scary noise @ start

88911coupe · 09-18-2005, 05:53 PM

Not sure how to describe this sound but it occurs for a split second just as engine fires up. The car starts quickly as always but I am noticing this sound and it seemed louder tonight starting it with the widows open inside the garage. It sounds like a sharp metallic ripping or scraping and as I said, it's only for the briefest instant at the moment of start. Engine runs and sounds fine otherwise. It's got 150k and has never been open and is a little overdue for a valve adjustment, if that helps.
Any ideas...
TIA

VincentVega · 09-18-2005, 06:13 PM

Could be a timing chain hitting the case, a tensioner might be on the way out. Similar issue with my 3.6, replaced a tensioner and all is well.

Jeff Higgins · 09-18-2005, 06:21 PM

Yup; I agree with Chris. I just went through this. It sounds like your tensioner, since it is pressure-fed, might be taking just a moment to "pump up". Try this - have some one else fire it up while you sit behind it with the hood open. Put the blade of the longest screwdriver you have up against one of the chain cases, and your ear on the other end. Watch out for that fan! Have your buddy start it as you listen. You are using the screwdriver like a stethescope; a rubbing chain will sound very loud through it. Try both sides of the engine.

88911coupe · 09-18-2005, 07:04 PM

I actually already own a mechanical stethoscope so I'll just use that. I assume it will be loud as he!! if it's really the problem. If that's what it is is that something that requires engine removal and will it fail catostaphically or just get slowly worse?
BTW, thanks for the quick replies.
Later

Zeke · 09-18-2005, 08:44 PM

No, you can fix it with the motor in the car. A partial drop will make it go much easier. I'd do something about it right away. Anytime you hear something loud or unusual, something is wrong and it is not good to keep starting it.

Jeff Higgins · 09-19-2005, 06:58 AM

Actually, when I did mine, all I took off was the muffler and the tine between the rear motor mount and motor itself. Take the oil lines off, about a dozen nuts per cover, and you are there. It took me less than half an hour to dig down to the tensioners. No motor drop, partial or otherwise is required.

When you remove the tensioner, make darn sure the chain doesn't fall of a sprocket and cause it to lose cam timing. That will break your heart... I just zip-tied the upper and lower sections together where they almost meet. If you rebuild or put a new tensioner in, make sure you prime it before installation.

petrolblue83911 · 09-19-2005, 07:07 AM

I've seen a few of the pressure fed tensioners self destruct over the past 5 years or so, everyone should keep in mind that they aren't bullet proof. In fact, I know a few very good local wrench's who aren't replacing the old style with the carrerra tensioners anymore because they don't have faith in them anymore. They've been instead just servicing the old style tensioners every 15k miles or so, and doing any work needed...I switched to carrerra's my self, but I'm not sure I would if I could do it over again..

dtw · 09-19-2005, 07:44 AM

What about a worn ring gear...

Mike Bonkalski · 09-19-2005, 07:48 AM

I would also check the ring gear. I had similar noises and just replaced mine this weekend. Take off the starter and use a mirror and a flashlight to look for damage on the ring gear.

Jeff Alton · 09-19-2005, 10:10 AM

Or a sticking solenoid on the starter......

Jeff

911mot · 911mot's Garage

Sounds like a sticky starter to me too.
If you're brave wait till the cars cooled down and get someone to start car while you press you hand against the starter. You should be able 'feel' the noise if it's starter/ring gear related.

88911coupe · 09-19-2005, 12:27 PM

I was wondering about a starter issue as well since I'd had some odd no start issues several months ago that mysteriously went away. The sound seems to have diminished quite a bit today and does not happen every start...only occasionally. Would the tensioner problem happen every time or could it be sporadic as well? I'll have a look at the starter gear too. Sorry to sound stupid, but is the ring gear the large gear the starter engages with to turn over the engine?
BTW, is there a way to check a tensioner to see if it's funtioning properly? I undertand how they work but can I test them?
TIA

buttjoint · 09-19-2005, 01:58 PM

I don,t know about the 88, But the 89 had problems with the ring gear being too narrow, and had to be replaced. And yes the ring gear is the gear that the starter engages. Don,t try to look for it in the little peep hole in the bopttom of the trans because thats the gear the reference sensor uses. JIM

88911coupe · 09-19-2005, 06:05 PM

OK...I'll try the listen when I start it and if I hear a horrible noise on only one side it's safe to say that's the problem...correct. I'm assuming there's no way both sides should fail at exactly the same moment...right. Otherwise it looks like (hopefully?) a starter issue since I think that may be a liitle easier to replace.
Thanks,

88911coupe · 09-20-2005, 08:55 AM

Just to clarify...is there a way to visually check the ring gear? I get the impression this is not possible from the prevoius post.
Thanks

Mike Bonkalski · 09-20-2005, 09:36 AM

Buck,

Just pull the starter and look through the opening with a flashlight and mirror. Rotate the crank to look for damaged teeth. 911 motors tend to stop in three locations, so the damage (if any) should be localized.

88911coupe · 09-20-2005, 04:22 PM

I'm going to dig into this to see what I find but is it obvious if a tensioner is bad...how do I tell? Would I just be able to push the tensioner down real easily or what? I did the stethoscope test and it does not sound really that different side to side between left and right but since I have never heard the sound of them when started before I don't know that I have any reference point. It's really noisy but it seems like the whole engine is when I've used the stethoscope in the past.
TIA

88911coupe · 09-21-2005, 07:52 AM

bump...sorry...how can I tell if a chain tensioner is bad, will it be quite obvious, i.e. the gear is not pressing on the chain at all?

88911coupe · 04:34 PM

OK, sound got much worse today so had it towed in. After speaking with someone at Pelican (Tom?) who also has an '88 he's thinking it may be the starter since his car was doing the same thing. The problem is how the heck do you all loosen the 2 allen bolts on the starter? There does not seem to be enough room on the more visible one and I can't even begin to access the one on the upper side. I also assume the large wires come off after it's partially dropped since there seems to be no room to loosen the nuts holding them on.
Thanks

syncroid · 09-21-2005, 04:40 PM

I usually lower the nose of the transmission to get the clearance needed to R&R the starter. G-50 equipt cars are no fun to do a starter change on. (even if you have a lift)
My money is on the bad ring gear and starter as well. I changed both when I did my top end over haul last month.