I have a 2016 Explorer. It doesn't have a radiator cap on the radiator. It has a pressurized cap on the reservoir. From doing research on Google, it seems that Ford has done away with the cap on the radiator.

I don't know what the Odyssey's are like, but you might only have to top up the reservoir bottle. If you totally out of water/coolant, you would be overheating already.

Anonymous wrote:

Anonymous wrote:When the engine is COLD (as in sitting overnight, cold), you need to remove the radiator cap and see how low the level in the radiator is. If it’s low - and it probably is - you need to top it off there first. Use distilled water.

Fill the radiator until the level is about a half inch below the top of the filler neck. Then put the radiator cap back on.

Then fill the plastic coolant overflow bottle up to the “cold” line.

As you drive, the coolant will mix with the water and flow in and out of the overflow bottle and everything will mix, so you don’t need to worry about adding straight water to the system.



You need to be more diligent about checking basic stuff on cars. You almost cooked your engine. If it overheated, the cylinder heads will absolutely warp, you’ll score your main bearings and probably cams, and your engine is toast. That’s about $7,000 plus labor.

Why would you do this instead of adding more coolant?

You mean adding just water and not coolant?

First off, water IS the coolant. The antifreeze component is just to keep the water itself from freezing. There’s sufficient antifreeze mixed with the remaining water in the system where a bit of dilution with straight water wont harm anything. And the MOST important thing is to get water back into that cooling system, immediately, before it’s started and driven again. Most people have water in their homes. Fewer have antifreeze sitting in a jug ready to use.


Or did you mean why fill the radiator first, before the overflow bottle? In that case, look one post up for the answer.

Anonymous wrote:

Anonymous wrote:When the engine is COLD (as in sitting overnight, cold), you need to remove the radiator cap and see how low the level in the radiator is. If it’s low - and it probably is - you need to top it off there first. Use distilled water.

Fill the radiator until the level is about a half inch below the top of the filler neck. Then put the radiator cap back on.

Then fill the plastic coolant overflow bottle up to the “cold” line.

As you drive, the coolant will mix with the water and flow in and out of the overflow bottle and everything will mix, so you don’t need to worry about adding straight water to the system.



You need to be more diligent about checking basic stuff on cars. You almost cooked your engine. If it overheated, the cylinder heads will absolutely warp, you’ll score your main bearings and probably cams, and your engine is toast. That’s about $7,000 plus labor.

NP here.

I thought radiator caps and actually putting water or distilled water directly into a radiator was a thing of the past? I always use pre-mixed coolant and refill the coolant through the reservoir. I don't even know how to find my radiator cap. I've just been refilling my reservoir bottle for years and never had any problems.

Filling at the overflow reservoir IS the proper way of topping off coolant *that is low at the reservoir*.

But once the overflow reservoir runs completely dry and starts pulling in air instead of coolant, then just filling up the overflow reservoir might not pull new liquid down into the radiator from the reservoir because there’s a air bubble trapped in the line now.

That’s why when the coolant has run that low, you have to make sure the radiator is full FIRST, before you fill the overflow bottle. Once the radiator is fully topped off, it will re-establish vacuum with the overflow bottle as the coolant heats up and expands, then start pulling from the overflow bottle again as needed.

But you MUST top off the radiator FIRST if the reservoir has gone totally dry. Trust me on this.

Is your van still less than 5 years/ 60 k miles? If so, just take it to the dealer to check for leaks. It should be covered under the power train warranty. Otherwise, just add coolant to the overflow reservoir and observe.

I've had a couple of Odysseys and here are my thoughts: Don't buy coolant at the random auto parts store and don't add water to your system. Go to a Honda dealer and buy a gallon jug of Honda coolant - it's already premixed, so it goes right in. Like the PP said, open the radiator cap when the car is stone cold and top up the coolant. Also, add to the reservoir up to the fill line, Then, watch it closely.

Best case, you oil change technician has not been checking it and the level has been creeping down for years. The level stays pretty much where it is and the jug lives in your garage until you sell the Odyssey in three years.

OK, that's too sunny. You have a leak somewhere. You might find drips on the ground after you park; check carefully. Maybe just a leaky hose or clamp. It might also be from the water pump, which gives you the opportunity to change the timing belt at the same time.

If you don't find a drip, it might be from a tiny hole in your radiator after it's been hit by 10,000 rocks over the years. The coolant simply evaporates because the radiator is hot when the coolant leaks out. When you're parked, there's no pressure and it doesn't leak and there's no drip on the ground. Maybe the heater core inside your dashboard is leaking; are the insides of the windows fogged with goopy stuff and the heat smells kind of sweet?

Worst case, the coolant is leaking through the head gasket into the combustion chambers (whitish smoke at the tailpipe) or into the oil system (foamy oil on the dipstick).

In almost any case, you're headed to the mechanic and your observations will inform their diagnosis. How quickly is it consuming coolant - 1 quart per year or 1 quart per week?
They might do a coolant pressure test, perhaps using a dye, that will disclose where the coolant is escaping from the system.

On one of my Odysseys it was the water pump and on the other it was the radiator, which I replaced over a weekend.
Good luck.

Your manual should have do-it-yourself maintenance instructions.

Mine was a little low too so was my transmission fluid.

Anonymous wrote:When the engine is COLD (as in sitting overnight, cold), you need to remove the radiator cap and see how low the level in the radiator is. If it’s low - and it probably is - you need to top it off there first. Use distilled water.

Fill the radiator until the level is about a half inch below the top of the filler neck. Then put the radiator cap back on.

Then fill the plastic coolant overflow bottle up to the “cold” line.

As you drive, the coolant will mix with the water and flow in and out of the overflow bottle and everything will mix, so you don’t need to worry about adding straight water to the system.



You need to be more diligent about checking basic stuff on cars. You almost cooked your engine. If it overheated, the cylinder heads will absolutely warp, you’ll score your main bearings and probably cams, and your engine is toast. That’s about $7,000 plus labor.

NP here.

I thought radiator caps and actually putting water or distilled water directly into a radiator was a thing of the past? I always use pre-mixed coolant and refill the coolant through the reservoir. I don't even know how to find my radiator cap. I've just been refilling my reservoir bottle for years and never had any problems.

Anonymous wrote:When the engine is COLD (as in sitting overnight, cold), you need to remove the radiator cap and see how low the level in the radiator is. If it’s low - and it probably is - you need to top it off there first. Use distilled water.

Fill the radiator until the level is about a half inch below the top of the filler neck. Then put the radiator cap back on.

Then fill the plastic coolant overflow bottle up to the “cold” line.

As you drive, the coolant will mix with the water and flow in and out of the overflow bottle and everything will mix, so you don’t need to worry about adding straight water to the system.



You need to be more diligent about checking basic stuff on cars. You almost cooked your engine. If it overheated, the cylinder heads will absolutely warp, you’ll score your main bearings and probably cams, and your engine is toast. That’s about $7,000 plus labor.

Why would you do this instead of adding more coolant?

Coolant evaporates over time. Your dealer is supposed to top it off when you take your car in for service. But you can do it yourself. Just buy it from a honda dealer and pour it in the reservoir.

When the engine is COLD (as in sitting overnight, cold), you need to remove the radiator cap and see how low the level in the radiator is. If it’s low - and it probably is - you need to top it off there first. Use distilled water.

Fill the radiator until the level is about a half inch below the top of the filler neck. Then put the radiator cap back on.

Then fill the plastic coolant overflow bottle up to the “cold” line.

As you drive, the coolant will mix with the water and flow in and out of the overflow bottle and everything will mix, so you don’t need to worry about adding straight water to the system.



You need to be more diligent about checking basic stuff on cars. You almost cooked your engine. If it overheated, the cylinder heads will absolutely warp, you’ll score your main bearings and probably cams, and your engine is toast. That’s about $7,000 plus labor.

There might not be a leak. Coolant does go down over time. There's most likely still coolant in there but it's too low to show up on your coolant reservoir.

Top it up to the minimum level and see what happens.

i have had this car for five years and never did anything with the coolant (never was suggested by honda where i did the oil changes).

Well you need to find out where the leak is.

I have a 20 odyssey and checked the coolant level for the first time this morning. It is under minimum, and seemed completely empty. I tapped it a little (that white bottle reservoir) and there didnt seem to be any liquid at all. Is this possible? I just took it for a honda recall and am surprised they never let me know about it (even though they suggested transmission change, pcv valve, cabin filter, steering fluid). Am I looking at this right? also, if true, this is something I can do myself by just pouring coolant in from the top next to the reservoir? Thanks.