Red coolant light came on suddenly on the freeway. Stopped immediately and it was steaming out of the coolant reservoir overpressure/overflow. There was immense pressure on the coolant hoses, they were inflated like Michelin Men and they were all hot. After cooling down and releasing pressure I could smell exhaust gases. Also persistent misfires on cyl 4, rough idling. When warm, I can drive only 100 feet and the engine overheats immediately. Engine oil looks good, not indications of coolant leak into the oil. I suspect a failed head gasket. Or could it be something else?

Car was meticulously maintained: 180 thermostat, new coolant hoses, new radiator, coolant system flushed multiple times. Oil change every 3-4k miles, installed an oil cooler to get better cooling. Prior owner did the head gaskets at around 80k miles (I am at 140k miles). No loss of coolant before, I added a few ounces only once per year. I always monitored the coolant temperature and it was in range of 180-190, never observed any overheating or codes.

What are my options now?

1) Install new head gaskets and stuff (risk is that the block is damaged)
2) Install a Turner short block (do they still make them?)
3) Do an LS swap, but has anyone ever done that in California?
4) Sell it for parts (otherwise in very good condition, so many new parts and TC, transmission, diff service just done)
Edit:
5) Get a used engine *** This is what I am doing right now. Scroll down for progress.

 

That sucks! head gasket until proven otherwise....that 'big fat sausage hose' sign is the key........

 

My guess it is not a blown HG, no coolant passages on cylinder four HG.

Two things to help with your diagnosis:

1. Run cap one full turn loose from full tight, it will not build pressure like that (I run mine like that all the time).
2. Pull thermostat out of the system. You did not mention inline thermostat mod so assume you are running factory style (likely what failed and sent you in to the red so fast) so you will need to put a hose splice in its place - the autoparts stores sell a hose repair kit that has a plastic one that will work temporarily. Route the top radiator hose directly to the manifold outlet - lose the tee and bypass hose.

Its almost impossible for an engine full of coolant with no thermostat to overheat. It might drink coolant but that will give you a better clue what is wrong.

If it is #4, likely cracked the block as there are no water passages surrounding the #4 cylinder. It is possible to pressure test the block.

Options if block is cracked:

1. 4.0 from one of the Rover breakers
2. Rebuilt engine from AB, Wedge shop, or UK engine shop (there are several).

 

Extinct: So if it is a cracked block why the pressurized hoses? Liner must have shifted? The crack must be open to the combustion chamber at some point (but not to the engine oil per OP's initial observations)....That's one way I could think that the pressure would have increased as much as described in the hoses...or by a cracked head....or by head gasket fail.....hopefully it's just the cheap easy fail....

dipstick might look OK, but I would also try a finger swipe on the oil cap undersurface and a small taste test...the moisture from antifreeze condenses under the cap, and you can taste it if it's there....

 

I just got it back to my driveway. Started up the engine and it runs without hesitation, but pressure is building up immediately while the coolant temp needle is still in "blue". Coolant hoses aren't even warm, but inflate already and I can release a decent amount of pressure from the reservoir. Thermostat is closed at that temperature anyway, so it can't be a failed thermostat.

 

Sorry Discorama. Terrible news. Wish we were closer. I’m working on an LS swap and would donate whatever you needed but not sure another 04 block would be worth the investment.

 

You can grab one of those exhaust gas testers for the coolant bottle. Should tell you right away if exhaust gas is getting into the coolant.

 

Pressure is building because you have cylinder pressure entering the cooling system. Most typically a blown hg, but rarely can be caused by a cracked cylinder and liner next to the water jacket.



Blown HG and/or cracked block rarely results in coolant in the oil, for that to happen the failure has to expose the coolant passages to the crankcase i.e. be below the piston. That rarely happens.

My comment on the thermostat failure was related to the original cause of you overheat, not the current situation. However if you remove the thermostat from the system AND run with the cap one full turn loose you will be able to drive the truck without it overheating (as long as it is full of coolant) because an engine full of coolant cannot exceed the boiling point of the coolant and if the waterpump is circulating it will not exceed the capacity of the radiator to reject the heat in the cooling system. Even with severely blown hg or cracked cylinders the combustion gas going in to the cooling system is not enough to change the heat going in to the coolant. It is enough to change the pressure, but not the heat.

 

I did some diagnosis on the overheat issue.

1) The thermostat is working properly, I took it out and put it into a pot of hot water. It opens at closes as expected, the flow in the open state is good. The water pump seems to be OK, no play, no noise, water is gushing out at the bleed hole when I spin the water pump by hand (belt removed). I flushed the cooling system and water flows through like nothing.

2) I removed the spark plugs to look inside the cylinder with an inspection camera (see pictures below). Cylinders 1/3/5/7 look normal to me for 140k miles. Inside cylinders 2/4/6/8 there was oil sitting, which isn't normal, but explains the internal oil consumption that I have had since I owned this truck (1 quart per 600-800 miles). Cyl 4 looks like it was steam cleaned by coolant, but not too much. I got misfires on cyl 4 when the engine overheated on the freeway.

3) I also noticed weird milkshake residues at the throttle plate and in the PCV hose (I have the PCV mod). The hose wasn't clogged, just filled with creamy stuff which could be shaken out (see pictures below).

4) Oil on dip stick looked excellent, so signs of coolant mixing into the oil. I drained a quart of oil from the pan and no signs of coolant.

Put it all together and the engine started right away. It runs smoothly and I could't notice any misfires, nor I found codes after the engine ran for 15 about minutes. But, there is white steam from the exhaust even with the warm engine and the cooling system builds up way too much pressure. I can drive slowly on my driveway, but under real load the engine will overheat immediately.

So what could be broken given all the symptoms above:
a) head gasket
b) damaged head
c) damaged block
?

Cyl 2:



Cyl 4:



Cyl 6:



Cyl 8:



Cyl 1:


Cyl 3:


Cyl 5:


Cyl 7:


Throttle plate:


PCV valve:

 

I would not keep starting the engine. You risk making a bad situation worse. Needs to be torn down and fixed. I would start with the heads. Hopefully, no bearing damage....