You know, the knock sensor wire was already exposed on the harness, and so I gooped it with a dab of gasket maker. I’ll double check that it’s connected and run safely...

 

I started the truck up today and the CEL came one an d flashed for about 20 seconds and then went solid. After a long drive I parked and noticed that the coolant hoses were rock solid and coolant was leaking from the reservoir drain.

what now?!?

 

Get the codes read but rock solid coolant hoses tends to be a bad thing

 

The codes are the same as always p0304 and p1319 they seem misfire related at start up.

the idle is rock solid at 800rpms, acceleration is a tad rough from start, just at the very beginning.

the coolant thing is new today. I will swap out the thermostat housing with a spare, bleed the coolant again by raising the housing and opening the bleed screw, and I can also swap the reservoir cap.

what are the worst case situations here, is it a cracked block or something? I just replaced the headgaskets and had the heads machined and the block was within spec as well according to my machinists level.

 

Does it run rough when you start it or when you go to accelerate?

did you swap plugs and wires around? How much coolant was leaking out of the reservoir?

 

It runs rough for 10-20 seconds when I start it up after a few hours, then the idle smooths out and it seems to drive fine with no flashing CEL, and the idle in park is dead even at 800rpms. If I erase the codes the CEL does not come back until I start the car again after letting it sit for several hours, or overnight. Always cylinder 4 misfire, and usually the p1319 code, and occasionally the knock sensor code.

There was a pretty steady stream of coolant coming out of the vent hose, we left the car before it stopped. The upper road hoses were rock hard.

The wires are brand new Kingsbourn (sp) ones, and are 8mm. I did a spark check and the spark plug in cylinder 4 seems to spark just fine. I have not swapped wires yet, and I did not swap the plugs, which are brand new as well.

 

Sounds like coolant getting into 4 and causing the rough idle while it burns off when you start it up. Pull the plug from 4 when the engine is warm and look for bubbles seeping into the cylinder with a boroscope. The only cause of coolant getting into 4 unfortunately is a cracked block. Is it an '03?

 

It’s an 04.

that makes sense, but definitely doesn’t make me happy. Is that repairable?

I do do have a parts 02 RR that also has the 4.6 so I could pull that and use it in the disco.

would this also cause the pressurization of the cooling system?

 

If coolant can get into the cylinder then combustion gasses can get into the coolant via the same cracks. First steps would be to look for signs of coolant in 4. This is what happened to me only on 5. The coolant just burns when the engine is hot (as long as the cracks are small) and then after shut down the system is still pressurized and coolant goes into the cylinder but does not burn... Then you start it up and it misfires from the coolant being in there until it does burn off. Eventually the cracks get bigger. In my case I did use the dreaded block sealer because I knew I needed a new engine anyway. It worked and bought me about 10k miles while I saved up for the swap. As you can see in my signature I found a block from a P38 and it has been great so far.

As I mentioned, check 4... Pull the plug and see if it is wet. Get it up to temp and shut it down, wait a bit then pull 4 again and inspect inside with a USB boroscope camera on your phone. Cheap online. look for bubbles around the top of the liner as the pressure forces coolant through any cracks that may be present.

I've read a cracked block is repairable with proper top hat liners... Not a cheap fix but there is a place in LA that will do it for $1500 ish plus back and forth shipping of the block. If you are thinking of going that route you would be best to pull the block and have it pressure tested (while hot) at a machine shop first... Just to verify the diagnosis.

If you have to take the engine out anyway and you own a P38 parts car with a known good engine that would seem like the better option to me.

As for your knock sensor, those wires are coaxial cable that shield the low voltage signal from electrical interference around the engine. If the coax is compromised the knock sensor will not work and you will get a code/CEL.

 

Hi Dave,

thanks a bunch, it’s kind of what I feared. I knew this was a possibility when I bought it so there’s that.

to be honest I’d prefer to use some block sealer and keep the truck going, it’s my wife’s work truck and generally runs less than 5000kms a year, until I’m finished stripping the parts RR.

My RR needs a bunch work too, hence the parts car, so I can’t exactly rush the Disco engine transplant at the moment.

My immediate issue seems to be the pressurizing of the coolant system. If coolant is leaking into the cylinder, can exhaust gas really leak out into the cooling system at the same time? I suppose I would need to buy a combustion tester to be sure?

as far as the knock sensor code, if the wires are exposed on the harness, eventhough I sealed it with RTV, how do I go about replacing that as it seems to be let of the engine harness?