help diagnosing engine noise?

[randyoo]

So, today I checked out a sweet '97 H22A Prelude in mint condition. Everything seems perfect, except for the motor. It's got a nasty tapping noise from the valve cover area, almost sounds like a diesel. You can hear it for yourself here:

http://www.youtube.com/watch?v=LWVyasVYZOk

I was able to drive it around the parking lot, but couldn't take it on the road, no chance to engage VTEC, but seemed to run fine in the lot.

Dealer claimed that the noise happened suddenly as he was driving, but that the shop couldn't tell him anything without taking it apart. Price is at least $1,000 under market...

I'm a decent home mechanic (managed an engine swap on my own a few years ago), but I'm not too good with noises. Any ideas as to what this might be? Simple valve adjustment? Cam bearings? I noticed two empty bottles of oil in the trunk: not a good sign. No evidence of smoke in the exhaust, or valve cover gasket leaks. No CEL, either.

Worth the gamble? Thanks for your ideas!

[spiffyguido]

That sounds metallic to me. If it's coming from the valve cover area, it's probably a valve rocker slapping the lobe of the cam. Hard to say what may have caused this. Adjustment nut coming off?

The engine doesn't sound like it's knackered, but I would give it a thorough once over (valve cover off, check everything, etc) before you take it for a drive anywhere.

Proceed with caution.

[randyoo]

The car was so cheap that I figured worst case, I'd just swap the motor out. So, I went ahead and bought it. Well, the dealer delivered the car to the house, and I pulled the valve cover off right away, and it looked like a chocolate milkshake in there.

The coolant reservoir and under the radiator cap looks like there's no oil in there, but based on the empty coolant bottles in the trunk, I can only assume that they refilled the coolant just prior to me checking the car out.

At this point, I'm having a hard time deciding if I should replace the head gasket, and try to track down the cause of the noise, or just swap in a good motor. I'd hate to waste time and money replacing gaskets, belts, etc, when it could be a cracked head or block. Also don't know how much the previous owner ran it in this condition, and the potential for bearings to be shot...

Does coolant in the oil help with figuring out where the noise is coming from? There weren't any adjustment nuts missing, haven't found my feeler gauges to do a valve adjustment yet.

I've also heard of a bad oil cooler causing coolant in the oil, but haven't really seen mention of it on Prelude forums. Anyone have any experience with it?

Advice and feedback are definitely appreciated!

[spiffyguido]

Coolant in the oil usually means a bad head gasket. There are other possibilities, but that's the common cause.

If it were me, I would probably make an attempt at finding out what was causing the problem. The easiest route is obviously to just swap in a good motor, but if you can quickly figure out where the trouble stems from, making repairs may end up being cheaper.

At the very least, you're going to have to tear down the engine to the head gasket. You might find the problem on your way there.

[randyoo]

Thanks for the advice. I've ordered a head gasket kit, water pump, timing belts, etc. I got part way through pulling the head off, when I got sent on a last-minute trip. I couldn't duplicate the noise by cranking the engine by hand, and all of the valve rockers looked okay, adjustment nuts were in place, cams, etc, all looked okay to my untrained eye.

I'm really hoping that by draining the contaminated oil out, cleaning the head, and getting good oil back in there, along with a valve adjustment (as well as the manual tensioner installed), that *hopefully* the noise will be gone, as well... Otherwise, I'll have to do the motor swap, and I can use all those parts on the new motor (except the head gasket, of course).

Meanwhile, on this trip, I'm using all my free time reading up on the work ahead of me, since I've never torn into a motor before, aside from a valve cover gasket or two.

Thanks again for the advice you've already given!

[spiffyguido]

No problem.

Keep us updated on how things turn out. I'm interested to hear what was wrong with this particular engine.

[prelude95]

what i would do is take the valve covet of and inspect for loose parts n turn the cam to see if anything is rotating out of normal.