Fitting double autobox coolers

[Frank87]

I am up for a waterpump job soon (almost done 100.000km on the 3.0 V8). In addition, I want to replace the A/C condensor as all other A/C parts have been replaced. This also allows me to clean everything from road gunk.

If I simply drain the radiator, steering system, autobox and remove the R134 from the A/C system, I can remove everything and easily replace the pump, pulleys, belts etc.. This also gives me the most space to clean everything and check for any bad parts.

In short, I will remove:
- Steering fluid cooler
- Aux. fan
- Condensor
- Autobox radiator
- Engine radiator

The cooler lines of my autobox are not in good shape. The metal connections are getting real rusty. I know this is a 10mm steel pipe with 1mm edge diameter. This is pretty solid but with everything open, I have the opportunity of improving the system. Since the E34 V8 have the wide radiator behind which the small cooler sits, I plan on fitting 2 brand new transmission coolers which will then be connected to each other. In addition, I will use flexible steel hoses to connect this system to the gearbox. I can then decide myself how I want these hoses to run.

Here are some pictures to give you an idea of my plan. I still need to do some calculations on the length of the hoses and how I will connect the coolers.




Stock radiator. As you can see, I have plenty of room to fit another cooler. The space between the radiator and condensor is empty.




Some more details on the setup. It is in Dutch but you will understand the plan.


Here's a guy who used flexible material on his M54.




My transmission guy also does hydraulics so I will ask him what he thinks and how he would make these connections.

Let me know what you guys think.

[632 Regal]

Double coolers are way overkill, as you know the transmission fluid should remain at around 190-200 degrees. I would run it so that the hot fluid goes trough the coolers first and then through the radiator to keep the temperature hot enough. If the radiator does not heat the fluid you will have too cold of fluid and will ruin the clutch plates in an early fashion.

I learned this from a very good transmission builder in the mid '80s, he told me that cooling the fluid below engine water temperature was the #1 cause of trans failures on modified engines/transmissions. His name was Darryl Young. He was a little older than me back then, not sure if he still builds converters.

[Frank87]

Ok so I gathered some more info and read what Regal said. The car uses a DIII variant and according to the experts, DIII should not reach 80c degrees.

I used a diagnostic device with live monitoring functions. Did some city driving and 20 minutes of highway driving. Outside temperature was 15c degrees and I did not floor it. There are no hills in the Netherlands so all terrain was flat.

City driving coolant temperature:88c
City driving ATF temperature: 70-72c

Highway coolant temperature: 84-85c
Highway ATF temperature: 65c

So that stock cooler, although old, does keep the temperature way under 80. However, during hot weather, the car sometimes relies on the fan. I also go to Germany often where there are alot of hills and mountains. It would not surprise me if ATF temperatures easily exceed 70c during those moments.

Additionally, when placing an extra trans cooler in series with the stock cooler, I can expect a 30-50% increase in cooling. In addition, my trans guy told me that I would not have to worry about overcooling as these coolers are mounted on the radiator on purpose. The radiator temperature keeps the ATF temperature in check.

I think I'll go through with this. With the temperatures measured, I can also do a decent post-measurement. Should I see dangerous values, I can always disconnect the 2nd cooler and remove it.

More soon.

[whiskychaser]

I'm no ATF expert but my understanding is that the ATF temp should be 80 - 95C. It may be OK to rise to a max of about 130C but only for very short periods. IIRC, Land Rover fitted some sort of ATF temp warning. You could perhaps use that sort of signal to open a valve and bring your second cooler on stream automatically as and when required

[genphreak]

Nice idea.

BUT;
1. That is not a big enough gap for your cooler (it is only there because the 2.5/3.0 radiator is thinner than the thicker M5/4.0 ones, however the aux fan may move forward a little and you may be able to get it to fit. You will need to remove the front grille, etc. BTW If yours doesn't have one, the top gap (and any at the sides) should have rubber seals over to help the fans do their job.
2. Internal trans coolers are better in cold climates where the radiator will actually help to reduce wear in the trans by actively warming it during warm-up. Also they are lighter.

The replacement lines look great, just make sure they route neatly and do not interfere with things, the small pipes the factory use bend neatly and stay out of the way of standard repair tasks. Also, they help cool/warm the fluid.

I'd just replace the stock stuff if it isn't too costly. No doubt you could augment new stock pipes with better fasteners and hardware whilst you are doing it.

Re the A/C, make sure you get someone to evacuate the refrigerant as it is expensive and most are happy to put it back in for you once you are done with your repairs. If you do that, do yourself a favour and replace the TX valve as it will rejuvenate the cooling capacity of the entire HVAC system. They are cheaply bought and installation isn't too hard if you take care and time with the screws, torx fasteners and the plastics in the dash beside the footwell.