Transmission Leaking From External Hose, New Clamps

2014 Acura TSX, roughly 110k miles, 4 cylinder engine, automatic transmission.

Got the car as a used car. Noticed that it was leaking from the bottom hose attached to the external in-line transmission filter, on the filter side. See black arrow for the area I’m indicating, and yellow for the filter.

It looked like it had been leaking for some time. Not bad enough for puddles on the floor, or enough for it register on the dipstick. It is likely seepage. The maintenance minder light came for transmission service. I figured the original clamps were “tired”, I drained and refilled it, replaced this filter, and added additional clamps. To attempt to fix this leak. In this order, for the hoses attached to the filter, on the filter end.

16 mm Spring Band Clamp | Original hose clamp | 16 mm Spring Band Clamp → Filter → 16 mm Spring Band Clamp | Original hose clamp | 16 mm Spring Band Clamp

I was not able to get any additional hose clamps on, because the length of the metal spigot on the filter was not long enough. A 15 mm Spring Band Clamp, I wasn’t able to compress it enough to make it wide enough to go over the hose. I’m pretty confident that 16 mm is the correct size. Unless of course, a imperial sized clamp is supposed to be on there, which I doubt for an Acura.

Well today I got back under the car, and it appears to still be leaking from the same spot.

Maybe it’s possible that when I reassembled it my hands were oily, but based on where the oil is located, it looks like a leak to me.

What is a guy supposed to do? Brand new filter and brand new multiple hose clamps. I supposed I could try a 5/8 inch spring band hose clamp. The only issue is that I can’t find a set of imperial spring band hose clamps, whose measurement is in inches and not mm that is a part of a set with various sizes. I suppose I could always try buying a bunch of 5/8 inch spring band hose clamps instead of a set. Perhaps a hose clamp between 15 mm and 16 mm would provide enough clamping force. I converted some nearby inch values to mm.

9/16 inch = 14.2875 mm - To small
15 mm - To small
19/32 inch = 15.0812 mm - ?
20/32 inch = 10/16 inch = 5/8 inch = 15.875 mm - ?
16 mm - Leaks
21/32 inch = 16.6687 mm - To Big
11/16 inch = 17.4625 - To Big
6/8 inch = 3/4 inch = 19.05 mm - To big

Besides, I feel like I’m splitting hairs at this point using 15.875 mm spring band clamp over a 16 mm spring band hose clamp. The difference of .125 mm. Not to mention would have to drain and refill the transmission again to.

Thanks for any recommendations. i don’t think replacing the hose would help at all, as the hose doesn’t look damaged or elongated, resulting in the diameter being larger than it’s supposed to. This seems like a design flaw to me, but this doesn’t seem to be a common issue on this car I guess.

The previous owner went to the dealership for the past 90k miles and they never mentioned anything. Previous owner is a family member. Some Honda Acura techs online have told me the filter is not meant to be serviceable. But it’s leaking for me.

Try replacing the hose.


Thanks. Not sure the pressure rating of the hose or the inner or outer diameter or length. I suppose I should just avoid the hassle and get the OEM hose?

Just get a hose from the dealer and use worm drive clamps. I hate spring clamps.

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It looks like you can use just regular fuel line hose from any parts store.

I stopped using worm drive clamps years ago.


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Do you guys think it’s likely a 3/8 inch fuel hose, based on me using a 16 mm clamp on it? If the fuel hose I purchase has a stated pressure rating, what should I look for and what should I stay away from?

You don’t measure them by the OD, find the open end wrench that fits the tightest on the OD of the base metal line and that is the ID of the transmission hose you need, then use a worm clamp to tighten the hoses in place or spring clamp, either work, not that hard…

Most transmission cooler lines are 5/16, these newer cars could be anything… lol

The hoses lasted 10 years, replace them.

It is best to have all the replacement parts before replacing the filter, avoids wasting a lot of time measuring and checking pressure ratings.

Most professionak mechanics recommend spring clamps, I have always preferred worm drive ones and have never had any problem with them.


My dad preferred worm drive clamps, so so did I, until the lower radiator clamp on a past Honda kept loosening itself. Changed it back to the OEM spring clamp and never looked back. Maybe it was a cheap clamp, but one of the reasons spring clamps are preferred is that they are considered to be temperature compensating.

I decided to cave in and buy the official hose to avoid having to worry about pressure ratings. Looked into getting generic fuel hose, but they were all rated to different pressures. Did not want to have to replace it again.

Anyone know fuel hose markings?
It seems to be
“TAS NOH-F 3402”. I tried to Google the manufacturer TAS, but couldn’t find anything. Also couldn’t find out what NOH-F means or 3402.

Part number 25213-RTA-007

Googling the part number shows that it’s a “Hose (175MM) (ATf)”

Outer diameter is approximately 17 mm or about 0.669291 inches

Inner dimeter approximately 5 mm or about 0.19685 inches

So very interesting indeed. Seems to be a non-standard size. Converter some nearby values

2/16 in = 1/8 in = 0.125 in = 3.175 mm
24/128 in = 12/64 in = 6/32 in = 3/16 in = 0.1875 in = 4.7625 mm
25/128 in = 0.1953125 in = 4.96094 mm
26/128 in = 13/64 in = 0.203125 in = 5.15937 mm
14/64 in = 7/32 in = 0.21875 in = 5.55625 mm
8/32 in = 4/16 in = 2/8 in = 1/4 in = 0.25 in = 6.35 mm
3/8 in = 0.375 in = 9.525 mm
4/8 in = 1/2 in = 0.5 in = 12.7 mm
20/32 in = 10/16 in = 5/8 in = 0.625 in = 15.875 mm
84/128 in = 42/64 in = 21/32 in = 0.65625 in = 16.6687 mm
85/128 in = 0.6640625 in = 16.8672 mm
86/128 in = 43/64 in = 0.671875 in = 17.0656 mm
44/64 in = 22/32 in = 11/16 in = 0.6875 in = 17.4625 mm
12/16 in = 6/8 in = 3/4 in = 0.75 in = 19.05 mm

Typical pressure in the trans cooler line is 5-10 psi. You could blow into it harder than that.

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That’s interesting. I’ve always thought the trans cooling line pressures was considerably higher.

Hey thanks. I think you are probably right about it not being high pressure.

What about the sizes though? It seems like an oddball size of 5.0 mm inner and 17.0 mm outer.

Who knows? The only dimension you need to be concerned with is the inside dimension.