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Old 03-09-2020, 02:05 AM   #1
oemoilleaks
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Default B20 intermittent clank/knock noise

A few months ago I had finally finished my initial breakin of my big bore b20. There were (and still are) around 1200 miles on the engine when the events below occurred.

I drove it to Palm Springs, ready to start a road rally the next day. But when I went to warm up the car in the morning I heard a weird clank/knock/clunk noise happening intermittently.

I put a stethoscope to various parts of the engine while it was running and the best I could tell it was loudest at the oil pan. I figured the oil pan baffle I had bolted in maybe came loose and was knocking against the oil pump.I figure that until I took the engine out today and the pan baffle plate and baffles were still bolted down tight.

I don't know what could even cause a noise that audible in such an intermittent fashion. I want to check as much as possible while the engine in on the stand again, but I have no idea what to even check at this point. Any ideas would be greatly appreciated.

OIL PAN BAFFLE FOR REFERENCE:
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Old 03-09-2020, 09:02 AM   #2
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Fore/aft play in the camshaft? It's not really intermittent, but it can certainly make some loud clunks that are hard to track down.
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Old 03-09-2020, 09:47 AM   #3
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I know my B20 oil pan sits really close to the cross member with bad motor mounts. Are you sure the engine vibrations aren't occasionally hitting oil pan against the cross member?
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Old 03-09-2020, 09:54 AM   #4
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Something loose and occasionally bouncing around in the bellhousing?

It doesn't sound like the description, but when the fiber timing gear came loose from the metal hub, the motor was making sounds like a diesel engine at low RPM's. Once revved up a bit, it would actually quiet down. How did it keep running? Dunno, the fiber portion fell off easily once the timing cover was removed.
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Old 03-09-2020, 11:35 AM   #5
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Intermittent is a pain!

This noise occurs with the engine running at idle? If so, since the engine is out and on an engine stand I suggest the following:

- check crankshaft end play
- as noted, check cam shaft end play
- check oil pump shaft end play
- check for damage on the distributor drive

None of these would normally be intermittent; however, since the engine is out they are easier to eliminate as possible causes. On my B20E I would get the occasional bang while driving which turned out to be the IPD / Patriot header contacting the end of the mounting bolt on the lower A arm pivot.
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Old 03-09-2020, 11:45 AM   #6
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My old 1800E made some weird clunks once when the heavy cast front pulley started to come loose. I was a bit stumped - didn't see it wiggling around.
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Old 03-09-2020, 12:23 PM   #7
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Did you make a recording of the noise before pulling the engine out?

Check the rear main seal housing bolts. If one backed out it can get thrown around inside the block/bell housing and occasionally get stuck on one of the reinforcing ribs in the back of the block.
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Old 03-09-2020, 01:57 PM   #8
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these are some great thoughts!

There was nothing bouncing around the bell housing when i separated the trans from the engine...
I will put a wrench on the front pulley as soon as I can, as well as check the endplay of the crank and cam.
I'm not entirely sure how to check the oil pump shaft end play, but I remember the distributor gear being really tight in the oil pump ears/retainer ring.

Motor mounts are new(ish) around 2k miles on them but it wasn't sitting particularly close to the crossmember when I pulled it.

Ian, I'm an idiot and didn't record it but from what I could tell it was only happening at idle... Or I couldn't hear it over the carbs when the throttle was applied. The car would idle without issue.. then you'd hear a CLACK CLACK... then it'd idle a bit, or i'd rev it and you'd hear nothing then. CLACK CLACK CLACK.. but it would never be a consistent nor would it ever match to revs.
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Old 03-09-2020, 02:34 PM   #9
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If a bolt fell out it'll be between the flywheel and block. Make sure all 6 bolts are still there.

Sticky lifter or broken valve spring? Didn't you have a problem with a lifter before?
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Old 03-09-2020, 03:59 PM   #10
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Quote:
Originally Posted by hiperfauto View Post
If a bolt fell out it'll be between the flywheel and block. Make sure all 6 bolts are still there.

Sticky lifter or broken valve spring? Didn't you have a problem with a lifter before?
I'll take the flywheel off and report back. There is no evidence of anything hitting the back of the flywheel but Better to double check. Are those flywheel bolts reusable?

I didn't see a broken valve spring, and the lifter problem was they were sticking but I honed / deburred the lifter holes so that they dropped without issue. Could it just suddenly jam after 1000+ miles of no issue?
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Old 03-10-2020, 02:55 PM   #11
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Just had a thought.. and probably a bad one at that.

Could it be something exhaust related?
I had a Merkur that had something that sounded like a spun bearing but turned out to be the baffling in the muffler had just broken....
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Old 03-10-2020, 02:59 PM   #12
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Go thump on the exhaust, see if it rattles.
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Old 03-10-2020, 05:18 PM   #13
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Quote:
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Go thump on the exhaust, see if it rattles.
Rubber mallet thump? Or sledge hammer thump?
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Old 03-10-2020, 05:48 PM   #14
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Hand, then rubber mallet. No need for a metal hammer.
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Old 03-10-2020, 05:53 PM   #15
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Quote:
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Rubber mallet thump? Or sledge hammer thump?
Depends on whether you want to get rid of the exhaust system sooner rather than later. A large rubber mallet should suffice to check for loose baffles in the muffler.

What exhaust system do you have? If you have the Simons sport system or similar those are absorption type systems with no internal baffles / chambers so nothing to come loose. No point in hammering on that type of system.
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Old 03-10-2020, 06:17 PM   #16
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Quote:
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I'm not entirely sure how to check the oil pump shaft end play, but I remember the distributor gear being really tight in the oil pump ears/retainer ring.
The Volvo service manual calls it end float. The description of the measurement process is rather vague; but, it appears that you remove the end cover and then fit various feeler gauges between the ends of the gears and the cover plate to determine that clearance. I would be inclined to put a machinists flat across the bottom of the open end of the pump and measure clearance between the flat and the bottom gear face. You need some float - negative or zero float will grind the pump cover. Too much float - not sure. Probably low oil pressure and noisy. The SM is not really specific about what you do if your float is out of spec.

I think the drive being a tight fit on the pump is not unusual, particularly if you install those aftermarket reenforcing rings on the oil pump shaft. You can have a tight fit there and the drive is still free to hop up and down axially if you have worn bushings or the like.
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Old 03-10-2020, 07:12 PM   #17
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Quote:
Originally Posted by oemoilleaks View Post
I'll take the flywheel off and report back. There is no evidence of anything hitting the back of the flywheel but Better to double check. Are those flywheel bolts reusable?

I didn't see a broken valve spring, and the lifter problem was they were sticking but I honed / deburred the lifter holes so that they dropped without issue. Could it just suddenly jam after 1000+ miles of no issue?
Yes, you can reuse the flywheel bolts.

It's unlikely that it jammed suddenly but you never know.

Are you using the IPD lifters that came in the big bore kit? I had one fail on me many years ago. The pushrod punched through the seat in the lifter. This was before they sold Isky lifters and I think the kit you bought is from that era.

I always grind the sides of the tang on the oil pump drive when using a reinforcing ring so that it slips in and out nice and easy.

You can adjust the end play by tapping the bushing in the block up or down. Just make sure you don't bugger up the hole. I had a drift made out of aluminum to prevent damage to the bushing.
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Old 03-10-2020, 09:06 PM   #18
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bolt in the bell housing maybe?
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Old 03-11-2020, 12:03 PM   #19
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Years ago I had an engine that started making an intermediate noise and as yours, it was from oil pan. Everyone said I was crazy and thought I was imagining things. Ended up taking it to the races anyway and I broke a crank shaft. Hope that isnt your case but I would look for anyting that is out of the norm. I would imagine you have a steel crank, I ve seen stress cracks in blocks cause a weird noise cause crank is flexing.
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Old 03-11-2020, 04:25 PM   #20
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Quote:
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Years ago I had an engine that started making an intermediate noise and as yours, it was from oil pan. Everyone said I was crazy and thought I was imagining things. Ended up taking it to the races anyway and I broke a crank shaft. Hope that isnt your case but I would look for anyting that is out of the norm. I would imagine you have a steel crank, I ve seen stress cracks in blocks cause a weird noise cause crank is flexing.
In your case it was the crankshaft itself was broken? Or was the block cracked causing a flex in the crankshaft?

I had the block magnaflux'd (or whatever it's called) to check for cracks before I sent it for machining and it came back with a clean bill of health. The crank was sent out for machining by the machine shop, and I don't know if they check it for cracks before they sent it out.
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Old 03-11-2020, 04:34 PM   #21
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Quote:
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Yes, you can reuse the flywheel bolts.

It's unlikely that it jammed suddenly but you never know.

Are you using the IPD lifters that came in the big bore kit? I had one fail on me many years ago. The pushrod punched through the seat in the lifter. This was before they sold Isky lifters and I think the kit you bought is from that era.

I always grind the sides of the tang on the oil pump drive when using a reinforcing ring so that it slips in and out nice and easy.

You can adjust the end play by tapping the bushing in the block up or down. Just make sure you don't bugger up the hole. I had a drift made out of aluminum to prevent damage to the bushing.
I was wondering about the lifter myself. I had meant to ask you if you remembered what the failure looked like, and if you were able to tell from just removing the valve cover. I couldn't tell if any pushrod had dropped, but there were no loose rockers.

I do have a fair amount of wiggle in the tube from the oil pump to the block but it's a lateral wiggle, not a vertical one where it could be coming out and going back in. I'm hoping to get a few hours in the garage this weekend so I can properly go through and check end play on the crank and cam, ensure that the timing gears haven't come loose some how, and check torque on the big end and the rod bearings, and then when all of that turns out to be normal have a good ol' cry.
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Old 03-19-2020, 08:49 PM   #22
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Ok... Finally got to spend some time out in the garage and check some things out.

Crank Endplay: 0.0045 - 0.005"
Cam Endplay: 0.0025 - 0.003"

No damage to distributor gear / Filed it down for easy installation.
All 6 rear main seal housing bolts are still there
timing gears were undamaged
pushrods all checked, all still complete.
every bolt/nut inside and outside of the engine has been checked for torque, nothing was loose.
New b30 motor and trans mounts have been installed (old ones had maybe 3k miles on them)
took a look inside the pushrod hole to see if there was anything obvious on the lifters, there wasn't.

I'm really at a loss for what this could be. I spoke with Volvo George (who had recently helped me tune the carbs) and he mentioned that he had heard it once on the exhaust side of the car and thought "WTF is that!?"

All of this is starting to make me think the unused exhaust hanger was just clacking against the exhaust.

Any suggestions for other things to check?
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Old 03-20-2020, 12:33 PM   #23
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Another option could be piston slap I suppose..

What would I check to see if there was evidence of a piston slapping the cylinder bore?
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Old 03-20-2020, 01:00 PM   #24
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Last ditch attempt. On a 140 there is a bracket that attaches to the transmission and supports the exhaust system. They commonly crack. Depending on circumstances they may fail without the crack visibly separating which then facilitates banging when there is movement of the exhaust system relative to the transmission mounted bracket.

As to piston slap. Piston slap will be continuous, not intermittent; but, will typically be more noticeable when the engine is cold becoming less noticeable or inaudible as the aluminum piston heats up and expands. If the clearances are really excessive the noise won't go away as it warms up. Slap is caused by collapse / excessive clearance of the piston skirt. Check your pistons skirt taper and clearances to the cylinder walls. Does your big bore kit use forged pistons? Forged pistons typically have higher expansion rates than the stock cast pistons and require higher cold assembly clearances. Net effect is that they will rattle away when cold which should become less noticeable / disappear when hot.

Last edited by 142 guy; 03-20-2020 at 01:13 PM..
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Old 03-21-2020, 11:04 PM   #25
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Quote:
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Last ditch attempt. On a 140 there is a bracket that attaches to the transmission and supports the exhaust system. They commonly crack. Depending on circumstances they may fail without the crack visibly separating which then facilitates banging when there is movement of the exhaust system relative to the transmission mounted bracket.

As to piston slap. Piston slap will be continuous, not intermittent; but, will typically be more noticeable when the engine is cold becoming less noticeable or inaudible as the aluminum piston heats up and expands. If the clearances are really excessive the noise won't go away as it warms up. Slap is caused by collapse / excessive clearance of the piston skirt. Check your pistons skirt taper and clearances to the cylinder walls. Does your big bore kit use forged pistons? Forged pistons typically have higher expansion rates than the stock cast pistons and require higher cold assembly clearances. Net effect is that they will rattle away when cold which should become less noticeable / disappear when hot.

To your point about the bracket: This is what I'm starting to think it is. It wasn't being used to support the exhaust pipe but it was still attached to the transmission. That said, the last time I put the transmission (and bracket) in, I noted that it was closer to the exhaust pipe than I felt like it usually was.

As per the piston slap, I still have to check the bore to see if there are any witness marks that would indicate a slap... I'm really trying not to take the pistons and rods out.. but I will if I absolutely have to.

Last edited by oemoilleaks; 03-23-2020 at 12:20 PM..
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