Noise on startup

[Dime]

I haven't started the car for 5-6 weeks. Start it this morning and heard a knock for a few seconds until oil pressure built up. Went for a drive with my dad and it never did it again on start up. This is the only time the cars ever done it, and it's the longest the cars sat with out being started since I've owned it.

Any ideas what it was, and should I worry, or is it normal?
Lack of oil until pressure is built?

[Z51JEFF]

Cam chains,the oil has drained from the filter and it takes a few seconds to pump up.The Bosch filter has a better check valve than the others on the market and it holds oil a little better.

[ScottZ95ZR1]

Cam chains,the oil has drained from the filter and it takes a few seconds to pump up.The Bosch filter has a better check valve than the others on the market and it holds oil a little better.

Marc's latest oil filter recommendation states he has found that some recently produced Bosch filters have leaking anti-drain back valve.
Read it here:http://www.zr1specialist.com/HAT%20Web/articles/Oil%20Filter%20Recommendation%20Update%202011.pdf

[mike100]

I bought mine at 27k miles and it didn't do it, but 5k miles later and some different oil filters, it finally started up with the noise. Really nothing has to be done about it, but you might be able to find a new cam tensioner to fix it,

[GOLDCYLON]

I bought mine at 27k miles and it didn't do it, but 5k miles later and some different oil filters, it finally started up with the noise. Really nothing has to be done about it, but you might be able to find a new cam tensioner to fix it,


Only if its the ugraded RH Cam Tensioner which allows the oil to pool a little

[VetteMed]

It's more an annoyance than a real problem. The chain guide is tapping against the cylinder head. The chain is not subject to any additional wear.

[Dime]

That's what I thought (or hoped) it was. I never heard it do it before. It was a lot more racket than I expedited chain rattle to be. I was wondering why other owners complained about chain rattle. Now I know. I'm just glad it has only done it this that one time so far. Hopefully I'm lucky enough that it will only do it after sitting for a long period of time.

[RHanselman]

I've never heard the chain make a knocking sound it's always been a rattle... You know it could have been the DMF. It can knock until the engine smoothes out...

[Jagdpanzer]

Here are a couple of excellent tech articles Marc Haibeck wrote on the subject of the LT5 cam drive.

http://www.zr1specialist.com/HAT%20Web/articles/Upper%20Camshaft%20Chain%20Guide%20Facing%20Failur es.pdf
http://www.zr1specialist.com/HAT%20Web/articles/Start-Up%20Engine%20Rattle.pdf
As our engines gracefully mature we need to be especially mindful about the condition of the upper cam chain guide strips as Marc points out in his article. Failure to maintain the upper guide strips will lead to the breakage of cam chains which otherwise would have served reliably for many more thousands of miles to come. I know of two recent cam chain breakages on higher mileage LT5s due to this issue. An expensive headache that one should avoid.

[zrwhat]

I know its not a end all, cure all but when mine sits for extended periods of time, I spin off the oil filter, dump some oil down the center cavity of the filter housing, spin the filter back on and start up, without doing this, I would get momentary chain rattle, by adding this small amount of oil, chain rattle is not heard or detected on a start up after extended inactivity.

My guess is this oil going to the pick up tube fills quickly and fills the oil filter much faster.

Has anyone ever done a oil filter relocation on a LT-5 where the filter sits in a right side up position and is always full and can't drain back , this in itself should slow down or stop the "Dry Filter Syndrom" and either slow down or stop this momentary rattle of the TC's......

Gibby

[Dime]

So, anything to be concerned with, or completely normal?

[Daniel_Mc]

Just a thought but could you plumb an Accusump system in to pre-oil the motor? I'm not sure how much modification would be involved.

Daniel

[Kevin]

chain rattle on start up, normal. after that, you may have a problem