The trans cooler in my folks 740 AW70L split yesterday with the resultant coolant in the trans fluid. I discovered it by pure chance as yesterday I flushed the fluid. This morning I checked the level to find it over-full. When I drained some fluid it came out looking like strawberry milkshake :(

I've drained the fluid and hoping like hell the gearbox will be okay. My question is can I safely bypass the radiator trans cooler and use an external cooler. The radiator will be replaced obviously but I don't want to risk another potential catastrophe. If the gearbox fails this car will probably be history.....

I would welcome input from people who use an external cooler.

Thanks
Brad

I finally finished repairing the 740's trans cooler problems adn got the car back on the road. We installed an external cooler between the A/C condenser and the radiator bypassing the radiator cooler. This was the easiest place to put it. So far so good. It's taken 3 days to get this car back on the road. Now I'm scared to touch it for fear of something else breaking.....

Brad

The reason we want to bypass the factory cooler is to eliminate the risk of the same problem occurring again. The existing radiator is only 5 years old and is genuine Volvo. It's very disappointing that the supposed best quality part for the car died an early death. As far as I'm concerned, it's a bad design. Why would they come up with something that could potentially cost someone big dollars to fix if it goes belly up or even write the car off. It's just a cost cutting measure. Then again, certain engines' timing belt setups come to mind.
I should also mention that I'm in Australia and an exchange Volvo radiator runs about $350 at least. Aftermarket stuff is hard to come by over here and we usually get screwed on prices anyway.
We bought an external cooler this morning and trans filter kit, coolant, trans fluid etc. Just about to go out there and start on this. Will report back later.

Hmm.. that is a premature failure. Usually the Blackstone (Volvo OEM) radiators usually last 7-8 years. How often was the coolant replaced on your parent's 740?

All the B280 engines (760 '87-'90 & 960 '91) as well as B234F engines with automatic gearbox have an auxiliary transmission oil cooler fitted as standard, between the radiator and a/c condensor.

By the way, any VCOQ news lately? When's the next club event?

Will

I dont run an external cooler on my volvo but I have a 77 dodge ramcharger mud truck that I run one on for pretty much the same reason (mine leaked out the radiator) and I am rough on that tranny going through and up anything I can, and have never had any problems with overheating. And I am running at wide open throttle at slow speeds from mud hole to mud hole just slamming through gears spinning all the tires. So I dont see a problem with it on a road car driving at a faster speed moving more air through the cooler.

Thanks for your reply scottb240. Don't think my folks will be mud running anytime soon :)
I got the filter and pan back on (wrong filter kit but that's another story...) and I've been flushing the fluid. So far I've run about 10 litres through the trans and it's still coming out like a strawberry milkshake, but it's slowly improving. I've run out of fluid so there'll be ANOTHER trip tomorrow to get more.
Still have to flush the cooling system and fit the external cooler. I've also got some plugs to block off the radiator cooler.

Brad

Should be OK. Hayden makes some good ones. Remember though that if you disconnect the tranny line the coolant will then start leaking out and you'll have another problem. Be sure to plug the radiator tranny connections.

While I can't specifically report on the use of an external cooler in place of the original cooler, I'd like to ask why not just replace the radiator? I don't think that a radiator is outrageously expensive, and I don't think that it is a difficult repair to make. This is one of those instances where I feel that the stock setup is better then trying to redesign what Volvo (and most every other manufacturer) has already engineered.

I know that this part isn't specifically what you asked about, but I will mention it since it might yield you some information about how the factory used external coolers: (some?) Turbo models had a supplemental 'air to air' cooler. It ran in series with the regular radiator cooler. In cases like that it is important to make sure that the added cooler is 'downstream' of the radiator cooler. If not, you might take heat out and then put it right back in when it goes through the radiator cooler. I still have an external turbo cooler (complete with lines) in my shed. I don't want to part with it at the moment, but if you are local and like to see how the layout went, you are welcome to look it over.

-Ken
(Long Island, New York)