Broken rocker arm

[anthony]

Making a left turn a horrible sound erupted from my engine. After towing the car about a half mile to work I was able to do some checking.

Number 3 exhaust rocker arm is broken at push rod end or not the valve end. The engine was running and I turned it off. I was able to turn it over using the crankshaft nut. No sound or anything unusual. I dropped the oil pan, I did not remove it, but was able to visually inspect and nothing out of place. I turned the crankshaft to see all the rod bearing ends and again nothing missing or out of place.

As soon as I can get some time I will remove the head. So far everything else seems ok. The big question is why did it break? I know there are no answers until the head is removed. But I hope it is limited to the rocker arm.

Do I need a new head gasket, it is only two months old?

And anything I should be looking for?

I did install 12 new rocker arms from autohauz AZ, and they are not BMW.

[Falkenberg]

I don't think anything bad happened to your engine. It just might have been a weak rocker arm. I've heard more stories about them breaking apart, especially on M20 engines but also M30. My mechanic recommends the original BMW ones, not aftermarket. He seems to think that they are of better quality.
On my car I had one that missed a piece as well:

I was lucky to find the missing piece in the head near an oil drain channel, so it did not go anywhere where it could do damage.

You will need a new head gasket.

[Mike W.]

While unusual, I have heard of it happening. Usually at higher RPM though. I've heard, what happens is the rocker slides a bit sideways and side loads are applied and it breaks. Early, meaning say E12 era and earlier, used heavier rocker springs, or longer ones that preloaded the rocker a little more. I like to use them if I have them, but I've never had a problem even on very high mileage engines like the old 2800 Bav where it saw over 7K RPM with ~250 K on the head components. On the HG, once it's been compressed, it's been compressed and needs to be replaced, not reused. Oh, you could probably get away with it for a while, but I think in 6 months or a year you'd be back at it again.

There is one longshot... It wouldn't be as easy on an E12, but I've heard of guys being able to slide a forward rocker out once they removed those head bolts. #3 would be ideal, it would require a minimum of movement to R and R that rocker. Sometimes those rocker shafts slide pretty easily, but not usually, but you might get lucky. If you do go that route, make sure you remove the oil from the bolt holes before you replace the bolts and retorque it.

[Blaise]

Making a left turn a horrible sound erupted from my engine. After towing the car about a half mile to work I was able to do some checking.

Number 3 exhaust rocker arm is broken at push rod end or not the valve end. The engine was running and I turned it off. I was able to turn it over using the crankshaft nut. No sound or anything unusual. I dropped the oil pan, I did not remove it, but was able to visually inspect and nothing out of place. I turned the crankshaft to see all the rod bearing ends and again nothing missing or out of place.

As soon as I can get some time I will remove the head. So far everything else seems ok. The big question is why did it break? I know there are no answers until the head is removed. But I hope it is limited to the rocker arm.

Do I need a new head gasket, it is only two months old?

And anything I should be looking for?

I did install 12 new rocker arms from autohauz AZ, and they are not BMW.

Anthony,

Sorry to hear this. I have a complete stock BMW head...if you need parts.

Blaise

[anthony]

Thank you Blaise, but have 12 rocker arms to find the best one. I have removed most of the stuff I should have the head off after work tomorrow.

A couple of weeks ago I merged hard onto 101, I think I was stuck behind some slow pokes getting on, then I had a couple of lanes free. I felt a vibration. I checked the flex disc and saw a crack and replaced it. Still there was a slight vibration. I know believe that I also damaged the rocker arm in such a way so it wasn't smooth and then finally broke it two weeks later.

Well I hope this will take care of it.

[DEMIURGE]

Maybe my reply is a bit late...
Sorry...

But, firstly, Bart (Falkenberg) is right - the old original BMW rockers are better than the aftermarket ones, like Febi for example. Generally the rockers from e12/e28 era are better (stronger) than e34 era.
If you want to have some new ones - maybe these are better:
http://www.iemotorsport.com/bmw/E28-E24 ... armHD.html
Their price is a bit higher than the Febi rockers, but I believe, they are much stronger and better.

Then, as always, Mike is right - you have very real chance to change the broken rocker without removing the head - it depends on the rockershaft - I'm not sure, but you can check it on your spare head - there are three or four bolts to remove, of course, the timing cover, the chain with the camshaft sprocket, but remove them together - after you change the rocker - you'll have no worries about the chain-teeth alignment. Check and retension the timing chain tensioner spring and piston.

I wish you luck...

[anthony]

Replace broken rocker arm. Started up sounded great. Drove around block to warm up. Removed valve cover to torque 30 degrees, what do I see but a Cafe latte.

Is there hope? When I removed the head coolant did spill into the cylinders and i did not re-drain oil pan.

but now there's a knock sound.

Could this sound be related to original problem thus breaking the rocker arm?

[Lmarkey]

I'm a bit late on this but....the broken arm happened to me, with no other damage. When i took the head apart I notices a notching in the rocker where it met the cam loob. So then i looked at all of them and most had the same notching on both the rocker and in some place on the cam. I had to replace everything; cam and all the arms.

[anthony]

Drained and replaced oil and filter solved a problem that wasn't.

knocking not so knocking. Plan to adjust valves.

All n all lot of work to fix just one thing.

[Falkenberg]

It's a bit late now, but you should have changed the oil before starting up. It could still be ok though. Knocking comes from lower end or upper end of the engine?