Hi-
I have a 1991 740 Wagon with 381,000 miles. I'm the second owner - first owner was a mechanic who kept it in great condition. I've continued to maintain it and repair whenever needed.

Had the oil changed, and a check of everything done about 2 weeks ago at the dealer. The said I needed new brakes, but other than that everything was fine. About a week ago I started noticing an extra sound under the hood while running (I hear it at idle, but it could be happening while driving too - just can't hear it). It's not a knocking, or a clacking - so light I might not notice it if I didn't know the car the way I do. It seems to increase when the accelerator is pushed further (someone turned the wheel under the hood that makes the engine rev and I heard it more - sorry I'm a bit clueless about parts and such). The car starts and runs without issue, and I have no other problems with it-

Took it back to the dealer today - mechanic listened to it for about 1 minute, checked the power steering fluid and oil, and then said it was a bearing or a valve and I need another engine. He insisted the noise was there before the oil change, even though I know it wasn't.

Stopped at the parts store on my way back home and asked the employee there to listen. He said he heard the sound, but felt like it might be a mild valve issue, nothing major, and suggested I add an oil additive.

Any thoughts on this? It's hard for me to believe the dealer - they already missed something important a while ago, and only after much heartache and irritation did they realize the error. I don't want to put another engine in because of the expense, and frankly I don't know that I need it. Could it be something else? A different part? I know it's hard to say without hearing it. Would an additive help?

Help greatly appreciated!!
Thanks!

 

Well, first of all, at 381,000 you may very well need a rebuild or new motor. If you're only now hearing the motor noise, perhaps they used a much thinner/lower viscosity oil than what was previously in it. I've known folks to use 5W-30 in redblocks w/ high miles and start getting bearing noise. Often times, minor bearing noise can be significantly quietened by using either a 20W or 30W oil. Here in Texas, I run 30W year long.

 

This is super helpful, thank you! Yes, it definitely could need a new motor - but I have been putting 40 and 30 in, with no noise, and I wonder if they did put in a lower viscosity...

 

Id put some 30w in it and see...

 

Oh yeah, if you did not specify, I would bet they used 10W-30.

 

380K the motor is young. We've got only 317 and it runs like a clock. I have always used 10W-40 year round. We life in the north east so temps range from -20* to +100*. Just ask what oil they used and if 10-30 change it to 10-40 and run it until it breaks.

 

I agree, the best oil that you can use is 10W-40. Shell Rotella conventional diesel oil is the one that I use on the Volvo and Land Rover and change it every 5k miles.

 

Uh...sorry but 10w-30 and 10W-40 are the EXACT same viscosity. Generalizations that red blocks are just broken in at 300k are just that. While extremely durable, B230's (especially 85-90) are as susceptible to the pitfalls of poor maintenance as any motor. I've seen them w/ heinous piston slap at 120k and I've seen them quiet as a sewing machine and compression at 180 across the board at 250k. While all redblocks may be born equal, they do not receive equal treatment and care. There are no young redblocks anymore. How long they last without a rebuild now is often out of the hands of the current owners. All one can do is give the best maintenance possible and hope for the best.

 

Thanks everyone - I appreciate all the input. I'm in the northeast as well so temperatures definitely vary. I've never had to specify - always assumed they were using 10w30 - I add 10w40 if it's low in oil. But it definitely seems like they used a lighter weight, or a synthetic, which I never use. I'm so irritated, and I think I'm going to someone different and get the oil changed again. Incredible.

When I think about the noise, it sort of sounds like a vacuem hose issue - like an open pressure being drawn in...I wonder if that's part of the issue...

But one would think after their stupid 20 point check, they would've caught something like that!!

Thanks again-