18R-GEU rattle at 4000RPM?

[Rcubed]

Hi,
My son has an 18R-GEU in his Celica. It blew a head gasket, and during the repair we noticed a small groove from pot #1 to water jacket. So the head was milled. All gaskets were replaced. It has all been put back together and seemed to run fine. Recently there is a strong rattle which starts at about 4000RPM and seems to come from the exhaust side of the head.

We have checked the cams [no1 @ TDC and the cam grooves are both vertical], timing chain tension, various ancillaries have been discounted [alternator, A/c], it doesn't sound like broken rings or spun bearings [have had both].

The noise doesnt happen at idle, nor does it become louder. It seems to be quite distinct RPM threshold which starts the noise. The power seems normal. The sound is similar to loose change rattling, but pinging doesn't seem to be it and it is distinctly from the exhaust side of the head.

Before we take it apart, can anyone suggest causes, and things to check?
Like valve springs, shims or other obvious stuff?

Cheers

[Omegaman]

i'm inclined to think the shims need checking.
i know that you need to replace the shims to the same buckets when rebuilding, as the wear is different on each lobe.
So check tolerances there. Also spring collets may have come loose.? justa thought!
Maybe also check chain tensioner has been primed with oil, before refitting.

[RA35GT]

Sure it't not just an exhaust leak or something?

Does it make the noise in neutral if you rev it up?

I'd imagine if it was anything valve train related it would make noise nearly all the time.

Maybe a recording would help?

[crowncustom]

Possible gudgeon pin rattle.
Cheers Brett.

[Rcubed]

The car has been run for about 300km before this noise became apparent.
Pretty sure it is not exhaust leak as it is metallic and has a distinct start RPM and occurs whether driving or in neutral.
The tensioner was also reset, but there would have been oil pressure rattle at low speed?
I'm also inclined to believe it is shim or valve spring related. Although I'm sure he was careful when replacing valvetrain components, a lot of them look the same.
Thanks for the suggestions - please add if you have any more!

[Rcubed]

Sure it't not just an exhaust leak or something?

Does it make the noise in neutral if you rev it up?

I'd imagine if it was anything valve train related it would make noise nearly all the time.

Maybe a recording would help?

How would you make a recording? iPhone doesn't really do a good job and filters a lot of the noise?

[youngster666]

Checked valve clearances all are set correctly

[71TA22]

Is the exhaust pipe strapped to a mount at the engine/gearbox flange?

Standard factory pipes have a resonance which this mount cancels out.

[RA35GT]

How would you make a recording? iPhone doesn't really do a good job and filters a lot of the noise?

I assume you dont have anything besides an iphone?

Could try holding the phone further away, or muffling the microphone with something


Could it be a valve spring let go? (assuming it has duals, maybe one of them has broken?)

[jabbatron]

..........

[youngster666]

As said yesterday valve clearances are all correct

It has extractors and there is no mount to gearbox

Springs had come to mind but trying to eliminate as much as i can before i have to take the cams out again

[Rcubed]

Thanks for the brain power guys!

Hey Mike,
It looks like we have to take the cams and look at valves/springs.
BTW have you taken compression?
I know the plugs all look normal

As said yesterday valve clearances are all correct

It has extractors and there is no mount to gearbox

Springs had come to mind but trying to eliminate as much as i can before i have to take the cams out again

[JustenGT8]

Just check for a cracked bracket before pulling it to pieces. The right resonance will make it vibrate and they can make all sorts of noises. Had similar on my turbo 18rg once and had us scratching heads for a while as the crack was hairline and not easily spotted, but sounded like detonation at 3200rpm

[ian]

this may be a longshot but pull the dipstick out and try revving it again
i have seen issues like this on other engines and it sounds terminal ,
i bought a so called stuffed 327 fuelie chev engine for $300
as the owner had just spent $2000 on a rebuild only to have a rattle appear at 1500 rpm
all that was wrong, was the dipstick was touching the crank

[MorgzMods]

I had a high pitched 'pinging' that sounded like valves after I put extractors on an 18rc. It wasn't noticeable until higher revs (about 3.5k) when the paper gasket the mechanic used blew out it was a lot more noticeable.

After using a metal gasket for the extractors and tensioning up all the bolts it's a lot less noticeable. I had two mechanics tell me it was something to do with the valves. Check the easy stuff first mate