Rattle at high rpm - PeachParts Mercedes-Benz Forum

pentoman · #1 05-16-2006, 07:04 AM

My 190E 2.5-16 has a rattle at high rpm.. like 5000 rpm plus.

It's pretty loud and noticeable, and it's not really a noise that is in time with the engine (i.e. So I'm pretty confident it's not in the valvetrain or anything).

Does anyone have any suggestions or ideas to trace this? I suspect it may be an exhaust rattle but can't think how to verify this? The exhaust has just been tightened right through as it was apparently loose..

joeym · #2 05-16-2006, 07:22 AM

Hi I would check the cat,you might try hitting it with a rubber mallet,and listen for a broken inside cone.The only other thing I can think of at that RPMs is a crack on the flex plate.Joeym

pentoman · #3 05-16-2006, 07:52 AM

My car is a euro with no catalyst

I did have the rear flex disc done recently.. the front is fine. It sounds more like it's at the engine bay/firewall sort of area, but of course sounds can travel....

t walgamuth · #4 05-16-2006, 08:37 AM

the exhaust doesnt have to be loose to rattle.

if any parts arent aligned exactly right they can rattle against things that they shouldnt be able to touch. this will occur under situations where the engine is developing full torque and is twisted on its mounts or perhaps under deceleration when it is laying over the other direction.

might look at your motor mounts too.

tom w

AF300E · #5 05-16-2006, 10:00 AM

Hmm, could be a rotten bearing. Would be very unusual at low km though.

pentoman · #6 05-16-2006, 11:27 AM

Quote:

Originally Posted by t walgamuth

the exhaust doesnt have to be loose to rattle.

if any parts arent aligned exactly right they can rattle against things that they shouldnt be able to touch. this will occur under situations where the engine is developing full torque and is twisted on its mounts or perhaps under deceleration when it is laying over the other direction.

might look at your motor mounts too.

tom w

Thanks,

Quote:

Originally Posted by AF300E

Hmm, could be a rotten bearing. Would be very unusual at low km though.

Is that an engine bearing you are talking about? I can't be certain of the mileage.. but it seems to run mostly OK. Power does noticeably die off over the last 800-1000 rpm (to 7000) where other cars would rev through right to the redline more strongly.. but max power is only at 6,200 so would that be expected?

AF300E · #7 05-16-2006, 09:33 PM

Yeah, I was talking about small end or big end bearing. Highly unlikely though. As the other guys say, look for misaligned stuff first. It's really hard to diagnose without hearing. Is it a constant rattle? More like a tapping? or does it sound like a loose bolt type rattle? In the 300e there are bell shaped bulges on the engine pipes. I think they slow the gases before they reach the cat so your car may not have them being a catless (yummy!) year. They rattled in mine at revs so I had new ones welded in and the noise went away.
Just an idea

86560SEL · #8 05-17-2006, 01:10 AM

5,000 RPMs and higher ?

Oh my! How often do you race the engine above 5,000 RPMs?

I think that 3,300 RPMs is the highest I have ever had my Mercedes V8 (so far) and that was a one time deal when I had to get up to 60 mph quickly up a steep grade on a highway. I just have never had the need to go any higher with the RPMs and I really baby the car anyway.

The highest RPMs I had a car was about 4,900 RPMs and that was in an emergency situation when I had to merge onto a busy expressway. That was many years ago in a 91' Camaro RS that had 34K miles.

Quote:

Originally Posted by pentoman

My 190E 2.5-16 has a rattle at high rpm.. like 5000 rpm plus.

pentoman · #9 05-17-2006, 04:24 AM

Quote:

Originally Posted by 86560SEL

5,000 RPMs and higher ?

Oh my! How often do you race the engine above 5,000 RPMs?

I think that 3,300 RPMs is the highest I have ever had my Mercedes V8 (so far) and that was a one time deal when I had to get up to 60 mph quickly up a steep grade on a highway. I just have never had the need to go any higher with the RPMs and I really baby the car anyway.

The highest RPMs I had a car was about 4,900 RPMs and that was in an emergency situation when I had to merge onto a busy expressway. That was many years ago in a 91' Camaro RS that had 34K miles.

Good old American cars..... loads of torque at about 10 rpm

.

Well in a euro 16v, the cam only fully comes on at just under 4000 rpm (underneath that it is not very fast), max power is at 6,200 and the redline is 7,000. So trips over 5000 are pretty common!

With a 5-speed manual, and agile W201 body on the 16v suspension, the car encourages you to do it!

86560SEL · #10 05-18-2006, 12:28 AM

I'll bet. Sounds like a fun car. I guess the 4-cylinders have a higher redline anyway. I had forgot about that. I bet the handling of the 190 is very agile as well. My 85' S-Class is like driving a boat.

Hatterasguy · #11 05-18-2006, 12:37 AM

Sounds like something is loose. Maybe a heat sheild of some sort? I'd head under the car and poke around a bit.

86560SEL don't baby it MB's are ment to run. The SDL sees 5k rpm at least once a day. The SD sees 4500 or whatever it will spool up to a couple of times a day.

I run every MB I drive up to redline actualy, good fun.

lkchris · #12 05-18-2006, 12:06 PM

Sounds like preignition to me.

OTOH, 4-cyl engines without balancer shaft usually have a "rough" period, but it will have been there since new.