[2Ridgelines]

2) They have a adopted the "new improved" trans fluid heat exchange port mechanism which *should* eliminate the possibility of coolant/ATF mixing if/when a port failure occurs.

Is this change present in the replacement radiators for the Ridgeline from Honda and / or Denso or did they just fix it on new production parts for newer vehicles?

Would be nice to have an OEM radiator without this issue.

 

[2Ridgelines]

OEM Denso is a completely different radiator than aftermarket Denso.

OEM is (IMHO) a high quality unit that is most likely manufactured in Japan. It does still have the same transmission line fittings that it always has and can be prone to SMOD type failures.

Aftermarket Denso is made in China or other similar low cost of labor locations. Manufacturing and material qualities are probably not as good as OEM and there are ample reports of shipping damage issues from various suppliers of the aftermarket Denso (as well as other brands).

Basically, you should pick your poison carefully. Remember that all it takes is one overheating event to ruin your engine. Plenty of aftermarket radiators arrive in good shape and work just fine without the SMOD prone fittings. Some however have been delivered damaged or are defective after install. To me its a tough call to choose aftermarket or OEM . . .

Seems that pulling the OEM radiator, or buying a new OEM unit and then carefully priming and painting the offending area, or applying some other long lasting anti-corrosion sealant would get you the best of both worlds. Might try doing that on my 2010 since it's got a significant amount of corrosion on it.

 

[2Ridgelines]

There's not much point of having more threads, as the first thread takes about 1/3 of the total load and the next 3 take successively less. A longer threaded area would most likely have the same end result.

I expect a careful analysis of these failures would show that the steel washer causes anodic corrosion in the aluminum due to electrolyte (water and contaminants) forming at that junction. Aluminum being turned into aluminum oxide due to the corrosion causes a large expansion force at the nut flat to radiator interface which eventually tears out the threads. Even tried to remove an old aluminum anode from a water heater? It's typically impossible since the diameter of the corroded anode is much larger than when it was when installed.

Stopping the corrosion by sealing the steel to aluminum interface should stop the problem from occurring since it will stay dry. There shouldn't be any corrosion on the inside of the radiator itself if you are running coolant in the radiator.

As aluminum washers are readily available, I wonder if that washer has another purpose. From your picture, it appears that there is thread sealant / lock on the fitting already, so I don't know why the washer would be there at all except perhaps to prevent galling the surfaces during installation or to index the fitting. Still doesn't explain why ND would use steel, as this combination for fasteners is a well known problem.

 

[2Ridgelines]

Split lockwashers and flat washers are commonly available in aluminum. Never seen a belleville washer made of aluminum, though it should be possible to make one. I don't see why one would be needed in that location, as they are usually used as spring mechanisms or for applications where a very exact pre-load is required. It certainly won't keep the fitting from rotating, which isn't an issue with a hose attached to the end anyway.

Aluminum will preferentially corrode when attached to steel. Again, this is a very well known issue and I can't believe ND would make such a mistake. The two dissimilar metals must have a conductive liquid in contact with them for the corrosion to proceed.

Keeping the metals dry is usually considered an acceptable solution for most applications when dissimilar metals must be in contact. The relative surface areas of the two metal types also has an effect on where the corrosion proceeds as well as what the electrolyte is composed of. I noted on my own radiator that all the corrosion is on the washer, rather than the aluminum, but they don't use salt on the roads here.

I'm about to pull and replace the radiator on my 2008 in the next few weeks. Have an aftermarket replacement with brass fittings, but I may opt to get a new OEM unit and try sealing the fittings on the outside as a long term experiment. Wish there was some way to detect coolant escaping into the transmission fluid. Measuring electrical conductivity of the transmission fluid might work for a gross leak.

 

[2Ridgelines]

After looking over the Spectrum radiator I opted to not use it due to a significant decrease in the number of cores. Went back to the OEM ND radiator, which still has the stupid steel washer. Painted the transmission ports with epoxy primer and then regular paint.