RTV is not an electrical shield. The entire length of coax needs to be intact up to the point it joins the harness where the two wires come out of the coax and join the harness. Where did you put the RTV? at the harness or somewhere along the coax? Any pinch or break in the actual coax will be a problem and is not fixable. You have to replace the coax from the harness out. You can take the one from your parts P38 out from the point the wires come out of the harness and use it to replace the damaged one. It is ok to solder or crimp connect the wires at the end of the coax on the harness side. You just can't repair the actual coax if its pinched, nicked, or cut. If you don't understand coax, look it up and it will make sense. The outer wire is grounded and forms a shield around the center wire to impede any electrical interference. Any break in the shield ruins the coax.

As far as the cracked block, do the tests and let us know what you find.

Keep in mind, once you use block sealer you will also need a new radiator and cooling system when you replace the engine.

 

Yes the wire was skinned open to expose the wire somewhere behind the crank pulley area. It must have been rubbing.

anyways, sounds good, I’ll use the entire
length from the parts truck.

ill be heading out to check the cylinder and swap the spark plug, etc...

as as far as replacing the cooling system, I have a Lincoln mk8 electric fan, and all of the parts ready to do the inline thermostat mod, so I might as well add a full aluminum rad into the mix and have a brand spanning new
cooling system to go with the replaced engine. I’ll likely do a top end rebuild on the donor engine and perhaps replace the rods, lifters, and camshaft as well as the water pump and oil pump.

i also have have a brand new reservoir to swap in, just in case the pressure issue is from the cap, as others have apparently experienced.

will report back.

 

Seems like maybe you could shove a rope or long cotton wick through the spark plug hole after it’s been sitting for a while, see if it picks up any coolant but yeah it sure sounds like a cracked block. I’m curious why you did the headgaskets in the first place

 

I have a camera so I should be able to see in there.

i did the head gaskets because there was a massive leak out the side of the head. Both 4 and 6 blew the head gasket right out the side of the block. Sounded like a freight train!

originally I bought it as a parts truck, but it’s far to nice to destroy.

i had a busy day today, but I’ll be able to get to the cylinder 4 tests tomorrow

 

Ok so this morning I’ve had some time to do some diagnostics.

i pulled the spark plugs from cylinder 4 and 6 and ran a borscope into each. Cylinder 4 looked like it could be a bit wet, or shiny because of the light, and while it did look a bit washed, it was like that when I put the heads back on.

cylinder 6 also looked shiny, so it was hard to tell if it 4 was actually wet. I swapped the spark plugs and put it back together. I also swapped out the coolant reservoir cap in case that was the case if the coolant pressure issue.

i hooked up my C-reader and checked the codes (p0304 as always, and the code for the knock sensor where we determined that the exposed wire in the harness was the most likely issue). I cleared the codes and started the engine.

no issues, no stumble, no flashing CEL, no CEL at all. This was the first start after sitting overnight, so there should have been some coolant in there no?

anyways, we’re about to embark on a short ride to see if we can get the codes to come back, and to see if the expansion tank cap helps with the pressurized coolant system.

as a side note, the three amigos are back. I’ll have to do the option b mod again as I did on my last disco.

thoughts?

 

Three amigos gone again, CEL back, and coolant hoses seem too hard.

any idea how stiff they should be? I’m not losing any coolant out of the expansion tank vent or anything, but they feel hard.

ill go out and get a combustion leak tester tomorrow and test the coolant for exhaust gasses.

 

My coolant hoses have always been hard when hot, for the last 40k miles anyway....

 

Soooo, I started up the truck today, had the flashing CEL again, and this time jumped out to look at the exhaust. Sure enough it was blowing white smoke pretty much until a bit after the flashing stopped.

same code for the cylinder 4 misfire.

it looks like the block is cracked in cylinder 4

I’ll pull the 4.6 from the RR and get it all sealed up properly, replace the head gaskets and install my studs from the blown engine, and hopefully I’ll be good to go.

thanks for the help folks, as usual with the Disco you trouble shoot like crazy to try and avoid the inevitable bad news about the engine block.

ah well, at least I have a spare.