Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Coolant/transmission flush

'97 buick Skylark V6 3.1ltr

i had someone take me thru brakes, plugs, tranny pan gasket… so i am not at a total loss but i do have some questions.

i am going to replace the radiator. it was leaking internally and i got coolant in the transmission(yes, strawberry color).

and i had used bar’s before i realized it was the radiator.

maybe i do not even need to flush?

1)coolant flush(and i cannot afford to take it in to a shop)

So there is a hose that goes from the coolant reservoir then ‘tees’ to the bottom of the radiator and to the water pump. Then there is a hose on the other side about halfway that comes from the thermostat.

Since my heater core has been bypassed I am not going to get a kit.

I am thinking just keep the reservoir filled with the radiator hose on the thermostat side unhooked and run the engine until the water comes out clear.

2)transmission flush(i am checking on the price for a shop to do it)

the radiator has a line at the top and bottom for transmission. i am supposed to attach a clear hose where the tranny fluid goes back to the transmission. so is it the top or the bottom? i know i can test it by unhooking the lines.

i figure to put the front tires on blocks since the car will have to be in drive.

after dropping the tranny pan, emptying and refilling, then attaching a clear plastic tubing to the return line. start the car, put in drive and wait for the fluid to change color meaning the old is out. does that mean the torque converter has been emptied of the old also?

also, gosh i hate to drop that tranny pan again. couldn’t i run the engine till all the fluid is out? then add new.

thanks for any advice.

thanks for any info.

Don’t even try to work on the car. You are hopelessly unqualified as well as dangerous. You will save money and you won’t get hurt.

You need to flush both the cooling system and the transmission. This is one of those rare situations where I would recommend a cooling system flush product to help clean out the transmission fluid.

Don’t even think about running the car in drive with it up on blocks. Too dangerous. You may have flow through the lines with it in Park. Just don’t let it run out of fluid. Personally, I would let a shop do the transmission flush.

While the above comment might be a bit unfair, I would still recommend going to a shop with professional equipment. I simply cannot tell if your method would be effective. If you mess up the transmission, well, it is not a cheap throwaway item.

understood about the flush product.
but the method i mentioned above about flushing the cooling system is correct - yes? that is basically what i did the last time i used a cooling flush product. and i figured i would start out with a clean radiator without any ‘extra products’ in it.

why is it dangerous to have the car in drive if the front wheel are on off the ground? i may or may not have fluid flow in park. the only alternative will be to get a length of hose that will reach to the driver side so i can keep my foot on the brake and have containers on hand at the door to catch and watch the flow. anyways i did not make up the method. got it from Automotive Forums.

Plus I called to see what a flush would cost and when I told the guy I had coolant in the transmission he said he would not put that through his machine.

And yes the above was a bit unfair. I do not think this is something I cannot handle.

Thanks again for your comments.

The problem is that blocks or jack stands can slip, sending the car forward. If you don’t have pressure in the transmission lines with it in Park, you probably will with it in Neutral. (Oh, Transman, where are you with your usual sage advice?)

Your cooling system flushing procedure should work.


well i replaced the radiator first.
then flushed the engine 3 times(or was it 4).
then dropped the tranny pan and replaced the fileter.

got 1/4" clear plastic tubing and a transmission line fitting which is a thread to tube fitting. connected to the return transmission line. containers were ready for filling and 4 gallons of new fluid.

had someone start the car, keep on the brake and put in drive. did this because someone mentioned the car might need to be in gear to engage the torque converter and thus make sure that got flushed also.

the fluid came out at a steady rate but definitely had enough time to switch containers and put in more fluid.

OK - again

So, does this mean you’re back on the road with no signs of fluid contamination or transmission problems? If so, good for you! You probably dodged a bullet and saved a bunch of money in the process by doing it yourself.

well, i will know in a few days.
then i will check the coolant level.

of course as soon as i can, dollar wise, in the future i will have the transmission rebuilt. since the start of the problem it was about two months before i diagnosed and fixed.

at that length of time do you think serious damage was done?