Transmission Leak At Radiator and Transmission Service

This is on a 1991 Buick Regal with a 3800 V6 and 113,000 miles.

If my diagnostic is correct I believe I am leaking transmission fluid from the radiator hoses. There are two small hoses connected to the bottom of the radiator on the drivers side that are visibly wet. The hoses do not look dry rotted and the radiator itself is clean, looking like it was replaced within the last two years. Nothing actively leaks when the car is parked or when idling, but after a drive there are one or two small drips underneath the radiator and the underside of the radiator and front end frame are visibly wet. As such, I cannot tell exactly where the leak is coming from, but I’m guessing it is at the hose connection.

I could probably work on this myself, but I’m short on time at the moment and it sounds like a mess of a job. What would I expect to pay to have this fixed, assuming the hoses just need to be cleaned and reseated/clamped or maybe just replace the hoses and top off the transmission fluid?

On a side note: I was wanting to have the transmission pan removed in order to replace the filter, gasket, clean the pan/magnet, and have some fresh transmission fluid replaced into the system. The local service shop refused to perform this service saying that “I would just be opening up a can of worms” and to leave it be so long as I was not having transmission problems. I’m assuming they didn’t want to be blamed for transmission failure on such an old car over an $80 to $100 maintenance job.

As of right now the transmission fluid is on the very-very light brown side of pink and aside from an occasional hard idle at start and a single noticed slip at high speed (70mph) acceleration, the transmission runs well. Is he right that this service could be “a can of worms” or am I wise to think that this is good preventative maintenance?


First thing to do is to fire the shop that told you not to bother.

They are just too lazy and would rather work on newer vehicles.

A filter and fluid replacement is a roitine procedure and should be done every 30,000 miles or so. With the low miles on this transmission…for a 1991…there should be plenty of life left if it is maintained. The symptoms that you discribe sound minor and and they are saying to toss the maintence to the wind…basicly junk it soon.

I’d find a good independent shop for your work, but in this case you may want to look up a good transmission shop…not a chain either…and see what they think.
It could be that the bands need to be adjusted, a sensor needs replacing, or maybe just a minor adjustment of something.
If they test drive it and think that it’s a minor repair, then have them replace those lines and do a filter and fluid change.

I can’t give a price, but they can test drive it and give you a price.

Personally I’d never hand one more dollar to the shop that you went to.


“The local service shop refused to perform this service saying that “I would just be opening up a can of worms” and to leave it be so long as I was not having transmission problems.”

First of all, find another shop

Telling somebody to NOT change the transmission fluid is just plain wrong

Perhaps you could do this service yourself

Do you have hand tools (sockets, ratchets, extensions, etc.), a jack and jackstands?

Are these leaking? If the hose itself is wet, you don’t reseat, reseal, reclamp, etc. You replace the lines.

Yes, changing the trans fluid and filter is good preventive maintenance. Every 30K in your case

Something else to consider . . . get this trans pan with a plug. It’ll make it easier for the next guy, which might be you.

Alright, my mistake on where the lines connect. I just took another look at the radiator and the trans cooling lines meet on the lower drivers side corner of the radiator and then branch off the to upper and lower passenger side corners of the radiator. I can clearly see trans fluid all down the side of the radiator, so it’s leaking from the top connection for sure; the bottom is harder to see and it is covered in fluid as well, but maybe just from the upper leak.

It’s a tight space, but I’m going to try to get a wrench in there and crank on it (fingers crossed that it’s just loose).


Yes, those appear to be the lines. I do have the tools and the aptitude to do this, but I’m short on time dealing with moving and a death in the family, so it’s going to have to be done in a shop.

Now I’m worried that it could be leaking out of the radiator wall itself.

So, there is a thread coming out of the radiator that the cooling line is attached to. On that thread is another nut, making it look like it is threaded into the radiator itself and seated on a big washer. The leak appears to be coming from behind this washer.

Could this be a fitting with some type of seal/gasket that can be replaced or a permanent part of the radiator itself?

THis sounds like the fitting that is in the radiator is leaking. That would mean a new radiator.

But the line could be leaking and the fluid migrating to that fitting.
Sometimes these lines start to leak right at that flare nut. That would mean just new lines…or a repair piece installed.

Because of your time constraints…like I said in the last post…find an Tranny shop and have them fix the lines and do the fluid and filter job.


I’m almost certain it’s coming from the fitting.

Bah, did not want to spend money on a radiator. No way to replace those fittings?

The radiator looks like it was just taken out of the box. I’m going to try the previous owner and see about the possibility of a warranty.

No replacing them…just the whole radiator. But if the radiator looks that new, maybe somebody forgot to snug them. Don’t over do it, But I’d try tightening them.

Still a new radiator is only going to be $150 and new hoses $35.



Is this what’s leaking?

Or this?

Here are some pictures.

In my opinion, you need a radiator

Looks like it’s going to be a looooong Monday.

Is there a type of pressure test I can do to better spot the leak location? Maybe have someone shift through the drive settings while I observe?

I found a radiator on sale at Pep Boys for $70 with free home shipping (it’s not available at the store for some reason). As such, I may just do this job myself.

A couple of questions:

On the other side of the radiator there are oil cooling lines which I’ve never worked with before. Am I going to get a lot of engine oil loss when I disconnect them?

So long as I monitor the leak and keep the trans fluid topped off, should I be okay driving the car before the repair or is there a risk of this thing blowing out? Also, the manual recommends Dexron II. Is it true I can use any Dexron fluid and that it’s best to stay away from the “multi-purpose” fluid?

Thank you for all of the help, it’s really appreciated.

Oh, and am I going to need to buy a GM quick disconnect tool in order to get the cooler lines off?

So, I finally found someone at an Auto Zone who actually came out and looked at the leak before trying to sell me a radiator.

He says all I need to do is remove the mounting nut and put some plumbing tape on it and, if there’s a broken one, replace the o ring.

Forget the autozone guy

Your car is old, and so is the radiator

Replace it and be done with it

Even if the autozone repair would work, that radiator tank is probably just about ready to crack or crumble away any moment now

Dexron 2 is an old standard. Look for fluid that is Dexron 3 compatible. Stay away from the multi-purpose fluid. Don’t use Dexron 6. No reason to spend that kind of money

I found out the radiator was replaced 18 months ago (and only has about 5k miles on it).

Isn’t it possible that the sealant on the connecting thread just wore out?

I’m going to pull the line out and try it with some Permatex and a sealing washer.

If it’s a flare fitting, Teflon tape won’t help. When you pull it apart, the solution might present itself.

I doubt that tape will do the trick, but you do have a new radiator.
I think the line is fatigued where the flare fitting is, and this is where it’s leaking. This happens all the time at the flare nut. Just cut the line back a 1/2 inch and reflare it. Simple fix and it will last another 100,000 miles.


It’s not leaking at the flare. It’s leaking from the threads that go into the radiator (the flare adapter I guess it is).

This part:

As I understand it there is an o ring seated in the botom of the radiators female opening. I’m thinking this has failed.