As you know since I had my BX19TRS I have been trying to find the cure of a mystery leakage that keeps flashing on the low water level light.
1st I replaced the sensor, 2nd the Radiator, 3rd kept the AC off because that seemed to make the water usage worse.
Now there are no external leaks or wet patches inside the car, but I have noticed that on cool damp days there is quite a bit more exhaust emissions evident.
The theory
Could it be that the Head Gasket is leaking when cold but on longer drives I do not seem to lose any water which I think means the gasket is resealing itself with heat expansion on the engine.
Although I'm far from being an expert on these things, I had similar water loss with my BX14 a few years ago. It never got any better or worse, just a slow drop in water level which reduced during longer (therefore warmer) drives.
When I finally stripped the head to renew stem seals a couple of months later, I discovered that the head gasket had indeed failed, but only very slightly, between one of the waterways and the number 2 cylinder bore.
There was no loss of power, overheating, or 'mayonnaise'in the oil. Similarly, no oil in the coolant. When cold, water had been seeping into the cylinder and getting chucked out the back end with the exhaust gases as steam!
Once the head was reassembled with a new gasket, all was well again!
Your theory could well be accurate (unless someone more knowledgeable can come up with another idea!)
Leaks..............don't talk about 'em; if it's possible to get a leak in a weird place, I've had it.
Here's some for you to look at.
Elbow on the hose where it returns from the radiator to the water pump. Will behave perfectly normally when operating and when engine is warm as opposed to hot, but if the CV boot has ever split and spat grease on that elbow from the inner CV joint, it goes soft and can either collapse under load or when the engine begins to cool and the advantage of the sucking of the pump stops, will leak. It can also shut off the supply of coolant to the pump under load and cause the cap to lift and dump some coolant that will have dried out by the time you stop.
Weakened radiator cap. Either wrong pressure or simply leaking slightly.
Heater matrix dribbling under the carpet.
One that is common to 16Trs in Oz. Internal corrosion of the block that eventually results in the metal weeping usually around the back and often at a thin spot such as between the liners on a couple of cylinders. I found a cure by externally cleaning the area, then using a reamer, rounding out the hole to get some "meat" to work with. Hand screwing a drill bit through the hole and then finding a thread tap to fit. tap thread, cut down a bolt just long enough to screw through but not too long so it fouls on the liners, meticulously clean the area and then coat the bolt with Devcon and screw in and tighten. Coat the head and surrounds with Devcon and wait 24 hours to cure before refilling with coolant.
Of course the old headgasket also. I've just whipped a head off a low mileage TZi and all that was left was the surrounds and 2 X 2 metal rings where it sits on top of the liners, so if you've got a combination of stray currents and weak or old coolant, yours could be the same.
Alan S
By the time you're old enough to know it all, you can't remember why you were learning.
