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Discussion Starter #1 (Edited)
Hello Everybody, I finally brought a Alfa Romeo 159 SW 2.2 JTS, a car I have been infatuated with for a long time. The car makes a knocking noise (among other noises), only when it's hot. I am concerned it might be a valve hitting a cylinder or something serious. Anyone else have the same problem? I'm not getting any failure codes from the ECU when tested with AlfaOBD android app.


Many thanks!
 

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I don’t think its valve hitting pistons as your engine would have had it by now if its doing in at tick over, so presumably you’re getting the noise when the oils warm, so thinner, or the thermostat is open for the cooling system?
 

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Discussion Starter #3
I don’t think its valve hitting pistons as your engine would have had it by now if its doing in at tick over,
True that. Can it be that the valves are possibly not closing properly and resulting in bad combustion? The sound seems to be coming from near cylinder 1. I've ordered a compression testing kit but will receive it only after Christmas. Is there a way to disable combustion in just one cylinder somehow? The Coilpack comes in one piece so should I tape off a sparkplug :rofl:


so presumably you’re getting the noise when the oils warm, so thinner, or the thermostat is open for the cooling system?
If it comes on when the oil's thinner, then it may be hydraulic lifter related perhaps? If it's due to the Water pump, is there a way to test it? The water pump is under load even when the engine is not fully hot for the interior heating circuit or?

I forgot to mention that there are no failure codes in the ECU when checked with AlfaOBD Android app.
 

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First of all, it’s usually difficult to diagnose odd sounds from remote.

The high ticking sound could mean (a) valve lifter(s) due to wear or indeed too low pressure at the top end of your engine. I would expect a warning light to be thrown up if indeed it’s low oil pressure, so might be just one valve lifter playing up.

But, and I may be well wrong here, it looks like there’s a deeper knock coming from below the cylinder head? If true this might indicate worn out bearings, usually from the conrods which becomes more obvious if you rev up to above 3,000rpm approx.

Furthermore, in case you wish to diagnose compression w/o a mano-meter, you alternatively can listen for the balance between all cylinders by shutting them off for a few seconds when running idle. In the old days, with carborretted fed engines, you did it by unplugging the silicone HIGH voltage wires (be careful: watch yourself!). On injection engines you simply de-connect the low voltage plugs from each injector. By doing this subsequently and if possible reading the drop in RPM each cylinder causes, it tells you something about how well they run as a set. You say to have AlfaOBD, so you can clear faults afterwards.

SAFETY WARNING: if you have no experience working on high voltage circuit, you best leave it to a pro. For at least the first time to show you how it’s done in a safe manner.
 

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Engine sounds even enough. That's good.
What is engine oil like? Direct injection engines tend to soot the oil quite a bit. I've seen these engines in Vauxhalls making a similarly clattery sound.

Failed thermostats and short trips can cause fuel to dilute the engine oil and this causes the film strength to reduce and cause wear. A 5W/30 oil tends not to have that much film strength anyway so it does not take much dilution before wear occurs. (smell the oil) Cars doing more short trips or urban use really need more oil changes than open road cruising. Modern lighter oils are specified for environmental reasons (less internal drag). Best idea would be to use a high spec API SN rated oil with as high an HTHS figure as possible. I use oil with a 5.81 figure. 5W/30 oils won't even reach 4 so perhaps a 5W/40 would make sense. However, that won't fix the problem. Check condition of cams and followers and make sure the cylinder head isn't suffering from carbon deposits, gum and varnish. Remove cam/valve cover to check. Cam lobe wear is often a feature of less than well maintained direct injection petrol engines.

Check the crankshaft vibration damper/pulley. They can make a sound similar to the deeper knock when the rubber bonding between the inner and outer metal parts start to fail.
 

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Mine sounds exactly like that but I just put it down to old age with 155K on the clock so it'd be interesting to know what your mileage is? Also you mentioned a way back getting a compression tester, did that show anything??
 

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The mileage was 130k kms. I think the DMF might have died early due to the previous owner driving it at low revs. I didn't end up doing anything with the compression tester unfortunately.

I think other than the knocking noise caused by the DMF (which is apparent on the right side of the engine), the rest is just what a normal direct injection engine sounds like (due to the high pressure fuel pump and hydraulic tappets I believe).
 
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