My sister's 2000 DX just overheated. It's a D16Y7 with 240K+ miles on it. It's been running GREAT since we've had it, no problems, religious maintenence, etc. until today. She was driving and and suddenly all of her coolant boiled out. She didn't look at the temp gauge so I don't know if it gave her a temp warning. There was no CEL. When I got there, I saw dried coolant splashed everywhere: front of the engine, underside of the hood, valve cover, dizzy, but I can't find where it all came from. There didn't appear to be any damaged hoses or telltale stained areas of the radiator. I started it up while there and the engine was shaking pretty bad, especially on the drivers side. We topped it off with water and I drove it home. It ran fine all the way here. It DID seem to be leaking a lot of water as I filled it, but when I drove it none leaked out.

One thing I noticed was the radiator cap. It had a little spring on it, but that spring was broken off. I had to pull it out of the radiator. There was another plastic piece, but I couldn't fish that out of the radiator. (Is that gonna be a problem?) I'm sure that spring is important, so I'm gonna have to get a replacement radiator cap.

The water I added looked murky and there were little particles of stuff floating in it once it had gone through the engine a bit. Dunno if that is significant.

Any ideas on what I should look at? Where I should look? etc?

I do know is that I am gonna have to empty all of the coolant and add the usual 50/50 mix because all that water is no good. I don't know how much to buy though. Do I just yank the big hose at the bottom and let it all pour out? That simple?

 

If you are lucky, the radiator cap simply failed and the coolant overflowed from the top of the reservoir. Stop by your local auto parts store and get a new radiator cap. Walmart sells some adequate inexpensive 50:50 coolant. I think you'll need three jugs. If you need less, just return what you don't need.

There is a drain spout at the bottom of the radiator. Just turn the spigot and the water/coolant will drain out. Collect the fluid in a container/bucket so that you can carefully inspect it. Look for anything unusual, particularly engine oil. Post any new observations that you make. Refill the cooling system and bleed it as detailed in the manual. Look for any leaks and locate them, if necessary.

The main concern about engine overheating is expansion caused by the excess heat. This can cause irreversible damage, so watch carefully how the engine performs for a few days and whether any smoke is seen in the exhaust.

Good luck.

 

I drove it to Autozone (closer than WalMart) and got some coolant, plus a new radiator cap. The new one is different looking from the old one. The tops look the same, but whereas the old one had a spring, the new one has an odd little round plastic disc. Their computer says it's the right part, so... whatever. The manual says the the capacity of the cooling system is 4.5 quarts total.

The engine will take forever to cool down, but this is the right way to bleed the coolant system. It's getting dark, so I might end up doing it tomorrow.

I'm just glad my sister immediately pulled into a parking lot and shut the car off. This is a high mileage engine. I'd rather it not die prematurely. We're gonna squeeze all the life out of it that we can.

 

Here is a comparison of the old cap (top) and new cap (bottom). Likely cause of the overheating issue? I'm still not completely convinced. It's just odd/lucky that this happened while she was home in Little Rock, not out on the highway driving between here and Memphis.



And again, the plastic from the old one is still floating around in the radiator. I don't know how radiators are designed, so I don't know if it'll clog anything. And since I'm working on the cooling system, should I go ahead and toss in a thermostat?

 

Yeah, it seems that the radiator cap failed. Use a flashlight to look into the hole at the top of the radiator. You may be able to see the missing pieces and pull them out. Definitely replace the thermostat, as the job is pretty simple and the part is inexpensive.

 

Well, I can't find the drain bolt on the block. Anyone know where it is? The system is halfway bled so far and the coolant looks clean and normal, despite the large addition of water.

 

The drain bolt is near the oil filter. I think it requires a 19mm or 20mm socket. I don't think removing the bolt is really necessary in this case. Just push the heater lever to full heat in order to allow coolant to drain from the heater core and then open the tap at the bottom of the radiator.

Bleeding is a separate process.

 

When I replaced the thermostat, the rest of the coolant came out. Now that it's all back together and refilled, it's running normally except that we've been sitting here for 15 minutes waiting for the radiator fan to come on and it hasn't. I've got both my Civic and my sister's Civic sitting side by side for comparison, and neither are coming on, so I guess it's not that big a deal. We're about to go drive it and see what happens.

 

It's driving fine now. Looks like the cap just failed, like we figured. I was able to verify that the cooling fan is functioning properly.

Since I was curious, I went through the records and found when the previous owner replaced the gauge cluster, then added that to the current mileage. That car actually has 262,891 as it sits right now. Crazy for a 2000 model, but still going. (hopefully still going strong.)

 

if you're concerned about the radiator cap not having a spring i have an OEM cap (93 Civic) that works good in my for sale thread.