New snag in project Astrid: rod bearing

veektor · Post by **veektor** » 12 Mar 2018, 01:27

I finally got around to washing Astrid.

I haven't had a white car in a long time, and this one is very pretty without all the gravel dust on it. But this was after I replaced the alternator in the morning ($40 at full service salvage yard beats hunting for the right one at self service yards), and then taught my son how to replace spark plugs.

Off the bat, second spark plug well looked dirty and rusty, while all others were shiny. All spark plugs had almost 1mm gap on them, but #2 looked like it hadn't fired in a while. I did the screwdriver test on all pistons, and #2 gave me that slight 'plunk'. Double checked all the pistons, and only #2 consistently showed symptoms of failed rod bearing.

Before I start ordering parts, I'm going to proceed with the plan to drop the oil pan (I have the gasket kit already, might as well use it), but now my scope expands to inspecting the crankshaft journal on #2. I understand that my range of options is between doing just one bearing to full rebuild, to getting a whole 'new' engine in it. I'm a little bummed about this, but I know how hard I kept trying to convince myself that the noise was only in the top end, and I really should have known better.

Post by **abscate** » 12 Mar 2018, 03:02

Can you describe the test ? The bottom ends of these engines are really strong

Astrid looks great and is definitely worth fixing!!

Post by **jonesg** » 12 Mar 2018, 07:16

abscate wrote: ↑12 Mar 2018, 03:02 Can you describe the test ? The bottom ends of these engines are really strong

Astrid looks great and is definitely worth fixing!!

Heres one way, put a 12" x 3/8 dia dowel on top of piston, all plugs out, rotate cyl until it starts on the downward stroke, stop , then push down on the dowel or whatever you're using.
Feel for a click or any movement.
It usually indicates for piston connect pin.

Post by **jimmy57** » 12 Mar 2018, 11:08

huge flaws in this test. Piston to bore clearance on modern pistons when cold will cause this. You can't push through plug hole squarely with certainty to feel up-down of loose rod bearing vs rock of across skirt extra clearance of cold piston that has not gone concentric due to thermal expansion. If the engine has a knock that lasts a few revs on start after hours of shutdown then you'd have a reason to explore. The dowel in plug hole might then help confirm which cylinder if the thump is isolated to one cylinder.

veektor · Post by **veektor** » 12 Mar 2018, 12:57

jonesg wrote: ↑12 Mar 2018, 07:16 Heres one way, put a 12" x 3/8 dia dowel on top of piston, all plugs out, rotate cyl until it starts on the downward stroke, stop , then push down on the dowel or whatever you're using.
Feel for a click or any movement.
It usually indicates for piston connect pin.

That's the method I used, only I had a straw indicate for up/down piston movement, and used the screwdriver to push on down on the piston on the downward stroke.

I really want this to be something other than spun bearing, but the symptoms are the following:

Misfire in cylinder 2

Liquid residue on #2 plug electrodes. In the pictures above the #2 plug is perpendicular to the other four.

Rust staining on spark plug boot, aluminum corrosion of the #2 well. My thinking is that condensation probably happens in all wells, but others get hot and boil it off, while #2 does not fire, thus retaining that moisture.

The piston push test only clicks on #2 cylinder.

Noticeable clunking when engine is running across the range of RPMs.

PCV is clogged, as indicated by inflating rubber glove on oil filler opening (one of the forum comments about Volvo spun bearings mentioned PCV as the primary cause)

The only thing that was confusing to me was that the knocking noise at times was not noticeable. It would knock right after the engine start, then quiet down at idle, but once i revved to 3K RPM it seemed to keep knocking at idle speeds. That allowed me to think the knocking could be in the valves, rather than rods. I will be dropping the oil pan pretty soon, so I should know better what it looks like in there.

veektor · Post by **veektor** » 12 Mar 2018, 13:01

jimmy57 wrote: ↑12 Mar 2018, 11:08 huge flaws in this test. Piston to bore clearance on modern pistons when cold will cause this. You can't push through plug hole squarely with certainty to feel up-down of loose rod bearing vs rock of across skirt extra clearance of cold piston that has not gone concentric due to thermal expansion. If the engine has a knock that lasts a few revs on start after hours of shutdown then you'd have a reason to explore. The dowel in plug hole might then help confirm which cylinder if the thump is isolated to one cylinder.

Jimmy, I appreciate you trying to give me hope that my problem may be elsewhere, but I just replied to another post with more symptoms, all of which indicate some problem with cylinder #2. Right now I am researching the proper sockets needed to inspect the connecting rod bearing condition.

Post by **abscate** » 12 Mar 2018, 14:12

Your rod knock should be loudest on float, just as you transtion from accelerate to coast (or gas on, gas off)

If it is coming and going intermittently as described, I doubt it is rod knock.

Your teardown will be be definitive, of course.

Post by **oragex** » 12 Mar 2018, 16:08

The gap on all those spark plugs looks so big I'm surprised there even was a spark in there.

Was there water inside the plug hole #2? If the spark plug wasn't firing, I don't see why the rod bearing would go, but maybe the piston rings have worn out being washed with fuel mixture. The main reason for worn rod bearings is a clogged PCV causing sludge inside the oil pan - mostly bearing #5 will be affected

veektor · Post by **veektor** » 12 Mar 2018, 17:14

abscate wrote: ↑12 Mar 2018, 14:12 Your rod knock should be loudest on float, just as you transtion from accelerate to coast (or gas on, gas off)
....

Yes, I noticed that happening, very loud.

I haven't heard 'float' used to describe this action, I'm adding it to my vocabulary.

I have built my stacks of lumber to support the car during this 'surgery', and have drained the old sludge out. Now I am looking at different write ups of oil pan removal, to pick and choose from different ideas on the procedure. I'm trying to figure out why subframe needs to be removed because it almost looks like the pan would just slide out, but I know that can be deceiving.

veektor · Post by **veektor** » 12 Mar 2018, 17:29

oragex wrote: ↑12 Mar 2018, 16:08 The gap on all those spark plugs looks so big I'm surprised there even was a spark in there.

I know, right?! With the first spark plug out I started laughing so hard, then had to explain to my son what was so funny about it. When I showed old plug next to new plug he was able to appreciate the humor. I also used that opportunity to show him how to check the gap with feeler gauges.

Was there water inside the plug hole #2? If the spark plug wasn't firing, I don't see why the rod bearing would go, but maybe the piston rings have worn out being washed with fuel mixture. The main reason for worn rod bearings is a clogged PCV causing sludge inside the oil pan - mostly bearing #5 will be affected

There was no water when we were removing the plug from #2, but the evidence of moisture having been present at some point is undeniable. I haven't learned enough theory to understand what happens to the cylinder when that bearing fails, but I remember that Subaru wouldn't idle at all, and when I was trying to identify the cause of knocking, the engine had to be revved somewhat to run long enough for a video. This was another reason why I was in denial about Volvo bearing failure: I assumed that the engine won't keep idling when even one bearing fails. But maybe it's the degree of failure that makes the difference. On Subaru the crankshaft journal was scored, and I had to buy a new crankshaft. Maybe (crossing my fingers) the one on Volvo still has enough remnants of the bearing to have left the crankshaft undamaged. Hope always dies last, right?