: '95 FWB "clack" at start up??



caddycruiser
03-15-06, 02:26 PM
Not a huge issue here, and I know every car has its own particular sounds, but I've been wondering about my '95 Fleetwood.

Sounds perfect cranking, but right as it fires and turns over, there's a semi-loud "clack" sound, almost kinda like a quick gun shot...well, sorta. Idles and runs as smoothly and quietly as a new Lexus almost, especially after having driven for a bit and being fully warmed up, but this odd startup sound always makes me wonder.

Any other LT1 FW person who's car has or did make a similar sound? Or, just any idea what it might be?

ocjmakaveli
03-15-06, 02:51 PM
you either need better motor oil

or its normal startup starter noises mine makes a noise like taht when its really cold outside almost as if the starter would stick slightly or something it hasn't done it lately though I was never sure about what the noise was.

Mine sounded like metal on metal contact very odd I was going to change motor oil to synthetic or heavier oil but it went away so I didn't

caddycruiser
03-15-06, 03:21 PM
Yeah, it's actually just a single "clack" and that's it. My father's been running it more while I'm gone, and he just said it was probably the way the starter sounds on that car.

Not really worried about it, just always wondered if that was a normal sound or what...though it does it regardless of temperature.

N0DIH
03-15-06, 03:50 PM
Change oil to 15W40 Rotella T and see if it goes away. If so, leave it in. I run 15W40 in Wisconsin year round, works fine for me.

caddycruiser
03-15-06, 04:27 PM
Yeah, I'll have to check on the oil. Dad changed it the day after I bought it, but I'm not sure which grade he used.

What, mechanically, then, likely makes the sound?

N0DIH
03-15-06, 05:17 PM
Hard to say not hearing it.

But my guesses would be excessive rod bearing clearance is #1 cause of engine cold start noise that stops as soon as oil pressure builds. Piston slap WILL NOT go away until the piston warms, it is not oil pressure changed. Next #2 on the list is main bearing clearance. Same result, will go away as soon as oil pressure builds. Now, eventually it won't go away, as once clearances get so excessive, it will rattle all the time, or take longer and longer to quiet.

Which is which? Tone of the noise. Mains are deeper sounding, rods are mich lighter in tone. Piston slap is different freq and will stop when the plug wire is removed from the offending cyl. BUT, so does rod bearing noise. Mains do not get affected by the plugs or injectors being shut down (some Cadillacs can do with the Cadillac V8 and DFI).

Running thicker oil helps, and will increase life, but ultimately work IS needed on the bottom end. Synthetic isn't a bad idea in my opinion if this is a problem and you don't have the ability to fix for a while. It might help bandaid it.... at least it won't hurt. But run thick, high zddp/zinc oil, Rotella T is claimed by the diesel community to have the most zddp, which is the anti wear additive, but Delo 400 and Delvac are also excellent choices. I recommend the CI-4 PLUS, not the plain CI-4. Something is different, so must be better, right? ZDDP negatively affects cat converter performance, so gas oils, like 5W30, 10W30, etc will have very little of. It coats the converter grids and degrades peformance.

caddycruiser
03-15-06, 06:00 PM
Yeah, see, I know all about that, and we had an '02 Avalance that had tapping piston noise at idle (as did most GM trucks from '99-03'ish), but this is NOT that.

It's just like a single decently loud "clack" kinda noise at firing. Nothing else before or after. Kinda like if you had a sheet of metal and just once, really quickly, smacked it with a hammer.

Still haven't checked them, but might it be something to do with a leak at either manifold (like if there's a missing/broken bolt or two?)? Wasn't sure, as I'm not too sure what something like that might sound like.

N0DIH
03-15-06, 06:28 PM
Lifter bleeding down? That is the next noise. The LT1's were known for some lifter clacking at cold start. Gets better once warm, but never goes away. That is more tick tick tick, and rythmic to one cyl operation.

With me running the 15W40, it has diminished a bunch, but it still there.

Can you determine which side of the engine? top? Bottom? Left? Right?, etc?

Exhaust will make noise that sometimes is interpreted as lifter/rockers.

Ahh, toss on some new springs and 1.6:1 LT4 rockers and call it done..... :)

caddycruiser
03-15-06, 07:31 PM
Lifter bleeding down? That is the next noise. The LT1's were known for some lifter clacking at cold start. Gets better once warm, but never goes away. That is more tick tick tick, and rythmic to one cyl operation.

With me running the 15W40, it has diminished a bunch, but it still there.

Can you determine which side of the engine? top? Bottom? Left? Right?, etc?

Exhaust will make noise that sometimes is interpreted as lifter/rockers.

Ahh, toss on some new springs and 1.6:1 LT4 rockers and call it done..... :)

No, it's just one single "clack" at fire and nothing more. No other sounds, no other vibes, just smooth and quiet as could be.

Just a single odd sound at fire...though, like I said, my father has been under the hood a lot more than me so far and said it's nothing more than the way the starter sounds on it. I couldn't tell, but that doesn't seem like it to me.