Start up rattle on 4200 - With sound

[hashluck]

On Aston Martins you used to be able to turn the engine without it firing (by flooring the accelerator) to build oil pressure after a period of storage, all detailed in the Owner Manual. No longer an option for whatever reason. Audis will also rattle away if stored a while Hydraulic tappets oil drains away.

 

[TimR]

My Yamaha MTO1 with hydraulic lifters has been prefect for over ten years and 60K miles...
Ive probably just shot myself in the foot saying that because they do fail. Having been around them for a decade, it's seems it is a common enough occurrence...!

 

[allandwf]

Turning it over on, or off, is surely just that, builds pressure both ways and both still effectively operating dry variatiors?

 

[TimR]

The energy involved under starter motor speeds is massively reduced is my guess....
Anything I can do to reduce the unwanted friction of banging around is better in my view..
But technically, you are right. Its dry, its friction, its not designed to work like that !

 

[CatmanV2]

The energy involved under starter motor speeds is massively reduced is my guess....

I struggle to see that the wear is defined by anything other than engine speed. No idea how turn over on the starter actually compares to (say) idle?

C

 

[Zep]

I struggle to see that the wear is defined by anything other than engine speed. No idea how turn over on the starter actually compares to (say) idle?

C

Engine speed, oil film thickness, clearances. Even if there is no oil pressure, it won’t be dry, but the cushioning of the oil makes a the difference. Starter speed is probably 10% of idle speed.

 

[Andy4200]

OK, here are a couple of recordings. Hopefully it works, I'm not very tech savy.
The first is cold, not having been run for 1 week.

The second is after running it for about 2 minutes, switching off and firing up 5 mins later.

Please excuse the state of the engine, it's work in progress!
Use headphones for the full rattle effect.

 

[allandwf]

We don't need headphones!

 

[TimR]

We don't need headphones!

Look..Im no expert - but that does seem prolonged.
Put it another way- I probably wouldnt buy a car that presented with so much noise, whether I knew what it was or not !
Take it to a specialist and see how worried they are..?
Otherwise it's £2.5K in parts to replace variators, solenoids and oil bag...

 

[TimR]

I struggle to see that the wear is defined by anything other than engine speed. No idea how turn over on the starter actually compares to (say) idle?

C

As Zep points out- its the presence of oil ( under pressure) that's the thing. Wear aka damage, must surely be happening to some degree until oil pressure cushions the moving bushing..which was allandwf's point I think. Sure...turn it over x number of revs @ idle ( 1000rpms) or at starter motor speeds...(100rpms?) I know where i think the more damage occurs. But Im dumb...You can ignore me. Or educate me...!>!

 

[Andy4200]

No, I appreciate your thoughts.

I must admit I didn't really notice any noise when I bought it. Well maybe a bit but I knew they had a slight tendency for it.

 

[jasst]

Sounds like a diesel to me!!

 

[Evo Cymru]

Hmm - no expert either but that does seem prolonged to me. Mine rattles for a few seconds if left for a week or so but not as long as that. I have mitigated in the short term by removing the fuel pump fuse and turning over on the starter for about 5 secs which seems to stop it although I was planning to investigate further in the winter….

 

[TimR]

I reckon that sounded like @ 9 secs....
Presumably, the dash pressure gauge shows minimal pressure and reaching 5 bar @ 9 secs also...
Just wondering if its possible you have a weak oil pump ?

 

[Zep]

It doesn’t sound happy.

What is your oil pressure like?

Perhaps @conaero and Ash can have a look at this.

 

[CatmanV2]

Engine speed, oil film thickness, clearances. Even if there is no oil pressure, it won’t be dry, but the cushioning of the Starter speed is probably 10% of idle speed.

As Zep points out- its the presence of oil ( under pressure) that's the thing. Wear aka damage, must surely be happening to some degree until oil pressure cushions the moving bushing..which was allandwf's point I think. Sure...turn it over x number of revs @ idle ( 1000rpms) or at starter motor speeds...(100rpms?) I know where i think the more damage occurs. But Im dumb...You can ignore me. Or educate me...!>!

Yes, sorry. Oil is obviously important But not 'energy' per se which is I think where I was coming from. Seems a long time ago.

I'm not sure I can educate you, but Zep's observation that starter is 10% of idle (so about 100 RPM) is probably most cogent.

I think the critical physical factor here is impulse.

C

 

[Andy4200]

I'll check the oil pressure tomorrow with another cold start. Fairly sure it comes up to 5 Bar pretty quickly.

 

[allandwf]

Pumps don't generate the pressure, it's the clearances between parts and restrictions, hence it drops when they wear. You could have excellent pressure yet still be starved in parts. Not quite as simple as having a decent healthy reading.

 

[TimR]

With the pump spline corrosion seen recently, IIRC ( & my memory isnt what it used o be..!) wasnt the pressure in slow decline until it dropped to catastrophic zero..?
That's why I ask about pressure...because of the shear length of time taken to pump adequate oil volume to the noisy variators in this case. I would anticipate that pressure reaches normal when the variators are quiet..
It tells you 'something' if the pressure reaches 5 bar quicker than the variators are silenced I think... very much along the lines of the above *38
Not sure what you can draw from it for certain however....

 

[Andy4200]

Has anyone got any good news?