Piston Slap? Help Advice please!

[drunkenmunkey 0]

My VR makes a very worrying noise on start up :? , particularly from cold -

 

It clatters/rattles all the way up to 3000rpm, beyond that it's fine and it's also fine when it's warm. Could it be something to do with the tensioner - chains were changed 20k ago. Does anyone have experience of this? If it is slapping what's gonna happen?

 

Thanks

[dinkus 10]

The pistons slap on mine and I've heard quite a few others do it when cold to.

 

I think it's just what old, tired VR's do :(

[eatthis 0]

if u make a habit of takin it over 3k rpm when cold its probably piston slap mate

what parts were changed when the chains were done ie were all the tensioners changed??

[drunkenmunkey 0]

I've only just bought it and didn't notice it at first. It was James's [CorradoVR6nos] car at some point & he did all tensioners as far as I know, along with the clutch, piston rings, shells & head rebuild.

 

Dinkus could you describe to noise you get?

[dr_mat 0]

I'm told by the erstwhile mr cheesewire that even new VR engines have a little bit of piston slap when cold ..

[dinkus 10]

It's a sort of clattering - sounds almost diesel like...

[drunkenmunkey 0]

Yep! Sounds like what I have, from what you guys have said it sounds like it's just an acceptable part of VR ownership - should I worry about it?

[dinkus 10]

Nah, just keep it under 3k rpm until it warms up (80ish on the oil) and then thrap it senseless :)

[drunkenmunkey 0]

:D Awesome, thanks guys :D

[CorradoVR6-Turbo 0]

Nah, just keep it under 3k rpm until it warms up (80ish on the oil) and then thrap it senseless :)

 

thats the advice we need here! :lol:

 

But i would budget for a rebuild at some point,the VR piston slap can kill innocent VR engine's,dont waist another V-soul!

[dinkus 10]

Shhh, I'm trying to be positive :lol:

[2_Door_fun 0]

Nah, just keep it under 3k rpm until it warms up (80ish on the oil) and then thrap it senseless :)

 

I always make sure I'm warmed up..Then thrap it senseless :oops: Oh the engine !

[drunkenmunkey 0]

Bugger! :shock: Thought I was going to get away with it there :wink: , when you say rebuild what should I budget for? Excuse my ignorance I've never rebuilt a bottom end before - can I look out for a 2.8 bottom end, have in overbored & slap on some thicker piston rings? :)

[dr_mat 0]

You will get away with it. As we said, all of 'em do it.

 

It's just generally good advice to budget for a rebuild, because these cars are old and nearly dead.. ;)

[Jim Bowen 1]

mine sounds a bit knocky and diesel like on startup, only lasts a few minutes tho

 

i'm not overly concerned tho, drives fine

[dinkus 10]

Yeah, mine only does it for the first minute or two after start up.

 

It still made 200bhp on the rollers, so I'm not in any rush to rebuild it...

[drunkenmunkey 0]

Cool, I'll budget for a rebuild then, but not just yet there's still some thrashing to be done :D

Thanks

[Roger Blassberg 0]

Sounds like I'm not the only one with this then. Mine (206k miles) does exactly the same and has done so for at least the last 35k. to my certain knowledge.

 

As others have said, it goes away completely after the engine has warmed up, presumably because the piston skirts expand and take up the clearance. I just take it very steadily during the warm up period and it hasn't got any worse for quite a while. Plugs are staying good and clean and there is no excessive smoking or oil consumption so I assume that the oil control rings are still in reasonably close contact with the bores (!!).

 

And on these cold damp mornings she absolutely flies.

 

Best wishes

 

RB

[Kevin Bacon 5]

Piston slap is normal when cold. 100s of different engines do it and that's a fact. My missus's Rover 25 1.4 16V has been slapping when cold from new, but it uses absolutely no oil at all between changes. So knocking noises are in no way indicative of the engine's health unless the engine is obviously f'cked. As Pinkus said, his slappy VR turned out 200hp and my own VR, at 73K and slapping, made 206hp with 199lb/ft.

 

Stock VR engines have a relatively slack (by modern standards) 0.010" piston clearance and bores 1 and 6 ovalise first, even as early as 60K, and those two give off the loudest slapping.....but as I said, that doesn't mean the engine is f'cked or the rings aren't sealing. It's just normal cold morning expansion, just ignore it.

 

You should hear a VR6 with 45 thou' clearanced forged pistons in the mornings if you think your cast piston slap is noisy :lol:

 

Larger bore tolerances = less friction and more power, simple.

 

Tight OE tolerances for low noise and vibration are for your dull family saloons...... if you want no noise on start up, I've said it before and I'll say it again.....Buy a Daewoo!

[dr_mat 0]

I think it's also because the pistons are made of a different alloy than the block - hence different expansion relative to temperature.

[Kevin Bacon 5]

Erm yeah, that's a very obvious statement for someone of your intellect :lol:

 

Pistons are an aluminium alloy and the block is a steel/cast iron alloy. Obviously the much smaller relative mass and density of a piston expands much more rapidly than a huge cast iron lump.

 

High silicon content forged alu' pistons expand faster than cast alu' pistons.

Engines like mine and Subaru's STI boxer motor are slappy for a lot shorter period than the cast mahles in a standard VR for example....

 

Don't forget that pistons don't actually form a gas tight seal, so although they're knocking around in the bores when cold, the piston rings are still doing the same sealing job cold as they do when hot.

 

It's best to just get in and drive the car..... don't warm the engine up on idle for X amount of minutes. Worn, ageing or forged pistons wobbling up and down the bore when cold at low rpms accelerates bore wear. This is why all this warming up from cold is a nonsense for long engine life. Just get in and drive the thing.....

[Guest]

I think it's also because the pistons are made of a different alloy than the block - hence different expansion relative to temperature.

 

:lol: :D

[dr_mat 0]

Was that funny? Perhaps I don't get it ...?

 

For sure it's a seemingly obvious thing to say, but my point was that in the context of this discussion it backs up everyone's statements that "this is normal" and not to worry about... And maybe not everyone thinks about this sort of stuff.. (My missus for example...)

 

Totally agree on the letting the car idle == bad thing on cold starts. That's (one of the reasons) why the book says you should get in and drive immediately rather than waiting for it to melt the ice you can't be arsed to scrape off the windscreen..

 

Glad to be of service, if I've amused anyone .. ;)

[Roger Blassberg 0]

The advice on just getting in and driving will change my winter behaviour as I have frequently let the engine idle for a few minutes in the cold weather. Many thanks. It should also have a beneficial effect on fuel consumption overall.

 

best wishes

 

RB

[dinkus 10]

I'm buggered if I'm gonna go scraping ice off the car first thing in the morning... well actually, as I walk to work now it shouldn't be an issue anyway :D