I accidently put Windshield Wiper fluid in the Coolant Reservoir

I accidentally put windshield wiper fluid in my Coolant Reservoir. It was dark and they are right next each other. Of course, I had already driven before I realized the mistake. So I can not just simply pump it out. Will it do any damage? If so, what do I need to do?

How much did you put in?

About 3/4 of the container. Filled up the overflow tank.

That’s a lot. I would carefully (it’s poisonous) siphon all of the contents of the overflow tank and refill with 50% antifreeze to the correct mark. I doubt much got into the cooling system.


Don’t worry. Washer fluid is mostly water with some alcohol mixed in. The alcohol will vaporize once the coolant comes up to operating temperture, and the worse that will happen is it’ll slightly reduce the 50/50 mix of coolant to water.



But 3/4 gallons? That’s a lot of dilution in winter.

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ps - this was in reference to a now-deleted post…

It’s unlikely that the washer fluid will do any damage other than increasing the freezing point of the coolant some. Also, mixing between the recovery tank and the rest of the system is a rather slow process as the fluid from the overflow tank only gets drawn in to mix with the coolant in the radiator, hoses, engine, etc when the car cools off after being driven and the first stuff drawn back will probably be mostly normal coolant pushed into the recovery tank when the car heated up.

I’d recommend sooner rather than later siphoning all the stuff out of the coolant tank – or simply removing and draining the coolant tank if that’s easier. Don’t worry too much about the liquid in the tank. It’s toxic, but it’s biodegradable. If you spill some, dilute it with a lot of water and forget it.

Refill the overflow tank to the bottom (“COLD”) line with an appropriate antifreeze.

If you live someplace where it gets REALLY cold, you might want to check your coolant at the radiator cap with a hygrometer just to make sure that you haven’t unduly compromised your freeze protection.

I don’t know what year the OP’s car is, but most Fords for quite some time now don’t have overflow tanks. They have a pressurized degas reservoir, so the fluid was poured directly into the cooling system.

You’re right, many do, but the photo I found of a recent Explorer still shows the overflow tank setup, so maybe the OP’s OK.

I would take 1/2 the water out of the tank and refill with straight antifreeze. I hate the 50/50 stuff, most cooling systems are very hard to drain completely . I always drain everything I can, flush with water until I’m sure water is the only thing in there then drain, refill with 50% of capacity of full strength antifreeze then fill with water until full. Then I mix up some 50-50 and fill the overflow tank and keep a gal of the mixture in the car to top off the cold radiator until it stops needing any.

3/4 of the bottle? And you’ve driven it?
Personally I’d drain and refill the system. Rub some coolant mix and some window wash fluid between your fingers. You’ll find the coolant mix slippery and the window wash not. As a matter of fact, you can probably wash the slippery coolant mix off your fingers with the windshield wash.

The reason for the slipperiness is the additives used as corrosion inhibitors and lubricants for the water pump. You may have effectively washed much of these additives off the surfaces of the engine’s insides and the water pump. You want the cleaning fluid (window wash) out of the system and the corrosion inhibitors and lubricant back on the engine’s internals…at the proper strength.

JMHO. Why not spend $5 to protect the insides of an engine worth a few thousand.

In the “good old days”, meaning the 1940’s through the mid 1950’s, we had two types of antifreeze. There was permanent antifreeze and an antifreeze strictly for winter use. DuPont’s permanent antifreeze was called “Zerex” and the non-permanent antifreeze was called “Zerone” As I remember, the Zerone would boil at 180 degrees. I think the windshield washer fluid may not be too different chemically from the Zerone antifreeze. The Zerone was not ethylene glycol as was the Zerex and other permanent antifreezes. I think Zerone was menthanol, but I’m not sure.

I don’t think it will come out, but form an azeotropic mix instead. Alcohol can be pretty corrosive. I would do a coolant exchange.

Well, I wouldn’t worry about it.

I have an Explorer & an Altima. I did the same thing on my Altima. I’ve been driving Explorers for the last 14 yrs & got the car 3 months ago. I thought I was pouring it in the right place… Anyhow an easy fix is just to keep pouring water into the reservoir until the color has faded, then watch your antifreeze level closely for the next few days and refill with concentrate antifreeze.

Why do people keep responding to posts that are YEARS OLD?


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Maybe after five years the OP will report back what happened.

It must be easier with this new Community Software to find old posts matching up with what somebody wants to know. That’s my guess anyway. I’ve noticed with this new version, that when posting a new topic, I’ll sometime see a list of older topics automatically come up that are similar to what I’m asking about.