Strange very light metalic rattle on startup?

[bobbyh]

Sounds like a heat sheald resting on the exhaust.

Had a quick lie on the floor and tug of exhaust/heat-shield and everything looked and felt ok.

The car has been pressed into daily smoker duty, untill I can get something more suitable. (Had company car in previous jobs.)

It quietens down when hot? Very odd, but sounds very embarassing when starting up after work with new collegues around!

With the dark evenings, it's not possible to look in the evenings, anyone had similar symptoms?

Cheers.

[PW@Woodsport]

Could be one of many things to be honest, but one of the possibles is a cracked exhaust manifold, they make a metallic noise on startup and the crack "heals over" when the engine heats up and the noise goes away.

Fits your symptoms spot on, but it could be literally anything.

[pk_090]

Wouldnt this blow aswell though Paul?
Alex

[JMR_AW11]

I had a mk2 golf where the manifold developed a slight crack.

It drove me potty trying to find out what was causing the noise. I ended up fitting microphones to the engine to try and isolate the noise.

It made a curious metallic noise rather than a blowy noise and I was convinced there was something loose somewhere or dying inside the engine.


A local garage fitted a replacement manifold from a breakers yard and the car was transformed.

I suppose you could also check the joint on the exhaust a bit further down although when this went on my blue mk1 MR2 it tended to make a clinky pinky noise on acceleration rather than startup.

[kevin..in]

Wouldnt this blow aswell though Paul?
Alex

as paul says when the manifold heats up it "heals" the crack you get a slight black sooty deposit around the crack usually where no.1 meets no. 4, its a hot spot on the manifold, its only evident when you take off the top heat deflector
probably caused by timing off, drove me mad on my first mk1 trying to set timing correctly to stop it "pinking", it was a cracked mainifold

[pk_090]

but shouldnt there be a blow until the crack heals itself?
Alex

[PW@Woodsport]

There is a blow, but it produces a metallic pulsing noise and not an exhaust blowing noise as you would normally expect, trust me, it's very common on mk1s.

[pk_090]

Whats your opinion on heat wrap on tubular manifolds Paul? Ive been told not to due to keeping the heat in and thus cracking them myth or fact?
Alex

[LimeyMk1]

OK for stainless as long as it's done properly and no good for mild steel/cast due to moisture retention resulting in rust.

Personally I'd go with an exhaust jacket rather than a wrap.

e.g:

http://www.agriemach.com/product_info.p ... cts_id=372

or

http://www.agriemach.com/product_info.p ... cts_id=392

[PW@Woodsport]

I agree with Chris, also it hugely depends on how well built and supported the manifold is, when I build manifolds I brace the crap out of them to reduce any chance of cracking