tensioner" they usually mean a pivoting arm on the top front of the engine that connects with a damper on one side and a spring on the other. It has a single pulley and tensions the serpentine belt that drives all the other devices like alter, ps, comp, etc.

Sorry for any confusion.

alec

Radioarch · #13 11-28-2002, 10:14 AM

Update

Having (finally) ruled out timing chain/tensioning, and belts, I am currently working on the basis that the starter is remaining engaged. I have a longstanding vacuum leak, and now wonder if this isn't connected to the problem.

can-do · #14 11-28-2002, 10:41 AM

Greetings,

Does this happen each time you start the car or just the first time in the morning? I'd have someone else do the starting and you do the searching during that time. Just a few things that come to mind if you can absolutely eliminate the running belts as a source. The blower motor will whine or squeal when they start going out during initial start-up. If the cooling fan clutch is going south it too may partially engage causing the squeal or slight grind. Maybe if you could narrow down the area more we could offer more prospective problems for you. I wouldn't rule out a sticking starter solenoid. Trying starting the engine from under the hood to isolate the problem.

Charles

Radioarch · #15 06-30-2005, 08:12 AM

As a postscript, I think I inadvertently discovered the cause of the noise. My car started whistling in a strange manner, and the power was way down. Suspecting the turbo I found a thread that dealt with the ALDA line. When I pulled it, this line was almost totally clogged, so that the aperture was greatly reduced. I replaced the line, and not only was my power/whistle problem gone, but so was the startup noise. I concluded that the now gone noise must have related to the ALDA or turbo compensating for the difficulty of drawing through this line.