Questions About Cooling System

[rv8er]

I apologize that the first post is to ask what may be stupid questions...but.

Car is a 93 ES300. Original issues were overheating. As it was a new project car, I didn't mind tearing it apart and checking things out. Tore it down to give it a timing belt and water pump. Tested the thermostat ( good) and pulled the radiator (tested bad and replaced).

Put it all back together and started right up the first try.

I wanted to see if there were any leaks before mixing in the anti-freeze. Things look good and nothing leaks. I noticed that once I turned the car off after driving it to operating temp, the overflow reservoir was blowing steam and bumbling a little. The temperature gauge was reading normal.

Is this caused by the fact I'm only using water? I poured out the overflow reservoir and will drive it a little more. I want to have it totally right before I mix in the anti-freeze. Can someone say whether this is normal or ...?

Thanks for you help. This site is great and gave me enough confidence to jump right to the timing belt without destroying anything.

[kingjack133]

Hi, I m thinking that ...yes...its because of the water its steaming. Never use 100% water only. Use a 50/50 mix and you should be ok. Also check after every cooldown and add at rad cap hole to eliminate any air pockets. Mine took quite a few applications untill it was finally air-free. No overheating problems since.....I don t worry about the expansion tank level as long as the coolant is at the top at the cap hole in the morning.

[eatingupblacktop]

I apologize that the first post is to ask what may be stupid questions...but.

Car is a 93 ES300. Original issues were overheating. As it was a new project car, I didn't mind tearing it apart and checking things out. Tore it down to give it a timing belt and water pump. Tested the thermostat ( good) and pulled the radiator (tested bad and replaced).

Put it all back together and started right up the first try.

I wanted to see if there were any leaks before mixing in the anti-freeze. Things look good and nothing leaks. I noticed that once I turned the car off after driving it to operating temp, the overflow reservoir was blowing steam and bumbling a little. The temperature gauge was reading normal.

Is this caused by the fact I'm only using water? I poured out the overflow reservoir and will drive it a little more. I want to have it totally right before I mix in the anti-freeze. Can someone say whether this is normal or ...?

Thanks for you help. This site is great and gave me enough confidence to jump right to the timing belt without destroying anything.

First of all, welcome to the club!

Replacing the rad & water pump should resolve your overheating prob, but I would replace the stat as well - cheap insurance. Shouldn't be driving with only water in the cooling system! Once water boils, it becomes an insulator, leading to a sudden loss of cooling where steam bubbles form. So an engine temperature gauge can indicate an acceptable temperature even though local temperatures are high enough that damage is being done.

Also, even though you're not running water for very long, hard water deposits a scale much like the mineral scales that clog your coffeemaker, humidifier or kettle. These mineral scale deposits reduce heat transfer in your radiator. So you're now polluting your brand new rad. Tap water may contain minerals, silica, chlorine and fluoride, all of which can add problems to the system.

Not only does coolant protect your engine from overheating/freezing it also lubricates the water pump and prevents any silicates that may be in ordinary tap water from eating gaskets etc. This is why only distilled water should be used. Pre-mixed coolants are already blended with distilled water. I suggest Toyota long life coolant and as KJ mentions, check for air pockets as well.

[LeodLion]

Aside from replacing the pure water coolant with a mixture of antifreeze and water, did you burp the radiator? You may have entrapped air inside the cooling system.

[rv8er]

Thanks one and all for the help/replies.

Even though I had tested the thermostat for multiple cycles, I decided that was part of the problem. It just wasn't opening consistently. Replacing it made the temps normal.

Started to get concerned about the heater core not working but "LeodLion's" suggestions about burbing finished the job.

Now wife is happy again.