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Discussion Starter · #1 ·
Ok I'll fess up, I actually have a 99, not a 900, but seeing as how its running the 8v Turbo engine from an '85 900 I figured I'd post it here as there seems to be more of you 900 guys... :lol:

First off a bit about the engine, I'm currently running it without a turbo (so its a Low CR engine but with no boost), and I'm running it with a regular N/A type dizzy (as I obviously only have vacuum without boost)

The problem is I'm getting a horrible ticking with the engine under load. I originally thought it was a leaking exhaust manifold, but I have pulled it apart and resealed (and its defintiely not leaking now!) and the ticking is still there.

The other issue which might be related is the way the engine runs. When you first start it from cold it runs lumpy, like its only on 2 cylinders. It smooths out when its warmed up, but it feels like the Ignition could use more advance. I currently have the dizzy set to as much advance as it will go (retarding it makes the engine running and the ticking much worse!) and it feels like I could advance it more.

So yeah, what causes ticking and how can I get my engine running smooth and quiet?

Link to my thread in the 99 forums which might give more clues to a diagnosis here
 

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Found my ticking! (by holding a wet rag in my hand and pushing it onto the exhaust joints).
It is leaking round the bottom of the flange at the top of the downpipe. Must have disturbed it when i took it on and off. Dont know quite how it is leaking there but it is! It could be coming round the stud that holds it to the manifold.
 

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The misfiring from cold sounds horribly like a problem I have had on more than one 900. Head gasket leaking coolant into combustion chamber overnight, plug gets wet, misfires, as soon as plug warms up everything seems okay.......until tomorrow! Hopefully its not this but have a look at plugs and at tops of pistons through plug hole with a torch first thing before you crank it over.
 

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Discussion Starter · #5 ·
That being the case wouldn't I get a lot of water and white smoke out of the the exhaust? I doubt it is the headgasket (and severely hope it isn't) as Tomarse replaced it less than 1000 miles ago and it still looked new when I worked on the engine before putting it in the car.

I'll certainly try and look at it though...
 

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plug lead ? shorting to earth ? Try giving a few revs in the dark .. I might be a mile off . but .. simple easy check .. IF you have the rubber boot over coil leads pull that back to expose during testing , could be broken down insulation , arcing to radiator support panel , just food for thought :D
 

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Discussion Starter · #8 ·
oh no! Somebody shoot that man! Are you trying to raise my blood pressure? :lol:

I have an 12 year old kid brother and this gets played to the point where you want to start murdering stuff, its possibly even more annoying than the ticking in my engine bay...
 

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What mileage has the engine done? Do you get the ticking noise when the car is idling?

Have you checked the valve clearances are within specification?
 

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Discussion Starter · #10 ·
I've no idea what mileage the engine has done, and I've not checked the valve clearances personally, but the engine was supplied to me by Tomarse there and he says he did the valve clearances less than 1000 miles ago, so I'm gonna take it on good faith and try and eliminate the easier possibilities before I muck about with valve shims...

I know for definite now thats its an exhaust related noise, I get that kinda of "phut phut" noise like an elderly farm tractor. I think though part of the cause is spark plugs not sealing properly, 2 of them have brown carbon marks down the ceramic of the body like they've been letting exhaust gasses escape. Not only that but the engine is running very rich, lots of carbon on the plugs even though they are new and been in less than 600 miles. So got something to go on at least...
 

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Discussion Starter · #12 ·
No its definitely not, its not that sort of noise, like I say you can hear crystal clear that it is an exhaust type "phutting" noise, rather than the crack that you get when an HT lead is arcing, I just need to find out where.

There are only so many places an exhaust can leak from, its definitely coming from the engine bay area, so essentially the checklists looks like this:

Exhaust Gasses getting past pistons on firing stroke
Leak from head to Manifold
Cracked Manifold
Leak from Manifold to downpipe
Spark plugs not seated properly and allowing exhasut to escape
Intake valves not seating properly and allowing exhaust gas back into the intake
Some other leak in the head that is allowing exhaust to escape where it shouldn't
 

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did you re torque the manifold nuts after 100 or so miles? I did my gaskets, did a 500 mile round trip and on the last leg of the journey it started putting, checked the nuts on the manifold studs and a couple had come loose, by then it's to late, i think the gasket gets distorted where it's leaking so won't seal properly again.

Before i worked on the car, i had to take it back to a garage 3 times because the manifold kept on comming loose and the car would go back to sounding like a tractor.
 

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for a misfire when cold. I had a leak from the coolant pipe above this distributor. It would leak a few drops overnight onto the dist, so in the morning it would misfire. My mechanic said it isn't common, but it happens. Headgaskets are replaced because of this, but a new HG didn't cure that, it did get rid of the white smoke and nearly exploding expansion tank tho.
 

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Discussion Starter · #15 ·
I'm not using gaskets any more, I've used a nice thick layer of copper silicone exhaust flange sealant either side of the spark plug heat sheild and bolted the manifold down, then retightened it after warming up the engine. It seemed like it should seal, but I can't be completely sure if it has or not...
 

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On some 8v engines the heat shield is the exhaust manifold gasket. There are no separte gaskets. This is what I found on my 1984 C900i.

I think turbo models have the separate exhaust manifold gaskets. Not sure the reason for this, and why the difference.

If the ticking is worse under load it may be that you are hearing pinking. Check and adjust the timing to specification. Check that the centrifugal and vacuum advance on the distributor is working properly using a timing light.
 

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My first 900 turbo (8V) made a spitting noise when warmed up and the engine was put under load ... that turned out to be a leaking exhaust manifold gasket. Personally, I'd pull the exhaust manifold off, clean the faces, re-seal and re-torque once warmed.
 

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RickyS said:
On some 8v engines the heat shield is the exhaust manifold gasket. There are no separte gaskets. This is what I found on my 1984 C900i.
I thought most of them (non turbos anyhow) came from the factory without gaskets and they are generally added by later owners when things are taken off.

It is very easy to make an exhaust manifold seal when it is shiney and new but when it is 20+ years old the gasket helps a lot!
 
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