[OhSix]

If other ROC forum members are like me, the thought of getting stranded on the road and facing mega dollar repair to "fix" an issue caused by the failure of a simple washer is disturbing. Especially because we've seen the outward appearance of the radiator/trans cooler interface doesn't necessarily indicate a failure in the near future.

Provided the discussions I've had with others isn't overlooking an unforeseen problem, there may be a permanent solution to Honda's serious design flaw.

Here's the idea: eliminate the trans cooler interface at the radiator entirely by having an all aluminum, exact replacement made, omitting the mechanical trans fluid interface at the bottom of the OEM radiator assembly. Naturally, this would require adapting the existing cooler plumbing for routing around the radiator to the OEM trans cooler location. Using hoses or tubing - adapting to - or replacing the factory plumbing would be a simple task for anyone handy enough to take on a radiator replacement.

I've contacted a radiator manufacturer with facilities equal to OEM suppliers. They have expressed interest in producing the radiator described above: an all aluminum replacement with dimensions and mechanical features to ensure direct replacement - and a core design to duplicate the thermal displacement properties of Honda's design.

True to all manufacturing efforts, it takes volume to drive cost down. And so, the first step to figure out if forum members are interested in a solution like this.

 

[zroger73]

Don't forget that another important function of the "cooler" is to bring the transmission up to operating temperature quickly by exchanging heat between the engine coolant and the transmission fluid. A separate cooler cannot perform this function.

 

[OhSix]

Don't forget that another important function of the "cooler" is to bring the transmission up to operating temperature quickly by exchanging heat between the engine coolant and the transmission fluid. A separate cooler cannot perform this function.

I've already blown it by failing to understand how the poll function works. Dang it.

Anyhow, I have yet to speak with anyone who fully understands how the supposed "pre-heat" function does anything beneficial. Almost everyone agrees that even in cold climates, a thermostat isn't going to allow warm engine coolant to flow into the rad until after (in many/most cases) the vehicle is already in motion. Logically, that means trans fluid is going to warm faster than engine coolant once the pump function of an auto trans is engaged. I'm sure there are many other opinions on that topic, but.... in the vast majority of vehicle use in nearly every environmental circumstance, trans fluid "likes" to be below engine temp so once all systems are up and running at normal temps. Engine coolant *can be* 20% to 30% higher than ideal trans fluid temps. That is: unless others and myself have overlooked something unique about Honda's ATF and trans assembly.

The proposed solution is not going to be cheap. And like most mods, it comes with other/new concerns. Speaking strictly for myself, the constant thought of electrolysis working on a washer to eventually kill the trans is totally unacceptable. And I'm willing to pay for a solution now, rather than be a victim to mother nature and Honda's terrible design flaw.

Not sure what to do now to get a poll going. Perhaps a new post.

 

[eurban]

So you are basically suggesting plugging up the trans fluid fittings on the radiator and simply connecting the hoses to each other?

This has been gone over many times. Some find it acceptable. Not for me. I want the heat exchanger inside the radiator to do its thing: help to get the transmission fluid up to temp to improve economy (thermostat will be open long before transmission is up to full temp)/ reduce start up wear and to provide some transmission cooling particularly in high demand situtations. Do you really think that Honda added this feature just for fun? I don't think they got the engineering part wrong on the need for the exhanger. Its the execution of the design with the corrosion issues where they should have done better.

Why not have improved fittings made with all the original style piping and figure out a way to properly reattach to the heat exchanger inside the radiator? Why not source a quality aftermarket with all brass / aluminum fittings and corrosion proof washers? Why not buy a known quality OEM radiator and simply plan on replacing it every 5 /7 years or so?

Radiators do loose some efficiency over time and replacing will eliminate any concern in this area.

 

[OhSix]

So you are basically suggesting plugging up the trans fluid fittings on the radiator and simply connecting the hoses to each other?

This has been gone over many times. Some find it acceptable. Not for me. I want the heat exchanger inside the radiator to do its thing: help to get the transmission fluid up to temp to improve economy / reduce start up wear and to provide some transmission cooling.

Why not have improved fittings made with all the original style piping and figure out a way to properly reattach to the heat exchanger inside the radiator? Why not source a quality aftermarket with all brass / aluminum fittings and corrosion proof washers? Why not by a known quality OEM radiator and simply plan on replacing it every 5 /7 years or so?

Radiators do loose some efficiency over time and replacing will eliminate any concern in this area.

No, I'm not suggesting that at all. From the OP: Naturally, this would require adapting the existing cooler plumbing for routing around the radiator to the OEM trans cooler location. Using hoses or tubing - adapting to - or replacing the factory plumbing would be a simple task for anyone handy enough to take on a radiator replacement.

The "heat exchanger" inside the rad has questionable benefit in the sense that it "solves" an issue that is not clearly defined or understood. Since the vehicle spends the vast majority of its life under power, driving down the road, max cooling of trans fluid makes perfect sense.

The issue here is simple" there is no reliable method to predict when the OEM desgin is about to fail. And the cost of that failure is hyper expensive and time consuming. Resolution to that issue is equally simple and minimizes unintended consequences to changing the OEM design.

There are many products available to solve finite issues. For example: engine "pre-oilers" that pump lubricant to the top of the engine in effort to overcome the physical delays of mechanical oil pumps residing in the oil pan at the bottom of the engine assembly. Great solution to an issue many are unaware of. Especially useful to engines that are not in everyday use - and even those that are used everyday benefit from the incremental reduction in valve train friction over the long run.

Simple solutions can sometimes be "controversial". This one is pretty straight forward. The biggest "issue" is initial cost to solve a hyper expensive failure that many have suffered from.

BTW: I totally agree with "why not solve the OEM issue". To best of my knowledge, no one has. Yet.

 

[eurban]

I've already blown it by failing to understand how the poll function works. Dang it.

Anyhow, I have yet to speak with anyone who fully understands how the supposed "pre-heat" function does anything beneficial. Almost everyone agrees that even in cold climates, a thermostat isn't going to allow warm engine coolant to flow into the rad until after (in many/most cases) the vehicle is already in motion. Logically, that means trans fluid is going to warm faster than engine coolant once the pump function of an auto trans is engaged. I'm sure there are many other opinions on that topic, but.... in the vast majority of vehicle use in nearly every environmental circumstance, trans fluid "likes" to be below engine temp so once all systems are up and running at normal temps. Engine coolant *can be* 20% to 30% higher than ideal trans fluid temps. That is: unless others and myself have overlooked something unique about Honda's ATF and trans assembly.

The proposed solution is not going to be cheap. And like most mods, it comes with other/new concerns. Speaking strictly for myself, the constant thought of electrolysis working on a washer to eventually kill the trans is totally unacceptable. And I'm willing to pay for a solution now, rather than be a victim to mother nature and Honda's terrible design flaw.

Not sure what to do now to get a poll going. Perhaps a new post.

What's the full fluid capacity of the transmission. I'm pretty sure it's greater than 10 quarts. Do you really think on a COLD morning that all that fluid will be up to temp before the thermostat has opened up?? NO WAY!

 

[rollinhonda]

I don't think he is suggesting coupling the hose ends together, but rather connect them to a separate cooler in place of the radiator's 'heat exchanger'.
It makes some sense. The 'cooler' could be bypassed with a thermostat control for those concerned about over-cooling during winter morning starts.

 

[eurban]

No, I'm not suggesting that at all.

Your orginal post wasn't very clear (you said you would have an "exact replacement made" yet it wouldn't be exact at all since it won't have the hose fitting on it. This is confusing!) And yes you are suggesting getting rid of the radiator heat exchanger. Connecting the two hoses to each other will not bypass the external cooler. If you are suggesting adding an additional transmission cooler then that wasn't really clearly stated either.

 

[OhSix]

What's the full fluid capacity of the transmission. I'm pretty sure it's greater than 10 quarts. Do you really think on a COLD morning that all that fluid will be up to temp before the thermostat has opened up?? NO WAY!

While it may be true engine coolant will warm faster than trans fluid in this design, two things remain questionable:

Without information to the contrary, no one has sufficiently defined the "problem" with cold transmission fluid.

In the same regard that 10 qts of trans fluid might not warm as quickly as engine coolant, the benefits of the WEENY trans radiator inside the engine rad pail in comparison to the damage caused by a nearly unpredictable failure.

 

[zroger73]

I've already blown it by failing to understand how the poll function works. Dang it.

Anyhow, I have yet to speak with anyone who fully understands how the supposed "pre-heat" function does anything beneficial. Almost everyone agrees that even in cold climates, a thermostat isn't going to allow warm engine coolant to flow into the rad until after (in many/most cases) the vehicle is already in motion. Logically, that means trans fluid is going to warm faster than engine coolant once the pump function of an auto trans is engaged. I'm sure there are many other opinions on that topic, but.... in the vast majority of vehicle use in nearly every environmental circumstance, trans fluid "likes" to be below engine temp so once all systems are up and running at normal temps. Engine coolant *can be* 20% to 30% higher than ideal trans fluid temps. That is: unless others and myself have overlooked something unique about Honda's ATF and trans assembly.

The proposed solution is not going to be cheap. And like most mods, it comes with other/new concerns. Speaking strictly for myself, the constant thought of electrolysis working on a washer to eventually kill the trans is totally unacceptable. And I'm willing to pay for a solution now, rather than be a victim to mother nature and Honda's terrible design flaw.

Not sure what to do now to get a poll going. Perhaps a new post.

Opinions aside, thermostats never close 100% during normal operation. Virtually all of them have a fixed orifice that allows a small amount of coolant to flow even when the thermostat is "closed". Some have a mechanical stop on the thermostatic valve instead of a bypass orifice. A few have a low-flow bypass around the thermostat through a channel around the thermostat housing. A small number of fancy designs are driven by electronic actuators controlled by temperature sensors. As a whole, thermostat design hasn't changed much in a hundred years. There are different shapes and sizes, but most of them share a similar design.

Automatic transmissions have used heat exchangers located inside engine cooling radiators for decades. I'll bet you the engineers who designed the system this way have good reasons for doing it whether it has to do with shift feel, durability, or emissions.

Personally, I'm not concerned about what "almost everyone" agrees on. "Almost everyone" is not as smart as the people who designed things to operate the way they do.

 

[OhSix]

Your orginal post wasn't very clear (you said you would have an "exact replacement made" yet it wouldn't be exact at all since it won't have the hose fitting on it. This is confusing!) And yes you are suggesting getting rid of the radiator heat exchanger. Connecting the two hoses to each other will not bypass the external cooler. If you are suggesting adding an additional transmission cooler then that wasn't really clearly stated either.

EXACT = mechanical features to facilitate installation. The only "MOD" I'm suggesting is by passing the exchanger inside the OEM rad - WHICH IS THE CAUSE OF THE CATASTROPHIC FAILURE being addressed in this proposed solution.

Thought the issue was clarified by stating "Naturally, this would require adapting the existing cooler plumbing for routing around the radiator to the OEM trans cooler location. Using hoses or tubing - adapting to - or replacing the factory plumbing would be a simple task for anyone handy enough to take on a radiator replacement."

 

[eurban]

Failure rate is pretty low overall. Replacing your radiator with quality aftermarket or OEM at the 5-7 year mark will pretty much guarantee that you won't have this issue.

Honda thought it was necessary even though it added cost and complexity.

The idea that a cold transmission equals greater wear, poorer shift quality, and lowered power train efficiency seems pretty obvious to me.

 

[eurban]

EXACT = mechanical features to facilitate installation. The only "MOD" I'm suggesting is by passing the exchanger inside the OEM rad - WHICH IS THE CAUSE OF THE CATASTROPHIC FAILURE being addressed in this proposed solution.

Thought the issue was clarified by stating "Naturally, this would require adapting the existing cooler plumbing for routing around the radiator to the OEM trans cooler location. Using hoses or tubing - adapting to - or replacing the factory plumbing would be a simple task for anyone handy enough to take on a radiator replacement."

Then why not just connect the two hoses together??

 

[rollinhonda]

I see nothing wrong with it, in principle. At least the way I envisioned it in post #7. I think it would work just fine. Finding a positive way to seal the lower radiator holes would not even be an issue. I would use shop air to blow out and dry the lower tank for the trans then seal it up.
Connect a decent cooler to the hoses. For more mild climates you might not even have to bypass it. The ATF Honda uses from Z1 forward, do not thicken up that much in freezing temps. compared to 'straight ATF (Dexron, etc.). Now if the radiator gets flaky, fix, replace it, etc. keep an eye on the coolant level as well as doing a test of the fluid. But no reason to worry about the trans. outside of normal maintenance.

If you are still under warranty you might reconsider only to keep the 'fine print' idiots off your back should you have an unrelated warranty issue.

 

[Carsmak]

Then why not just connect the two hoses together??

Because the Internal Trans Cooler and supposed pre/heater which resides in the lower half of the tank would still have the belleville washer which is the cause of the catastrophic failure.

 

[eurban]

Because the Internal Trans Cooler and supposed pre/heater which resides in the lower half of the tank would still have the belleville washer which is the cause of the catastrophic failure.

??? Yes I understand that! Reread what he has said. He is suggesting replacing the existing fittings on the radiator with plugs or actually having a new radiator made that has no exchanger in it. He then talks about rerouting the hoses that connected to the original fittings to the area by the existing external transmission cooler. My comment is why do you need to reroute the hoses at all? Even if it is not a good idea, you could do the mod he is suggesting and simply connect the two hoses together rather than extending them somewhere else.

 

[OhSix]

Then why not just connect the two hoses together??

If I understand your suggestion correctly, connecting the hoses together would bypass the external trans cooler altogether, which IMO, would be foolish. In fact, if I do go with this idea, I'll likely add a larger trans cooler to resolve concerns of the environment I live in.

This proposal comes from the perspective of a South West U.S. citizen who doesn't experience other climates and rarely deals with the cold extremes others live in. In fact, my routine and use case is quite the opposite. There is no single solution to everyones issues and concerns.

As far as comments about the engineering efforts of Honda as an OEM, I agree, they put deep thought into the overall aspects of their final products. Suggesting there is no "better way" is false and ignores the contributions of aftermarket product development across a broad spectrum of consumer level products. And lets not fool ourselves, Honda, like all auto OEM's are forced by market pressures to design for the "average" use scenarios, hence known issues and failures in every vehicle on the market. I place little confidence in accepting a 5 to 7 year replacement cycle as a "rule of thumb", especially when the vehicle is purchased with unknown, undocumented provenance.

Am I spooked with the idea of falling victim to Honda's very clear design flaw? You bet your bee-hind I am. Visual inspection and the reliability of replacement part timing cycles only go so far - and suffering the ill effects of a poor design decision is simply too hard to swallow.

As always, to each his own.

 

[eurban]

Just to be clear here . . .Fluid goes in one side of the in radiator heat exchanger and out the other. If you replace the fittings on the radiator with plugs and take the two hoses that were originally connected to the exchanger and connect them to each other with some sort of union then you will have only removed the heat exchanger from the circuit. YOU WILL HAVE NO IMPACT ON THE FLUID FLOW TO THE EXISTING EXTERNAL COOLER.

 

[rollinhonda]

Am I spooked with the idea of falling victim to Honda's very clear design flaw? You bet your bee-hind I am. Visual inspection and the reliability of replacement part timing cycles only go so far - and suffering the ill effects of a poor design decision is simply too hard to swallow.

As always, to each his own.

Is it only a 'Honda' design flaw??? I thought using the heat exchanger (which I think is the proper name) at the bottom of the radiator was a matter of convention and is still found on most production cars and trucks today.

 

[rollinhonda]

Just to be clear here . . .Fluid goes in one side of the in radiator heat exchanger and out the other. If you replace the fittings on the radiator with plugs and take the two hoses that were originally connected to the exchanger and connect them to each other with some sort of union then you will have only removed the heat exchanger from the circuit. YOU WILL HAVE NO IMPACT ON THE FLUID FLOW TO THE EXISTING EXTERNAL COOLER.

That was my thought also.