My friend's 2000 4.0 Discovery had frozen coolant this past week when it hit -40F (without windchill). Blue 50/50 mix, head gaskets are around 12,000 miles old. We never EVER had the thought of it getting that cold here in WI.

He first noticed this when he started it and it overheated in about 5 minutes (on the readout, no Ultragauge). No strange noises besides a cold whiny power steering system.

I drove over in my 2014 RRS (the only thing that started nevermind the only one in the garage, and it is on summer tyres!) and check the coolant res, it was indeed frozen and pretty low. The hoses were cold but liquid.

(Edit) No waterfall sound, no overheating, no loss of power, no codes, no misfire, no smell of coolant.

I told him to put it in his garage, which included some clearing of things but it liquified the coolant after around 4 hours of being in 50F.


A few days later (actually Saturday) he complained about a possible coolant leak and mentioned possibility of a cracked block. I dismissed that thought and we checked oil level which was a little low but normal after around 2500 miles, and checked the bottom of the engine for any signs of a coolant leak. That was a negative. I did notice the throttle body heater plate was leaking, but it is a very slow leak with little coolant residue to show.


Today he shows me a photo of where the truck was parked, and marked into the ground is a metric TON of coolant spread over in little drops basically the entire right side area of the engine. This is where I start getting worried. That would mean the bank 2 HG is leaking from every available cooling passage, plus all the hoses, rad, etc.


I plan to get it onto my lift again and pressure test the cooling system, see if I can find any other leaks. I will also bypass the TBH until the new one is ordered from LK8 or PT Schram.

tl;dr:
coolant froze in -40f, now leaks coolant from unknown locations all across the ground in little puddles on the right side (US pass side) of the truck. Worried about a cracked block.

 

I blame it on Global Warming. /sarc

 

Pressure test watch for drips. IL was Cold as hell.. should have thought about running it for a bit, researching the coolant used, parkign it in the garage, prepping in some way.. I hope it's just a rubber/plastic hose leaking.

 

Or a freeze plug

 

Sandman, I installed BMW Blue 50/50 coolant, rated up to -35c. This is good enough for the -20F they said it was going to be, as I mentioned we never ever have a. seen this temperature and b. expected this temperature. It was run for a little bit, "warmed up" and he went back inside, when he came out it was hot and he shut it off. He would have parked it in the garage, again, if he knew the temp would go to -40 without windchill. Absolutely insane.

I live in IL, he lives in WI.


I too hope it will only be a hose or similar, would a heater core leak to the outside? Most hoses are new besides IIRC the lower rad hose which is only a few years old. I can't check the carpet for a leak as it is saturated in moisture from snow covered boots.

I have the vehicle in my posession now, I think later in the day after I come home from Chicago I will put it on my lift.

I will check around the freeze/core plugs. Although if those are bad, I assume the rest of the block is too.

 

Nope freeze plugs are supposed pop to save the block that is the whole idea behind them. They do not always work, but generally they do their job.

If the plugs are leaking in theory your block should be ok

 

That's what I was thinking

 

This is incorrect. The "Freeze plugs" are called that because they do frequently pop when a block freezes, but that is not what they are designed for. They are actually casting plugs that are part of the block manufacturing process. This is why they do not always work when blocks freeze.

Every engine is different depending on the design of the cooling passages in the block. I froze a 3.8 Buick V6 once and it cracked the block next to the lifter valley. Good news if there is no coolant in the oil you don't likely have a cracked block. Good luck with the inspection.

Also, lived in Northern IL for 8 years - my trick was to put an incandescent trouble light under the hood or my dual halogen work lights under the truck pointing up when it got really cold. 20 degree day the engine compartment will heat to 70. -40 it would probably stay above 0.

 

Extinct interesting I have always heard of them referred to as freeze plugs - learn something new everyday.

 

Did not get it on the lift. Finishing a CNG conversion on a Transit, fuel lines are disconnected so no moving it.

I looked, the coolant bottle was about a quart low. Quite a bit less than the last time I checked it.

I looked at the head, no coolant residue there so no head issues.

Hopefully I can get the thing on the lift soon.


Has anyone replaced a core plug? I've had my machine shop install them.