Engine forensic experts needed

Forssling · 11-03-2019, 03:18 AM

Hi All,
I'm restoring a -71 T engine. The other day we took the block apart and through the whole process everything has looked good. No damage or metal flakes.

I'm now cleaning the block halves, working the right side. One of the oil pressure relief valves still in the case, I remove the plug and the spring but the valve seems to be stuck. No problem, I use a thin aluminium tube and gently knocks it out from the other side

To my big surprise a pile of metal debris comes out with the valve. (so it must have been to the "other" side of the valve). It is not magnetic, but "feels" heavier than magnesium or aluminium.

I do not have the history on the engine, I don't know how long or why it has been sitting. But as I said, everything else has been good.

I am amazed by the amount of debris, I have the valve in the image for reference.

What could this be? Any suggestions?

Appreciate all input,
Jörgen Forssling
Gothenburg

SWEDEN

356RS · 356RS's Garage

Can you post a picture of the all the bearings. This will help on trying to figure out what happened.

Discseven · Discseven's Garage

Jorgen... if I understand correctly, debris was on pressure side of relief valve. I'm not familiar with '71 T engine so am applying later knowledge---that being there being nothing between the pressure pump and the relief valve (but for the safety valve.) I've heard of oil pumps going bad which is a possibility (provided '71 T engine oil system is configured similar to later models.) Can't see any gear "teeth" in debris so am not 100% sold on "oil pump failure." Regardless, that's an impressive volume of whatever it is. Something that may be a clue is the fact that debris logged in the pressure relief. The "event" must have triggered an oil blockage downstream from the relief forcing the relief to open ahead of that material making passage in system. The relief must have remained open while the debris settled there---total speculation on my part.

Am very curious where forensics leads here.

.

dannobee · 11-03-2019, 07:41 AM

Oil pump gears, left over from a previous failure that didn't get caught (if the current oil pump looks ok). There's nothing else that it could be since the J-tube goes right from the pressure side of the oil pump up to the T-stat, then to the pressure relief valve. Anything else would have had to pass through the pressure side pump gears. That's my guess.

Make sure that you replace the engine mounted oil cooler, too. There's probably left over trash in it.

bpu699 · 11-03-2019, 08:34 AM

Wow. That’s an impressive amount of shrapnel...

You would think that’s from a prior engine failure...just trying to imagine how someone could have rebuilt a motor at some point and missed that...

If that a motor that is new to you, and never run, then the same shrapnel might be down stream...somewhere...

Forssling · 11-03-2019, 10:27 AM

Thanks all for your input.

First to clarify, it is the pressure relief valve positioned to the front/right of the engine. When tapping out the valve I put the aluminium tube in the hole where the oil pressure sending unit goes so all that shrapnel was pressed down towards the valve.

I don't have the bearings at home, so no images of them, but I can assure if they've lost big chunks of material we would have noticed

Another clue to this mystery is that I took one of the small flakes and held it to an open flame of a candle, just to see if it was magnesium that I know would burn. Instead it melted instantly. So I would guess lead or tin...

Where could some soldering come from? The oil cooler? It looks great and have no signs of leakage but with this info I will take it to someone to test for flow.

Also, I have removed the oil pump, taken it apart and cleaned all parts before reassembly, no problems there. Not a sign of shrapnel there or anywhere else in the engine.

Could it have been a oil sending unit of a questionable brand. Or some PO-hack job on that end?

Appreciate your input as always!

//Jörgen

bpu699 · 11-03-2019, 04:42 PM

Doesn’t make sense...

Too big to get through oil pump strainer...yet looks like it went through the oil pump?

Are you saying this was in the pressure relief piston near the spring? Meaning, not in the oil path? Or, you took the piston out, and then this came out of the passage?

Anglocanadian · 11-03-2019, 06:30 PM

Could it be an oil way baffle plug ?

Walt Fricke · 11-03-2019, 09:00 PM

Melted in a candle flame?

The engine oil temperature thermostat operates on the expansion of wax due to heat. As the oil going through the thermostat heats up, the wax expands and forces a plunger out of the unit. The force this plunger exerts opens the "valve" to the engine mounted oil cooler. When cold, the oil goes directly to the engine oil passages (starting with the big one heading to the rear of the car along the top of the engine). All the oil flow to the engine goes by the pressure piston, which is sort of down in its tube below the level of the oil gallery, if memory serves.

If this is wax from this source, you'd expect some would get into some of the smaller oil passages, causing problems. And some would be bypassed (starting cold in the winter, for instance) back into the sump, where it would end up on the scavenge side filter.

I'd guess this didn't get through the oil pump - I'd suppose it would look much different, as it would be in thinner and more uniform shapes.

But that's just my guess. The part which is pressed outward in the thermostat looks sort of like a nail with a round head. It amazed me that pressure on something of so small a diameter as the shank of this piece could be so forcefully moved.

If examination doesn't show anything suspicious about your oil thermostat, put it in the freezer for a while. Then toss it into a pan of boiling water, and watch to see if the "nail" starts to emerge. If it doesn't move, the internal unit has failed. They can be replaced, though opening the internal thermostat isn't as straight forward as is opening the external thermostat - which the '71s didn't have, I think - certainly not the T model.

But if it is wax, I'd think you could deform it with your fingers. I'm pretty sure these cases were not cast using the lost wax process.

Forssling · 11-03-2019, 10:37 PM

Hi All, and thanks for trying to solve this mystery.

First, it is not wax, it's definitely metal. It was not between the spring and valve, it was after the valve. I took the spring out but the valve was stuck, so I forced it out from the other side. I got it out with this debris.

I agree that nothing of this makes sense. When I got the engine it lacked both oil thermostat and oil pressure sender so my guess is that at some point this got into the engine when it was sitting (for how long, I don't know).

I don't know what an "oil way baffle plug" is. Taking the cylinder bolts out we used heat from a heat gun. Is it possible that we could have melted something?

//Jörgen

stownsen914 · 11-04-2019, 05:54 AM

I second an earlier opinion that this stuff may be residual from an earlier rebuild that involved an engine failure, and the rebuilder didn’t bother to open the relief valve to clean it. Since your oil pump looked good, it couldn’t have passed this stuff. I can’t see how the debris would get there otherwise.

Forssling · 11-04-2019, 06:02 AM

I agree, no signs of any wear on pump or bearings.

But what would use a soft metal as lead?

I think it might have gotten there sometime during storage. Maybe someone doing a bad prank for the next restorer...?

I'm not too worried, everything else looks good and all bearings will be new since I'm doing a complete rebuild.

//Jörgen

Walt Fricke · 11-04-2019, 09:01 PM

Nothing I can think of which could melt due to use of a heat gun to loosen the cylinder head studs. Anything plastic is a long way from where this stuff was. Sounds like it was something which dropped in through the hole left by the engine oil thermostat's removal from the period of storage. Could be about anything.

Lead? Weber carbs have some passage ways sealed with round led balls as plugs. Don't know about Zeniths. Hard to imagine body lead getting in there. What else is lead in the engine or engine bay? Melted bearing lead isn't going to look like that, plus you said bearings look pretty good.

I've had the oil pressure sender apart. Little bits of solder for the little wires, nothing to amount to this. The idiot light sender has none, or at least even less.

Might be a good idea to pull the plug at the alternator end of the main oil gallery and see what might be in there, though.

If you decide to replace the plug with a screw thread plug, be very careful, as there is an oil passage at 90 degrees to the main gallery very close to the plug.

dannobee · 11-05-2019, 06:08 AM

I'm with Walt on this one; there is no solder in the engine, AFAIK. The only thing that I can possibly think of was that someone tried to repair a leaking (engine mounted) oil cooler by soldering it up with household solder. Since it doesn't appear that the trash went through the oil pump, that leaves a very limited amount of things that could have possibly happened. The only things that are after the oil pump but before the oil galleries are the engine mounted thermostat and the engine mounted oil cooler. The external oil cooler(s), lines and thermostat are on the scavenge side of the pump and if soldered up, the trash would have ended up in the oil filter or the oil tank, but even then, nothing that big could have passed through the oil filter bypass. That's my wild ass guess. Other than that, I'm at a loss to where it all came from.

Forssling · 11-05-2019, 06:31 AM

I'm just as puzzled as you are... The only thing I can do now is clean everything thoroughly and put it all together with new seals and bearings. It will be one of the unsolved mysteries I guess, but I would really like to know what actually happened. Conspiracy theories welcome!

Thanks for your input!
//Jörgen