Before posting this, I checked sticky threads and searched the forums. My 2006 V8 Vantage 4.3L has started making a brief rattle sound at cold startup. It lasts for about 1 to 2 seconds and goes away. On subsequent starts, it doesn't rattle. Could it be a timing chain tensioner (oil pressurized?) or hydraulic valve lash adjusters (also oil pressurized) losing pressure overnight, and getting pressurized at startup? Should I be concerned? I know that some very brief rattle at startup is normal for some cars but this is new to my car. I've owned it for about 18 months and drive it every two weeks. About 43,000 miles on the clock. Thanks!

 

What oil are you Using?
My merc AMG did it after about 10000km and dealer said it was oilpressure drop when standing overnight related to the valve lifters, said it was normal did over a 100k in it never missed a beat.

 

Mine does the same, (06 V8 Vantage, low milage) and I'm 90% sure it's the hydraulic tensions for the timing chain. I understand the older cars use plastic cased tensioners which crack, newer cars have alloy. There are kits around with all the parts, it's the same parts as the Jaguar engine it seems. I plan to take mine apart and change out the parts over the coming winter, there's good how to guide on the Jag engine on youtube.

To guess if it's the tensioner vs a lifter I suggest the following process, note the rpm's are a bit of a guess as obviously it's building as the noise disappears.

Tensioner: Let's say 70 chain links, engine turns at say 200 rpm under the starter, so the noise should be 233 'rattles' per second, so a pretty fast brrrrp kind of noise.

Lifter: (lets assume only one has gone), 1 lifter, at 250 rpm, so 4 'rattles' per second, so quite a slow sound.

It's pretty easy to tell the difference. I recorded mine and slowed down the noise on the computer.

A second test, use the instructions in the manual to crack the engine without starting, (key off, accelerator to the floor, key on, clutch in, press start button, crank until oil light goes off.Then key off, to end. Start normally after this It should start silently if it's oil pressure related.

I'd love to hear if the rest of you agree with my process here.

 

Also I'd add that on my last couple of oil changes there have been tiny flecks of yellow / brown colour plastic in the oil, this is the colour of the chain tension shoes pressed into the chain by the hydraulic tensioner. A loose tensioner on start would allow the chain to drag on the tensioner briefly knocking little bits off.

Again I'l only making an educated guess here.

 

Really interesting thread. Do we know which year Aston switched to the alloy tensioner?