Aux trans cooler stealth leaking?

[NoVA_T4R]

Hi all,

I've had a B&M trans cooler installed (bypass radiator) since 2015 and had no trouble until recently. I've had a very slow leak that I've noticed after parking overnight. I tightened the B&M provided hose clamps, then replaced them with appropriately sized 3/8" spring steel worm clamps, but it's still leaking.

I'm getting ready to move the ATF hoses back to the radiator and delete the B&M cooler, but was wondering if anyone has experienced the aux cooler leaking unexpectedly? No exterior damage to the B&M as far as I can see.

Thanks in advance!

 

[Bad Luck]

Did you clean all the residual transmission fluid off the fluid lines when you changed hose clamps? If not I would start with that and check for your leak after cleaning it and driving a couple times.

 

[Mark_BC]

If you have any threaded fittings maybe those are leaking.

 

[LittleCaesar]

Replace the hoses. The climate in N. Va. can wreck havoc on hoses, believe me I know.

 

[NoVA_T4R]

To Mark_BC:
No fittings, just a straight connection from the ATF hose to the smooth B&M cooler connections (smooth just like the factory radiator connections).

No leaking anywhere else except at 1 of the B&M cooler connections.

To BadLuck:
While I did not wipe out or rinse off the residual ATF fluid on the tray beneath the radiator, there is a constant leakage. Every night I put down newspaper beneath the B&M cooler side of the radiator and there's a small circle (~2-3") of ATF fluid on the paper in the morning. Over a month, it was enough to drop the fluid level on the dipstick from the bottom of the COLD range to about 1/8" below the bottom of the COLD range.

I am considering replacing the hoses, but it's been less than 4 years after installing the B&M with NEW ATF hose lines. Since it's only leaking at the B&M cooler connection and not at the trans pan send line area, it makes me consider it's something with the cooler. I do ATF fluid 1-for-1 replacement every 60K miles and did a drain and refill just 200 miles ago, and the fluid looked dark red and not burnt.

To LittleCaesar:
BTW, what about NoVA climate makes it worse for hoses than, say the desert southwest or the rustbelt area? Just curious what you know that I'm not aware of.

 

[LittleCaesar]

To Mark_BC:
No fittings, just a straight connection from the ATF hose to the smooth B&M cooler connections (smooth just like the factory radiator connections).

No leaking anywhere else except at 1 of the B&M cooler connections.

To BadLuck:
While I did not wipe out or rinse off the residual ATF fluid on the tray beneath the radiator, there is a constant leakage. Every night I put down newspaper beneath the B&M cooler side of the radiator and there's a small circle (~2-3") of ATF fluid on the paper in the morning. Over a month, it was enough to drop the fluid level on the dipstick from the bottom of the COLD range to about 1/8" below the bottom of the COLD range.

I am considering replacing the hoses, but it's been less than 4 years after installing the B&M with NEW ATF hose lines. Since it's only leaking at the B&M cooler connection and not at the trans pan send line area, it makes me consider it's something with the cooler. I do ATF fluid 1-for-1 replacement every 60K miles and did a drain and refill just 200 miles ago, and the fluid looked dark red and not burnt.

To LittleCaesar:
BTW, what about NoVA climate makes it worse for hoses than, say the desert southwest or the rustbelt area? Just curious what you know that I'm not aware of.

The change in humidity over the course of the year, from cold weather and snow to the blazing summers don’t do well with rubber.

I purchased some ATF from Advanced Auto. Terrible stuff, leaked like a sieve despite being 3/8”. Find a named brand hose to use IMO.:heh:

 

[NoVA_T4R]

The change in humidity over the course of the year, from cold weather and snow to the blazing summers don’t do well with rubber.

I purchased some ATF from Advanced Auto. Terrible stuff, leaked like a sieve despite being 3/8”. Find a named brand hose to use IMO.:heh:

What I'm running right now is Autozone 3/8" non-branded bulk ATF hose.
Not sure what is named brand hose or what names to look for.
Amazon has a Derale named ATF hose.
Napa parts has their in-house hose at 5/16" inner diameter.
Would appreciate any brand names and if going down to 5/16" is part of the solution.

 

[jgue467]

Unusual issue - system doesn't develop much pressure, so does the 3/8 slip on easy? If so then Yes I'd say move down to the 5/16, Gates or Grainger brands but I think it's more about size and making sure its a hose meant for oils. Luck. :cowboy:

 

[LittleCaesar]

What I'm running right now is Autozone 3/8" non-branded bulk ATF hose.
Not sure what is named brand hose or what names to look for.
Amazon has a Derale named ATF hose.
Napa parts has their in-house hose at 5/16" inner diameter.
Would appreciate any brand names and if going down to 5/16" is part of the solution.

Derale is not bad stuff, I have used their line before with success.

Would I go down to a 5/16” hose? No, I would just get better hose and be finished with it.

 

[NoVA_T4R]

It turns out there was a small crack on the back of the B&M aux trans cooler facing the AC condenser.
So I deleted the B&M and went back inline to radiator.

There did not appear to be any impact that caused the crack. So I'm not sure whether to go back to B&M in the future.

3/8" hose was just very stretched to the point where it was a loose fit on the 3/8" fittings on the B&M. I will definitely go with Gates (which is carried by Napa Auto Parts BTW) in the future. The existing 3/8" hose was from Autozone.

The 5/16" hose I brought along would be considered cruel and unusual punishment to try to fit on both the B&M as well as the transmission send/return hard lines. It's definitely 3/8" hose for this application.

Thanks for all the replies and input.

 

[3bears]

boy I could swear I used 5/16 with a 5/16 magnafine filter with no issues, why do you say cruel and unusual to use 5/16

 

[kball]

The B&M kit comes with 11/32 hose which is a hair smaller than 3/8. I think trying to fit 5/16 hose on the cooler barbs and 4runner trans lines would be quite frustrating.

 

[NoVA_T4R]

The B&M kit comes with 11/32 hose which is a hair smaller than 3/8. I think trying to fit 5/16 hose on the cooler barbs and 4runner trans lines would be quite frustrating.

"Quite frustrating" is an understatement of putting the 3/8" hose on the trans lines and the B&M fittings 4 years ago.
5/16" is in the realm of possibility, I suppose, but the 3/8" I already installed held up solid. If you need to combine a chest, shoulders, and arms workout to your trans cooler install/maintenance while paying for a lift by the hour, then 5/16" it is.

I didn't use the hose supplied with the B&M kit since it was only long enough for 1 of the lines to the cooler. Went with the Autozone purchased hose for both runs to/from the cooler.