Mounting a Davies Craig Transmission Cooler with KAON Brackets

[GeeWhizz Senior Member Find all posts View Profile Close GeeWhizz]

I've just ordered the KAON Transmission Cooler kit for my 1GD GX Prado. I like the idea of a mounting bracket kit rather than the plastic through-radiator mounts that Davies Craig supply.

However, the KAON brackets are stainless steel and the oil cooler mounting flanges appear to be aluminium. From my recent experience with a aluminium/stainless steel combination, when exposed to the weather, the aluminium corodes relatively quickly where it touches the stainles steel.

My question: does anyone know what sized bolts are supplied with the KAON kit? I'm thinking of ordering some nylon shoulder washers (also called "top-hat" washers) to keep the two different metals apart. (I know the KAON video refers to M6 bolts on the body ends of the mounting brackets).

[Prada Lurker Find all posts View Profile Close Prada]

Love the KAON gear! I've lived and cruised on a yacht for the last 6 years, and have plenty of dissimilar metals issues. I doubt that your Prado would be exposed to enough conductive electrolyte ie. salt water to cause a corrosion issue. But just in case, good seamanship would require you to apply a liberal coating of Tefgel or Duralac between the two metals. I'd go for the Duralac as it dries to bond the fasteners, just like Loctite.

Duralac Jointing Compound 115ml, $34.95 | Whitworths Marine

[GeeWhizz Senior Member Find all posts View Profile Close GeeWhizz]

I'm back from our first trip towing a 2 tonne Camper Trailer and very pleased with the result.

To answer my own question in post #1, the bolts supplied with the KAON / Davies Craig kit were M5. The mounting holes in the new radiator were just under 8mm, so I ended up buying a pack of 5mm x 5mm nylon shoulder washers and a pack of 8mm nylon flat washers. This keeps the aluminium radiator electrically isolated from the rest of the vehicle, minimising future corrosion due to salty roads and tracks in rural areas and the outback.

Mounting the transmission cooler radiator was the easy part, except that five of the thirteen plastic push-rivets that secure the cover between the grille and the radiator snapped or shattered during removal. I replaced them with Champion TF81 Scrivets from Repco. Rearranging the ATF plumbing to route the fluid from the existing radiator outlet to the new radiator and back to the transmission's return pipe without losing too much of the (old) ATF was quite a challenge. The rubbery plastic protection covers that come with the Davies Craig ("DC") radiator were invaluable for temporarily plugging the existing fittings while getting reading to connect the new hoses. Not an easy task, though - the space to get your hands in to fit the new hoses is very limited!

Once fitted and clamps tightened, the new configuration was leak-free after a test drive. I've now done 1,500km with the new radiator and ATF temperatures, as read from the CAN bus "OBDII" network, are between 15 and 20'C lower than before - typically below 80'C when towing the big trailer.

I've seen questions and discussion on which way the ATF should route through the two radiators. The vehicle's main radiator typically keeps the engine coolant in the range 80 to 90'C, although it can get up to 100'C under load in hot conditions. It makes sense that the ATF should route to the existing radiator coil FIRST because that radiator can't get the ATF cooler than the engine coolant temperature. ATF is best kept under 80'C for longest transmission life. Unfortunately, the transmission's (hot) outlet needs to go to the top connection of the main radiator. Then out of the lower connection (much harder to get to) via a new hose to the DC radiator and then back to the transmission's return pipe.