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Accidentally putting windshield washer fluid in coolant tank

I accidentally put about 1/4 of a bottle of windshield washer fluid into my coolant tank last night, I had driven elsewhere before noticing the mistake. I have a 2006 Chevy Cobalt.
Is the washer fluid just burn off and not create an issue? Or should I go and take my car in to the repair shop?

Flush the system with fresh water (a garden hose) and refill with the proper mix.
The washer fluid will adversely affect the ability of the coolant to lubricate the water pump and maintain the anticorrosive coating on the system’s internals.

NOTE: be sure you have the heat on when you do this so the heater core gets flushed too.

I thought most of the windshield fluids were just water, blue dye and isopropyl alcohol.

I think that some of them also contain ammonia, which wouldn’t be good for the metal parts that it would come into contact with.

That creates a surfactant. Since most coolant inhibits corrosion by leaving a coating of silicates on the surfaces and lubricates the water pump via a coating, I’d want the coolant out of the system. My feeling is that the wash will be fighting with the coolant’s efforts to leave needed coatings.

I’m not a very hands-on person with my car- is this easy to do?

What brand and variety of washer fluid was it and how large was the bottle?

I should add that I doubt of windshield washer fluid will have the same ability to increase boiling points and lower freezing points that ethylene glycol has. I still think the safe action is to flush it out and refill with the proper coolant mix.

I’ve only ever seen windshield washer fluid in gallon bottles, so I’m assuming that the OP put 1/4 gallon in the system. Since washer fluid is only sold in gallon bottles, I think it’s a safe assumption.

If it is IPA it should not be a problem. If there is ammonia in it, you should change the coolant.

Short term, I feel there is very little problem and the ratio of one to the other is sufficient to dilute the washer fluid. But, long term I would make sure it is changed within the next year. If it were my car though, given the formulation of long life coolant, I would probably not sleep at night till it was flushed and replaced. It’s a situation where advice to you and your car is different then what we might really do especially in light of, the level must have been down enough for you to get that much in. If you aren’t confident doing it yourself, take it to a service station for sure !

Regular -20F washer fluid is about 40% methanol and will lower the boiling point. I’d suck the reservoir empty with a turkey baster and refill with 100% antifreeze. Then have the coolant changed before hot weather returns. Keep an eye on the level, too.

Have you determined yet why the coolant was a quart low?

They don’t use methol alcohol in washer fluid anymore. It’s vapors are hazardous to breathe. They use ethanol instead.

They don’t use ammonia in washer fluid. It’s vapors are hazardous to breathe.

Since you’ve already driven the vehicle, I wouldn’t worry about the small amount of washer fluid you added the cooling system.


“They don’t use methol alcohol in washer fluid anymore.”

Wrong. If it says “danger poison” its got methyl alcohol in it:

They’re changing over to ethanol just for that reason.

I just bought two bottles and it states: DANGER: CONTAINS ETHANOL.



(A little bit for the car…a little bit for me…) I suspect they denature the ethanol first!

d_lee writes …

I'm not a very hands-on person with my car- is [flushing the coolant system] easy to do?

No, this is not easy to do correctly. Not for someone who isn’t DIY experienced anyway. Best to ask an inde shop to do it for you. Doesn’t take much time for an experienced tech to do, so it shouldn’t be overly expensive. You’re supposed to change out the coolant periodically anyway, so no harm done to do it a little sooner than maybe the owner’s manual calls for.

If you wanted to learn to become a DIY’er, this might be a way to start. But you’d want someone experienced, like another DIY’er you know, to be there and show you step by step while you watch and help the first time. After that you could do it yourself the next time if you own the necessary tools.

If it were my car anyway, I’d want all that WW fluid out of the cooling system straight away. You never know if it has something in it that will corrode the aluminum parts in the engine, damage the head gasket, or adversely affect lubrication, engine cooling, or freeze protection. It’s not something I’d lose sleep over, but I wouldn’t defer getting it done either. Worse case, if left unchecked, the damage could become extremely expensive to repair.

To save you some money in the future, if something like this happens again – like any time you think the wrong fluid may have been used – very often it is possible to undo what happened inexpensively as long as the car isn’t started or driven first.

I support George’s recommendation to hook up with someone experienced. Nothing ever goes perfectly, and it’s good to have someone knowledgeable there to deal with the unexpected. He/she can also show you where to check the weephole around the water pump and help you understand all the plumbing. It’d be a great learning experience. He/she can also show you ways to get stuck hoses off without damaging the radiator pipe, show you which is the radiator, which is the A/C condenser, and which is the tranny cooler (if they’re separate), and tell you what NOT to disconnect to gain access. He/she can also show you how to do a cursory inspection, like looking for green crusty spots… a sure sign of an impending failure.

He/she might also be able to help you find out why the coolant was low. When you invite him/her over, ask if he/she has a pressure tester. If not, you may want to pick a kit up at the parts store. That’d be a good procedure to learn too, and it’s really easy to do. A basic kit will cost about $50, but it’ll be money well spent.

My standard process is to put the car on ramps and remove the splash shields, remove the radiator cap, turn the heater to ON and the ignition key to ON (to open the heater valve), disconnect the lower radiator hose, and have a cup of coffee (just kidding). Then, when the fluid is drained, I simply reconnect the hose, put it all back together, and fill the system with the key ON to allow the heater valve to open and the heater core to purge. I then run the engine until the T-stat is open, shut the engine off and top the level off, close it up again and do it again. I then take if or a drive and recheck it once again, and then monitor the level in the reservoir for a week or so.

Many people use this procedure as an opportunity to change the T-stat too, and that’s a good idea, but if it’s just a routine flush I don’t bother.

I use the ramps even if access to the lower hose is good, because it ensures that the radiator cap will be the highest point in the system… and that’s where the air migrates to when you’re purging the system. Some systems have a bleeder valve in a heater hose, and if the system does have one I use that too.

“I suspect they denature the ethanol first!”

The most common denaturant is methanol.

I’m used to seeing 2-propanol 5% as the denaturant. Ethanol has to be poisoned or it is drinkable and a liquor tax is due. If the ethanol is used with other toxic ingredients, denaturant is probably not needed since the mixture is already undrinkable.