Bad day at the dyno

[Fred]

I took my car to another dyno day last Saturday and on the very first run the engine decided to blow something. Exactly what, I'm not sure. At about 6800 RPM there was a loud PSSSH! sound (almost identical to a blow-off valve, but much louder) and some smoke coming from the passenger side of the motor. I immediately ran up to see what the problem was. The dyno guys looked a little nervous, but said that it was probably an exhaust gasket blowing off. It was not. When I started the car back up, there was a loud tick-tick-tick noise that increased with RPMs. Kinda sounded like a broken rocker arm.

Since I live about 5 minutes away from the shop, I managed to limp it home, keeping it under 1500 RPM the entire time. I popped the valve cover off and didn't see anything wrong, no broken rocker arms, no broken valve springs, etc. My heart sank as I realized it could be a bent valve, so I borrowed my coworker's compression test kit today. The engine hit 185 psi on all 6 cylinders, so I suppose that's a good sign. It's too dark out to continue to do anymore work, so does anyone else have any ideas?

EDIT: Here's an 8MB video clip of the run. Right before it ends, you can hear something blowing off:

http://www.strictlyeta.net/videos/dyno1.avi

Fred

[aaron_silva]

So sorry to hear this terrible news Fred. Sorry, I am no help here but best of luck to you getting your car back on the road.:up:

[Bill 84 318i]

Man, it's one thing after another for you, Fred. I'm sorry man. The compression thing is great news though!

Is it out of line to ask how much power you put down before whatever happened happened?

[Stu]

Hey Fred---

I emailed my dad and copied/pasted what you wrote to the email. He will probably have a good idea of what it is. He will probably email me back in the morning, so I can let you know....unless you figure it out first.

I initially wanted to say a rod-bearing or a thrown rod. However, a rod bearing wouldn't make an explosive sound on failure, and you probably wouldn't be able to drive it on a thrown rod. Possibly a rear-main seal, but then you'd be dumping oil. So my guess is as good as yours. :?

[M3 Ryan]

sounds like an exhaust leak to me... check the manifolds for leaks and see what you can find, you might have cracked something there...
sorry to hear it bro, good luck!!

[Ryan Stewart]

yeah, my dads manifold gasket blew on his chevelle and it sounded like what you described. Driving down in low RPMs it sounded like the injector tick but really loud. IT took a long time for carbon to build up before he could tell It was the manifold gasket.

[Stu]

Hey Fred--

My dads input: "Check for a broken inner valve spring, or problems with the spring retainer washers. Check for coolant leaks and tension on the cam drive belt. Check oil pressure. Have him call me in the shop with the results."

[Jonathan M3]

I would definitely check your exhaust maifolds for a leak. They almost always make a ticking sound when they leak. With the engine running, carefully put your hand down in the area of the manifolds and see if you feel any blasts of warm air hitting your hand.

Does the car seem to run fine otherwise besides the ticking noise?

HTH

[Fred]

Bill, I honestly don't know what the numbers were. I glanced at the screen, but I didn't really pay attention to what it said. The guy didn't give me a printout, so maybe I'll head back there later.

Stu, thanks man, I really appreciate you asking your dad for me. I didn't really check out the inner valve springs, so I'll take a look at that today. There any coolant in the timing cover area, though I will also check the belt tension. Oh, that reminds me. Right after it happened, there was a weird smell coming from the cylinder head area. It was sort of a mix of a burning coolant smell, but very faint. :?

Hopefully it is something as simple as an exhaust leak. I'll go back and double check to make sure, but I'll keep everyone posted...thanks a lot guys.

Fred

[Digitalwave]

Hope you work it out... I'd like to hear the numbers!

[BrianF 88iS]

Ya that didnt sound good. But once you do get it fixed and get the numbers, could you show us?

[SickE30]

Not to be an ass guys. But I doubt he really gives a shit about the numbers right now.

[AdamF 88iS]

Pressure test the cooling system. It's simple enough and will give you an immdiate answer. If you can smell coolant then I would suspect a head gasket, or cracked head.

Maybe you can get one of those inditcator tests where it changes the color of the coolant if there's hydrocarbons present in it?

[Bryson]

if the tick is only under load on the engine (ie. accelerating), there's a good chance it's an exhaust leak.. usually exhaust leaks won't tick when free revved, unless maybe they're uber leaks
hth