Coolant Disappearing

[prix]

Last week, I saw fluid under my car so have been tracking it since. It's the coolant that is disappearing. I fill it up in the morning and by the end of day the reservoir is almost empty (I only drive a few miles here and there in city traffic). I took it to an indie shop today who said they would give me a quick diagnosis for free. I appreciated the effort, but they really were not much help (there was no room to put it up on a rack). Instead he poked around with a flashlight and said he could not see anything (I could have told him that!). He offered to top off the 1/4 full coolant reservoir with WATER. I protested a little, since I have no idea whether that is safe, but he said it made no sense to keep pouring coolant in when I will just lose it. I drove the few miles home and the car did not overheat. Ran just the same. It has never overheated all week (but I have been putting coolant in every day too), and only one time did the gauge get close to 'hot'. Just when I was getting ready to pull out of traffic, the gauge dropped back to normal. SHOULD I have let him put water in the reservoir? I don't think he put in more than about 12 to 14 ounces. Thanks.

[larryp]

If there's no chance of freezing temps, water is OK - however, 100% water is not as effective at cooling the engine as the 50/50 mix of antifreeze and water - but it'll do in a pinch. Without any info on your leak, i'd guess it's the water pump. You should see a puddle toward the front of the engine. There is a "weep" hole behind the crankshaft pulley where it can drip out.

[wwest]

Last week, I saw fluid under my car so have been tracking it since. It's the coolant that is disappearing. I fill it up in the morning and by the end of day the reservoir is almost empty (I only drive a few miles here and there in city traffic). I took it to an indie shop today who said they would give me a quick diagnosis for free. I appreciated the effort, but they really were not much help (there was no room to put it up on a rack). Instead he poked around with a flashlight and said he could not see anything (I could have told him that!). He offered to top off the 1/4 full coolant reservoir with WATER. I protested a little, since I have no idea whether that is safe, but he said it made no sense to keep pouring coolant in when I will just lose it. I drove the few miles home and the car did not overheat. Ran just the same. It has never overheated all week (but I have been putting coolant in every day too), and only one time did the gauge get close to 'hot'. Just when I was getting ready to pull out of traffic, the gauge dropped back to normal. SHOULD I have let him put water in the reservoir? I don't think he put in more than about 12 to 14 ounces. Thanks.

"...only one time did the gauge get close to "hot".....

The engine coolant temperature guage in my 92 LS (150k miles) and my 01 RX (63k) initially rises to about 1/3 point and then remains ROCK SOLID right there otherwise.

You need to check that the electric radiator cooling fan(s) are fully operational at both low and high speed, the pressure relief valve integral to the radiator cap is operational, and barring problems there then change the thermostat.

When you park the car, any car, it is not unusual for the coolant temperature to continue to rise for a few moments thereafter, sometimes the electric fans will come on and in some cases continue to run even after the inginition is off for this reason.

If the coolant is already close to "hot", boiling over, it will be vented into the reservoir as the engine "overheats" when you shut it down, a portion overflowing from the reservoir as a result. Then as the engine sets and cools the coolant in the reservoir will get sucked back into the radiator leaving you with an empty reservoir and water on the ground.

[steve2006]

Be careful as not only does antifreeze prevent the coolant freezing but it also has additives to prevent internal corrosion of the waterways and engine block.

This is especially important on alloy blocks.

Lexus also recommend using distilled/ionised water not tap ( sorry UK to US conversion) faucet water.

Adding just water will dilute the antifreeze to a point where the anti corrosion properties are removed.

Even though you are losing coolant I would top up with a 50/50 mixture of distilled water and antifreeze