High Mileage BRM Post Mortem

[325_Guy]

It took a little over 462,000 miles, but I finally ran into some unexpected engine trouble yesterday that I'm in the process of narrowing down to simple injector replacement or something worse.

Yesterday my BRM developed a serious shake and intermittent white smoke at idle. It drives fine, although I feel that there's less power, but I'm also not going to floor it at this point to check. I had to drive it about 200 miles after the symptoms began in order to make it home.

CEL is lit, VCDS reports Cylinder 2 misfire. IQ Deviation is:

2.99 Cyl 1
2.99 Cyl 2
-3.01 Cyl 3
-3.01 Cyl 4

I'm going to perform compression test once I get home to see where the block is at. In the meantime, my two questions are:

What would I look at to refresh the head? I have what I think is a small head gasket leak as well, so the head will be coming off. What needs replacing to bring the head back to new condition? Is it worth it to do the parts individually? Or should I look into a replacement head from Franko6 if he has them?

Injector / nozzle recommendations? I'm currently running a GTB1749V from Darkside Developments along with a Malone Stage 4, the 3 bar MAP, mated to a South Bend stage 2. I'm not looking to push too far past my current power levels, but if I understand right the stock injectors are just about maxed out with my tune.

Thanks!

 

[325_Guy]

Well, looks like I will be refreshing the long block.

Compression test (left to right):
430 140 370 380

The 140psi reading tracks with cylinder #2 misfire. That cylinder's glow plug was soaked in diesel when removed.

Nothing of note under the valve cover. The expected rough cam lobe chamfering (current cam and lifters have 125k on them) but the lifter faces aren't dished.

Also, the dipstick was bone dry when I checked. When I get to draining it I'll see what's left in the sump. The oil pressure light never came on, so there's something in there.

I check my oil (along with all other fluids and pressures) weekly with about 1.5 quarts added here and there at fluid inspections between oil changes every 10,000 miles. Last check was on Monday....between then and yesterday...684 miles....the engine drank enough to not reach the dipstick.

Oh well. I honestly can't complain one bit. 462k with nothing but routine maintenance and the steady diet of cams/lifters while the engine endured a lifetime of what the manual calls severe service: extended idling, high temperatures, full-rated-capacity towing across states, high speed / high RPM, extended operation on dirt roads, you get the idea.

My only complaint is to come sooooo close to half a million miles on the original engine!

Anyone selling a long block? I'll come to you!

 

[325_Guy]

As I do failure analysis on this engine, is there anything I can deduce from the glowplug tips?

Two of the four (the 370 and 380 psi cylinders) are covered in powdery white ashy deposits and the tips are eroded.

 

[325_Guy]

Well, while I'm pulling the engine and trans, what better time to replace my 0A4 with an 02S with under 10,000 miles!?

 

[325_Guy]

So I finally got to disassemble my old BRM and found some things:
Cracked #2 piston
Upper cylinder scuffing in line with the wrist pins (scuffing is on the left and right side of cylinders 2, 3, and 4)

Question about scuffing. Is there an upper coolant temp. limit that I should observe?

Why do I ask? I tow, and I have access to some wide open roads. I've gotten up to 230* observed via ScanGauge, and then I'll back off and cool down. Is that a little too much?

In my mind it makes sense that localized overheating would cause scuffing- Cylinder #1 is pristine. 4 is slightly scuffed, and #2 and #3 are severely scuffed.

 

[turbodieseldyke]

I've gotten up to 230* observed via ScanGauge, and then I'll back off and cool down. Is that a little too much?

Doubtful that alone killed anything.

If you can't find a replacement, maybe switch to oversize pistons & drive it less hard.

 

[325_Guy]

If you can't find a replacement, maybe switch to oversize pistons & drive it less hard.

That's the plan, replacement and slightly-beefed up engine is already back in place. Going to rebuild this one in some free time. Any particular pistons to use? I see Nural and another brand.

 

[325_Guy]

Everyone likes pictures

Cylinder #1

IMG_0146.jpeg

• 325_Guy
• Jan 5, 2025

Cylinder #2

IMG_0152.jpeg

• 325_Guy
• Jan 5, 2025

Cylinder #3

IMG_0151.jpeg

• 325_Guy
• Jan 5, 2025

Cylinder #4

IMG_0149.jpeg

• 325_Guy
• Jan 5, 2025

I actually know how the #2 piston cracked. Way back, around 180,000 miles, I finally replaced the #2 glowplug. I let it sit with the CEL for it for too long, as I did not know better. About 1/3 of the ceramic portion of the GP was gone.

Fast forward 285,000 miles, and that piston crack runs right through the round divot on the face. It was carboned up, but using a pick I pulled out some brownish chunks from the bottom of the hole. There's a matching mark on the valve face. Presuming the cylinder ate the GP tip and eventually cracked through just before Christmas.

 

[bmwman91]

Wow! That sure is a big crack in #2. It is impressive that you got so many more miles out of it before the glow plug bits finally worked their way through the crown enough to propagate a crack. I guess these little engines are built like tanks (minus the top end lubrication nonsense).