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I recently picked up a 99 OBS 2.2 AT   126K   timing belt and water pump done at 104K   

It ran a little rough sometimes, but most of the time it was ok.  The check engine light was on when I got it, but went out shortly afterwards. There are no codes stored on the computer.

 

I was driving about 50mph and it started losing power, I was on a busy road with nowhere to pull over, the shoulder was filled with a mountain of plowed snow, so I tried to keep it going until I could get off the road, by the time I got to where I could pull over, I had it floored just to keep it moving. The engine was still quiet at this point.  As soon as I let up on the gas, it died. I tried restarting it and it cranked but sputtered and stumbled and would not restart.

  The temp gauge never went over half (don't know if it's accurate or not), and the heater blew hot air the whole time. The engine compartment smelled really hot. The oil level was good. I added about a quart of coolant.  

 After I let the car sit for about 45 minutes, I tried to start it again. It fires right up, but it sounds like someone is taking a hammer to the engine.  I tried moving the car to a better place, a parking lot instead of the side of the road, and it had very little power. 

 After having it hauled home on a flatbed, I pulled the accessory belts, still the same noise.  I pulled the timing cover and the noise didn't get any louder. The timing marks are still lined up, and I put a stethoscope on every non moving part under the timing cover, including the bolts on the idlers, Noise isn't coming from there.

 I pulled spark plug wires one at a time, it changed the idle of course, but that's all. No one plug wire made a difference in the sound other than slowing it down a little. 

   

 What do you guys think? main bearing?

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Why was it a quart low on coolant? Was the reservoir empty? What was the code it was storing?

 

If it's knocking really bad, it's probably a main bearing. Best bet is to drain the oil, BUT, go and buy a strainer with a metal screen (or get some metal screen at Lowe's with a fine hole count). Drain the oil COLD and let it all pass though the screen. If you see a bunch of glitter or chrome/copper looking specs, etc. it's safe to say a bearing got chewed. I'd pull the pan at that point and inspect the connecting rods (w/o unbolting the caps) and see if they are really loose or if you might have a snapped connecting rod.

 

It's possible the engine isn't original, or got a hack replacement job, etc.

 

 

Also, with the timing cover off, does the belt tensioner bounce? That can cause a knocking too, but I forget which year they started using those.

Edited by Bushwick

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I put about a quart into the recovery bottle. not sure why it was low. 

It didn't store a code. I'm not sure why, I figured since the light had been on, that even though the light was off, that there should have been a stored code. 

If it's not stupid cold I'll drain the oil tomorrow and strain it and report back. 

The belt tensioner isn't bounching.

 Can the oil pan be pulled while the engine is in the car?

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Main bearings don't knock. You just get low oil pressure, which then leads to rod bearing damage, and that makes all the knocks.

 

Loss of power and then lots of noise is either jumped timing or a rod bearing eating itself. Time to drain the oil and look for chunks and sparklies.

Cut open the oil filter and look in there too.

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always check the oil and add if needed. Subraus use oil, this is a fact of life.

thanks, I had been keeping an eye on the oil. The level was good

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odd thing, not sure if this means anything or not. I got a better stethoscope today. And I noticed that the sound is just as loud on the right head as it is on the block. And with the scope on the front edge of the head right up by the valve cover mating surface, I can hear a metallic kind of timber to the sound, a brighter, almost ringing tone amidst the knocking sound. Is this just bottom end echoing through the head, or is a sign that the problem is inside the head?

 And I don't know if its just because of acoustics, but, the loudest place for the noise is on the intake manifold. Is that just the bottom end noise echoing through the hollow intake manifold, or is that a sign of something else?

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Those heads do seem to have trouble with the dropping valve guides. If one of those has lossened it would hang the valve open and cause power loss. And would cause a tapping sound since there would be excessive clearance between the valve and rocker arm.

If it hangs open far enough it could hit the piston.

 

Pull the valve cover and check valve clearance.

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pulled the valve cover anyway, haven't checked clearance yet, too cold outside, the lock was frozen on the shed and I couldn't get to the feeler gauges, LOL

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You don't need feelers. If the lash is great enough to make a noticeabley loud tap the clearance will be HUGE!

Turn the engine over and compare with the cylinder next to it.

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doesn't seem to be any excessive lash in the rockers

not sure if this matters, but I just drained the oil and strained it.  Couldn't find my strainer or any screen, so I used a t-shirt, boy that was fun, LOL.
 Anyway, there was a SLIGHT, very slight hint of sparkle in the oil, small enough that it went through the shirt, if you look at the oil at just the right angle, you can sort of see really fine sparkle.  It doesn't show up in pictures. A rod bearing would have left more than that in the oil right?

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A very small amount oflateral play is acceptable, but there should be springs on the rocker shaft to keep the rockers in position. Of you can move it side to side more than about 1mm there is a problem.

 

Any glitter in the oil is a cause for concern. I would still cut the oil filter open and see what's in there.

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There should be a spring "wave" washer between the rocker and the support bushing that is bolted between the rockers for each cylinder on the intake side. I can't find a good picture of it online.

Check between the rockers on the other cylinder and you should see them. Those washers have a tendancy to break in the middle and fall off. They just settle to the bottom of the oil pan out of the way, but it can cause issues with wear on the valve stem because the rocker is not held in the correct position without that spring.

This doesn't typically cause a lot of noise, unless it has worn the valve stem so much that it pushes the valve sideways as its opening. It might make a click or snap noise as it starts to push the valve open, then again when it closes.

 

Put a drain pan under the head and start the engine and see if the rocker is knocking around.

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Everything looks good with the engine running. And the noise isn't any louder without the valve cover on. This tells me that it's not in the valve train

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Main bearings don't knock. 

Sorry, I was referring to the connecting rod bearings on the crank.

 

I think I have more than 1mm. And I'm not seeing any spring.

Did the video of the side play work for you?

It's not a traditional "spring." It's a flat piece of metal that's formed with contours (think of an "S"-like shape) that keeps some tension on the rocker IIRC. If you decide to ever pull the rocker assembly, it's something like 8 bolts, then the entire assembly lifts off. Very nice and simple setup. You'll need to remove an extra screw to get them off the rocker arm shaft.

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