Transmission cooler 1997 Pathfinder

[A1218]

Can anyone recommend a good transmission cooler?
Several years ago one of the hoses were leaking I believe and my father took it to his Nissan tech who decided to bypass the cooler instead of just changing the hose. The line coming from the transmission to the cooler was disconnected and so was the line from the cooler to the bottom of radiator. The line from the transmission is now directly connected to the bottom radiator spout.

I would like to get the cooler hooked up back, but I’m not sure if I should hook back up the original one sitting there or get a new one? And since I’m not sure which hose exactly was leaking can I replace all of them with generic aftermarket hoses or does it have to be the Nissan molded hoses?

Thanks

[VStar650CL]

I have a Hayden 512 6-pass on our Altima and it's pretty much overkill for the job, good quality unit and easy to tack on. I'd think it would work fine for your Pathy. Guys disconnect the original heat exchanger in the radiator because they're afraid of the exchanger failing and mixing coolant and transmission fluid. That was really only a big issue on early~mid R51's, but some mechanics hear "Pathfinder" and do a bypass like a knee-jerk. If you want to leave the OE exchanger disconnected, there's nothing wrong with a radiating cooler like the Hayden. Same job, different mechanism.

[VStar650CL]

PS - To your other question, use hot-oil rated hoses and not fuel line. Any parts store will have it.

[A1218]

I have a Hayden 512 6-pass on our Altima and it's pretty much overkill for the job, good quality unit and easy to tack on. I'd think it would work fine for your Pathy. Guys disconnect the original heat exchanger in the radiator because they're afraid of the exchanger failing and mixing coolant and transmission fluid. That was really only a big issue on early~mid R51's, but some mechanics hear "Pathfinder" and do a bypass like a knee-jerk. If you want to leave the OE exchanger disconnected, there's nothing wrong with a radiating cooler like the Hayden. Same job, different mechanism.

Thanks for recommendation!

And would I hook this up the same way the original one was? In terms of the hoses routing back the original way? Not too familiar with this so I may be misunderstanding.

There are still two transmission hoses going to the bottom of the radiator. One of them is supposed to be coming from the separate transmission cooler but has since been coming straight from the transmission pipe since the cooler was disconnected. Haven’t had any mixing problems. Radiator was changed once.

I’d have to figure out which is the return line and which line sends the fluid.

[VStar650CL]

Then they put a separate radiating cooler on but disconnected it. Maybe it leaked and they just unhooked it, or maybe it was a temporary measure because of an issue with the OE exchanger. The lines going to the radiator are for the OE. If that works then a radiating cooler will just be insurance, the OE coolers are excellent unless you do the kind of driving that overworks the cooling system.

[A1218]

The Pathy came factory with an additional cooler for the transmission that is mounted in front the A/C condenser. It's pretty small. I believe the fluid flowed from transmission to the radiator then from radiator to the external cooler, and then back to the transmission.

Also, does it matter which port the hose is connected on the aftermarket coolers?

[VStar650CL]

Yep, my bad I forgot about those. It's a series hookup, though. I don't think I'd trust anything that's been disconnected unless you want to test it for flow and leaks, because who knows why they disconnected it? You can easily drop a Hayden or Tru-Cool aftermarket unit in there and know it's good. The routing isn't complicated because it doesn't matter which order you put the coolers in. The only caveat is that radiating coolers should generally be fed bottom-up if they're mounted horizontally, it helps chase bubbles out that can cause air-binding.

[A1218]

Yeah, I'm not trusting the OEM cooler after sitting so long and not knowing the true reason. I'm going to remove that one completely and put a Hayden in. I know you mentioned a Hayden 512, but is a Hayden Automotive 678 Rapid-Cool Plate and Fin Transmission Cooler fine as well?

Thanks for assisting me on this!

[VStar650CL]

If you expect heavy duty heat or it's a better mechanical fit, sure. The 514 is about the same BTU's as the 678 but the 514 is physically larger. The Rapid-Cool series has a different tube and fin layout that's more efficient, so you get the same BTU's in a smaller package.

[A1218]

I went with the Hayden 677 rapid cool. Should be fine as I don't tow much but do end up in a lot of stop and go traffic so that's one of the reasons why I wanted a cooler back.

It comes with 11/32" hose, and I ordered 3/8" size extra hose. I'm not too sure the exact sizing on the hose and wouldn't be able to bring a sample with me without disconnecting the lines. Or is the size 5/16"?

[VStar650CL]

That I can't help you with. Nissan doesn't publish sizes and specs, just part numbers. However, like I mentioned earlier, practically any parts store will have hot oil hose. Most will have NPT barb fittings as well. So if you need to get spur-of-the-moment hardware, it probably won't be difficult to find.

[A1218]

I have one more question. There are two metal lines coming from the rubber hoses from the old cooler that went back to rubber hoses which then connected to radiator and transmission metal line. Would it be safe to use the metal lines back or bypass that using rubber hoses straight to the radiator and transmission metal line?

Just concerned about the hoses touching the radiator or kinking when routing it. Though I did purchase hose that is compatible for transmission and engine oil.

Hope I explained that properly.

[VStar650CL]

I don't see any problem with retaining the existing metal lines as long as they aren't corroded and don't leak. You'll know that pretty much as soon as you start it. They do make FMT tubing up to 3/8" if you need to fabricate something, it's pricey in sizes above 1/4" but it is available. There isn't a lot of pressure in trans cooler lines, typically no more than 15 psi, so hefty-duty stuff isn't necessary.

[A1218]

Nope, no corrosion. Just that they weren’t in use since the cooler was disconnected. But ends were not open. One side capped and the other side left in cooler.

Does it need to be flushed?

[VStar650CL]

Probably just blown clear if they were capped off. The cooler would be a different story, but you aren't re-using that.

[A1218]

So it turns out that I found the real reason the cooler was disconnected. The approximate 1.5-2 ft metal line coming from the cooler hoses to the transmission and radiator hose was leaking. Several seconds after I started it up the fluid began leaking at a pretty good rate.

So instead I ran a hose straight from the radiator to the cooler and then from the cooler to the transmission metal line. I ran the engine for a bit and drove it around, no leaking or any other issues noticed as yet. This method shouldn't affect anything right? Or is it necessary to have the those two metal lines in between?

[VStar650CL]

No, rubber should be fine as long as it's not flopping around or chafing on anything.

[A1218]

No, not moving around at all. I should also mention I requested transmission fluid hose at the parts store and was given SAE J30 R10. When I look that up it mentions fuel line but compatible with oils also, which is what it states on advance auto parts website listing when I search it.

A different auto parts store was providing me the same type of hose as well. Hopefully it is the right one.

[VStar650CL]

Most hot oil hoses are also fuel rated, but not vice versa. R6 is regular lift pump hose, R10 is for both fuel and low pressure hydraulics (like your transmission). It will do fine.

[A1218]

Everything’s hooked up and working fine. But the only thing is that the cooler hose fitting is 3/8 but the return line on the transmission is 11/32 or a tad smaller. I was thinking of using a 3/8 barb brass splicer fitting to connect the 3/8 hose to the 11/32 hose.

Is this alright to do? I had to tighten down the clamp strong to prevent a little seepage that was occurring so that’s why I think it about doing this.

[VStar650CL]

Yep, NPT plumbing reducers and barbs are just fine. Use brass or stainless and not plain steel, and try not to mix metals in any one assembly.