2000 Honda Insight - Heating the manual trans with engine coolant

[Daox]

I swung by the local welding supply store after work yesterday night. I asked if they had any aluminum brazing rod and mentioned the few names it goes by (durafix, hts2000, aladdin 3-1) and he knew exactly what I was talking about. We walked over and grabbed a 1lb tube of it. The cost was significantly lower than any online source I was able to find. Online the lowest price I could find was about $40 per pound. This was $25. I'm not sure how much I'll need for the project, but 1 lb will be way more than enough and should last me quite a while.

[Daox]

Now that I have the transmission out of the car, I can finally see where I'd like to run coolant along the casing. Here is a rough idea of where I'll be adding the 2nd layer of aluminum over. I'm hoping I can cover roughly a third of the surface area of the case. The more surface area the better.

[Daox]

I got my aluminum sheet ordered today. I used a local metal supply house that has no minimum quantity order, Midwest Metal Warehouse. They're only a few miles from home and they'll probably have my order ready tonight. I got a 24" x 24" piece of 16 gauge (.06") aluminum for $53. That should be WAY more than enough, and I'm thinking that 16 gauge will be a good thickness. I want it to be able to hold up to the pressure from the cooling system without ballooning out. I had looked at some .025" aluminum at the local big box store, but it was really flimsy. If this stuff isn't thick enough, I'll just braze some ribs internally (ideally) or externally.

[teoman]

You could put an egr valve and have hot exhaust blow on to it. That would heat it up quickly.

Or maybe as one other poster said, modify a drain or fill plug to have a metal pipe loop that will circulate coolant and transfre heat directly to the oil.

[oldtamiyaphile]

I bought some alu brazing rod a while back when I was going to build an alloy camper trailer. Problem I had was unlike welding, there's no way to tell a good joint from a bad one. I don't remember how many test pieces I made, but only one survived destructive testing. I'd be wary of using this process for anything important.

I now have a FLIR camera so that would at least mean no more guessing how hot the work piece is. Alternatively some heat indicative paint could also be helpful, there's not much room between hot enough and burning a hole when working with ally.

All in all, I'd rather have a messy weld than a neat braze.

[Daox]

Great point about the unreliable brazing joints. I had similar thoughts, but more about bowing of the aluminum plates. Therefore, I do plan on pressure testing it to something like 50 psi (well above what it would see in operation) before putting it in use. But, with your comment I think I'll do some brazing on some scrap before going right at the trans! Thanks.

[Daox]

Originally Posted by teoman

You could put an egr valve and have hot exhaust blow on to it. That would heat it up quickly.

Or maybe as one other poster said, modify a drain or fill plug to have a metal pipe loop that will circulate coolant and transfre heat directly to the oil.

Those are both interesting and good ideas. I'm pretty settled on my technique for this go around. However, if I do it to another vehicle in the future I'm sure there will be tweaks to be made. It would be great if this could be done in a way that you don't have to remove the transmission from the vehicle for instance, and using the drain/fill plugs would probably be a way to do that.

[oldtamiyaphile]

Originally Posted by Daox

But, with your comment I think I'll do some brazing on some scrap before going right at the trans! Thanks.

The instructions that came with my rods were adamant about ensuring a 100% clean surface, cleaning with a stainless wire brush immediately prior to brazing. Even with new ally extrusion, I suspect that was part of my problem. I fear that using the process on a used trans casing will be just about impossible. I think brazing a cast part will be a whole lot more difficult.

I'd consider bashing some plate over a spare casing then maybe using thermal transfer paste between the two? How much is a replacement Insight trans?

[ar5boosted]

I know that I suggested the alu brazing rods. Yes, getting the surface roughened properly and the getting the temperature of the base metal are critical to success.

On second thought - I wouldn't do it this way.

An easier/better way might be to use a standard racing transmission cooler (for Honda) and heat that, eg:

- https://www.autoaccessoriesgarage.co...ion-Cooler-Kit

If you want to heat that, wrap in nichrome wire, and apply power ie:

https://www.youtube.com/watch?v=9D2G50NK4Do

[cajunfj40]

Hello Daox,

Neat to see a mod like this go forward!

For either welding or brazing, you will need to do extensive cleaning of the empty case (pull out bearings, gears, everything) - perhaps a pass through the cleaner that your local aluminum engine/transmission/cylinder head rebuilding shop uses? Hit the surface with an abrasive flap-wheel first to take off the heavy corrosion.

Brazing *may* happen at a low enough temperature to avoid warping the case. Your welding supply shop or local welding house may have the experience to know for sure. If low enough, you can maybe get by with just a good de-greasing spray on the inside/gear/etc. (still need aggressive cleaning on the outside) to get the trans fluid off the spots that will get hot during brazing, so as to avoid a trans fluid fire and/or coking up the gears/bearing/shafts/etc.

Maybe find a nice used housing that's not as surface-corroded as yours? Or at least as a spare?

Another possibility: Use high-temperature-resistant epoxy. No warpage issues and you may be able to get away with just a vigorous surface cleaning and no full dis-assembly of the trans.

Yet another, or an adjunct to the epoxy version: design your second skin to have flanges all the way around. If you can, get those flanges to lay flat on existing through-bolt surfaces of the trans, that nice rib between the trans and the differential, etc. You'll want a vertical rib along the long smooth side of the trans (opposite the diff) to keep that edge from bowing up. Drill and tap the case to allow bolting down your second skin - use the bolts as the primary strength connection, and the epoxy as the bulk fluid pressure seal. Leaks can be patched with a bit of grinding and some more epoxy. If your second skin is stiff enough, you can use a sealant instead of epoxy.

You also have the possibility of using EGR-valve controlled exhaust blowing through your transmission housing second skin envelope rather than using coolant. Much lower pressure! No pre-warm from thermosyphon action block-heater heated engine coolant, but the failure mode is a minor exhaust leak, and you can shut off the EGR valve if it's a problem while you figure it out.

Note: When pressure testing whatever you end up making, do so with a liquid, pressurized using a hydraulic pump or cylinder. The failure mode of a crack or similar is thus a stream of liquid and rapidly dropping pressure. City water pressure is generally about 60PSI, FYI.

*Do not pressurize it with air.* That creates a shrapnel hazard.

Air-over-water is probably safe enough, if you have minimized the air volume, and keep below ~45psi. Basically replicating how cooling systems are pressure-tested. Do the math on pressure vs. surface area to see what you are up against.

Off-topic of sorts, in that they are not your "fluid heated jacket directly bonded to transmission case" idea:

ar5boosted suggests an off-the-shelf transmission cooler heated electrically. If going electric, I'd use a tube/plate cooler with a flat adhesive "oil sump heater" wired in parallel with your block heater, rather than using the 12V electrics. Alternately, put said cooler in a box you can fill with heated engine coolant, or just get a liquid/liquid heat exchanger. Either way, make sure the cooler is mounted between the fill and drain levels of the transmission, or at least below the fill level and add a second drain at the low spot.

Did the CVT version of the Insight have a transmission cooler in the radiator? You could plumb to that and use a lift pump/filter combo, and a spring-loaded check valve inline right where the fluid goes back into the transmission housing to make sure the pump/lines/cooler stay full of fluid and doesn't all drain back into the transmission housing, messily overfilling it. Harder to get this type right, though.

Yet another another possibility: Either tap two more holes in the transmission housing for bulkhead fittings, or use "T" pipe fittings on the existing fill and drain holes, and fish a piece of metal tubing through the transmission housing. You need access to the inside of the transmission housing and will need to remove all of the gears, bearings, etc. to do any of the welding or brazing options, so this isn't really much more involved mechanically. Route the tubing to miss all the gears, etc, and make sure it passes through the main sump area. Run your coolant through this tube. To figure out what fittings to use, check out how the in-radiator transmission coolers are hooked up. IIRC, they thread into the plastic from the outside. Probably a form of compression fitting. Probably want to use stainless steel or aluminum. Copper/brass or galvanized/aluminized steel may also work - see what the in-radiator transmission coolers are made of.

Good luck!