Under the Hood There Arose Such a Clatter

"Urambo Tauro" (urambotauro) 05/07/2018 at 12:00 • Filed to: saab story, saab 900, project, wrenching

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We shut off the engine to see what was the matter...

Exhaust parts are here! New tailpipe, mufflers, catalytic converter, gaskets, and hangers.

When we picked up the car from Ron’s, the Saab’s exhaust had already rusted off. I threw the cat/midpipe/muffler into the bed of my truck, but once the car was home we realized that we were still missing the tailpipe and other muffler. Oh well. Probably not worth going back for anyway.

Upon closer inspection, not only were the rubber hangers shot, but the bolts holding the cat to the downpipe had rotted away. Unfortunately, there was little left of the cat’s flange to fasten it to the downpipe anymore. And because of the cat’s very short neck, we didn’t see a way to reattach it if we were to cut the old flange off...

The downpipe flange didn’t look all that great either, but there was enough metal left to do the job, so we kept that and the old mid-pipe while firing the parts cannon on the rest of the exhaust.

While waiting for parts to come in, we removed the down-pipe from the manifold, put it in a vise, and wrestled the oxygen sensor off. I chased the threads before putting it back in with anti-seize. No need to replace it yet, but when the time comes, it should come off easily with a wrench, without having to remove anything else.

While the down-pipe was off of the car, we found a tiny pinhole by the rusty but serviceable flange, and got it welded back up. Good, for now.

Until now, we had been running the engine straight-piped with a dryer hose hanging outside the garage. It was great to hear the engine roar to life, but the exhaust note is really nothing to write home about. We’d been looking forward to hearing it with mufflers on.

So with the mostly-new exhaust all bolted up, we ran the engine again. It needed a little persuasion with the throttle to get running, but hey it hasn’t been run in a few weeks anyway, and once it warmed up a little,it easily sustained itself.

We let it do a full warm up, allowing it to open the thermostat and cycle the cooling fan on and off. Once it was up to temp, we decided to rev it a little. Not quite all the way to its 5500 RPM redline, but a modest 3500. Y’know, enough to simulate everyday driving.

*BOOM tinkletinkle*

Shut it off, shut it off! I shouted to my brother.

WHAT. was. that?

From the driver’s seat, he said it sounded like a hose *pop*ping off. But from my angle next to the engine, I thought it sounded more like something shattered. Something metallic, with tiny bits falling down somewhere... The noise lasted only for a second or two, and the engine seemed to return to normal in the brief moment it took for us to react to the noise and shut it off.

We pulled both dipsticks- but found nothing out of the ordinary. Unsatisfied, we gathered up enough courage to start the engine again, fully prepared to turn it off IMMEDIATELY. But the noise never returned. Everything was back to normal, it seemed. We were hesitant to bring it back up in revs to where we had it before, but we gently poked it up to aroudn 2000 RPM, and ran it through the gears. Well, except for 5th. We’ve not been able to move the shifter into that position yet.

We’d known about this 5th gear engagement issue for a while now, and our plan was to pull one or both of the side covers on the transmission to inspect and hopefully see what the issue was. Now, it would seem that we have even more reason to look inside.

Side of transmission, underneath engine

But we’re not even sure if it’s the transmission. Could be the engine. The noise was so brief that I wasn’t able to locate it before it disappeared. So it looks like we’ll be giving the engine an early oil change too.

Part of me wants to find nothing out of the ordinary. But another part of me needs to know the answer to what happened here. Could it have been some rust flakes breaking free inside the clutch housing? There’s already a scattering of rusty crumbs on the floor underneath the engine from other wrenching. Guess we should have kept that mess swept up, then we’d have a better idea.

So I guess our next step is going to be to drain the oil. Both the engine, and the transmission. Might as well cut open the oil filter too, and have a look inside. Ugh. Wish us luck.

OPPOsaurus WRX > Urambo Tauro 05/07/2018 at 12:19

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Check the fan for damage. I’m thinking you left something in the engine bay that feel and hit something moving

Urambo Tauro > OPPOsaurus WRX 05/07/2018 at 12:21

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I would LOVE for it to be just a fan blade. But I don’t think the fan was cycled on at that moment. But we’ll check it out anyway.

OPPOsaurus WRX > Urambo Tauro 05/07/2018 at 12:35

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really anything that moves, it could have bounced off a belt and just ricocheted around sounding liek u described

MM54 > OPPOsaurus WRX 05/07/2018 at 12:35

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This is a possibility, the revs knocked something into the belts or fan or such, which made a noise as it fired off then clinked down to the floor (or lower in the car never to be seen again)

Urambo Tauro > OPPOsaurus WRX 05/07/2018 at 12:40

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Well in this case, the belts are against the firewall (it’s a Saab thing), nowhere near the fans. I thought at the time that it sounded like it happened inside a confined space (like inside the engine, trans, or behind the clutch cover), and that it was somewhere central in the engine bay, and not towards the very front or very rear.

But I’m second-guessing myself like crazy, since the noise was so brief. I kinda want to hear it again, but I also REALLY don’t want to hear it again. 

TheRealBicycleBuck > Urambo Tauro 05/07/2018 at 13:28

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“Under the Hood There Arose Such a Clatter”

There’s your problem. Ladders should be transported on the roof, not under the hood.