Why would you replace a part not knowing if it's the problem? Go rent a pressure tester from AutoZone. Pump it up and let it sit. Watch for the leak.
The original hypothesis behind Dex-Sludge and sudden coolant loss on GMs in the 1990s-early 2000s is that Dex-Cool attacked the IMGs - GM used a glass-filled nylon gasket with a printed silicone bead. However, glass-filled nylon fittings have been used with modern coolants for a while and even the Japanese are starting to use them with their coolants. Toyota used plastic impellers on their water pumps in the 1990s and Mercedes was first to switch to plastic-tanked radiators - which all have stood the test of time but plastic gets brittle over time. A boneheaded move - using RTV to seal coolant passages. Toyota loves that practice - but silicones don’t tolerate plasticizer exposure, all the organic acid salts in today’s coolants are plasticizers(benzoate less so than sebacate/2-EHA).You should apply with Ford and help them 'cause they love it. There's the notorious 4.0 V6 plastic thermostat housing, and the 2.0 in the '08-11 Focii use a weird (and relatively huge) coolant manifold that inevitably fails.
In defense of the engineers, though, these plastic cooling system parts do last a surprisingly long time and much longer than any manufacturer would consider the "lifetime of the vehicle"
Last winter, in the dead of winter in February, the coolant level is the surge tank started going down. I had to put in a half litre of coolant every 500 kms. This only lasted for less than a month and the truck stopped using coolant after that. I carefully checked all the hoses for leaks, checked the tailpipe for wetness and found nothing. No drips from the drain pipe for the heater core compartment. I ordered a heater core from Rockauto, figuring I would replace the core come spring after the weather moderated. In April I pressurized the cooling system to 15psi with compressed air and watched the drain tube from the heater core compartment and did not see a single drop. I have not replaced the heater core yet.
I never smelled any coolant in the cab. I use Dexcool, replaced every five years. No white smoke from the exhaust. I just went and checked the coolant level, it is full and I have not topped it up in four months.
Wondering if I should just replace the heater core. It is a fairly involved job, requiring dash removal.
Yep^^^^https://www.ebay.com/itm/2225926018...DjCNyRANY5PNjCdW6feFaX1VI=|tkp:Bk9SR8zwkKfqYA No such thing as inexplicable, at least not under the hood of a car.If it was me, I’d do a overnight pressurize of my cooling system and add UV dye to the coolant beforehand, drive the truck. That way, you can find a leak where a mirror can’t pick up on.
He did.Why don't you try and pressure test the cooling system?
And looked for a leak out of the heater core drain tube, quote "not a drip".He did.