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

https://uploads.tapatalk-cdn.com/20190303/3004a82bf80e75fedef2a35bed1534f5.jpg

[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/parts/sum-331000/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...


https://www.youtube.com/watch?v=oSR7B2WoMHw

[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 (https://www.amazon.com/OPL-HPO014-Universal-Aluminum-Cooler/dp/B00G6UW8OO). 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

[jangell]

#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.

That makes a lot more sense.


I used this cooler (https://www.amazon.com/OPL-HPO014-Universal-Aluminum-Cooler/dp/B00G6UW8OO). 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.

That's great -- the video was certainly useful, but some pictures of how everything is mounted would be great. Although if my fixes from the weekend work, I probably won't do anything until it starts leaking again, so no need to hurry. Just next time you happen to be under there is fine. I'm mostly collecting information at the moment. :)

I do have a couple other very minor leaks. There seems to be one at the center of the case where the two halves come together, but I'm not totally sure if it's just fluid collecting there from somewhere else, or an actual leak at that join. The other is around the pan, which I guess is just a thing we deal with at this point. I'm using DPI's silicone seal, which is definitely better than the cork ones. I think I put it on dry, but I don't remember anymore.


Oil filter is an STP S6941.

Excellent -- I'll hunt them down, or whatever they cross-reference to. Thanks!

-- Joe

[Farrar]

Excellent -- I'll hunt them down, or whatever they cross-reference to. Thanks!

Try using a 1989 Porsche 944 Turbo as a cross-reference. I *THINK* that's the cross-reference, but I'm not sure.

I'll get pics of my setup the next time I have the front end in the air (soon - I'm replacing the horns next) -- but I hope you won't need them. :)

[jangell]

Well, I didn’t even make it to the transmission cooler test. I poured in a quart of fluid, and found it dribbling out around the base of the tube. It’s basically how it was when I used the wrong sized O-ring.

So I guess I’m ordering an otterstat seal and hopefully installing that this weekend. I’ll post an update again once that’s in and tested.

I’ll also check for the Porsche crossover for that oil filter.

Thanks!

— Joe

https://uploads.tapatalk-cdn.com/20190305/ee031d6ddfb70d5b92bfac11d7b257c0.jpg

[Chris 16409]

Joe, I've heard that the otterstat seal works best for the auto transmission dipstick tube. I would just get another one of those.

[jangell]

Just to wrap this up:

- The otterstat seal on the dipstick worked perfectly and there aren't any leaks there anymore. At least I'm pretty sure it's not leaking anymore (there's still left over fluid on the transmission). The dipstick doesn't quite sit vertical once mounted to the cylinder head, but it seems to be sealing just fine.

- Unscrewing and re-attaching the cooler line seems to have fixed the leak there as well, so I think I'm good to go. There was a tiny bit of seeping that may have already been there from when it was last tightened up a week prior, so maybe it needs to be a touch tighter, but that's it -- it's not like it was before, where there were visible drops pooling on the floor of the garage. If it starts leaking again, I'll explore some of the other cooler options.

My test was just to run the car up to operating temperature and then let it idle for a few minutes. Once I have a chance to drive it (next week sometime) I'll do another check for leaks just to be sure.

Thanks again everyone!

-- Joe

[Farrar]

Hooray! Easy fixes are great. They're so rare on these cars. :)

[Jonathan]

Just to wrap this up:

- The otterstat seal on the dipstick worked perfectly and there aren't any leaks there anymore. At least I'm pretty sure it's not leaking anymore (there's still left over fluid on the transmission). The dipstick doesn't quite sit vertical once mounted to the cylinder head, but it seems to be sealing just fine.

- Unscrewing and re-attaching the cooler line seems to have fixed the leak there as well, so I think I'm good to go. There was a tiny bit of seeping that may have already been there from when it was last tightened up a week prior, so maybe it needs to be a touch tighter, but that's it -- it's not like it was before, where there were visible drops pooling on the floor of the garage. If it starts leaking again, I'll explore some of the other cooler options.

My test was just to run the car up to operating temperature and then let it idle for a few minutes. Once I have a chance to drive it (next week sometime) I'll do another check for leaks just to be sure.

Thanks again everyone!

-- Joe

Any difficulty getting wrenches on these fittings? I ask because of hearing they are a pain in the butt to get loosened off (or tightened back up). I have had off and on leaks with my cooler lines for a while. I actually have both brand new cooler hoses ready to go, just haven't put them in yet. Those fittings aren't available at the moment as new replacements, so need to reuse the ones I have. One comment I heard was the tendency for the fitting to come out of the transmission, but not separate itself from the other half (that's connected to the hose). Maybe just a lot of unnecessary paranoia or fear factor in starting this job from reading too much about it and not enough just going ahead and doing it? :)

[jangell]

My friend had the wrenches on the cooler this time, so I can't really say what they were like.

However, I did disconnect the transmission lines from the cooler when I pulled the engine and transmission a few years back. I left the hoses in the transmission, but I had a lot of trouble getting the one of them back on the cooler. From my notes, it seems that I wound up binding the rearward transmission cooler line to the point that I just assumed I was going to strip the threads in the line. I also wound up bending the metal portion of the line near the transmission. I decided to remove it instead, but my wrench just turned the adaptor on the transmission, and there wasn't enough clearance to turn it around completely from there. I wound up getting out my angle grinder and cutting off the line and ordering a replacement. I had to clamp the adaptor nut into a vice and put quite a lot of torque on the wrench to break it free from the line.

So yeah, the fittings in the transmission do seem to come out with the lines sometimes. But you can just screw them back in after you get the old lines off of them.

-- Joe

[jangell]

Some follow up on this: The reason I couldn't get the dipstick tube to seat properly is wasn't bent enough, which caused it to hit the body, and thus required the tube to sit at an angle. The only way to get it to seal properly like that is probably to use a lot of RTV.

Instead, I wedged it in a vice and carefully bent it (ie: pulled real hard) until it cleared the body. After that, I was able to get it properly aligned in the transmission. I used the otterstat gasket and Right Stuff on it, and now it appears to be sealing properly and no longer leaks.

As a bonus, the problem I had with not being able to get the dipstick all the way in the tube much of the time is also fixed, since the tube is now aligned properly. Instead it gets a little stuck trying to remove it, but it's pretty easy to dislodge when that happens.

The cooler nut seems to be tight enough that it's not leaking anymore, so I think I'm good there.

Thanks again!

-- Joe

[jangell]

Ok, so there's still a leak showing up at the lower cooler nut. Today I had the car up and the engine running, and I noticed that there's fluid on the PJ Grady heat sink fins. It seems like it's the upper connection that's leaking, not the bottom -- it's just leaking under the heat sink fins, which is why I didn't see it before.

Off to tighten that up now, which I'm sure will be lots of fun thanks to its location.

-- Joe

60531

[David T]

The hose can also leak where the hose is crimped onto the pipe that goes to the cooler. It can run down and make it look like the nut is leaking.