Metallic knock in 401 but not all the time.

[Pete Phillips]

1963 Electra 225 with the 401. Car has 39,000 actual miles, one-family ownership since new, no question about the mileage (owner has proof). Had a metallic clanking noise that seemed to be coming from the torque converter or flywheel/bell housing area. Not all the time, but now and then, and usually went away after engine warms up or is revved up. Thought it might be a loose bolt in flex plate. Removed flywheel cover, found that the flex plate was not properly installed or indexed by the transmission shop that worked on the transmission four years ago. No loose or missing bolts were found. We rotated everything, found no cracks in the flex plate, no loose bolts, but one bolt head was sticking up farther than it should due to improper indexing. We removed the bolts, rotated flex plate to its proper position, reinstalled all bolts, tightened them down. Started up the engine (cold start). LOUD metallic knocking sound in lower part of the engine--frequent, two or three times every second. I felt the bell housing--no vibration or pounding seeming to come from there. Felt the oil pan but could not feel any vibration there.  Revved up the engine after a minute or so, metallic knock got worse then completely went away! Now it runs fine. Car has an after-market oil pressure gauge and oil pressure is fine according to it. What could it be????  Owner says there is low compression in the two rear cylinders on passenger side. Haven't checked that yet, but it idles smoothly enough. Any ideas before we tear into this engine?

 

Pete Phillips, BCA #7338

Leonard, TX.

[Pete Phillips]

It's not a dull, deep thud like a bearing knock. It's too loud and sharp to be a piece of broken piston ring. And why does it go away when the engine warms up?

Pete

[60FlatTop]

Just a hunch but the transmission shop may have supported the engine against the oil pan. And put an oil can dent in it. That would be my first check. The crankshaft may be tapping the pan.

To fix it use two ball peen hammers to tap the vertical sides of the pan while it is running. It is easy to do and may save a lot of aggravation.

 

See how little I trust the work of others.

[avgwarhawk]

Possible piston slap on the two cylinders that are low in compression. 

[Smartin]

Agreed on the piston slap or broken rings.  Low compression is the key here.

[joelj]

Random noise at idle, kind of like loose change in a clothes dryer? Not at all rhythmic and goes away with higher rpm kind of reminds me of a problem I was having with a 65 401. I ended up finding part of a piston skirt in the oil pan. That engine always ran well, it never seemed to burn oil excessively or lack power. It just had the random noise at idle even with the broken piston pieces removed. I think that the noise was caused by the piston itself not being guided by the skirt and hitting the cylinder wall (theory). After ruling out any external causes, I think your next step should be to run your own compression test, just to know for sure. Then remove the oil pan  and inspect as thoroughly as you can from the bottom up. 

Edited December 20, 2022 by joelj (see edit history)

[Pete Phillips]

Joelj, I thought of that and think you are on the right track. Oil pan removal will be next. Unfortunately, that's not easily done on this car, but it's going to have to be done. Thank you for your educated opinion.

Pete

[NTX5467]

What about a piece of carbon on the top of one piston?  Had someting similar on our '66 Chrysler years ago.  Ran fine but had a loud tapping noise with each revolution of the engine.  The old-line Chrysler service manager suggested putting some Shaler Rislone through the carb to soften it so the carbon would go out through the exhaust valve.  Don't recall if we did that, but the noise went away as quickly as it came . . . never to return.  The car had about 40K miles or so on it at that time.

 

Best to pull it out and see what's going on.  Fixing ONLY what needs attention.  Using a wire brush on a drill motor to clean the combustion chambers and tops of the pistons.  New standard-sized rings as needed.  With no lower=end knocks, just look at the bearings to see what they look like, if desired.  DO put a new timing chain in it, though.  At least a steel sprocket item or (best) a Cloyes roller chain set.

 

Just some thoughts,

NTX5467  

[Pete Phillips]

Willis,

Now that you mention it, I did have a carbon noise like that years ago when I had my white '61 LeSabre (364 V-8). I was always babying that car, never accelerating very hard, and did have that problem with a piece of carbon.

 

[Smartin]

Do you have a borescope?

[EmTee]

8 hours ago, Smartin said:

Do you have a borescope?

Inspect through the drain hole in the pan?  That might be tough...  Could check the piston tops through the spark plug holes.  That would at least show any carbon accumulation.  I'd start with a compression test and focus on any cylinder showing an abnormally low or high reading...

[Smartin]

Through the plug holes.  If ring is broken it will score the wall and you can see it.

[60FlatTop]

Removing the pan requires unhooking the exhaust, center link, and other attachments. Just be sure to remove the distributor cap. It is that tight.

 I got my pan off and found some Chiclets

.

 

I had a slight miss that I couldn't identify. I think it may have been a cracked piston. My daughter started my '64 Riviera at full throttle through a miscommunication about starting a car with an automatic choke. The untenable diagnostics was over in seconds.

 

I have seen a few nailheads with broken pistons. I am sure they crack before they break completely. 55 years and long periods of sitting to keep the mileage low are not a good combination. My Riviera pistons are fairly new. If the '60 Electra gave me any reason to question the internals I'd pull it down.

 

Things like this give me indigestion.

[Smartin]

The engine sits back much further in the 60 than it does in the later cars.  And if it's a dual exhaust car, exhaust shouldn't have to come down.  But if there are already two down cylinders, just pull it.

[Ben Bruce aka First Born]

11 minutes ago, Smartin said:

The engine sits back much further in the 60 than it does in the later cars.  And if it's a dual exhaust car, exhaust shouldn't have to come down.  But if there are already two down cylinders, just pull it.

 

  Even if the problem is just valves?

 

  Ben

[Smartin]

I suppose not, which is why I asked about a borescope.

[Pete Phillips]

Got the oil pan off this a.m. Nothing loose, nothing broken. Looking up into the bottom end of the engine, everything looks fine. The mystery continues. I"m beginning to wonder if it is something loose inside the torque converter. It just doesn't sound like it is in the top of the engine.

Pete

[pont35cpe]

I`m a little late to the party.. Take the torque converter loose from the flex plate, push it back towards the trans, should have clearance, and spin or start the engine.

[Smartin]

The torque convertor is fixed in place on a dynaflow and can't be pushed back like on a T400.

 

Pete, I literally ran into a very similar problem a couple weeks ago.  Dropped pan and didn't see anything weird.  Performed compression check and all cylinders were at 165 except #8.  It was 70.  Shoved an articulating borescope in the plug hole and saw some scoring on cylinder wall.  But it looked like the exhaust valve was stuck open a touch.  Removed head and both valves were fine......but the cylinder was is scored so badly that I can feel it with the tip of my fingers.  Surely a broken ring or piston skirt (on the one I'm working on).  I suspect either the same for you or a couple burned valves.

[60FlatTop]

Moving in the right direction. Can you someone  do a leakdown test while you are up in the crankcase cavity?

 

An average of 660 miles per year over 59 years means an awful lot of dry starts even if a lot was put of in the first few. It could fall into the abused bracket by some and unconventional problems surely can arise.

 

Just a thought, while you are there, take a good look at the ring gear and check the action on the starter Bendix arm to be sure it doesn't show a little bit of lightly engaged dancing.

[pont35cpe]

3 hours ago, Smartin said:

The torque convertor is fixed in place on a dynaflow and can't be pushed back like on a T400.

That eliminated my idea..

[NTX5467]

Be SURE to check the anti-freeze!!

[EmTee]

If you're sure the noise is coming from the back of the engine then disregard, however, V-belts can make some pretty scary sounds sometimes...

 

Edited December 21, 2022 by EmTee (see edit history)

[drhach]

Collapsed lifter that oils up after the engine starts? 

[old-tank]

4 hours ago, EmTee said:

If you're sure the noise is coming from the back of the engine then disregard, however, V-belts can make some pretty scary sounds sometimes...

 

As a test run it briefly with the belts removed.

[NTX5467]

On 12/20/2022 at 10:23 PM, NTX5467 said:

Be SURE to check the anti-freeze!!

 . . . Considering . . . the projected single-digit temps on Thursday night and into the 26th . . .

[60FlatTop]

Now you have the oil pan inspection cover off. There is a lot of inspect and a lot of reasons why you should. You are only getting one shot at fixing it at this point and the future is hinged on what you do.

 

Think about that 39,000 life very seriously. Antifreeze? How long has it been in there? You can pick up a pack of litmus strips at a drug store and check it for acidity. Are all the coolant hoses 50 years old or were they changed out only 25 years ago?

 

Right now is a good time to run a pressure test on the cooling system. There have been instances where nailhead timing chain covers have become porous in the water jacket area. It wouldn't hurt to look for a tiny green drip where the oil pan covered the lower timing cover.

 

Has the oil been changed ever 3,000 miles a total of 12 times, or once a year at 50 times? Oil will go slightly acidic from sulfur in the fuel. Each time it sat for long periods of times the dirty oil can lightly etch the bearing surfaces.. You can pull a couple of caps now and inspect them. Don't forget there are circular bearings harder to get to. Checking an easy one would be a good assessment of surfaces overall.

 

I am pretty leery of low mileage cars. Long periods of idleness and the potential for long intervals of minimal maintenance are easy to slip into.

 

There was a mention of lifters. Each time that engine sat long enough for the lubricating surfaces to dry it was like a fresh start. Dry cams and lifters don't like low RPM's. Initial starts with a 2000-2500 idle is sometimes recommended to reduce wear on lobes. I see a lot of stored cars start and sit right at minimal idle as the smoothness and quiet are appreciated, not really the right thing to do.

 

I could go on. When I was operating buildings I heard a lot of complains from the directors about why everything I looked at turned into such a project. The "other guys" never had so many problems.

[EmTee]

[60FlatTop]

Actually this is the one I go by. Best read.

 

 

[Pete Phillips]

Rest of the story: We pulled the passenger side head off yesterday; found no damage on any of the cylinder walls, no busted piston tops, no valves that look burned, but there is evidence of head gasket failure between the two cylinders that have low compression. We did a compression test before pulling the head and one cylinder had 20 psi; the other had 40; the remaining two were around 150 or so. Head gasket failure appears to be the culprit. I called the owner today and asked if the car had ever over-heated. He confirmed that it had overheated before they replaced the radiator. Sad to say, we then found a crack in the block, between one cylinder and a cylinder head bolt hole. It does not seem to go very deep, so I'm wondering if that can be repaired (stitched) or should we replace the block. I do have another 401 here.

Still don't know where the metallic clanking was coming from. All that's left is inside the torque converter or behind the torque converter. We found no loose parts nor any carbon chunks in the engine. I'm going to take the Dynaflow to a transmission shop and let them go through it, because it does leak in a lot of places and the shop that rebuilt it in 2017 (and charged the owner $3,850!!!) does not seem to have done a very good job.

The third photo shows where the crack in the block is--between cylinder wall at bottom of photo and the head bolt hole in front of my finger.

[JohnD1956]

Hope the block can be salvaged. But that means a full rebuild doesn't it? 

[tenugent]

On 12/23/2022 at 2:25 PM, Pete Phillips said:

Rest of the story: We pulled the passenger side head off yesterday; found no damage on any of the cylinder walls, no busted piston tops, no valves that look burned, but there is evidence of head gasket failure between the two cylinders that have low compression. We did a compression test before pulling the head and one cylinder had 20 psi; the other had 40; the remaining two were around 150 or so. Head gasket failure appears to be the culprit. I called the owner today and asked if the car had ever over-heated. He confirmed that it had overheated before they replaced the radiator. Sad to say, we then found a crack in the block, between one cylinder and a cylinder head bolt hole. It does not seem to go very deep, so I'm wondering if that can be repaired (stitched) or should we replace the block. I do have another 401 here.

Still don't know where the metallic clanking was coming from. All that's left is inside the torque converter or behind the torque converter. We found no loose parts nor any carbon chunks in the engine. I'm going to take the Dynaflow to a transmission shop and let them go through it, because it does leak in a lot of places and the shop that rebuilt it in 2017 (and charged the owner $3,850!!!) does not seem to have done a very good job.

The third photo shows where the crack in the block is--between cylinder wall at bottom of photo and the head bolt hole in front of my finger.

Sleeve it ?

[Frank DuVal]

Really late to party, but the bolts you found in the flex plate, did they all match, or maybe the shop put in one slightly longer? Did the heads or tips have odd marks on them, from hitting something? The mark would be slight, as the noise would go away as things heat up and move.

[NTX5467]

I know that many "love" those OEM steel shim head gaskets for their .018" compressed thickness, BUT a modern Fel-Pro composition head gasket (with a stainless steel Fire Ring) might not have rusted-out.  Just a suspicion.

 

Might get that part of the block magnafluxed to see how far that crack really goes.  With a stock motor that is driven normally, it might not cause any problems . . . BUT that would be the judgment call of somebody more knowledgeable in such things.

 

Please keep us posted,

NTX5467

[60FlatTop]

I was thinking about this job. I would probably replace the block. BUT if I had reason to keep the original I would repeat a procedure I did almost thirty years ago. I had a '59 Caddy come in with a stripped headbolt and damaged block. That car was damaged on reassembly from a very expensive restoration.

 

In that instance I debrred and smoothed out the damage and then installed a Heli-coil to strengthen the bolt hole. I replaced that single bolt with a stud. The stud was tighented just slightly more than the headbolt spec and closely checked for a good seat and no drawing of the casting. I used the Fel-Pro style gasket and torqued the nut at the cylinder head. I wanted to avoid chance that anyone might disturb the threads. It was the bolt that held down the power steering bracket and might be loosened in the future.

 

On this '64 I would drill each end if the crack to prevent propagation and smooth every radius around it. Then do the Heli-coil and stud installation.

 

The car left my place and the following day driven 100+ to Syracuse where they picked up an Elvis impersonator on the hottest day that Summer and was the hit of the Pigula Family Picnic. Whew!

 

I would do the same here.

 

If anyone has a really nice red '59 Caddy convertible that has one nut and one bolt on the pump bracket it is probably the car. I did the job expecting it to be permanent.

Edited December 27, 2022 by 60FlatTop (see edit history)

[Pete Phillips]

I have a good 401 replacement engine, so the owner is going to go with that. The most experienced machine shop owner around here did not recommend trying to fix the cracked block. 

And another interesting development--I took the transmission to a trusted local transmission shop with lots of experience, and asked them to see if they could find something loose inside the torque converter or transmission case. The foreman took one look at it and said it looks like the starter has not been retracting all the way and has been hitting the top of the ring gear intermittently! Hmmmmm.....never had that problem before. But that might explain why the clanking noise goes away when the engine is revved up.

Pete Phillips

[NTX5467]

Way back in 1967, my uncle knew he was going to be deployed to Viet Nam, flying missions out of Cambodia, so he bought a new '67 Caprice 4dr ht for his wife to drive and haul their two kids around in.  A 396 4bbl car with 8-track stereo tape.  One day, it developed an odd/random metallic scraping sound that was hard to locate WHEN it happened.  Eventually, though, it was tracked to the torque converter area.  Upon further investigation, there was a converter bolt laying in the metal pan that covered the torque converter.  Somehow, it had gotten loose and fell out of its threads, landing in the pan.  On random times, it would "move" and get picked up by the spinning torque converter, making a loud racket when it did.  Then it'd get quiet again, for variable periods of time.  A new converter bolt in the appropriate threads and everything was silent again.

 

Just one of those things?

NTX5467

[Pete Phillips]

Apparently the metallic clanking noise in the engine was the starter randomly hitting the flywheel/ring gear. Transmission shop took the torque converter apart & also resealed the Dynaflow transmission, and found no loose parts. That's a new one on me. It certainly caused a lot of grief and misspent time. I may be looking for another starter for the 401 if the starter rebuild shop can't fix the problem. Could also be lack of shims?

Pete Phillips, BCA #7338

[NTX5467]

Usually, shims are needed only if the starter gear and ring gear do not mesh all the way, or the starter gear is too deep in the flywheel/flexplate teeth.

 

Great that you have rebuild shops nearby!

 

Might check for voltage to or from the starter relay when the engine is running, too.  Might be bleeding over from another circuit or have a chaffed wire insulator allowing voltage into that "apply" circuit when it should not be.  Or a shift fork in the starter that might hang-up /not fully retract under certain conditions.  Solenoid spring?

 

Sometimes, when "all of the doors close", another one might open to reveal where you need to be?

 

Just some thoughts,

NTX5467

 

 

[JohnD1956]

32 minutes ago, Pete Phillips said:

Could also be lack of shims?

For whatever it's worth, I have never met a Buick that needed shims on the starter. Cadillacs. oh yeah.  Buicks, not so much.