It's been in the 100s around me lately, and the car has been running just fine, with coolant temps in my car's normal range between 178 and 199.

This morning, after starting it and driving about 1 mile in an ambient temp of 86, over the next mile I noticed the coolant temp rise VERY quickly to over 200 then bounce around for another mile until it settled into the normal operating range for the rest of my 13 mile drive to work. Same thing happened on the way home.

Of course, when I got home I looked at the coolant level, and it was down near the bottom of the overflow tank. I don't remember if that's what it does when hot, because I don't have leaks and it has always run just fine, and too be honest, I haven't even looked at the coolant tank in forever. I realize that over time coolant levels can drop, even without a leak, so is it possible that I ignored the level so long that the tank has gotten to low that upon startup I'm getting air in the system, which causes the spike, or does the coolant tank level normally drop that much when hot and rise back up when cold? (Yes, I will know if it does that in the morning, but if I sure would appreciate getting a head start on this potential problem.)

Or, could it be that there is something wrong with the sensor, or something else?

Can anyone point me in the right direction here, or give me a prioritized ist of things you would check? FWIW, the service engine light is not on.

Thanks.

 

happened to me before on a sbc. was the thermostat sticking.

 

What is an "sbc"?

 

small block chevy. aka mouse.

 

What would that indicate? Also, what do you make of the fact that when hot, the coolant level was at the bottom of tank? I'm getting ready to think water pump. I did have a belt squeak the other day that magically started then magically went away 2 days later. A few months ago I replaced ac belt idler and tensioner pulleys, and both belts, but not main pulleys because they weren't making noise. When I heard the squeaking, well more like squealing, the other day, I figured it was time to do the main pulleys. But, then the squealing stopped. Now, I'm wondering if it was actually coolant dripping on belt. If it is a leak at water pump, it must be a real slow leak though because i get no spots below car, nor do I see any wet spots under the hood anywhere. But, now that I've had time to think about it more, how else would coolant level drop? Car has 120k on original water pump.

 

Refill your tank and watch for leaks. Small leaks can evaporate and be hard to find. I had one on an old Chrysler I chased for months before I found it. Was swapping out a headlight after coming home from work and could smell the coolant.

Water pump might be a good place to look for starters if you suspect a leak.

 

sounds like a leak. The Reservoirs are known to crack, that is one place, then there are several gaskets that can leak, the water pump connections, steam vents, pinhole in hoses, etc. Then the bad news would be blown head gasket or cracked head/block.

(this is not a product testimonial) I suggest you go to this website http://tracerline.com/ and look for the item number for the coolant leak detection. Then it is way cheaper on Amazon. You will need a cheap black light; Ebay is your bet, you can find black light LED flashlights for $4 or so.

Once you find the leak then the fix can be on. If you just go blindly swapping parts, that will get expensive fast.

 

OK, no collapsed hoses, no leaks in reservoir that I can tell. Filled the tanks, which was down to the bottom. Went for a drive and everything is back to normal. I believe the coolant level got so low that an air pocket developed, but it is all good now.

After more investigation, I noticed that my coolant bypass hose going to that weird tiny metal hose behind the throttle body was showing signs of that white powdery type buildup you get from water, but it was orange like DexCool. Hose was old enough to be pulled off without much effort as it had worn down to the point that the clamp was actually lose, so replaced hose and tightened clamp. It is possible that that tiny bit of seepage, which didn't even run down anywhere, caused my loss in coolant over a long time in the form of stesm? I ask this because coolant levels must normally drop SOME. Why else would an owners manual have a section on topping off coolant? To be honest I think the last I even looked at my coolant tank was last summer when I cleaned my radiator and condenser fins. So, is it possible a tiny venting could cause coolant level to drop that far in a year, over two hot summers in my area which sees 100+ degree weather in the summer? (BTW, what does that tiny metal hose behind throttle body do anyway? Looks like it has two dead ends bolted down to the block and goes nowhere.)

Regarding smelling coolant, I smell a tiny hint of it when hot around the reservoir near the cap, but see no evidence of it spilling.

​​​​​​Of course, with 120k on the water pump, it is a suspect. I'm scheduled to drive from Northern California to San Diego in the next 3 weeks, which has me a bit concerned. A month ago, I did the run in my Suburban, and two days after I got back, the water pump blew. I am so lucky it didn't happen on the trip, and lucky I was in a parking lot when it said goodbye. Needless to say, I am a bit paranoid about my C5 water pump now. FWIW, my Suburban went 195k on the water pump before it finally gave up the ghost.

Should I change it before the trip, to be safe, or should I drive around for a few days to see what happens with my coolant level? I kind of think if it is such a tiny leak that there is no wetness to be found, that it will take months for me to see my level drop again. If it is a tiny leak, is it safe to drive 550 miles one way in summer?

Is there a recommended replacement interval for water pumps, like there is for other maintenance items, or is it a wait til it goes type part?

 

I humbly apologize to everyone on this thread. There is indeed a leak, as I see staining all along the bottom of the water pump assembly, and on the steering rack. I just did not recognize it as such. Apparently, it has been slowly seeping for some time, which is why it is not wet. I saw something a little wet-ish on the leaf spring, and it just looked like oil seepage that gets covered in dust. I wiped it with my finger and smelled it. It is indeed coolant. I am happy that at least I know what I need to do.

Some of you may know that I started a new thread for a water pump instead of asking water pump-specific questions on this thread. I did this because I wanted to get opinions on the water pump itself.