Did a super flush on the cooling system on my xjs 2+2 4.0 1994 as winter was here, as I wanted the heater core which is used rarely, to get a good cleaning. With a prestone cooling flush, ran the car about 50 miles and when drained the liquid was a medium brown color. Did a second straight water flush, still brown but a little lighter. Did a third flush with the prestone and the liquid was clear. I had removed the thermostat to get maximum flow. After the last flush the coolant was returning to the engine at 68c, so during the flush periods the ecm thought the engine was running lean, closed loop to open loop, so I could feel slight surges at idle. reinstalled a new thermostat and ran just cooling liquid, as there is no need for anti freeze here. So running a 4.0 with no thermostat is not a good idea.
John

 

John,

Out of interest, how did you do the flush? Was it by disconnecting the bottom hose or by a different means?

Also, when you say you "just ran colling liquid", you don't mean plain water, do you? Even if you don't need anti-freeze qualities, the real value in dedicated coolant is the anti-corrosion ingredients, to avoid the type of sediment and corrosion that you saw in the brown fluid you flushed. I'd strongly suggest you fill with proper anti-freeze / coolant.

Cheers

Paul

 

Hello Paul,
No I do not use just water, I use a coolant system liquid which has no anti freeze. Even here in Miami only the specialty auto shops carry it. The big auto parts chain stores do not even know what it is. lol The nature of anti freeze is primarily alcohol and is corrosive, so a dedicated cooling system liquid is preferred. It has never reached freezing temp here and the winter time low temps are around 18c. I took at tip from an 1962 austin healy sprite which I had years ago, and I put a shut off valve to the hose entering the heater core. Most years I never use the heater.
John

 

Of the 50 used Jaguar engines I bought/ was given. I could instantly see which had used antifreeze that was properly changed every 2 years. None of them had any corrosion.
Anything you put in the coolant system needs to be flushed every 2 years. The dissimilar metals cause electrolysis. The resulting acid is what causes corrosion. Never use tap water!
. Use distilled water and antifreeze changed every 2 years. That’s what the factory recommends. I’ve tried others like water wetter, waterless coolant etc. they all seem to have issues. Either over heating, water pump failure, hose reaction or something.
Maybe there is something new out there. In 48 years of working on Jaguars I haven’t found any items that work better.

 

Antifreeze is cheap, and every shop can flush/replace it when its time? (Two years is the right idea)

Why overcomplicate this? Specialty shops probably charge a premium for this?

 

Hi Vee,
Straight coolant is way cheaper than antifreeze coolant. Antifreeze coolant is simply coolant with alcohol added, thus the antifreeze label. In my Jag, straight coolant runs at a lower temperature. So it keeps the engine cooler when running the ac and it's 98 f outside.
Of course there are very few areas where freezing doesn't happen.
John