looking to buy 325i.. engine tick questions

[genocide98]

I'm thinking about checking out a 325i w/ a stroker E bottom I top end iirc. Says it runs/drives but he hasn't been driving it since the problem developed. I'd like to drive it home, I can trailer/dolly it home if I have to... it's about an hour and a half drive from my place to the car but for the right price I'd be willing to go the distance.

Problem is the engine ticks starting around 2500rpm. The owner said it developed this problem and he parked it. He was led to believe its a rocker arm, but he hasn't investigated it himself.

I figured that it could also be a rod bearing or wrist pin, but does anyone else have an idea of what it could be? Are there any other symptoms of a thrown rod bearing or wrist pin I could look for? Has anyone ever attempted to replace a rod bearing or a wrist pin with the engine in the car?

sticky lifter or valve?

Open to ideas. I plan on running it, if I can't figure it out I'd pull the valve cover. I'm not an m20 guy so this stuff is all over my head.

Thanks in advance. Cross posting here and on BFC

[Sagaris]

It sounds like there could be an oil pressure issue (weak oil pump) if it starts making noise as the rpm increases. Otherwise there may be loose valvetrain components. Something that I am not too familiar with.

Exhaust manifold leaks (cracks, or bad seals) and obvcan also make ticking sounds but I have never heard one that is rpm depended like that so that is probably not the issue.

I once bought a $500 car, took it on a 5 minute test drive around the neighborhood. Everything was great, but then on the drive home when the oil got warm and less viscous it lost oil pressure and the oil pressure idiot light came on :DOH: So if you get a chance to drive it / run it, keep an eye on the oil pressure light and make sure you get it up to operating temperature to avoid falling into the same problem I did.

[genocide98]

It sounds like there could be an oil pressure issue (weak oil pump) if it starts making noise as the rpm increases. Otherwise there may be loose valvetrain components. Something that I am not too familiar with.

Exhaust manifold leaks (cracks, or bad seals) and obvcan also make ticking sounds but I have never heard one that is rpm depended like that so that is probably not the issue.

I once bought a $500 car, took it on a 5 minute test drive around the neighborhood. Everything was great, but then on the drive home when the oil got warm and less viscous it lost oil pressure and the oil pressure idiot light came on :DOH: So if you get a chance to drive it / run it, keep an eye on the oil pressure light and make sure you get it up to operating temperature to avoid falling into the same problem I did.

Ya I figured that if there is some kind of bearing damage its because there is an oil problem.. both would have to be addressed at the same time.

still trying to figure what else it could be.

[jlevie]

A tick that isn't present at idle, but becomes pronounced with an increase in engine speed is more likely to be a rod bearing than valves. But a bit of investigation with an automotive stethoscope should pinpoint the source of the noise.

[genocide98]

A tick that isn't present at idle, but becomes pronounced with an increase in engine speed is more likely to be a rod bearing than valves. But a bit of investigation with an automotive stethoscope should pinpoint the source of the noise.

That's the same thing my old man and I said about it. I don't have access to a stethoscope (surprisingly.. I have too many other tools at my disposal.) but I might be able to pick one up locally.

Car has 180k, would I need to machine the crank down and go with oversized bearings or would simple replacement bearings be typical of an m20 with that mileage?

I wonder if it would be worth the trouble to service the bearings or if I'd be better off with another motor entirely after bearings + gaskets + possible oil pump/oil delivery problem.

[nando]

don't bother machining BMW cranks, it will cost a fortune and you have to deal with oversized bearings and other nastiness. throw away the bad crank and find another good used one, and get standard sized bearings to match.

[genocide98]

don't bother machining BMW cranks, it will cost a fortune and you have to deal with oversized bearings and other nastiness. throw away the bad crank and find another good used one, and get standard sized bearings to match.

So you're saying that I'd be better off re-using a good crank or finding another?

I guess its time to weigh the pros/cons and see what I can do with this car...

[nando]

yep

if you got the car cheap a used B25 shouldn't be that bad, or even an M50.

[genocide98]

I'd prefer to avoid an entirely different motor, but if I had to it would definitely be a 24v swap... I'd like to have this thing on the road by friday...

[jlevie]

Car has 180k, would I need to machine the crank down and go with oversized bearings or would simple replacement bearings be typical of an m20 with that mileage?

I wonder if it would be worth the trouble to service the bearings or if I'd be better off with another motor entirely after bearings + gaskets + possible oil pump/oil delivery problem.

Until you tear down the motor and check the crank journals there's no way to tell whether the crank needs work (or replacing). In most cases, the crank won't be worn enough to justify a re-grind or replacement. A polish of the journals is typically all that's needed. A 180k engine may have enough cylinder wear to require boring & new pistons. Otherwise a hone job and new rings may be sufficient. The head will almost certainly need to be rebuilt.

While this is more work and cost than dropping in a junkyard motor, if the job is done right you'll have a zero time engine.