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EcoCivic 10-21-2019 12:00 PM

Trans cooler lines too big?
 
Somehow I accidentally kinked one of me OEM transmission cooling lines on my 05 Civic. No idea how that happened, my best guess is it happened when I changed the trans. So far the kink is not causing any problems, everything is operating correctly and the trans is running nice and cool with my aftermarket cooler. However, the kink obviously can’t be good, so I am going to replace those lines.

I would rather use braided stainless AN hoses all the way to my cooler than those OEM metal lines and rubber hoses because IMO they look much better and may be more reliable. I was initially going to go with 8AN lines (1/2 inch) rather than the stock 3/8 inch lines since the price difference is negligible and I figure less restriction could never hurt. In my mind, even if flow doesn’t increase, the pump won’t have to work as hard to circulate the fluid through the larger lines, possibly extending its life, reducing fluid temps, and slightly improving efficiency by reducing the power required to run the pump.

However, I have read that using cooler lines that are too large can actually be a bad thing because they may flow too well and will cause lower line pressure in the trans making it shift softer, which I certainly don’t want since I did mods to raise the line pressure since I like firm shifts.

So my question if restriction in the cooler lines is actually desirable. I don’t see how restricting the flow could ever be a benefit, but I just want to be sure that I am not going to cause a problem by installing larger lines. Thank you very much in advance!

oil pan 4 10-21-2019 01:52 PM

As long as it's designed like other auto transmissions I have worked on it won't.

EcoCivic 10-21-2019 02:03 PM

Quote:

Originally Posted by oil pan 4 (Post 609889)
As long as it's designed like other auto transmissions I have worked on it won't.

You mean it wont cause a problem?

2000mc 10-21-2019 08:46 PM

Id bet the main restriction is the cooler(s). 3/8 or 3/4 lines might see almost the same pressure and flow.
If you did flow more, I would think it would be maintained at the same pressure, and actually increase the load. You would also be warming up more fluid, and increasing vehicle weight. Probably going to cost you 0.00021mpg
I would think the factory setup would be the most reliable, unless they have to be modified to use.
It may be slightly easier to route and secure smaller lines.

EcoCivic 10-21-2019 09:54 PM

Quote:

Originally Posted by 2000mc (Post 609944)
Id bet the main restriction is the cooler(s). 3/8 or 3/4 lines might see almost the same pressure and flow.
If you did flow more, I would think it would be maintained at the same pressure, and actually increase the load. You would also be warming up more fluid, and increasing vehicle weight. Probably going to cost you 0.00021mpg
I would think the factory setup would be the most reliable, unless they have to be modified to use.
It may be slightly easier to route and secure smaller lines.

The cooler wouldn't be a significant restriction, my cooler has 1/2 ports on it and is quite easy to blow through compared to a couple feet of 3/8 rubber hose. I don't have the stock cooler in the rad anymore because I installed an all aluminium Mishimoto racing rad years ago, so the only cooler the fluid flows through isn't restrictive.

I would think that the load on the pump would be a tiny bit lower when it is working against less pressure, but I may be overlooking something. I don't think the cooler line pressure is regulated.

me and my metro 10-21-2019 10:41 PM

Cooler flow is a controlled and calculated bleed to the system. The new Fords I work on have a thermostat in the cooler line system that only allows flow when the oil is up to temp. This makes my flush machine not work properly because the thermostat stops the flow. So it is back to drain and refill on the new stuff.
Use whatever lines you feel good about.

EcoCivic 10-21-2019 11:42 PM

Quote:

Originally Posted by me and my metro (Post 609950)
Cooler flow is a controlled and calculated bleed to the system. The new Fords I work on have a thermostat in the cooler line system that only allows flow when the oil is up to temp. This makes my flush machine not work properly because the thermostat stops the flow. So it is back to drain and refill on the new stuff.
Use whatever lines you feel good about.

Thank you. What is the order of fluid flow? Pump to valve body to torque converter to cooler I think? Or is the cooler in parallel with the pump's output so more flow through the cooler means less flow through something else?

me and my metro 10-22-2019 12:25 AM

I think it is pump to converter then everything else. On a Ford 4r100 if the cooler plugs up the rear bushing doesn’t get lube and fails quickly.

EcoCivic 10-22-2019 01:09 PM

Quote:

Originally Posted by me and my metro (Post 609961)
I think it is pump to converter then everything else. On a Ford 4r100 if the cooler plugs up the rear bushing doesn’t get lube and fails quickly.

Thanks. So what is the cooler supply line connected to? Is that the fluid directly out of the torque converter?

EcoCivic 11-14-2019 07:58 PM

Quote:

Originally Posted by me and my metro (Post 609950)
Cooler flow is a controlled and calculated bleed to the system. The new Fords I work on have a thermostat in the cooler line system that only allows flow when the oil is up to temp. This makes my flush machine not work properly because the thermostat stops the flow. So it is back to drain and refill on the new stuff.
Use whatever lines you feel good about.

Thanks. Does the trans rely on restriction in the cooler lines to build enough pressure to operate correctly, or is less restriction in the cooler lines good? For what it's worth the return line dumps the fluid right back into the case of the transmission, it doesn't go to anything. Thanks

teoman 11-21-2019 02:23 PM

I suppsoe heating the engine is much more important.

Therfore the transmission constantly cooling it upon startup would be detrimental from an efficiency and emissions standpoint.

EcoCivic 11-21-2019 04:05 PM

Quote:

Originally Posted by teoman (Post 611994)
I suppsoe heating the engine is much more important.

Therfore the transmission constantly cooling it upon startup would be detrimental from an efficiency and emissions standpoint.

I don't have a heat exchanger in the radiator, I just have an external radiator style cooler, which the fluid circulates through at all times. I was wondering if the lines that go from the trans to the cooler could be too big.

EcoCivic 02-12-2020 12:46 PM

I have an update. Long story, but I ended up with an extra 10AN hose kit. What happened is I ordered a 10AN hose kit on ebay for my custom oil cooler setup, but I got a defective fitting and the seller sent me a whole new kit of 12 feet of braided stainless 10AN hose and fittings. I would like to make transmission cooler lines out of this hose. Would it be okay to have really low restriction and use 10AN hoses? I know that’s way overkill but it’s what I have. Thanks

IsaacCarlson 03-15-2020 02:06 AM

Bigger cooler lines won't hurt. The cooler does not regulate pressure, it only cools the fluid. There is very little pressure in the cooler and lines compared to the transmission. The valves control the pressure. Any reduction in return line restriction is a good thing.

EcoCivic 03-15-2020 11:32 AM

Quote:

Originally Posted by IsaacCarlson (Post 619035)
Bigger cooler lines won't hurt. The cooler does not regulate pressure, it only cools the fluid. There is very little pressure in the cooler and lines compared to the transmission. The valves control the pressure. Any reduction in return line restriction is a good thing.

Thank you! I didn't think that the cooler lines needed restriction, but I wanted to make sure since it would really suck to go through all the work and expense of changing out the cooler lines and then find out that the trans no longer shifts correctly and need to reinstall the stock lines. I have been thinking about this for a while, and I realized that the fluid flow through the cooler lines varies with RPM and that it needs to be designed in a way that the trans will function correctly with varying amounts of backpressure since it needs to be able to function correctly from idle to redline.

What benefit would I see from less restriction in the cooler lines? I presume I would get more fluid flow through the torque converter and the cooler and therefore overall better cooling? Also theoretically fractionally more MPG and power to the wheels due to less work required by the pump to push the fluid? Thanks in advance!

ksa8907 03-15-2020 01:29 PM

The only detriment I can think of from having too large of cooling lines is the extra time it will take to move more fluid. More of a cycle time issue than anything else I would imagine. But honestly, it's not going to cause a problem. Using smaller hoses from the factory is also cheaper which is 99% of the reason for their selection.

EcoCivic 03-15-2020 02:47 PM

Quote:

Originally Posted by ksa8907 (Post 619051)
The only detriment I can think of from having too large of cooling lines is the extra time it will take to move more fluid. More of a cycle time issue than anything else I would imagine. But honestly, it's not going to cause a problem. Using smaller hoses from the factory is also cheaper which is 99% of the reason for their selection.

Thanks. By extra time you mean it will take longer for the fluid to fill the hoses and start circulating once the engine is started? If so that's not a problem since the returning fluid isn't going anywhere except back into the sump, nothing is relying on it for lubrication or anything like that.

ksa8907 03-15-2020 04:14 PM

It's a closed loop system, as soon as the fluid is pumped out it is immediately replaced. The cycle time I refer to is more of the thermal energy. If you have, say, 1qt of fluid and a pump rated at 1qt/min then we know we have a 1 min cycle time. If the larger lines hold 2qts now we have a 2 min cycle time.

Again, ultimately for heat these are good things, more fluid in the system means more heat capacity.


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