I have a '05 LR3 4.4 and earlier last year, I started having to top off coolant every several months (I check fluids very regularly). I took it to a reputable LR shop and they found that it held pressure fine via a pressure test. It seems that my coolant level is starting to drop off a bit quicker now and I'm probably going to purchase my own pressure tester since LR shops are not that close to me. Are there any leaks that typically wouldn't be found by pressure tests and maybe would just be found while engine is running?

 

Heat will always have an impact so yes, there could be a slow leak somewhere that only shows up when the engine is running. You can run a dye test to see if you can spot where the coolant is leaking from. Separately, see if you can see any coolant under the front part of the intake manifold -- there is a valley hose there.

In addition to heat having an impact on the expansion/contraction of connection points, head gasket failure can lead to gases in the coolant system which can pressurize the cooling system above its max operating levels. I had this happen in a Jaguar with the 4.2L AJV8 motor and the issue manifested itself as a leaking radiator cap once the cap pressure rating was exceeded.

But to start with, I would assume you just have a hose that is aging and needs replacement, so my first step would be to look for the leak.

 

I have struggled with a similar issue this year and think I just fixed it.

Was loosing coolant and filling it up from the low mark to the high mark on the expansion tank about every 500 miles.

I could not find the leak using a pressure test.

No puddle under the engine with the small front skid plate removed.

Finally the defect in the hose where I believe it was always leaking from got larger so a puddle finally was created over night under the engine.

The culprit was the hose connection at the throttle body. It is a small hose that is hidden behind the larger hose going to the radiator. I think the leak was so small any liquid was burned off so you could not see any puddles on the engine parts. Once the defect was large enough there was enough coolant laying on top of the thermostat housing below it not able to be burnt off.

The hose clamp had damaged the hose at the attachment. Most likely due to the factory pressure clamp was removed so a tighter fit with a worm style hose clamp could be made with the older hose that had lost it's softness.

I've got about 1,500 miles so far with no puddles and the expansion tank shows the same level every time I check it now.

Hope this helps.

 

I too have struggled with this same issue as of late on a recently purchased 05 LR3. I had to replace the upper and lower thermostat housing and while doing that replaced the water pump as well. I could smell the faint odor of coolant afterwards. no fluid on the ground and it tested good with a pressure test. I drove it for about 10 days and very small spot began to form under the truck but only after warming it up. Then the puddle started to get larger, but still could not find the leak. Most of the coolant approved for the LR3 has florescent dye in it so you can see where the coolant has been in the evening with an ultraviolet light. I ended up taking the the fan, belts and water pump pulley off again and pressure testing the system. with the advent of a larger "puddle" I was able to see the coolant coming out of the lower water pump seal vent hole. The brand new water pump was bad! I ended up replacing the new water pump again and while I was in there replaced all of the coolant hoses along with a new coolant reservoir. Happy to report that I now am not loosing coolant ("knock on wood"). hope that helps somewhat with you quest to find the leak,,,

 

Well, my pressure tester arrived and this time, it did not hold pressure. I immediately started to get leaks almost directly under the bottle. The leak seems to be at the coolant tank outlet. I'll get that taken care of and re-test. Thanks for the tips!

 

Btw, is there recommended interval for changing coolant hoses, thermostat and thermostat housing?

 

Atlantic British recommend coolant/hoses/thermostat every 105k miles