Tapping problem when cold

[Nick P]

Hi,
Well I'm into my first potentially major problem with my latest Chimaera. When cold as i accelerate away (not hard), i get a machine gun type tapping noise....this continues until the car is warmed up. then when I 'give it some beans', it tends to go away.....am i correct in thinking that this could be a sticky tappet/rocker/whatever? Its as if when i get the oil pressure pumping at higher revs, the offending problem goes away. Could it be a worn cam? It only does it under accelleration and when not fully warmed up.
p.s its a '94 Chim 400 with 75,000

[bobs4c]

Sounds to me like leaking exhaust manifold gasket, so not too bad!

Bob

[that daddy]

nick ill go with robert on this one.keep us posted.

[Nick P]

how come it goes away/becomes less evident when warmed up and I have given it some hard acceleration?

Is it worth whipping the Exhaust manifolds off to change the gasket?

Edited by Nick P on Tuesday 17th October 09:07

[that daddy]

because the manifolds expand with heat thus closing the gap,and the head faces to a degree.

[Nick P]

cool...cheers.

I'll get my head under the bonnet and see if i can tell which side its coming from.

I want to sort it as i'm trying toget the old girl as near to perfect as possible. I'm a fussy git like that

Edited by Nick P on Tuesday 17th October 09:34

[aaandy]

From experience I would say that the manifold gasket noise would not completely go away when hot, and sometimes being hot or cold will ot make any difference to the gasket. A blowing exhaust gasket can be very loud under load and can sound quite alarming.

Maybe try sticking your head under the bonnet and see if you can hear where it is coming from.

But would get it seen to before driving any more just in case it is something mechanical.

[that daddy]

could also be a cracked manifold,but aaandy is right if your unsure get it checked by someone who knows,just in case its more serious.

[Nick P]

aaandy said:

From experience I would say that the manifold gasket noise would not completely go away when hot, and sometimes being hot or cold will ot make any difference to the gasket. A blowing exhaust gasket can be very loud under load and can sound quite alarming.

Maybe try sticking your head under the bonnet and see if you can hear where it is coming from.

But would get it seen to before driving any more just in case it is something mechanical.

on tickover i cnt hear it, but cold and under load it is obvious. I still exists when hot but to a lesser degree and almost goes away when very hot.

[Mad Mitch]

Check the manifold bolts. Mine was just as you explain and i was ready to do the gaskets but found n/s rear bolts loose. Tightened up and have been fine for last 3 months.

[Nick P]

Mad Mitch said:

Check the manifold bolts. Mine was just as you explain and i was ready to do the gaskets but found n/s rear bolts loose. Tightened up and have been fine for last 3 months.

thats gonna be my first step tonight

should i see any soot marks if it is a loose bolt/gasket gone?

[mongoose]

Mad Mitch said:

Check the manifold bolts. Mine was just as you explain and i was ready to do the gaskets but found n/s rear bolts loose. Tightened up and have been fine for last 3 months.

Just what i had recently,as well.Mine were loose on the offside rear though.If you can't tell the bolts are loose visually(lock washer looks 'open')then hold some tissue paper around the headers when started up from cold and youll see which are blowing when the tissue moves caused by the escaping gas.They warm up too bly quickly to feel around all of them with just bare hands!