Accidentally put coolant stop leak in transmission fluid

That looks like the cap for power steering.

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Transmission fluid dip stick for the Acadia.



If the whole assembly looks like Tester’s picture, get a transmission flush and hope for the best, as he advised.

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What is the model of the Acadia. I am still confused

On some cars, transmission fluid is the correct fluid for the power steering system.

The cap says transmission fluid only, but that does not necessarily mean the fluid is going into the transmission.

You still need to determine for sure if you added something to the transmission or to the power steering or…

Good luck. Please let us know, once you know. Find out for sure, first.

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If by “stopped working” you mean the engine runs but the car won’t move I think you should probably get pessimistic.

before replacing the transmission try flushing the tranny fluid and have the transmission filter changed too. try this easier cheaper option first. you may be lucky. good luck

Well…I’m more worried about the stop leak plugging up the valve body and torque converter, but don’t give up all hope. Few weeks ago someone waa driving his 05 Caravan and it started overheating. He checked the coolant and found very little on the dipstick. He grabbed a funnel and a jug and added a gallon of water. But the car kept overheating and now the transmission wasn’t shifting right. He had added water to the trans and not the radiator.

I had to flush 42 quarts of fluid through the trans to get the fluid clean, but it shifted fine afterwards. How long it will last is anyone’s guess, but the customer was willing to gamble on a few hundred to flush before jumping to a few thousand for a replacement trans.

There is a big difference between adding plain water to the transmission, versus adding coolant or even worse a cooling system stop-leak product. I would not expect plain water to cause any permanent damage as long as the mistake is caught quickly. I suspect your customer will not have further problems with his transmission after getting all the fluid changed.

I’m not nearly that confident. The trans control module had a handful of fault codes for a bunch of the electronics and the neutral safety switch, which is inside the trans, was flaky when the car came in. It worked when it left but electrical switches exposed to water often fail soon after.

The car left with a 50/50 warranty: when it breaks you keep both halves. :grinning:


From past experience with even very minor amounts of water contaminating transmissions I’d consider the OP’s is trashed. As soon as it gets up to speed and the clutch plates get hot they will slough off the friction material bonded to them due to steam generated in the bonding. Or that’s how it was explained to me as I viewed the pan full of oatmeal long ago.

Just in case the OP is lost in the weeds at this point, I will try to summarize for him:

The power steering system takes the same fluid as the transmission.
The cap that you displayed is the cap for the power steering fluid reservoir.
So, if you added coolant stop leak to the power steering system, at the very least that system will need to be flushed–but it is possible that some actual repairs will be necessary.

If your car “stopped working”, that could mean many different things.
Did the engine stall/stop running, or was it a situation where the engine kept running but the vehicle wouldn’t move? Is the Check Engine Light lit up?

In any event, while the vehicle is in the shop to flush the PS system, this would be a good opportunity to fix the coolant leak at the same visit. If the engine stopped running, your mechanic should be able to diagnose the problem. If there is indeed a transmission problem, he should be able to tell you that there is, even if he can’t diagnose the exact nature of the trans problem, and that would mean that it is time to visit an independent trans shop (NOT Lee Myles, Cottman, Mr. Transmission, or AAMCO) for proper diagnosis.

Since you didn’t add the coolant stop leak to the transmission, if there is a trans problem, it is purely coincidental, but I somehow doubt if you do have a trans problem. For some reason, a lot of people incorrectly attribute engine problems to a problem with the transmission.


It actually hasn’t been determined that the OP was showing us the power steering cap. The tops of the PS and transmission caps are similar, and the OP hasn’t revealed the length of the attached dipstick or a picture of where the cap was removed.

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The key to me is whether there was excessive revving of the engine; both at a set speed and and as the engine revved before each shift; causing a shift flare. If so, I agree with asemaster and Rod-Knox’s summations.
It only takes a few minutes to trash the clutch linings. At this point change the fluid and say a silent prayer. Even if a fluid change gets it going one is still left with the question of how long will it be going.

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Post # 5 has a picture of the transmission cap, post # 12 shows the power steering cap.

The transmission cap has a gear on it, the power steering cap has a steering wheel on it.

OK. Now I understand what those pictograms mean. I’ve been around mechanical stuff all my life and it was not obvious to me that one was a gear and the other a steering wheel. Now how about someone not at all familiar with mechanical things? The average person at the gas station? I’ll just say I think the markings for these systems are terribly inadequate. Pretty sure my wife would have no idea that a picture of a gear means transmission. No idea there is a gear in a transmission or what it looks like, and she is a farm girl.

There has to be a better way. I’ll have to say in the Acura, the washer fluid and coolant are pretty similar and even I have to look pretty close and that pictogram of a windshield wiper on the cap is not real helpful.

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I’m betting you’re ok. Not sure how soluble radiator stop leak compounds are in trans fluid but do a drain of the sump then. Do a complete flush. Then do another, as well as change the filter after the flush. They’re a cheap procedure.
What’s done is done. The only way to know if it’s trashed is if it acts trashed. Well, the other way, possibly, is that you could have it removed dismantled & inspected but why? You could probably get a used trans and have it fitted for the same cost.
Driving it after flushing is inspection enough.

Aluminum power would be a disaster for the transmission. Disassembling and cleaning a polluted valve body is a tedious job, unless the transmission is cleaned of all contaminants the valve body will become fouled again. This means a complete overhaul.