Hey fellas, quick background info.


2nd owner '03 disco with 86k miles. One year under my belt as a second owner. Soccer dad, everyday car, no off-roading. Average between 1,000 to 1,500 city/highway driving a month. Disco Mike's 60k check off list completed, and then some. So, here's the scoop:


Replaced t-stat back in October and switched from orange goo to green goo. Since then the fluid in the coolant reservoir has slowly gone down. Just added about 5 oz. of green goo this morning to bring the coolant level back up to normal. FTR, I was loosing coolant even before the t-stat change. About the same amount....5 oz. every 4 to 6 months.


Am I looking at the inevitable HG job sooner or later? Can't see where I'm loosing the fluid, so its gotta be going into the engine somewhere. As for the Disco and how its been running? Like a top other than oil "weeps." My garage floor does seem a bit more spotted with oil than when I first performed the t-stat change back in October. However, still can't seem to trace specifically where the weeping is occurring; oil filter vs. rocker or cylinder gasket. Using T-6 oil. Oil changes reveal just a slight pasty texture but only occurs toward the end of the drain process. I'm thinking that some engine detergent cleanings dislodged some built up gunk. Oil cap seems fine and color of used oil is coffee/dark, dark brown, almost black. Change oil every 4k miles.


Anyway...went off topic a little, but was wondering IF and when I need to perform an HG job.

 

A cooling system is a pressurized system so if you're losing ANY coolant then it will never be able to hold the pressure it's designed for. These trucks can also go from perfect to dead after overheating only once so it's best to fix any and all leaks if you can.

Also if the coolant reservoir is low, then you're probably short coolant in some of the upper hoses as wll since the tank sits below some of those hoses.

 

borrow a pressure tester and go to town

 

Look closely at the Radiator, mine was weeping a bit ( couldn't tell where it was coming from) then one day it started leaking worse. I was lucky that I noticed it after a short drive and replaced it. Heat can kill like Brokeit says. Watch closely. Monitor with a aftermarket gauge like an Ultragauge. I use an ELM 324 with my Android phone. Works well for me and is cheaper. It will alarm when temp gets a bit too high, Unlike the gauge on your dash. It's a good or I'm dead gauge.

 

You shouldn't see any coolant loss, although a consistent loss of a shot per month isn't much. It sounds like just a small leak somewhere.


I had a similar amount of coolant loss in my truck that I couldn't find until I replaced my power steering pump. There was a very small area of green coolant on the block below the drivers side of the water pump. However replaced it before me hadn't tightened all of the bolts correctly. I snugged up the loose one to the correct torque and it hasn't dropped since.


If you do have a head gasket leak, it would typically be at the rear of the engine near the firewall.

 

There are plenty of reasons for coolant loss, aside from head gasket failure. My last two project cars had persistent coolant leaks, that turned out to be for the most trivial reasons :

1) A leaky cap on the expansion tank (Triumph TR8). System wouldn't hold pressure, constantly boiling locally, generating gas, blowing coolant out of the overflow.

2) Leaking waterpump.

3) A kinked pipe between the expansion tank and the atmospheric catch tank (Jaguar V12). The kinked pipe allowed coolant out of the expansion tank when hot, but closed up when the system tried to suck it back on cool-down. Result : constantly dropping level in the expansion tank.

This is just to say, there is no substitute for proper diagnosis. Why assume the worst right away? There are tests for leaking head gaskets, do them.

 

Somewhat similar issue and my HG had been replaced by previous owner so I was hoping that is not my issue. For the last year I had been fine with temps (190 to 194 average) but if I filled the coolant reservior to full it would drop over several months to only have a few inches in it but it wouldn't drop any more. This last week it started getting over 200 at idle and every once in a while I would hear the heater core water noise. So at this point I started to really look into it and I still have the original upper radiator hose (old design) and it has a netting over it. It looked ok at first but once I popped it out of the cover the underside of it was a little damp with coolant and there was dried coolant in that entire channel. I have ordered a new style replacement so hoping thats all I have. I dont know if my radiator has been replaced or not but I dont see any signs of it leaking anywhere. Had a squeaky belt tensioner start up as well so replacing all that should be my next weekend project. I ordered a 180T stat when I bought the car but with my temps I never installed it. Think I will go ahead and do that as well for piece of mind. Then the fun part of bleeding the system

 

One observation is some of these trucks don't stabilize at the level marked on the reservoir. Mine consistently drops down an inch below the 'filled' line, then stays there. It did the same thing after I bought a new cap.

So, I'd suggest you let it bleed down then watch it very carefully. It may not 'leak' anymore.

 

That's odd. It should be able to hold the full level. I guess a coolant change on your truck requires less antifreeze than the rest of us.

 

It is weird. I know others have seen the same behavior, or else I'd still be trying to figure what the problem is.