Well, looks like my 740 is getting a fifth radiator.
Original one lasted about 18 years, replaced with three more in about nine years time, all but the most recent one being out of warranty.
I am just tired of having to pull the damned thing out so often and am looking for a complete metal replacement, but can't find one anywhere. Anyone know where to find one?

 

at one time IPD had a batch of brass 240 radiators custom made, I put one in our 240, but I don't think they ever did 740/940. fyi, the 740/940 radiator got bigger in 1992 so older an dlater ones aren't interchangable.

if you can find an old school radiator company, they could probably make one out of generic bits. bring them an original to use as a template. no idea how much a custom one would cost.

 

You should check your cooling system and perhaps also check for exhaust gasses in your coolant. If you are replacing a radiator every three years, then something is causing the seals to give way (assuming that it is leaking at the tank).

You should get 10-12 years out of a radiator.

 

Have checked for exhaust gasses with none to be found, thankfully. Tested that after I found the latest leak. Have also replaced the coolant hoses, water pump, thermostat, and expansion tank. Pretty sure at this point it's just crap quality products.

 

Just google custom automobile radiators. They are out there and run around $500 . Shouldn't be a problem making one. Do I assume you have already gone to a radiator shop to see what replacements they can get. I'm on my 2nd one in my 89 740 . The plastic tanks hold up better then the OEM brass which rotted out .

 

the OEM radiators for these cars were made by Nissen. Thats the only brand of stock style radiator I'd use. Be sure to use a suitable antifreeze, the factory coolant was the equivalent of Zerex G05, commonly available, mix 50% with distilled or deionized water (unless you buy the pre-diluted variety). if you use generic green prestone type coolant, change it annually. G05 will last 3-4 years at least before its anticorrosive compounds 'wear out'.