B230f Infamous rattle when cold

morch_66479

Hi All,

I recently purchased a 1991 Volvo 240 wagon with 279,000 kms to rescue and move onto a good home.

I've managed to get most things completed bar pin pointing an engine rattle as per the video: https://www.youtube.com/shorts/0mu0YXxkrMI

I tried using a stethoscope to see whether it's the engine or trans but it's hard to pick :/

checked valve clearances - all okChecked compression: 1: 170psi, 2: 179psi, 3: 175psi, 4: 176psi.Checked oils, levels - all okDrive line ok, it makes the noise under load with brakes applied.

Any way of breaking down this diagnosis so i can try find the problem?

Regards,

Martin

paul0075

Oooh piston slap and a lot of it.

morch_66479

paul0075
Oooh piston slap and a lot of it.

Darn, this is what i feared. Maybe i need to chase a 2nd hand block :-/

jamesinc

It could be, although your compression figures look pretty healthy, usually when the bore is so worn you are getting audible slap, your compression is much lower in the realm of 100psi-150psi. It would be good to look at the piston crowns and the bores with a borescope. It could be knock also ?‍♂️

morch_66479

jamesinc
It could be, although your compression figures look pretty healthy, usually when the bore is so worn you are getting audible slap, your compression is much lower in the realm of 100psi-150psi. It would be good to look at the piston crowns and the bores with a borescope. It could be knock also ?‍♂️

I'll try get my hands on a borescope and check for wear inside the cylinders.

I wasn't sure if piston slap would cause a reduction in compression, in my head i thought it would but from research online it didn't mention anything about loss of compression when dealing with piston slap. Interesting.

morch_66479

jamesinc
It could be, although your compression figures look pretty healthy, usually when the bore is so worn you are getting audible slap, your compression is much lower in the realm of 100psi-150psi. It would be good to look at the piston crowns and the bores with a borescope. It could be knock also ?‍♂️

I tried checking the bore with a borescope but I was unsuccessful in getting a good image.

I've since removed the straight pipe and put on a standard exhaust and it only knocks when cold and seems to mostly disappear when warm.

Would you have any info on how to check the knock sensor for diagnostic codes? I'm guessing it's an LH2.4?

ramrod

Something is definitely loose or damaged

From what I can hear, it sounds like something in the top end. What were the valve clearances? I would not hesitate removing the camshaft and inspecting all eight lobes, buckets and shims

Also drain the oil into a clean bucket, empty it out and look for metal particles on the bottom

Add fresh oil (15w40 or 20w50 as a test) then listen for more/less noise, at cold start, warm and hot running to get more of an idea

Roinik

Any codes being displayed?

ramrod

There probably won't be any, if the nature of the problem is mechanical

Fault codes are more to do with fuel injection control

morch_66479

ramrod
There probably won't be any, if the nature of the problem is mechanical
Fault codes are more to do with fuel injection control

I can try check for codes on the weekend. How does this knock sensor work?

I'm suspecting that it's some major mechanical issue like piston slap etc.

Roinik

I was thinking it could rule out a knock sensor. An easy check.

Roinik

The knock sensor is a microphone attached to the block under the intake manifold.

jamesinc

Well, you usually get piston slap because the bore is severely worn and oversize, and that is usually accompanied by poor compression figures.

morch_66479

Ok, would i be best swap out the knock sensor with a known good sensor and check results?

I was also wondering could this noise be the valve hushers/umbrella cushions that have disintegrated and causing this loud rattle.

I hope to put a borescope in the block tonight to check condition.

Anthony

Im wondering also if its down stairs in the bell housing area near the torque converter mounts up - as in badly cracked plate pressure plate.

Compression readings are too high. Perform with throttle body wedged fully open.

Something is not adding up its just weird because if real, its the worst piston or conrod slap ive ever heard. Unless motor siezed once, but it revs very quickly up.

On mentioned valve bucket cushions its an valid interesting point, so needs checking and replacing and valve lash adjusted again.

morch_66479

Anthony
Im wondering also if its down stairs in the bell housing area near the torque converter mounts up - as in badly cracked plate pressure plate.
Compression readings are too high. Perform with throttle body wedged fully open.
Something is not adding up its just weird because if real, its the worst piston or conrod slap ive ever heard. Unless motor siezed once, but it revs very quickly up.
On mentioned valve bucket cushions its an valid interesting point, so needs checking and replacing and valve lash adjusted again.

I retested the compression with 2 separate meters with throttle body fully open and figures are similar to that listed in my original comment in this thread. In fact, having the throttle body open made the compression pressures increase by approx 5psi on each cylinder.

I also rechecked the valves clearances and they're all within spec and the noise sounds more like slap than valves.

morch_66479

Yeah, it's so hard to detect exactly where the noise is coming from but i also hoped that the characteristics of it not rattling when idling would help me close in on this issue.

Hmmm, i wonder how accurate my gauge is too. At least all the compressions are similar though. What should the compression figures be and is it even a concern that they are reading high?

I've never heard any other piston slap so thanks for the comment as i had nothing to compare it to.

Since my valve clearances are ok, i wouldn't need to adjust anything again i guess? Just put it back exactly how it came out?

Anthony

A stethoscope from an auto shop is a worthy addition to the toolbox. Typically used to listen to fuel injectors to detect variations in pitch (especially on the old k-jet mechanical types).

And placing it around the head and block area it will quickly tell you where rattles are. Listen for clear click clacks for valves and valve buckets colliding.

Stand at the exhaust pipe and have a good listen, any unevenness in running or valve problems will be apparent.

In coolant reservoir, any froth?

Compression readings - around 154psi for aged motor.

Other than valve bucket cushions, I wouldn’t be planning to spend any money on that engine at this point, as a replacement might be the best way ahead. Maybe someone could lean over your shoulder when checking valve adjustments, as its not easy to get the feel of the feeler guages.

Like i said also try and hear if there is noise around the transmission to engine area.

Anthony

Spac

Does it turn into World War 3 if you rev it harder?

It sounds like it is a dead big end from the video. They’re usually fairly easy to identify because they get MUCH worse if you rev it harder.

ramrod

There's your clue, disappears when warm

When engines warm up the metal construction expands and the gaps become smaller. If piston to bore clearance is excessive, this will tighten up as the engine gets hot

I don't think the noise is electrical

morch_66479

My money is on it being piston slap after today's efforts but ill check it again in the morning and see. If it disappears when warm and doesn't get worse when revved (warm) then it's probably ok?

I'll recheck the compression and update too.