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Coolant overflow empty twice in last 20K

Have a 2007 Isuzu I290 four cylinder with 5 speed manual transmission with 116000 miles on it. have used Mobile One oil from day one and replace it and the filter about every 8000 miles. Twice in the last 20,000 miles the coolant overflow tank has been empty and an antifreeze puddle on the ground. Both times it was just before an oil change so the truck had gone roughly 8K and the engine oil was down about a half quart to a quart. Engine temperature gauge stayed normal, midway on the gauge, or very slightly above normal, never got hot. Can’t find a leak in the coolant overflow tank or hoses. thought it might be tied to the low oil so was going to check it on a more regular basis and keep it topped up. other than the coolant puddle twice, nothing leaks on it and thus far has been a nice, reliable, maintenance free truck.

Do you have a radiator cap on your vehicle? If you do it’s time to get a new one.

U should check coolant level more often. Weekly?

After the first instance I replaced the radiator cap, roughly a year ago.

I would buy a new cap anyway. I had gotten a new one once that did not work right out of the box.

Also, these coolant tanks get brittle after a few years and it could have a crack in it. The hose running to the overflow tank could also be old and either cracked or no longer tight fitting.

Next tile the engine is nice and hot, crawl under and inspect the tank and that hose…looking for leaks.


Time for a coolant system pressure check, it should show up quickly. And don’t let the tank go dry, you will overheat your engine, potentially ruin it.

Texases is right, it is time to have the coolant system checked before a rapid failure ruins your engine. The oil level has nothing to do with the coolant level. I check our vehicles oil level on the 1st and 15th of each month and every fill up on trips.

Is The Puddle Beneath The Coolant Pump? Find The Weep-Hole On The Coolant Pump And Inspect It For Evidence (Staining, Corrosion Like Build-Up, Wetness, Etcetera) Of It Weeping. Also, Look Below The Pump For Evidence, Too, On Engine Or Chassis Components.

The pump seal could be leaking. It could be time for a new pump. If it is the pump then it could be getting ready to really let go!

Look above where the puddle is found. I’ve had hoses leak at clamp locations in cold weather. Some will drip when cold and reseal when hot and things expand.

Whatever it is, find it now or severe damage could result. If you can’t do it, seek professional help.

Try getting the engine really hot, shut it off, and pop the hood. Look around for a few minutes and see if anything leaks. I once had a coolant leak that only happened AFTER i shut off the engine. A bad seal in the radiator would squirt out a small amount of coolant for few seconds and then stop.

I had one leak only after it was shutdown too, but I had to wait a half hour to see the leak.

Next time you find a puddle of coolant on the ground, look at what is directly above it. If it is the edge of the front shield, then look at the shield from the top of the engine and look for where the coolant is hitting it, then go up from there to see what is directly above it.

I sometimes place white paper towels in various locations under the usual suspects for leaks and run the engine for a few minutes to see which one gets wet first.

thanks for the recommendations. I’ll get the system pressure checked. After driving today I went over it thoroughly and no evidence of coolant leaking. looked under the water pump, all the hoses, etc. the coolant tank seems sound. tapped around it today and no evidence of cracks. nothing leaks on this truck except for those two instances. nothing gradual about them either. one day the coolant is at normal level in the tank and the next its on the ground. Then after refilling the tank, it holds just fine. The coolant puddles those two times were by the passenger side tire, under the coolant tank. thanks again and hopefully a pressure check will reveal something. until then, the mystery continues. One last thing. both times it was after driving to work…maybe the truck’s telling me its time to retire…

Running low on engine oil can cause the engine to heat up more than with the proper allotment of oil. One function of engine oil is engine cooling. But if the oil is still above the “min” mark on the dipstick, the low oil level would only cause a small amount of increase engine heating. Still, it could be enough to push whatever’s failing over the limit I guess. In any event, I concur with the above advice, a cooling system pressure check is the place to start.