Anitfreeze Reservior

Hi McGov. Yeah, "concerned" is probably overstatement. If you know the total cooling system volume, pour in half the total volume in concentrate, then top off with distilled water. Half the volume doesn't usually equal even gallons, so maybe you're under/over 50/50 according to required freeze protection and preferences.

 

I think it’s fine. Mine is the same way.

 

I thought that was more like an overflow tank when the coolant gets hot and expands inside the radiator so it doesn’t bust the radiator. I guess it could get low there, but I think you have to check it at different engine temps to find out before you overfill it.

 

The coolant res level on my '13 4.6 fluctuates the same way as does the level on my friends '09 4.7. He said his has always done it and he has never found a leak. He adds a few ounces every year. I'm guessing it's perfectly normal!

hth,
B

 

I agree with 15whtrd, most likely air trapped in the heater core and when used this winter, it purged.

 

Do not know the answer to that but when I take my truck in on March 8th, I will let everyone here know whats up. Just never seen levels to be that low or had to add coolant in any other vehicle I owned. I guess thats why Tundra's are so special.

 

Good to know...this was taken after I drove for 40 minutes last night. It’s at the same level as my previous pic from the day before.

 

how about mine? When I went in for 20K mile service it was right at if not a hair below the low line. Just checked (23,000 miles now) and it’s well below the low mark. Bought brand new October 2018.

**note — it’s 64 degrees outside, engine is cold I haven’t started it in 6-7 hours and that was just to move it 10’ across driveway

 

The level in the overflow tank is constantly changing with engine temperature. A hot engine pushes fluid out of the radiator into the overflow tank... fluid is sucked back into the radiator as the the engine cools. Check the fluid level in the radiator when the engine is dead cold, it should be full to the top. If both the radiator and overflow tank are low, you may have a leak. Top off the radiator and monitor closely.

 

Thanks, radiator is full

 

Mine looks exactly the same as yours but the radiator is full.

 

This same issue drove me crazy, too. I finally figured it out. When I would start the truck inside my garage to just back it out to wash it or check fluids I noticed my coolant was damn near the low line. Freaked out and started monitoring the situation. I finally realized that when I start my truck for only a few seconds to back it into driveway or whatever, the coolant would be super low. If I’d go for a typical drive, getting everything up to running temp and then checking coolant level (with truck off) it will be at its highest, “normal” point. Bottom line; a short, brief start of the engine will cause your coolant level to drop super low inside the overflow reservoir. Someone with much more knowledge will have to explain why this is...

 

As I said in post #35 above, it’s more of an overflow tank for when the coolant gets hot and builds pressure. Cold coolant doesn’t have the same pressure. That’s why you can open your radiator cap when it’s cold and not always when it’s hot. The pressure has to go somewhere, like an overflow tank.

 

I guess I need to go check mine.

 

What he said!

 

The overflow tank can overflow - my experience.

 

Coolant is 50 percent water. Water has a coefficient of expansion like other substances. When heated, a fixed volume of water (or coolant) expands until it reaches its boiling temperature, then it begins to change state to steam.

In a fixed volume like a cooling system, the radiator cap set pressure raises the boiling point of the coolant beyond that at ambient pressure (~212* F). The coolant volume expands until the set pressure of the radiator cap is met, then the excess volume begins to relieve into the overflow reservoir. Engineers know how much the coolant will expand at the normal operating temperature, and design the minimum size reservoir to contain the expanded volume. When the engine cools, the excess coolant is drawn back into the cooling system as the expansion reverses at cooler temperatures.

Everything is fine until the engine begins to operate outside of the normal range (overheat). The expansion of the coolant when the engine runs hotter overfills the reservoir and the excess expansion overflows out onto the ground. When the engine cools, it draws all the coolant in the reservoir back in the radiator, but that part that ran out on the ground is not recoverable. Cooling system then sucks in air instead, and then the reservoir becomes a catch can. Overheating will likely worsen as more coolant is lost.

 

The overflow reservoir is also called an expansion tank.

 

As a graduate student, I had a 72 Impala with the siamese-cylindered 400 SBC. It overheated from the day I bought it. Back in those days, few cars came with radiator expansion tanks. I retrofitted a GM expansion tank to the radiator for absolutely no relief. It wasn't big enough to solve my problem.

I tried new radiator caps, coldest thermostat I could find, new water pump, nothing kept it cool. On a long trip on a hot day, it was simply going to boil over. To get home, I had to keep a jerry can of water in the trunk. There was no point in putting anti-freeze in it. I began to run straight water in the cooling system (Texas winters helped with that). Eventually had to replace leaking rusted out freeze plugs with the engine in the car.

Even then, I still bought GM products. After the next pathetic loser (80 Cutlass wagon), I discovered Toyota.