2004 Disco 2 4.6

Hello all, new to the forum, semi-new to discos, not so new to fixing broken cars.

I bought this disco 2 one year ago, 150k miles, unknown head gasket history. Motor ticked when I purchased it, I did my research on what the common internal failures are on these motors, and for the price of the vehicle decided to take on a future project.

​​​​​​Engine tick is sometimes present all the times, sometimes just under 2000rpm, sometimes not at all.

I decided to drive it until it went kaboom and it ran great until a couple weeks ago. Overheated, noticed it was low on coolant. Filled per rave manual instructions, limped the car home. Finished filling coolant, started and ran/sounded normal, not running rough at all. noticed the throttle body heater gasket leaking so I bypassed it, in the process spilled a little coolant onto the spark plug wires and possible in the plug area, not enough coolant for real concern IMO. Started it up and it barely ran, misfiring like crazy and pumping coolant smoke out the tail pipe. So I thought, okay head gaskets have finally failed, not surprised or really even upset. I found it odd that before the coolant spill it ran normal, then suddenly had major failure symptoms. Possible the gaskets just failed even more by running it longer?

Anyways, I'm certain the head gaskets need replacing, but am also wondering if the block is cracked and the engine noise was a slipped sleeve the whole time, or something else but the overheating caused the block to crack.

I've done a fair amount of research on how to pin point if the block is shot.

but my question for you all is do you think it's worth finding a junk yard engine and doing a top end rebuild or just scrap the whole car and move on?

I have plenty of experience rebuilding motors, I'm not concerned about the difficulty or time involved.

The chassis is clean and the frame is in great shape for being a Minnesota car. I'd love to keep driving a disco and wouldn't be opposed to finding a different one but surely to just have similar issues down the road.

Thanks in advance

 

Try to find a P38 4.6. The engines seem to be of better quality for whatever reason. I had the same issue - engine was ticking and died at 140k with overheating. I found a running P38 with 111k miles. Pulled the engine, tested it for leaks and compression, did all the seals and gaskets without heads and it worked out well. I kept the old block and think about rebuilding it if that is possible.

 

In my experience cracked blocks are extremely rare. I have had one suspected in 20 trucks almost all of which were overheated at some point. and that one is only suspected (have not confirmed yet with hot pressure test). The only way to really confirm is a block pressure test with the block hot, most folks don't have that equipment. It might be possible if the crack is bad enough to detect with a normal pressure test you can't really try without the heads off. You can get the heads off in about 4 hrs with the engine in the truck, and if the gaskets are obviously blown then you probably have found your issue. You can also have the engine out of the truck in the same 4 hrs and much easier to rebuild on an engine stand out of the truck. You can easily pressure test, inspect bearings, seals, and even pin the cylinders relatively easily with it out. Running the engine cooler than the temperature point (usually around 200 degrees) using an inline thermostat sometimes resolves the ticking, pinning the liners always does. I have only seen one 4.0 ever that had slipped cylinders, usually it is the 4.6's. You can swapp all the 4.6 internals in to a 4.0, I have driven dozens of trucks and cannot detect the power difference seat of pants. Rebuild parts cost have a huge range but you can get away with less than $500 pretty easily.

Truck is likely worth less than $1000 in current condition with blown hg, with a refreshed top end or engine likely worth a minimum of $5000 if the frame is as good as you say. So probably worth the investment even if you do sell and replace with better.

 

How much coolant ran into the spark plug hole? If it was a significant amount, it’s possible that the cylinder hydro-locked when you started it. This could cause several types of engine damage. If this is what happened, a damaged HG might be the best case scenario.

 

A few ounces at most. Just whatever came out of the TB heater hose when disconnecting. Can't imagine that much got into the cylinders. I ran it for 10 mins and it was thick white smoke that didn't decrease.

 

Was the spark plug out when you spilled the coolant? I assume it was, otherwise it doesn't really bear mentioning. If so, perhaps instead of hydrolocking it blew the headgasket out worse in that cylinder and is causing the excessive steam. If it did hydrolock I think you'd be hearing some pretty awful noises and have running issues beyond just steam. These motors are simple to work on and assuming the interior is nice too I'd say it's worth fixing regardless, as a bonus as an 04 it's got the upgraded front end and a CDL as well. You can have the block tested for cracks.as added insurance, but as pointed out, you can get the engine out fairly easily and once on a stand address the liners as well. 150k is relatively low for a well maintained truck so once back together it should be worth the T&M investment.

 

This is what I'm thinking as well. Seems like not that bad of a project. The pinning process seems straight forward. Are top hat liners necessary as well? Or is that just if a block is cracked?

Plug was not out, but possible it was loose and some coolant seeped down. Unlikely, but just wanted to explain the order of events for accurate feedback.

 

Nothing will fix a cracked block, not even top hats. Top hats are to eliminate cylinder slippage. If you decide to pin the cylinders pm me and I will provide some details.

 

Finally got around to pulling the heads off this today. No evidence of HG blow on the gaskets themselves.

Cyl 6 piston appears steam cleaned. The sleeves is flush with the deck however.

Being that this is an inside cylinder not near a coolant port, my research tells me the ONLY way coolant can get into this cylinder is from between the sleeve and cylinder due to a cracked block. Is this correct?

 

That is correct. Hot pressure test is in order if you saw no evidence of blown hg.