Noisy tappets - how bad can it be ?

[carrera]

My assumption is that the turbo is the one it left the factory with, so it's from 2006, and done 128,000 miles

She's back together. My technique for getting a king cobra back on is improving, but they are still a pain.

The car fired up first time, which is the good news.

The bad news is it is still knocking. After a bit more listening with the bonnet down I am beginning to think that this might actually be bottom end, so it's off with the sump again. Strange it doesn't really sound like classic big end, but there is one way to find out, and big end would be consistent with the previous owner running it low on oil.

It's still smoky, but I am taking the optimistic view that this is the residues yet to find their way out of the intercooler and exhaust

Of course, if you have any other ideas, I'm all ears 

[carrera]

After a few days off I'm back on the cars. As promised I have dropped the sump and removed the big end caps.

I would say I have just about caught this in time. There is damage to the shells, greater on cylinders 3 and 4,  so perhaps that is where the knock is coming from. I must admit I was expecting the damage to be greater for the noise being made. 

Next job I think is to measure the crank, at first sight there does not seem to be any damage there.

Winding the clock back you may recall that I had to put well over a litre of oil in this to even get it up to the minimum mark. Running low on oil is never a good idea and perhaps this is the consequence.

What do you guys think ?

Crank side of shells



Rod side of shells



Close up of numbers 3 and 4

[carrera]

One more I took yesterday, showing the crank for cylinder 3 with some axial banding. This only became visible after cleaning the crank of oil.

It looks like some type of skipping / hammering of the crank, maybe depositing of bearing material on the crank. It is not detectable by touch / fingernail.

I have mic'd the journal and it's well within spec so am fairly sure I can polish this out in situ, unless the materials / surface treatment for Saab cranks is significantly different to other marques.

Though the bearings are worn I would probably not have predicted that they would knock based on sight only. However after reading https://www.saablink.net/forum/general-ng900-old-9-3-posts-information/49887.htm it seems that this condition of big end bearings can cause rod knock.

I'm convincing myself that the turbo seals having failed, the engine used oil, it went low in the sump causing starvation and a failure of the oil film at the big ends at the end of the crankshaft oil gallery run.

[carrera]

The bearing journal cleaned up fine, picture below.

New bearings fitted (but reused the bolts as there are none available with an up to 6 month back order backorder  , knowing I will have to replace them and do the job again)

The engine is running again, quieter but, there is still a knock from the bottom end.  This is challenging me now as the journals for the crank big end are OK, new shells, main bearings worn but serviceable and I would not have expected them to knock even if worn. Maybe I do need to pull each of those for inspection

[carrera]

Today I have dropped the sump again and set about inspecting the main bearings

Previously I just pulled number 4, and though it looked worn I deemed it "ok".

Number 3 has been removed with the thrust wshers and that seems to be in considerably worse condition. I still need to remove / replace numbers 1,2 and 5, one at a time to avoid the crankshaft oil seals being damaged by the weight of the crankshaft assembly, but thought it would be worth posting this up at this point.

Can you see the copper showing through, especially on the bottom bearing ?. The big ends are not damaged, but they have incurred some light scratching, so perhaps I should have changed the filter as well as the oil. I was quite meticulous in cleaning the journals and oiling the shells upon insertion

It needs mains, which will of course make things better, but and struggling to understand how worn main(s) can give a big end type knock   

[carrera]

Time for another update. It's been a while as I had to wait 9 days for parts to arrive from Sweden.

New main bearings have been fitted alongside the new big end shells, the car was run up with the oil pressure gauge in position.

I cranked her over a few times to try and build some pressure before putting the plugs back in. Nothing showed, so I had no choice but to start her. Oil pressure initially went to 2 bar on the first start after which I cut her off immediately, and then 5 bar as soon as she was restarted.

She was top end rattly, but the bottom end was fine. I ran her up to temperature including some periods holding it a 2000 rpm. The engine quietened down and was running smoothly, with the top end rattle / knock only returning when engine speed was below 1100 rpm. Further experimentation showed that the knock could be induced by accelerating the engine at speeds below 2000 rpm, above that speed she was running fine.

Oil pressure is OK, but not stellar. 3 bar at 2000 rpm when the water temp was about 80. The min spec is 2.5 bar at 105 degree oil, so I suspect that it will be down around that minimum spec for the stated conditions.  Oil pressure at idle was still 1 bar, which is pretty good and well over the 03-0.55 bar the warning light is triggered at (from a different location)

Tomorrow I think I will repeat oil pressure test from the pressure sensor location and see what it looks like at that point. The rattle is definitely coming from number 4, I think I could feel the knock when I listened on the exhaust manifold. There's a slight misfire and plug number 4 is oily

Possibilities
Little end knock -  sounds too loud / deep
Broken valve spring - I would have hoped to have spotted this when testing the tappets
Bent valve head - compressions seemed fine
Cracked piston
................ any further suggestions ?

[sgould]

I was wondering if it was a little end, but I don't have enough (any really...) experience of a damaged Saab engine.  But it's almost all that's left, unless it's a broken ring.

[carrera]

Yeah, the thing is I know it's not right, so it's a futile effort dismissing things without a proper examination / diagnosis.  What I have read is that Saab little ends are not pressure lubricated, so if pressure is low it tends not to affect them, other components fail much earlier. The mains / big ends were really not that bad at all

But as someone might say, Everything will be OK in the end. If it's not OK, it's not the end...

... and I'm not at the end yet

[sgould]

I show this from the car that my wife owned when we first met.  The engine started knocking quite badly!!

Mercedes diesel...

[carrera]

That's an interesting pattern on the top of the piston. The side view is just plain nasty

I have also heard that pistons can fracture on 9-5's, maybe triggered by blockage of the piston oil jet or rings getting jammed in the groove caused by dirty oil gungeing them up or oil starvation with associated bore scoring and consequent big end shell damage. 3 and 4 mains and big ends seem to be the most frail.

[carrera]

Just a little update.

Put the oil pressure sensor in position in place of the oil pressure switch.

Oil pressure on start was good, temperature was up to about 65 and still showing 1.3 bar on tickover. The union on my oil gauge however had decided to fail and upon checking there was an oversized pool of oil on the floor so I shut off before causing further damage

There was a bit of listening and the knocking was loudest from the outer stud on number 4 exhaust manifold.

I think the next step is going to have to be off with her head.

Coming back to the title of the thread, I think the answer is: quite bad, nothing too major but lots of stuff to do and it's all going to have to come apart.

Working assumption is little end / gudgeon pin / piston cracked

[Audax]

You do remind me a little of a case where we had a 9-3 with a B205 engine where no. 4 piston had started to break apart, at first we thought it was big end knock but when the engine was stripped we saw the piston was in a state. Anyway, due to various reasons a second hand block was put into the car using the old head and ancillaries and it came back after a week or so with the same problem again, turns out that no. 4 injector was shot and under high load it was frying the pistons and causing them to overheat and break apart...

[carrera]

Hmm, so I'm doing dealer level fixes now am I 

Seriously, that's actually really helpful, knowing that a broken piston can sound like a big end.

I'm taking the view that the misfire could be caused by the oil, or oil bypassing the piston if it is broken.

Strange that cold compression tests gave a good result on that piston. Maybe it's not completely broken yet, and it's only the explosions when running that open the crack up on some strokes. Dunno

I'll have to remember to do a volume check on the injectors before I reassemble then 

Just had a read back and I saw this:

Strange it doesn't really sound like classic big end, but there is one way to find out, and big end would be consistent with the previous owner running it low on oil.

[carrera]

I bought myself a cheap endoscope to go onto my phone. Not brilliant, but for £6 a lot better than nothing. The user needs a bit of practice too by the looks of things

Some photos of number 4 and 3 pistons.

Definitely oily

and in Rolf Harris style, can you see what it is yet ?

[carrera]

So, as the Queen of Hearts would say, off with her head !

My first time, and it hasn't been too difficult, lots of 10mm screws holding brackets etc in place, but I found them all. The job was probably made considerably easier because the exhaust manifold and turbo have just been refitted with new nuts so no rust to contend with

First of all here's the block / pistons - minimal cleaning done at this stage, just a wipe to get rid of coolant



and then the head. You can see a progression of oil contamination going from cylinder 1 to cylinder 4. It doesn't look like there is any contact or bent valves though, so that's good 



Now at this stage all I can do is compare the amount of rock on the piston in the cylinder. Most tellingly, there is virtually no movement on number 1, while on number 4 I reckon there's about 1mm of rock in total. That's a smoking gun, but it's time to call it a day, so nothing more for now. Next activity will be dropping the sump (for the 4th time in my ownership) so I can release the pistons and rods upwards

I didn't have an elastic band so used a tie wrap to hold the chain together. I need to discover how to make sure the chain hasn't moved on the intermediate shaft, but that's for another day too