Flushing the transmission cooler??? - Corvette Forum : DigitalCorvettes.com Corvette Forums

DTOM · 12-19-2012, 07:29 PM

I came up with this related question in my earlier thread.

How do you go about flushing the transmission cooler?

It is easy to identify issues such as plugs, wires, leaks, and changing the oil. But, my guess is the only reason my car turned 40 last Oct in the condition that it is in is because the owners before me paid attention to issues like this that don't show up till they are neglected.

I am sure a lot of the members have this down cold, but if you are willing to share any experience, it is greatly appreciated.

radi8 · 12-20-2012, 12:54 AM

I've always assumed that if I kept clean fluid in the transmission and serviced it correctly, the cooler would stay clean as well. Now I'm curious too, lol.

HardcoreABN · 12-20-2012, 04:27 AM

The only method to flush a cooler of any kind (trans, oil, coolant) that is worthwhile is back flushing. This method helps remove any crud that has accumulated along edges inside the cooler.

What I would do is get a piece of hose and clamp 1 end to a piece of cooler line. clamp the other end around the end of your hose. Then turn the water on. Let the other hose drain into a bucket. Continue flushing until nice and clean. You can also get a gallon of mineral spirits, mix it with a gallon or so of water, and let it just sit in your radiator for 15mins ish then back flush the cooler. In most transmission coolers, bottom is supply and top is return.

DTOM · 12-20-2012, 06:56 AM

I know I started this thread, but is it normal / recommended to flush the transmission cooler?

The only issue I have had with the cooler is the rubber hoses that connect the in / out flow to the cooler getting old and leaking. They are a real pain to get into to replace.

Like with the radiator, the fluid looks good (nice and red), but I am thinking in terms of preventive maintenance.

I was surprised about using water in the transmission cooler though, even with the mineral spirits, could that cause any damage to the transmission?

HardcoreABN · 12-20-2012, 08:45 AM

even if the fluid looks good, I recommend flushing it every time the fluid is changed. the more junk that is trapped in the cooler, the less efficiently it will work. Heat is the #1 killer of automatic transmissions. The 15-20 mins it takes to give it a really good flush is well worth it.

Gah, should have edited that more closely.

You can use water to flush it, but after you must use something that will push the water out. The method I use is to use pressurized mineral spirits or brake cleaner and back flush until it comes out clear. If you don't want to buy several gallons of brake cleaner (in the bulk gallon jug) or mineral spirits you can flush first with water, then with mineral spirits. Make sure you use shop air after to blow as much water out as you can. What little water that is left will evaporate out when the trans gets hot enough.

496BBC · 12-20-2012, 08:48 AM

Most trans shops that sell and warrant their rebuilds require the cooler, if you have one, be flushed.

Their is a product called trans flush that has the fittings to connect the can to the cooler lines. Its an areosol product with some sort of solvent in it.

Here is a link to the product;
http://www.transdepot.net/product.as...FcKPPAodAFYAxw

Neal

DTOM · 12-21-2012, 04:11 PM

Thanks again to everyone for the info.

The radiator and transmission are a good couple of projects before I get back to that damn pitman arm

Sly Vette · 12-21-2012, 04:33 PM

Again,it seems that the car was well maintained and if the fluid is clear the most I would do is maybe a filter change and that would be a good time to replace the hoses as well. Unless all the fluid in the trans can be changed including the amount in the convertor you will just be mixing old with new. Years ago I recall that some cars that I worked on had a small plug in the convertor to drain the fluid. I don't know if that is true in this instance or not.
Good Luck!

72SBVet · 12-21-2012, 05:23 PM

The one you're thinking of with the drain plug is Ford's, Chevy didn't have one although it probably wouldn't be a bad idea to put one in the converter. A shop trans flusher will remove all the old and replace with new so I'd suggest taking it to a shop that you use and have them flush it for you.

diehrd · 12-24-2012, 10:13 AM

I can relate to preventive maintenance , but the trans cooler should not even be a thought or a target of such maintenance unless you have had a trans failure. All it takes is to dislodge one tiny almost invisible metal shaving to hang up a valve body and then your causing problems you otherwise may have never had for years to come.

Also note a transmission does not build up sludge like an engine although it will build up deposits of worn internal parts from clutches , steels, bushings ect .

So if you insist on flushing the cooler use trans fluid in a reverse direction that is filtered. You can usually get this done at a Valvoline oil change shop or even a transmission shop.

But based on your statements I would not do anything until after the trans pan is dropped and you can look at what if any debris have built up in the pan. If it is slight just change the filter and oil and you are all set.

72SBVet · 12-24-2012, 01:17 PM

How many miles are on the car? Mine had around 120k maybe a little less and one of the band's was nearly wore out, and it chewed into the drum so I had the trans rebuilt.

DTOM · 12-25-2012, 08:02 AM

I have 114k on the car. When I bought it two years ago it was at 102k so I have put a decent number of miles on it.

I changed the transmission fluid and filter and was pretty happy with the way it all looked. No sludge, no burnt smell.

I did find that I have two stripped bolts holding the pan on though. At least that answers the mystery of the tiny bit of fluid I always find on one of the bolts.

72SBVet · 12-25-2012, 02:16 PM

Mine I think had maybe one filter change in it's life and when I pulled the pan it had a chunk of metal in it so I freaked out and had the trans rebuilt, and that's when the shop discovered the wear. Still to this day we have no idea where the metal chunk came from as it wasn't part of the tranny.

DTOM · 12-28-2012, 08:08 AM

Thanks for the all the advice.

In the end I changed the filter. The fluid looked really good, only a little black at the bottom of the pan that wiped right out.

I think it is pretty obvious I am a novice, but just looking at the condition of the transmission I think someone rebuilt it at some point.

My only (small) concern now is there are two bolts on the pan that are stripped. I put a little gasket sealer on the two bolts when I put them back in. That explains the small drips I always have on the front of the pan.

Tapping them out will be a project for another day.