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2005 Deville Base, 2004 Escalade AWD
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Discussion Starter · #1 · (Edited)
Transmission Cooler Line – O Rings

I drained / replaced the transmission fluid this past weekend and now have a leak where the hose connects from the transmission assembly out to the radiator (bottom fitting). I do not recall any o-ring when I removed this hose but the absence would certainly explain the leak from an otherwise snug connection. There seems to be some thread sealant on this connection. Is there an o-ring for this fitting?

EDIT: Also, if I loosen this connection (engine off) will I have a gush of trans oil or maybe just an ounce or so?
 

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2010 DTS
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87,954 Posts
Re: Transmission Cooler Line – O Rings

Have you tried snugging up that fitting just a tad?
 

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1996 Eldorado
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2,814 Posts
Re: Transmission Cooler Line – O Rings

The quick connector can be removed & resealed for the cost of "O" rings or replaced for about $6
 

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2005 Deville Base, 2004 Escalade AWD
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Discussion Starter · #4 ·
Re: Transmission Cooler Line – O Rings

I need to troubleshoot the radiator lower cooler line fitting (flare nut) as this is where the leak is, not as originally described. If I remove the line from the fitting how much fluid can I expect to lose (engine off)? A new fitting would have an o-ring inside, right?
 

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1996 Eldorado
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Re: Transmission Cooler Line – O Rings

That fitting is at the transmission? That may have a "O" ring or a crush gasket.

Lines can developed cracks initiating at the tube flare.
 

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'98 Seville STS (gone); 2001 STS
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156 Posts
Re: Transmission Cooler Line – O Rings

If I remove the line from the fitting how much fluid can I expect to lose (engine off)?
Assuming you pull the line right out, you'd loose the volume of the hose, plus whatever is in the cooler. I'd guess around a pint tops? Stick a rag under the fitting, pull the line off at the trans, slap your thumb over it, then direct it into a container that you pre-placed underneath. Just make sure you can point the line down so it'll be lower than the rad's bottom.

I just replaced my rad two days ago, so it's all semi-fresh in my head!
 

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2003Cadillac Seville STS 75,000k
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178 Posts
Re: Transmission Cooler Line – O Rings

I am working on changing the trans ATF and wanted to know which line is the send and return from the radiator? I am guessing the top is the send from the trans and the bottom one is the return, but I'm not sure? These lines are connected to the radiator on the driver’s side.
Also how do you release the fitting on the top one, any tricks?
 

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'98 STS (RIP @ 206,xxx miles)
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4,854 Posts
Re: Transmission Cooler Line – O Rings

I am working on changing the trans ATF and wanted to know which line is the send and return from the radiator? I am guessing the top is the send from the trans and the bottom one is the return, but I'm not sure?
The UPPER line is the fluid return to the transaxle.

Also how do you release the fitting on the top one, any tricks?
Slide the nylon cover away from the fitting and remove the U pin clip from the radiator end tank quick release fitting. Gently pull the metal line away from the radiator end tank (DO NOT lose the O ring or the U pin clip).

If you plan to use the transaxle pump to remove the fluid, you will need to remove the quick release fitting from the radiator end tank and temporarily install a pipe thread fitting to adapt the plumbing to a flexible hose setup in order to capture the fluid.

This probably sounds more involved/complicated than it is. The second time you do the job will be much easier.
 

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Re: Transmission Cooler Line – O Rings

on a 2002 Seville STS, the upper fitting is a quick release fitting the bottom one is a flare type. You also have to remove a clamp holding the trans line in place about 3 inches back from the radiator, before the line can be pulled from the fitting once the spring clip is removed. The upper fitting is 18mm x 1.5, finding a fitting that you can screw in with a tube barb is not easy.
 

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'98 STS (RIP @ 206,xxx miles)
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Re: Transmission Cooler Line – O Rings

....finding a fitting that you can screw in with a tube barb is not easy.
It is easy enough at Lowes or Home Depot plumbing sections.

 

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Re: Transmission Cooler Line – O Rings

It is easy enough at Lowes or Home Depot plumbing sections.

@ Hi JimD,

I tried Lowes and Home Depot, they don't carry metric fittings.

What I was looking for was a m18 x 1.5 adapter of any sort that could get me to a barb, so I could get a piece of rubber tubing on it to a bucket.
I tried Autozone, Advanced Auto, NAPA, PepBoys, Home Depot,Lowes, Menards, McMaster, Grainger, Fastenal and gave up. I realized in my search that NAPA had solid hex head O2 plugs that were m18 x 1.5, so I drilled and tapped an O2 plug to 1/4" x 18 FPT and used a 1/4" x 5/16 barb fitting from Menards. This plug was a flange type, so gripping the hex head was difficult, having a m18 nut too would have made it much easier in the vise for drilling and tapping (Fastenal was already closed on the weekend).

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@JimD
Are you saying a flare fitting is metric? I will have to go to HD or Menards to see what flare fitting size matches up. Thanks but I had already drilled an O2 plug.
 

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'98 STS (RIP @ 206,xxx miles)
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Re: Transmission Cooler Line – O Rings

JimD
Are you saying a flare fitting is metric? I will have to go to HD or Menards to see what flare fitting size matches up. Thanks but I had already drilled an O2 plug.
It's been many years since I picked up that brass fitting and I simply do not remember the size. I took the end tank adapter from my '98 model into the plumbing section and started searching the bins for an exact thread match.
 

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Re: Transmission Cooler Line – O Rings

Hi Jim,

The flare fitting size that matches closest to the m18 x 1.5 is the 1/2" flare, however its a very loose fit and would require probably at 20 wraps of telon tape to keep it from leaking during the process of pumping out 2 gallons of fluid. If I didn't have a good drill press and tap set, I would have tried the flare fitting.

To all:
Dropping the pan and pulling out the sump plug yielded just under 8 quarts of fluid on a 4T80E. That means about 50% of the old fluid still remained in the torque converter and radiator according to the owner's manual stating 15 quarts. I used 1 gallon washer fluid jugs to pump out two more gallons while simultaneously filling with 7 more quarts, running the engine for 30 seconds at a time, this after intially filling it with 7 quarts while the engine was off. While letting the engine pump out the fluid, I shifted though the gears a few times too. Then removed my adapter, reinstalled the upper tubing, then lowered the car to put in the remaining 15th quart.
 
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