Volvo 940 radiator leaking - what are my options?

[Laird Scooby]

Originally Posted by TonyS9

I don't see how waterless coolant could "cause" a leak its oily and thicker than waterbased. I do understand how it could cause overheating as it has a lower thermal conductivity than water. I have been there and bought the T-shirt with the 360 B230FT, using the 360 rad.
Initially with waterless coolant, 12psi boost, hot days on the track temperature would rise up to about 3/4 gauge, but not into the red. I plouged on and didn't back off, brakes were a bigger problem lol.
Changed back to water based, temperature in better control but the cap (360 spec lower release than 940) was leaking pressure and there was bubbling in the expansion tank after a session. The 32yo plastic tank was also very pressurised. Decide the 360 parts weren't rated for turbo heat waste.
Changed back to waterless,
After a few mods, removed the cowling, blocking bits on the rad and air directors at the side, track day drilled bumper. The temperature is now normal at full power/topspeed. Can rise up a little in traffic without the cowling though.

So it entirely depends on the cooling, and the 940 has good cooling even with the manual non-AC rad. Even if you run out of capacity an auto/air con rad is huge and an OE fit.

With waterless the lack of pressure is a big benefit and it can goto 180C before boiling. It never needs changed and doesn't corrode the block.

Additionally I use OATs in the 940 for 10yrs or more, without any issues so far, what should I expect and when?

Interesting stuff Tony! Thanks for pointing out exactly why the waterless coolant will cause leaks, the extra thickness is likely to breach a small leak that would contain a tinner liquid at the same pressure by putting strain on the periphery of that leak.
That's why i always advise a course of part-changes on ATF rather than the flushing method.

As for using OAT coolant, i daresay you've rebuilt the engine a few times with new gaskets? They are usually the first to suffer from OAT coolant as most gaskets won't resist the acid. Next, the acid will attack the cast iron block a lot more than ethylene glycol will attack the aluminium head.

Additionally, most people won't flush the system properly when changing coolant, even if they think they have. Refilling a previous ethylene glycol system with OAT will cause the formation of silicone plugs because the acid will cause the silicates present in EG to precipitate out of suspension and form a gel which then blocks various waterways inside the block, head and anywhere else.

Setting aside the fact OAT will attack the block and potentially the gaskets in a 940, the fact most people won't strip, clean and dry every cooling component in the system before changing to it or at the very least, flush it forwards, backwards and then flush it again to ensure all the EG is removed, it's safer to simply say don't use it. Factor in the damage the acid in OAT will cause to the cast iron block and it's a case of don't use it.