help! strange thudding noise from rear end when accelerating

[Oolop]

also when i start from a stop and make a left turn, like top of 1st gear or accelerating harder on 2nd. been happening since i got the car about 3 or 4 months ago (1987 325e 5-speed bone stock)

i checked my guibo's they're fine, checked my axles and one boot is torn but i think that just happened, 2 different shocks in the back...

speaking of the axles, i can somewhat pull them out of the diff, like an inch and a tad but not completely out. one was a bit out but i pushed it back in, drove, and same thing happened.

my co worker said it might be my diff

any suggestions? thanks very much

[jlevie]

A thuding noise that only occurs when turning will be a half shaft or the differential. But if the noise occurs under acceleration in a straight line the probability moves to the CSB and drive shaft.

[Fidhle007]

Check your Subframe mounts too...

That may not be the source of your noise but I can still guarantee you that they're broken if you haven't changed them. If they are it replacing them should quiet things down a lot.

[Oolop]

Thanks guys for the quick response

Sorry, what exactly is the csb?

And I'll check for all that tomorrow, hopefully, and let u guys know what I find out, thanks!

[Dude]

Thanks guys for the quick response

Sorry, what exactly is the csb?

And I'll check for all that tomorrow, hopefully, and let u guys know what I find out, thanks!

Center support bearing. Its what holds the driveshaft up between the tranny and the diff.

[Vince30]

The csb is the center support bearing, it is in the middle of your driveshaft, mine is out right now, it sounds like your driveshaft is banging on the bottom of your car (because it is) lol.

[Oolop]

Lol thanks guys, when I read csb for the first time I tried coming up with all these things that it could stand for but yea that totally makes sence now

But one thing, I never hear it while I'm going fast lik 60 on the highway or even slowly accelerating from that. Could it still be that?

[KVF]

Lol thanks guys, when I read csb for the first time I tried coming up with all these things that it could stand for but yea that totally makes sence now

But one thing, I never hear it while I'm going fast lik 60 on the highway or even slowly accelerating from that. Could it still be that?

Yes. Hard acceleration applies enough snap torque to cause the issue. If you are just cruising (regardless of the achieved speed) you are not applying enough load to force the issue. Unfortunately, the issue is hard to diagnose. If you have access to a lift, put it in the air and try to push the shaft side to side and up and down. Also take a look at you rear diff bushing and mounting bolts.

[Oolop]

Yes! U guys were right! It's the CSB, the drive shaft is totally just hangiing there so I'll be ordering the part tomorrow.

Now for my next problem lol, my temp gauge won't go past 1/4. Of the way, and the coolant light goes on. My coolant level is fine, although dirty coolant which I plan to flush out soon. I think it's one of my coolant temp sensors but there are like four of them and I don't know which one it is. I know there's two, one for emissions the other for cold starts and the rest idk...

[Fidhle007]

I'd look more at your thermostat then the sensors... Coolant level sensor is in the tank, easy fix and a common issue on cars of this age.

[Oolop]

Ah that's what forgot to mention, I did change the thermostat and it didn't change anything

[Fidhle007]

A lot of t-stats seem to be running cold right out of the box, I've seen it in several cars we've done at my shop but it never hurts to check the sensor. The brown one is the one for the cluster.

[Oolop]

Ok sweet! Thanks for tellin me which one it is, it's been bugging me for so long lol

But if a thermostat would stay open from the beginning, wouldn't it just mean that it'd take longer for the motor to heat up? I mean it'd get to the optimum temp it'd just take longer right?

[dkbmxer002]

I'd look more at your thermostat then the sensors... Coolant level sensor is in the tank, easy fix and a common issue on cars of this age.

on that note, what should be looked for with the check panel coolant gauge that is in the reservoir? same with the oil light? my buddies 325i will show those lights but the level and pressure will be fine.

[Oolop]

About that brown sensor for the cluster, on my motor, I have two brown ones, the one furthest forward on the motor has two prongs I guess u call them and the other brown one is further back and that one has just one prong. Which one is it exactly?