Transmission oil cooler leaks

Transmission oil cooler leaks

Postby Rod's Trucks [OP] » April 14th 2020, 8:20pm

I have recently replaced the little seals at the transmission oil lines to the radiator, but I see they are leaking again. It has returned as a very minor, but fairly constant, seepage.
I have seen the various postings about cutting the aluminum lines and putting in rubber hose 'couplings'.
I am curious what the actual root of the problem might be, that causes the leaks.
Is it because the rigid aluminum lines do not allow for any flexing, so vibration are transmitted directly to those O-rings? Because the seepage is so slight, I cannot seem to determine if it is the actual O-rings that are leaking, or maybe it is from the joint with the actual metal radiator fitting.

Does the flexible rubber hose coupling in the aluminum lines solve the issue completely, or should I also replace the fittings in the radiator with barbed adapters. If the barbed adapters are recommended, what is the thread needed? Is it a pipe thread or an 'AN' style etc? I would like to have everything needed when I open it up.
Thanks,
Rod
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Re: Transmission oil cooler leaks

Postby Wiley » April 14th 2020, 9:39pm

Are you positive you connected the wire hook/plastic cover properly....I have read posts where people have reattached them and the issue resolved itself. Maybe wishful thinking but take another look at the connector.
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Re: Transmission oil cooler leaks

Postby Mmusicman » April 15th 2020, 12:00am

Be sure you removed all of the old o-ring
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Re: Transmission oil cooler leaks

Postby Rod's Trucks [OP] » April 15th 2020, 12:59am

Thanks for the suggestions.
RE: Old O-rings and snap rings...Yes, and Yes.
I replaced the fittings, along with the seals, so there was no 'old' o-rings; and the spring clips 'snapped' into place as they should. There was no leakage for several months, and no it is very slight, but noticeable after driving a while.
The upper end of the radiator tank eventually gets wet around the upper fitting, and I wipe it off with a rag. If I let it go long enough, it will eventually drip off the lower corner of the radiator.

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Re: Transmission oil cooler leaks

Postby Leeann_93 » April 15th 2020, 11:23pm

Were the replacement fittings AC Delco or Dorman?

I am told that the Dorman fittings only work really well with the replacement Dorman lines, that they're slightly different from AC Delco and the two don't mate perfectly.

So if you still have AC Delco lines, get AC Delco fittings. Dorman lines, get Dorman fittings.
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Re: Transmission oil cooler leaks

Postby Rod's Trucks [OP] » April 16th 2020, 9:53pm

Well, I cannot answer that question. I have no way of telling if my lines are original ( I suspect they are original, because nothing is rusty on my van); and I have no idea what brand the 'new' fittings were... it has been quite a while since I purchased then, and did not notice any particular labeling. It was just a 'bag-o-parts' as I recall.
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Re: Transmission oil cooler leaks

Postby gavio » April 21st 2020, 2:40pm

There is a fitting made by one of the companies that makes transmission coolers (Hayden I think) that is made to replace that radiator fitting and give you a 5/16 barb.... I installed one and then put in a short section of transmission cooler hose (it’s different from fuel hose, so get the right stuff) and I haven’t had a leak there since... Before I did that I was replacing that stupid quick connect fitting every 6 months... It’s very hard to get the hose over the barbs,I heated it in boiling water (and dried it off, of course) and then it slipped on...


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Re: Transmission oil cooler leaks

Postby gavio » April 21st 2020, 4:20pm

The part I used was Hayden 390... It's sold as an installation kit and contains two parts, but you only need the half that screws into the radiator....
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Re: Transmission oil cooler leaks

Postby Mmusicman » April 21st 2020, 4:24pm

gavio wrote:It’s very hard to get the hose over the barbs,I heated it in boiling water (and dried it off, of course) and then it slipped on...

Hose over barbs is not really that difficult.. but if so you can lube the inside of the hose (with ATF.. or even lube it with any soapy cleaner like Windex or 409) then slip it on.

There are two popular hose sizes 5/16 and 3/8... with 3/8 being the most popular.
A 5/16 hose over a 3/8 barb might be more troublesome, especially with reinforced trans hose.

Here's a photo of my trans-cooler lines hooked to my barb fittings (on my 2000)
(this is a non-stock radiator with larger fittings)

My cooler hoses were simply slid over the stock steel lines and clamped

20190909_112242a.jpg

Here are my 3/8 barbed fittings (non stock for 3/4 NPT)

20190824_114714.jpg

Here is the correct barbed fitting on a stock radiator...

20180610_154528.jpg
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Re: Transmission oil cooler leaks

Postby Rod's Trucks [OP] » April 21st 2020, 5:18pm

Great! Thanks to all who offered suggestions and 'Pictures'.

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Re: Transmission oil cooler leaks

Postby augidog » April 21st 2020, 5:34pm

In my past, when splicing steel line with hose, I put a teeny tiny flare on the line, just enough for the clamp to sit behind, locking the hose in place like a barb do.
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Re: Transmission oil cooler leaks

Postby Mmusicman » April 22nd 2020, 2:03am

There is already a "factory flare" on the end of the steel line (unless you cut it off for some reason)... use it to your advantage. Otherwise, good tip on the flare.
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