PORSCHE 944 DIY: Engine Diagnosis - Failed Timing Belt? Spun Bearing? Bore Score?

[@toupeiraproducoes]

Im Amazed by your calm addressing the issue. If this was to happen on my 944 i think i just would Panic and Cry 😅.

[@GTArmstrong]

Haha - that was happening off camera 😁😅

[@toupeiraproducoes]

@@GTArmstrong 😄, but cool head ist always the best to solve an issue. Best of luck, i will follow the advance and learn along.

[@GTArmstrong]

Thank you very much! ...looking forward to more interactions 👍🏻

[@davidraeside]

For what it's worth, I think those cylinder bores look just fine...I wouldn't say that looks like scoring, more like just normal wear. I would be happy if that was mine! It looks like there's just some carbon buildup which is normal. My old 944 had a cylinder with HORRIBLE scoring and the compression/leakdown numbers were still great.

[@GTArmstrong]

Thanks David! Yeah, these motors are super tough - hats off to the engineers for their approach to the design. I just wish I could have caught what I experienced on camera - our community is filled with great insights, and someone would be able to pinpoint where to next... Thanks again for the encouraging words!

[@janwergeland5586]

Nice documentation/presentation you make! Own a 1988 924 S with the same 2.5 engine. It does NOTsound like bearing failure/slack from: Alternator, Water pump, idler for drive belt & balance. I also don't think it has anything to do with, for example, errors in the steering wheel, clutch/clutch pump adjustment - you've probably checked this. Would have unscrewed the cylinder head cover, to see if there was something mechanically wrong while turning the crank manually.

[@GTArmstrong]

Thank you, and thank you! Someone else on another platform has suggested something similar so I'll need to look into this asap. Thanks again for weighing in and offering a possible solution.

[@Seagrams]

Your timing is good. Other then confirming cylinder compression, I wouldn't think something like a spun bearing would stop the car from starting (not to say it rules out a spun bearing). Your no start is prob caused by something else, so for that I would go down the list of the usual checks (tach bounce/reference sensors, fuel, spark, etc...). As for the noise, I'm not sure, but I hope you can identify that.

[@GTArmstrong]

Thank you! 🙏🏻 After the grit and metal bits in that small oil sample, and the noise - which seems to be coming from the bottom end - it feels like the right thing to open her up and do a visual inspection. Apparently a big pain of a job because the crossmember needs to be removed along with other bits and pieces, which means engine support as well… But I cannot, with any amount of confidence, turn that key again without worrying about causing more damage - and it can only get worse if things are not as they should be.

[@Seagrams]

@@GTArmstrong right, the metal in the oil. Yeah I agree, I think you should deal with that first and hopefully it sorts out your nose issues too. Support bar is the way to go and drop the cross member and oil pan. Best wishes

[@GTArmstrong]

I wonder if the borescope / videoscope would work through the sump plug hole? …once in, possibly quite difficult to get it pointed in the right direction.

[@Seagrams]

@@GTArmstrong Just a hunch, but I have doubts you would be able to see much. I think the oil pan has a bunch of baffles that pretty much block all visibilities of the bottom end. Still worth a try

[@svenscholz3412]

@@GTArmstrong Also check the oilfilter - get it out and cut it open. Most metal chunks should be in there.

[@mr.toasty1972]

Your cylinder walls are fine. 944 cylinders tend to look like that even when there's no issue. The black specks are probably tiny chunks of carbon that get blown off the piston and/or valves; again, no need to worry. I wouldn't bother checking anything else on the top end. What you've found so far makes me thing rod bearings. Why: you can hear and feel something wrong when turning the crank by hand; metal bits in the oil; doesn't want to start; #2 rod bearing failure is common on 944s due to relatively poor oiling. What weight oil is in there, and do you have good oil pressure (~5 bar idling cold, ~3 bar idling hot)? If a rod bearing fails in just the right way, it could make a nasty noise and also make it hard to start the engine. What's next? Drain all the oil and sweep that magnet around in there before deciding to pull the sump (or engine). There should be a big plastic baffle in the sump, so you shouldn't see anything with the camera. I'd check to make sure that baffle is actually there and not badly broken. The good news is that rod bearing failure is not a death sentence for a 944 engine. The cranks are very tough, and often don't really suffer when the bearings go. If the crank is damaged, you should be able to buy a good used crank for relatively little money.

[@GTArmstrong]

Thank you for taking the time to help analyse my findings! And thank you for this lovely breakdown. From what I understand, there is very little one could do if there is scoring because of Porsche’s decision to use alusil…it’s more cost effective to find a good, secondhand block when it comes to this. Thank you for your input on its current condition. I use 15w-40 because here in South Africa the temp rarely drops below 0 C, and I’m always obsessively watching my oil pressure which has been great (just as described here) up until now. Yes, getting a magnet in there is a great idea - and it’s a pity about the camera but I may just give that a go anyway and hope to get lucky. It’s a relief to hear about the crank’s durability. Thank you again for your time and sharing your knowledge and understanding 🙏🏻

[@mr.toasty1972]

​@@GTArmstrong happy to help. I'm glad you're using a heavier oil. You could go even heavier, up to 20w-50 if you want, but sounds like your oil pressure is spot on. If your current oil doesn't have zinc in it, consider an additive to beef it up beyond just viscosity. Hopefully the camera shows a nice solid baffle. If you see chunks of black plastic, well that's not great but also not a slam dunk diagnosis. While you've got the camera, you might as well look at the clutch end of the crank as well and see if there's anything stuck or obviously damaged in there. Just to clarify: a bad rod bearing could prevent the engine from starting after it was just run because the added friction would make the bearing material heat up and expand (especially if bearing material got jammed between the crank and connecting rod). In theory at least, it's possible the crank was seized right after the engine quit running, and then freed up as it cooled. Curious to see where this winds up going. Good luck!

[@GTArmstrong]

@@mr.toasty1972 - thank you, and thank you! It’s a pain but also a lot of fun too, and I appreciate all your insights and help!