I have a 2001 Disco with 110,000 miles. I am stationed in Montana and moved from New Mexico, the Rover and myself are not used to the extreme cold winters here. I did a tuneup last year when I got here, replaced the spark plugs, got the larger magnecore cables, and switch to 5w40 for easier startups in the winter along with a cold cranking amp battery. Recently the temps dropped to -45F with windchill, I started the Rover and let it run for 10-15 mins to warm up before my wife would drive it to work. A few minutes after she leaves she calls me and says there’s smoke billowing out of the engine bay and the trucks overheating. She pulled over ASAP and turned it off and I was able to pick her up and tow it home later that day. After inspection I find that all of the coolant hoses have shrunk, loosened their fittings, hardened, and dumped antifreeze all over the exhaust manifold. I order a complete hose kit from Lucky8 along with a new low temp thermostat and install it and bleed the system. Run the engine let it warm up and cool for a day, check and fill the system as well as bleeding it again. Let it sit for another day and verify coolant stayed level so I start it up and take it for a test drive. Everything seems fine as I pull over and check that the hoses are not leaking, continue to drive, then slowly start to see the engine temp rise. I make it home turn it off, pop the hood and see coolant coming out of the expansion tank cap along with the drain on the expansion tank. Luckily I had a spare expansion tank cap, so the next day I refill and bleed the system and put on the spare cap, and take it for a drive, same thing, temp goes up and the cap is leaking. I plan on ordering a new cap to hopefully resolve the issue, but am I possibly overlooking something else? Could the threads on the expansion tank have a hairline crack I can’t see causing the leak? Could the water pump be busted and not pumping correctly causing too much pressure to build up and blow out of the cap? I’m at a loss. Additionally as for the original hoses shrinking I assume it was due to the extreme cold and that some of the antifreeze froze in the hoses and the drastic change from cold to hot then back to cold caused them to compress on themselves, so I’m assuming I will also need to install a block heater and oil pan heater for days like this as well. Any input or suggestions are appreciated.

 

The first issue almost certainly was due to fittings having shrunk. Plastic is especially bad for that. I hope your current issue isn’t serious.

 

Had you tested the protection level of your coolant prior to this? -45°F is pretty cold and while wind chill won't have any effect on the engine, it had to be pretty cold out to get that low with the wind chill. First thing is to get a cooling system pressure tester. Fill/bleed the system, let it cool, and attach the pump to the overflow. Pump it up to about 10PSI and see what happens after an hour. Park over cardboard so you can identify any leaks. Listen for leaks around the overflow bottle as well. If there's a crack above the fluid line it will leak air and not coolant. Once you have all the leaks sorted out, loose clamps, cracked fittings, etc if it still won't hold pressure for an hour it's time to consider damage from either freezing or the overheating. "Turning it off right away" once steam is billowing out is not a guarantee that something bad didn't happen. Once the needle begins to rise in these trucks you're well on your way to a dangerous situation. I've never had mine over 210° but I can tell you that the needle is right in the middle at 165° and 210°, which makes it completely unreliable as a data point for overheating.severity.

 

No I hadn’t tested the protection level, I’ve been here coming up on two years and haven’t had this problem with the negative weather before but then again it had never been that cold. I had read having a higher mixture of coolant could help stop any freezing occur, so I could change the ratio if that’s the case, but the following week the temps jumped back up to positive 40F, so I would have to change out the fluid again. I will get a cooling system tester to pressurize the system, but the system was pressurized when I had driven it for the test drive, and I have no leaks from any of the new hoses or clamps, no leaks on the block, no leaks from the heater core either, the only thing leaking is the cap on the expansion tank. The plastic yellow warning label around the collar of the expansion tank was drenched and fluid was hissing out from around the bottom of the cap. I’ll be replacing the cap once it arrives from Atlantic British but didn’t know if this was a sign of something else like the water pump, etc, causing the coolant to fill the expansion tank and force its way out of the cap

 

The cap's a great idea however in most normal situations a cap that won't seal is not a problem. The cap just allows the system to pressurize which raises the boiling point of the fluid, but a normally operating Disco won't boil regardless of the internal pressure (or lack of). Most of our trucks run in the 185°-210° range, or at least that's what we all seem to strive for. Coolant escaping the cap is a symptom and not a cause.

Also, there's no need to be changing your fluid, if you go with a 50/50 concentration of antifreeze in your cooling system you're good to about -35°. If it gets significantly colder then a 70/30 mixture might be more appropriate but there's no downside, other than it's more costly. 70/30 should protect you down to -60° and up to 235°.

 

Okay I’ll try to get a pressure tester and see what happens. It’s weird that I had been driving for about 10 minutes with the gauge in the middle before temps started to rise, and
got it home, so it’s been in my driveway since but the only wet spots and signs of a leak are from the cap and expansion tank. And as far as the fluid ratio I hadn’t changed anything it was a 50/50 mixture prior to this happening

 

Just a simple suggestion you have a few possibilities a :

• cooked water pump no circulation will over-heat pretty quick.
• Dead thermostat
• I hate to say it but it could be a failed head gasket - when mine failed it was just a hairline crack but it over pressured the system. I never overheated 197ish at hot idle, but it dumped af out of the overflow hose. Passed an Exhaust gas test too.

 

Thats what I had assumed as well, I was trying to get other suggestions prior to purchasing anything so I could get it all at once, but right now I only have the cap and a new tank in order. And the head gasket might be the case, I had replaced them a few years ago due to an oil leak but that is a possibility. I should be able to get my hands on a pressure tester this weekend and I’ll see what happens

 

Pressure tester revealed a leak coming from the water pump, ordered a new pump and gasket from Atlantic British, will install that and then run another test