Auto trans leaking at cooler nut

[jangell]

Just wanted to check before I order a new line: my transmission is leaking at the nut to the cooler. I’m guessing it’s deformed at this point, since it doesn’t want to get any tighter and still leaks. Is there a trick to this, or is it just damaged? I’ll be dropping it in another hour or so to check the threads, but I wanted to get some advice first.

On the same note, I had to remove the dipstick recently, and the otterstat seal I was using in place of the o-ring swelled and wouldn’t fit back in. I tried just using an O-ring and RTV, but it leaks when filled, without even turning the car on. Is there a trick to getting the O-ring to work, or should I just order another otterstat seal?

Thanks!

— Joe

[Farrar]

It's probably damaged. Those fittings are kind of terrible. (The ones at the transmission are worse.)

[David T]

Take the fitting apart and inspect for cracks or deformation. There are copper seals that can be bought to help seal or maybe a smear of RTV can help. You cannot properly seal the "O" switch with an "O" ring, you must have the correct seal. If it swelled it is no good. NEVER use any kind of sealant on the silicone seal, it causes it to swell and split.

[Chris 16409]

The original automatic transmission cooler pipe is terrible. The lines never seal very good. My buddy Ryan King had never ending issues with his transmission leaking. The only way we were able to fix it was installing an external oil cooler and by passing the original pipe. We used something like this:

https://www.summitracing.com/nv/part...0/applications

You can get fitting that connect right into the transmission. Ryan can post pictures of his set up.

[Farrar]

The original automatic transmission cooler pipe is terrible. The lines never seal very good. My buddy Ryan King had never ending issues with his transmission leaking. The only way we were able to fix it was installing an external oil cooler and by passing the original pipe.

Exact same thing happened on my car, right in the middle of testing the replacement engine...

[David T]

The lines are steel and you must really crank hard on them to deform the flare to make it seal. You must also "hold back" on the fitting on the cooler or you can twist it right off.

[jangell]

Sorry for the late reply; I missed the notifications on this thread for some reason.

My friend (a classic car mechanic) and I removed the trans cooler connection and checked for damage. He couldn't find anything, so his guess is that it was misaligned a bit, so he re-installed it and tightened it down. We haven't done a test on it just yet; I'll be doing that this afternoon.

That said, I the cooler is damaged but we just didn't notice it, do you think it's more likely to be the coolant pipe, or the hose from the transmission to the cooler? I'm wondering if I have to replace just one or both if there is damage there.


For the transmission dipstick tube, we tried one O-ring, but it leaked. We're pretty sure we just used the wrong sized one, so we tried again with a new ring. We did RTV this in place just to be sure (I don't think it needs RTV, but my friend was insistent about it, so we did it). We did this on Sunday, and needed to wait for it to dry before testing, which I'll be doing in about 3 hours.

To be clear: RTV was only used on the transmission dipstick tube, not on the cooler -- the cooler is just a straight metal-to-metal connection.


David, I'm not quite clear what you mean by "You cannot properly seal the "O" switch with an "O" ring, you must have the correct seal" -- did you mean the O-ring on the transmission dipstick tube, or the cooler (which doesn't have an O-ring, right?), or the otterstat switch seal? If it's the latter, I have removed that from my car entirely now, as MegaSquirt controls cooling fans and there is a simple straight pipe in its place.

Chris, if I can't get it to stop leaking I'm rather curious about that alternate transmission cooler setup. I'm very curious about how that is connected in Ryan's car. (Edit: a closer look at the picture revealed that it just has two connections -- for some reason I thought there were two more on the other end and ran cool fluid next to hot fluid, but now I see that it's a radiator that you run the trans fluid through. I'm still curious about where Ryan chose to mount it, since I'm guessing just sticking it next to the trans isn't going to get enough air over it if you're stuck in traffic).

Farrar, I'm also curious about that radiator setup. Is there an issue with how much further the trans fluid has to run? I'd heard something years ago that long cooler lines could damage the transmission pump or something, but I don't really know enough about it to know if there's anything to it. I also assume that this radiator is mounted in front of the condenser, which is mounted in front of the engine radiator, so you now have three stacked radiators and that there's actually enough room for that?

Also, what oil filter are you using for the 3.0L? I'm using a Wix 51626, which is the fat style that barely fits next to the oil sender. I didn't have much luck trying different filters from Advanced Auto, and I wasn't sure which narrow filter would actually work to order one online.

Thanks!

-- Joe

[David T]

I was saying you must use the proper seal for the Otterstadt switch but if you don't have one forget it. Some owners doubled up on the "O" rings for the dipstick tube and that stopped the leak but a dab of RTV should also work. You do need to use the correct size "O" rings. If you twisted the connection on the oil cooler then that could be the problem but the more likely cause is you just don't have it tight enough.

[Farrar]

Farrar, I'm also curious about that radiator setup. Is there an issue with how much further the trans fluid has to run? I'd heard something years ago that long cooler lines could damage the transmission pump or something, but I don't really know enough about it to know if there's anything to it. I also assume that this radiator is mounted in front of the condenser, which is mounted in front of the engine radiator, so you now have three stacked radiators and that there's actually enough room for that?

Also, what oil filter are you using for the 3.0L? I'm using a Wix 51626, which is the fat style that barely fits next to the oil sender. I didn't have much luck trying different filters from Advanced Auto, and I wasn't sure which narrow filter would actually work to order one online.

#2613's ATF cooler is not mounted in front of the condenser. There wouldn't be any room for that. The cooler is mounted behind the radiator fans in the "empty space" there in the curve of the frame. I used this cooler. Because the fittings are so large (10AN) Bill used brass reducing couplings to connect to the 90-degree copper fittings, thus allowing a more or less straight piece of hose to go to the copper pipes that are mounted to the frame. I haven't checked but I think he used 5/8" hose. I'll ask him the next chance I get. In the meantime, let me know if you want pictures.

Oil filter is an STP S6941.

[jangell]

I was saying you must use the proper seal for the Otterstadt switch but if you don't have one forget it. Some owners doubled up on the "O" rings for the dipstick tube and that stopped the leak but a dab of RTV should also work. You do need to use the correct size "O" rings. If you twisted the connection on the oil cooler then that could be the problem but the more likely cause is you just don't have it tight enough.

Ah, gotcha. I was looking at using the otterstat seal for the transmission dipstick again, rather than for the otterstat itself. I'll report back once my I've run my test in another two hours.

Thanks!

-- Joe