Towed it home - PeachParts Mercedes-Benz Forum

John Schroader · #1 01-02-2010, 07:21 PM

Been kind of revelling in driving old MBs all over creation and never broke down once. Well that day is done. My 300D (220K miles) had to be towed home a few days back. Could use some insight before I delve into this one. About a week ago my wife noticed a high pitch rattle when the car was cold. I couldn't hear it (due to less than good hearing) but she said it quit when the car warmed up. I figured if I couldn't hear it then it must not be too bad. Other things to think about right now. Anyhow a couple of days ago I was cruising down the interstate, travelling about 70, and heard a rattle coming from about midship. Slowed down and the rattle stopped. Sped up and it resumed. Seemed to be more dependent on ground speed than on engine speed. At 70 mph, it clunked about once every two seconds. A rest stop was coming up and I decided to investigate. Slowed down, clunk stopped, pulled into rest area and noticed slow drip from where engine meets transmission. Shut down and called a wrecker. At home I checked engine oil and transmission fluid - both good. The dripping oil seems to be engine oil (not much drip, but it's new, along with clunk). I'm guessing something to do with torque converter and seals, but I'm basically out of my element here. Do these symptoms tell anyone anything?

leathermang · #2 01-02-2010, 08:04 PM

It is probably the rear main seal...
but it could be the ball retainers in the end of the oil passage .
But it is a pretty safe bet you are going to have to drop the trans to determine for sure...
I am pretty sure that you can NOT replace the rear main seal on one of our engines from below... as can be done on some cars.... this has been discussed in the archives...
You were really cautious in your actions when these symptoms appeared. I think that is to be commended and may have saved the engine.
A thorough and detailed inspection of the engine is in order now...

layback40 · #3 01-02-2010, 08:25 PM

John,
High pitched rattle & rear main seal dont normally go together.
I do agree with leathermang that if oil is coming from inside bell housing its probable the rear main seal. If it is the rear main seal, then there will most likely be oil sprayed all over inside the bell housing.
If you remove the starter, or any other cover around the bell housing you should find its wet with oil inside there. Is the starter sounding a bit quieter than previous? If its not wet with oil inside the bell housing, probably not the rear main seal.

Alt could be the high pitched rattle was a oil line vibrating in a mount as the rubber was missing. Eventually it would fail. Only a 1% chance it would be that.
We will all wait with bated breath on what you find!

John Schroader · #4 01-02-2010, 08:51 PM

Thanks fellows. Gonna have a couple of mechanic pals (professional) look at it and steer me the right way. I've never taken either of my MBs to a shop, but I guess that time has come. I just like to try to analyze these things myself, even if I don't trust my mechanical abilities to make the repairs. Will report when the jury comes in.

kerry · #5 01-02-2010, 09:39 PM

Flex plate? Flex disc? Driveshaft bearing?

t walgamuth · #6 01-02-2010, 09:47 PM

If tranny fluid it will be red and clear. If engine oil black and opaque. Could be vacuum pump which is nothing to fool around with....though that would not generate oil leaking anywhere.

John Schroader · #7 01-28-2010, 10:03 AM

It's been a month since I had the 300D towed home. Let is sit for a week or two while it was bitterly cold. Made appointment with mechanic to check it out. I started it up and decided to drive it a bit (with a watchful eye) so I could better describe the symptoms. It had lost about a quart of oil during the aforementioned episode. I did check the valve cover and slightly tightened the nuts. Anyway, it drives great and is losing no oil. Thought I could sort of hear a whine at 70, but I now feel that it is my imagination. A month ago, there was definitely a sound. Now I think it's gone. So -- my mechanic is on hold on this one. The car is doing great. Again -- I love these cars. Three years and 35K miles and never a trip to the mechanic.

stimpy451 · #8 01-28-2010, 10:07 AM

Grenade imminent; at least pull the starter and check for oil

LUVMBDiesels · #9 01-28-2010, 10:11 AM

My 300SD made a similar noise. It turned out to be the bolts in the flexplate were working loose! eventually the plate cracked and the engine STOPPED! Both John H and I thought the engine was toast until he pulled it and removed the trans for parts. The flexplate had jammed against itself and the bellhousing jamming the engine.

If you can, drop the transmission and check the flexplate.

John Schroader · #10 01-28-2010, 01:02 PM

Stimpy and LUV, OK you guys brought me back to reality. I surely don't want to cause damage. Will continue to check it out. Thanks for the advice. Darn!

DocSarvis · #11 01-28-2010, 01:27 PM

My 2 cents, I don't think the oil leak is related but I guess it could be somehow. Trouble shooting without the symptom is difficult at best and can get very expensive and time consuming. Yes I agree don't ignore it but...If you tear it down then it's even harder to find. My recommendation.. get you friends and go for a drive, you know the drill, fast, slow all gears, stop hard accel ect. If it wont show up get in the garage and do the same. If it is a flex plate putting it in gear and holding the brake so it loads and unloads SHOULD make a noise. Jack the rear wheels up and try again. If after all this you can't find it unless you are just that way I would drive it. If you can't stand it tear into it but....You may never find it either.

Since you let it set for a month that tells me you should do as I suggest. Get at least two of you friends and see if you can "hear" the problem. If not drive it. That's what I would do. I drive old cars and if I stopped every time I heard something different I would just sit in my driveway. Thanks

John Schroader · #12 03-01-2010, 11:17 PM

I feel a bit sheepish telling this tale, but, more than that - happy. Some may recall that a couple of months ago I posted a story about my trusty 300D leaving me stranded 100 miles from home. As the saga went, I was tooling down the interstate in Tennessee when I heard a distressing ‘thunk’ sound coming from somewhere near midship. I was passing a semi, travelling about 75 mph when I heard this dreadful sound. At first I thought the semi was having some malfunction, but soon realized that it was coming from my car. I pulled over immediately and, to my dismay, saw a steady drip of oil coming from the rear portion of my engine. Since the weather was cold and nasty I didn’t even try to diagnose the problem – I just called a wrecker to haul my car home. Upon arriving home I put the car in the garage and posted the symptoms on this forum. As expected, I soon received several sound pieces of good advice. Since the weather was so cold, I waited a few days to even try to diagnose the problems. Upon checking out the oil leak, I found I had lost about a quart down the left side of the engine block. Further investigation revealed that the valve cover had a slight leak. Tightened up the bolts and no more oil leak. But what about that awful ‘thunking’ sound? It sounded ominous – not to be ignored. I started the car up to take it to a mechanic, but as I drove, there was no ‘thunking’ sound. I reasoned that it must be a higher speed problem, so I took it out on the highway. No ‘thunk’. Talked to the mechanic and we decided that I should drive it some more with an ear tuned for telltale problems. For the next two months I did not take this car far from home, but experienced no problems driving it around town. Finally I decided to try another road trip. Sunday before last my wife and I put on our walking shoes, charged up the cell phone, packed a few snacks, made sure we had the number for roadside assistance, and took a 200 mile cruise. All the while we were listening carefully for any sounds that might indicate trouble. We had a pleasant drive and the only sounds we heard were the normal sounds of a masterfully engineered automobile. Maybe the Lord had healed the maladies of my beloved MB. Heady with this success, I decided last weekend to take a real road trip. I loaded up my kayak on the roof racks and headed out to the mountains. I was cruising down the interstate about 150 miles from home, grooving on some Bob Seger tunes when, to my dismay, I heard that awful ‘thunk’. My heart sank; trouble was on the horizon. Trying to determine if the ‘thunk’ was rhythmic with the ground speed or the engine I slowed down and downshifted, Seemed that the sound had nothing to do with either ground speed or engine speed. I turned the music down to better hear what was going on. The sound stopped. Aha ---- I turned the music back up and the sound came back. By now you have probably guessed, but here’s my lame excuse. A couple of years back I replaced the factory radio with a fancy one with more bells and whistles that I could ever understand. One feature was a sub woofer boost. Since I was still using the original speakers, I just connected the boost to the existing speakers. Somehow when adjusting something on this sound system, I must have cranked up the low boost. I only turned the volume way up when I am going 75 mph with roof racks on. When I did this, my poor 27 year old speakers were trying to do something with this signal they are receiving. The sound they made was a puny rendition of those big box bass speakers the young guys have in their cars – more of a pitiful ‘thunk’ than a window rattling ‘boom’. When this realization finally hit me, I had to pull over and have a good laugh. I am somewhat embarrassed, but mighty glad that my beloved MB is no longer on the ‘ailing’ list. Again – thanks to those who tried to help diagnose this problem.

pawoSD · #13 03-01-2010, 11:20 PM

See, always blame everything else but the car itself first!

dadette123 · #14 03-01-2010, 11:24 PM

at least now you are more "in tune" with your ride. too funny.

Skippy · #15 03-01-2010, 11:27 PM

That put a smile on my face.