Saab: Couple of C900 Questions..

Mike P wrote:
 

Pretty easy - you remove the plastic trim on the inside, and
you'll see the mounting screws.

 

Hmm...
The most common noise that comes in under load is pinking. There
are lots of reasons why an engine pinks - incorrect timing, weak
mixture, incorrect plugs/sooted plugs to name but a few.

First thing I'd do would be to pull the plugs and inspect them
carefully. What do they look like? Are they all the same?

--
Grunff

"Grunff" <com> wrote in message
news:uk.clara.net... 
the 
something 
high 
quietens 
doesn't 
a 

Thanks for the suggestions Grunff..

Plugs - Done that this morning before I set off back down. They are all
about 300 miles old NGK BCP7EV plugs, new leads.

The noise *doesn't* appear to be pinking, it's a metallic noise, that
increases with engine speed. Never gets louder or softer. It's not dependent
on throttle position. It's NOTHING like the noise I presumed to be
pinking - harder knocking noise, accompanied by instant boost cut when my
intercooler>throttle body pipe blew off when I forgot to tighten a clip.
It's not the noise I get if I try to accelerate at 20mph in 5th either.. It
is definitely coming from the top end of the engine, but I can't drive far
enough along the car park leaning out the window with the hood open to work
out exactly where from...:-)

It started after a long motorway journey, before the APC units were swapped.
There has been no change in it's volume or frequency. The replacement APC
unit appears to work as it should. I've got more power and torque, it
boosts into the red and cuts the boost when it starts to pink.

It's not a massive problem if it is a camshaft or knackered tappet. I plan
to either take this motor out and rebuild it, or drop in a lower mileage
motor in the spring anyway.Mine needs a timing chain, so it's engine out
anyways.

I'd just like to know, because it sounds like I'm driving around in a
knackered old Ford at the moment... :-)

Mike

Mike P wrote: 

Tappet noise when cold is normal, but it should go away when the engine is
warm. If it stays on then maybe the oil channel is blocked or oil level is low.
In any case you shouldn't put the engine under load before it is fully warm.

"Johannes H Andersen" <com> wrote in message
news:com... 
the 
something 
high 
quietens 
doesn't 
a 
low. 
warm.


Oil level is OK, oil is about 1500 miles old, though it's only Halfords
15/40 own-brand semi-synth at the moment.
The noise gets quieter when warm, but doesn't go away. In my old Orion an
oil change cured it. I put this down to old oil being too thin for the
hydraulic tappets. Could it be the same thing? Don't really fancy changing
the oil tomorrow as it's cold and I've too much to do..

Mike

Mike P wrote:
 

If it isn't pinking, then I'd say either chain rattle or
tappets. You need to check the tappets are holding oil. To do
this, you take the cam cover off, and apply firm finger pressure
to the tappets which are not under a cam lobe. Should be firm,
with very little movement. Turn the engine bit by bit, and check
all the other tappets.

To check the chain, you need to measure the tensioner extension.
Is it at it's max?

--
Grunff

in article bsuv9j$1nrh1$news.uni-berlin.de, Mike P at
com wrote on 31/12/2003 16:59:
 

Is your exhaust manifold cracked? My first 900 sounded like it was spitting.
This could be what you're describing as tapping noise.

Paul

1989 900 Turbo S
http://saab.go.dyndns.org/

Paul Halliday wrote:
 

Good one Paul - I'd completely forgotten about that. A cracked
exhaust manifold, or even a slight leak between the manifold and
the head can sound exactly like Mike's description, and come on
under load.

--
Grunff

In article <uk.clara.net>, com
spouted forth into alt.autos.saab... 
Yep, I think Beemer 4 cylinders have the same problem with cracked
manifolds which open up when the engine is hot and loaded.

I know 8v's had a tendency to crack the manifolds, didn't know 16v's did
the same?

Maybe just loose and needing a new Gasket?
--
Carl Robson
(The poster formerly known as Skodapilot)
http://www.bouncing-czechs.com