Eats coolant half a cup every 4 months BMW 318ti `96.

I'm guessing I could have a head gasket leak. But it idles smooth. We've been driving around with the temp needle beyond max countless times before but not anymore. The cooling system is becoming reliable again, except for half-cup loss. A half-cup is critical because a loss of about a liter will cause the radiator fan switch to become useless because the switch is mounted way to the top of the radiator.

I will do the cooling system pressure test next week and post the findings if I can. I admit I made mistakes, which cause the radiator rupture, but still baffled as to what have caused the rupture. Could it have been a bad cap? Or the mistake of the driver not noticing the high temp & driving too long without stopping? Or is it just bad radiator design? (I'd actually reinforced the new radiator with fiberglass w/ epoxy, so I'm confident it will not repeat the burst at the same spot. But would probably blow out the heater core and risk scalds to the occupants, as reported on BMW bulletins on some vehicles. Rick

Doesn't really sound like much of a problem to me. A half a cup in four months isn't terribly significant. Could be a leak so small you can barely see it from any number of places. Unless you just love messing with it, I'd leave it alone and keep doing what you've been doing: check the coolant every now and then. If it starts REALLY eating coolant, like a noticable amount in a day or two, start working on it.

This is just my opinion of course. A half a cup really isn't much.

Harry

Thanks, Harry. It`s good to know that it`s about normal. I`m unable to refill the coolant as often since a female drives the car at another city. I`ve taught her many times how to refill. I soon gave up when she said it overheated again, only in about 6 months. After looking down the reservoir tank, a liter of coolant had been missing. That`s about half a cup every month. I may have been incorrect by saying half a cup/4 months. I also gave up when later she added liquid from many sources, things other than OEM brands at various quantities. A Honda will not overheat from a liter loss, if I recall. But she does not want a Honda. So it`s just my good old 270k mi, 15-year-old Honda with no coolant loss or other problems and me. Rick

Rick, at the very least I'd get a sample of the motor oil tested:

Costs about $20 and once you get the test kit (a bottle within a bottle, essentially) it takes only a week to ten days to get your results back after sampling.

Traces of coolant will show up in oil even when the leak is very small ... and it doesn't sound like yours is small.

My '95 Civic ran fine with a significant headgasket leak and many of the common indicators (milky residue on the dipstick, etc ...) were missing. Temp fluctuations were minor and coolant loss (intermittent at best) was no where NEAR what you describe. Without used oil analysis, I would have shrugged it off as air bubbles in the system.

--- Bror Jace

Perhaps this is a philosophical question, but if a problem has no noticable symptoms, is it really a problem? His coolant loss could be due to any number of things, and a bad head gasket is fairly low on the list of possibilities. Sure, you can argue that an undiagnosed minor problem could turn into a major problem at any time, but then, anything could go wrong at anytime. The thing could burst into flames and kill everyone inside in a flaming hell. Sure, unlikely, but possible. Realistically, the average person is going to wait until a problem becomes significant to fix it. I maintain that keeping an eye on it (coolant level, leaks, the condition of the oil, etc) will be enough. If it turns into a real problem fix it then, don't waste time fixing stuff if it's not broken.

Harry

Harry, if the coolant loss is not leaving a visible trail outside the motor (puddles or even droplest on the ground, etc ... ) then it's probably a head gasket. Could be a cracked block, cracked head or leakin freeze plug ... but most likely a head gasket.

If you want to keep the car for a long time, then it's best to get a handle on this early. Just a little glycol mixed in with the oil causes bearing material to deteriorate rapidly. So, if you like the car and want it around for a while, this needs to be addressed as early as possible. By the time you find white, sticky gobs in your oil and/or a steady stream of white smoke (steam) in the exhuast, quite a lot of damage has been done.

--- Bror Jace

Found the problem. Was changing the difficult alternator belt today and saw some built up dust below the thermostat housing and with more examination reveals a coolant leakage from the housing o-ring, visible only by brown dust. When the O-ring was brand new, it appeared so thin that I refused to installed it because by the way it looks. I had to install it, so it leaked. It`s an OEM thermostat-housing combination, and not sure if they sell a better, larger o-ring individually or where to start finding one. Everyone's posts are helpful and hope I didn't waste anyone's time.

Like you guys said, only if it`s worth a repair, do it and do it soon. Rick

Update: No problems found. I apologize for any inconveniences. The dusts built up are oil, not coolant. No T-stat leak found. Original problem not solved. Will consider mail in test. Rick

Good point. Refilling is messy for her, but she even changed the breather hose yesterday, to prove something. A refilling-female, is it normal? Rick (SF Bay Area)

I am not sure where you live, but I am on the west coast in the desert areas. It is very common here to lose a little antifreeze just from the heat and normal water dissipation. I go through the same amount of coolant just from environmental effects.

Take Care, Sharon