It dipped below -30C where I live recently and my tacoma overheated. I noticed slush and ice in the radiator overflow container. I let my car cool down and drove home. The weather was above 0C today so I flushed my coolant system with water. The truck drives fine now with just water, but I noticed a small leak at the bottom of the radiator.

I can't leave only water in the cooling system because it will be below freezing tonight and tomorrow (Sunday). I don't want to fill it with 50/50 antifreeze/water because that will be a waste when I replace my radiator during the week due to the leak. Toyota coolant is expensive.

Can I drain all the water out of the cooling system and just leave the system dry during this cold weather, until the weekend is over at which point I can fill up the system with water and drive it to a radiator shop to get it replaced?

Any other advice will be greatly appreciated, thanks!

I would get some antifreeze soon and let the car run to get the antifreeze in the engine and radiator. Water alone will freeze in your engine, radiator, and heater core and cause problems later on. Even if some leaks it would be better than water. Ue it full strength if needed.

Thanks for the info, I've started draining the water, will top it up with 60/40 antifreeze/water.

I had my car running about 20 minutes ago. When draining the water at first it was very very cold (probably just above freezing), after it drained about 1.5 liters it started to get warm and eventually quite hot. Is it typical to have such a range in the temperature of the coolant?

I imagine a radiator works be bringing hot liquid in the top, as the liquid runs down the radiator it cools and then is pumped through the engine from the bottom of the radiator, so I would expect the liquid in the bottom to be colder, but this felt rather extreme, ice cold to extremely hot. It's about -5C right now.

The coolant was probably cold because it hadn't circulated yet. Make sure the thermostat is not stuck which would block coolant to the engine. The warmer coolant drained at last had been warmed by the radiator and possibly cycled. where is your leak at? Do you have a block heater you could plug in overnight? That may keep things warm until you can get that radiator fixed.


(This post was edited by sonordrumr on Jan 5, 2008, 9:59 PM)

I don't know exactly where the leak is, I believe it's on the driver side of the radiator near the bottom, but it's a very very slow leak.

I let the car run for about 30 minutes and the temperature gauge in the dashboard stayed right in the middle. I figured the only way it would do this is if the system was circulating the water properly, otherwise I would expect it to overheat.

It was overheating earlier before I flushed the system really good and squeezed the hoses on the top and bottom of radiator, I think I had air in the system.

Is there a way to tell 100% if the coolant is being circulated? I wish they used clear hoses.

Would be nice eh? You might want to patent that idea! Full circulation should be felt at the heater hoses at the firewall. Both should be hot to the touch. If not, the water pump could be at fault. If one is cold you may have a block in the heater core, bro.

When the car has been running and the temperature is normal, the top hose going into the radiator is hot to the touch, which I figured was normal. The bottom hose was cool to the touch, I figured that was normal because the water would have cooled off by the time it made it to the bottom of the radiator... you're saying the bottom hose should be warm?

I drove my car for about 5 minutes with no heating problems, if it wasn't circulating I figured I would start to overheat fairly quickly while driving, especially since I just had water for coolant.

I do have a block heater, I'll be plugging it in tonight.

Both hoses should be hot after normal operation on radiator. You may have a block in the radiator that needs to be reverse-flushed. Yeah, plug that sucker in to keep it warm overnight.

From what I've read most people say what you are saying, that both top and bottom hoses should be hot, or at least the bottom should be warm, but I'm skeptical. Logically, if a cooling system is functioning extremely well, the bottom hose should be cool, because it's this liquid that is going to take the heat away from the engine, if it's already hot, it won't be able to do its job.

This post confirms that at least one other person has the same opinion as me:
http://www.yotatech.com/f2/cooling-woes-83093/


I have my block heater plugged in for the night, I'll take it for a long test drive tomorrow. If I have a problem with my radiator or other part of the cooling system, when I go for a drive, eventually it should overheat, correct?

Thanks for the all the help!

Wow - lots to read and I'm late to chime in. Lower hose will be cooler or plain cold as it has lost its heat as it is supposed to. Colder air will do that fast. If there is low anti-freeze concentration it will freeze instantly in a radiator whereas the engine holds heat longer. The engine needs to run long engough to cirulate and mix what was put in. Slush won't circulate and ice can certainly break things.

Run engine and block radiator if needed and run heater, watch gauge. When it's mixed up the coolant shouldn't freeze. Air can be tricky to purge out on a warm day. Colder days the thermostat isn't open as long.

Note: Straight anti-freeze will slush up but when mixed with water it won't!! 50/50 is the target which gets you -34F. Stronger is ok for very cold climates but hurts you in hot weather.

In an emergency like this with know water only in system use 100% anti-freeze until you have added at least half the system's capacity.

Note II: draining the sysem doesn't get all the water out. There are plugs on the block that would have to be removed and you still have the heater core and other places to worry about. Never leave just water in a system - not even in climates that never freeze. It protects against corrosion which will quickly be a problem in most cars with just water.

Note III: anti-freeze alone or mixed can still freeze. The big difference is that it contracts vs expands which breaks parts and doesn't circulate.

In a jam with super cold, run engine every couple hours and cover the hood/grille with a blanket. Just the heat of the engine itself gives off heat under hood and should get you thru a night if in doubt - and it is much more likely to start for you later,

T
Tom Greenleaf - MetroWest Boston - USA
_________________________________________

http://www.autoacsystems.com/tomgreenleaf/