Multiple Noises... Uh oh

[fiftytakedowns]

A problem My car has always had, is at about 2500 RPM & Up s a llight Rattle starts sounding from (Mid to left) part oif Motor. IT occurs only Under acceleration, or when the Motor is under load. Just revving the motor doesnt bring out the sound. it is hard to diagnose from the drivers seat, but I have been trying. I tried to open hood and rev motor, but couldnt find anything. The Noise gets louder as the motor revs, but seems to die after about 5-6000 Rpms. It Is a consitent rattle, but not like to a perfect 'beat'.

Secondly Ever since there was one day of heavy rain 3 days ago a sort of squeeling comes from the motor, or screech. It only occurs at about 2500Rpms toooo about 4000Rpms. Then dies out. My hunch is that it is thhe Fanbelt, but I dont know.

[bingbong]

fanbelt is wet thats the squeeling for ya but i have no idea about the other one.

[Guest Anonymous]

could the first be engine knock? Try a tank of premium fuel.

[brad_c-ville_VA]

could the first be engine knock? Try a tank of premium fuel.

or lean out your mixture just a touch and re-time. it does sort of sound like it could be engine knock.

[jgerry2002]

What is the mileage?

You may need a new timing chain tensioner.

[bcthomas122279]

Your exhaust mounts are shot....crawl under there and check em out. Then replace and properly tighten your fan belt.

[InkaSteve]

Do you have a metal heatshield bolted to your exhaust manifold?? These sometimes loosen up or crack, and create an annoying rattle. I believe Brad could be correct about the exhaust mounts. There is also a "U" bolt exhaust clamp under that car that loosens and rattles. The squeal should be the fan belt. Careful...too tight will prematurely wear out the waterpump bearings.

[Guest Anonymous]

could the first be engine knock? Try a tank of premium fuel.

or lean out your mixture just a touch and re-time. it does sort of sound like it could be engine knock.

I always use the 91 octane fuel, but engine knock sounds kinda bad, what do I have to do about that?

The Odometer is broken so I dont know the mileage, but It does have performance headers.

Where do I find timing chain tensioners?

[Guest Anonymous]

engine knock is premature ignition of the fuel - high octane fuel doesn't ignite as easily - you get the noise under load, not when you just rev the engine in neutral. Re-tune, use higher octane gas, or an additive to your fuel. It's hard on the engine over time, not a problem if it only happens a little. Check out the other suggestions as well. U are going to need a good mechanic or a repair manual to get familiar with stuff like proper timing chain tensioning and bleeding.

[bcthomas122279]

There is also a "U" bolt exhaust clamp under that car that loosens and rattles.

If it's even there

[Benz02]

For your mystery sound, I recomend opening the hood again and listening really carefully. You should be able to determine where it's coming from even if you can't see anything loose. Could be pinging, or valve chatter, or rockers, or wrist pins, etc. Still, with a bit of patience I would think you could isolate the area from which it emanates.

Good Luck!

[brad_c-ville_VA]

Your exhaust mounts are shot....crawl under there and check em out. Then replace and properly tighten your fan belt.

when i had that noise it sounded more like it was coming from under the trans tunnel, obviously. mine sounded more like someone tapping on the trans tunnel with a tack hammer. not so much an engine noise but it certainly could also be a culprit.

engine knock will sound more like a quick ticking sound, almost like a sewing machine on a sheet metal blouse...or the woodpeckers that tap on my steel chimney cap in the morning, idiot birds.

[fiftytakedowns]

engine knock is premature ignition of the fuel - high octane fuel doesn't ignite as easily - you get the noise under load, not when you just rev the engine in neutral. Re-tune, use higher octane gas, or an additive to your fuel. It's hard on the engine over time, not a problem if it only happens a little. Check out the other suggestions as well. U are going to need a good mechanic or a repair manual to get familiar with stuff like proper timing chain tensioning and bleeding.

One of my good friends has a timing gun, and Is a real good backyard mechanic, however hes not a pro in BMW... would he be able to do the timing assuming he has the restoration guide.

Also Where could I find a fanbelt? would Napa have a fanbelt for a 74 tii?

[Guest Anonymous]

call NAPA and ask them. or try a dealer or any of the many afrtermarket places on-line - I like Bavarian Autosports. Yes, your friend could time it - with the manual and some coaching here the first time. Also check the archives here.