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B20 intermittent clank/knock noise

oemoilleaks

oemoilleaks

Member
Joined
Mar 26, 2017
Location
SoCAL
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:
IMG_5078-2_670.JPG
 
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.
 
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?
 
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.
 
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.
 
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.
 
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.
 
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.
 
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?
 
hiperfauto said:
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?
Click to expand...

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?
 
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....
 
oemoilleaks said:
Rubber mallet thump? Or sledge hammer thump?
Click to expand...

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.
 
oemoilleaks said:
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.
Click to expand...

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.
 
oemoilleaks said:
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?
Click to expand...

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.
 
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.
 
90volvo said:
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.
Click to expand...

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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