Previous owner used Dexcool in Modular 4.6

[Falcon_LS]

I did a coolant flush on my Grand Marquis back when I got it in May, using over 20 gallons of distilled water and a 50/50 ratio of Motorcraft Gold G-05. The stuff that came out was as brown as chocolate milk and initially a bit thick like pudding. I even used Liqui-Moly Radiator Cleaner to flush out the stuff in the cooling system. I was tempted to do another round after the water came out clean, but because I was running out of distilled water, I said I'll do a coolant flush after 20,000 km. I also replaced the radiator cap and installed a 180 F thermostat for an F150 Lightening (Motorcraft RT1144).

Yesterday I found out, from the garage this car was taken to, that when the water pump was replaced a few years ago (2006) they added ACDelco Dexcool into the system because 'it's all they had'. They didn't flush out the old coolant either - just topped up with Dexcool and tap water. I reckon that explains why the coolant came out brown. This is a Job 1 (early production batch) vehicle, built in September 2000, and comes with Motorcraft Premium Green from the assembly plant. There was no way green coolant was going to turn brown.

Although I already did a coolant flush, and when I take out a sample from the radiator with a turkey blaster it looks a nice shade of bright yellow, I am worried. You cannot see inside the coolant reservoir because the sides are all caked in brown - despite the flush.

I'm going to be doing a coolant flush earlier than I initially wanted to. Considering they also ran tap water, I am going to be using an anti-liming agent in the cooling system for a while. I know there are multiple approaches to clean this up, but I'm not keen on running something like a Prestone 10 minute flush. The Liqui-Moly Radiator Cleaner contains a mild soap type solution, which is why you run it for 30-45 minutes.

Although this sounds crazy, I even thought about replacing the thermostat with an originally fitted 195 F one, flushing out all the coolant and running clean distilled water with small dose of Tide or a dish washer tablet for 1,000 km (625 miles). Would this be a decent approach?

Thanks!

 

[bluestream]

Ford Green coolant can certainly change to brown with age and rust/dirt from internals. I would not worry much about the Dexcool, its actually a good coolant ind is used in millions of vehicle worldwide.

 

[rslifkin]

Bluestream - Dexcool in itself isn't an issue if the conditions are right. However, Dexcool (or dexclones) mixed with other coolants makes for nasty sludge.

 

[wapacz]

Originally Posted By: rslifkin
Bluestream - Dexcool in itself isn't an issue if the conditions are right. However, Dexcool (or dexclones) mixed with other coolants makes for nasty sludge.


I think its one of those myths you hear about the stuff. Probably to do with people who have to add coolant have a leak. Then they let it get low again before they fill it up. Which lets air in the system and that when dex has some problems with sludge.

Just heard to much contradictory statements to think that just plain adding it to coolant its self causes it to sludge. Also the all makes and models stuff is usually a type of dexclone and I can't see a company marketing an all makes and model if it will sludge when mixed with other coolants.

 

[rslifkin]

I've seen the all makes all models stuff create nasty brown sludge when mixed with regular green, even if the system has never been low. Then again, I've seen other systems where it's been mixed with no sludge. It seems to depend on the cooling system and luck.

I still wouldn't mix willingly, however.