Adding an (additional) automatic transmission fluid cooler to the 850

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Before we get started on this modification, read some of the justifications for it on these pages;

"POS Aisin transmission" - a brickboard discussion on inadequacies of the Aisin Warner auto boxes supplied on FWD Volvos (850/S/V/C/70...)
"transmission mortality"  a quick rant on ATF temperature and what you can do about it
"atf-essay" a larger, more detailed essay on the ins & outs of overheated ATF

The long and short of the discussions on these links and others on this site is that

• automatic transmissions get too hot in many circumstances,
• automatic transmission fluid (ATF) is inadequately cooled by the cooler supplied within the car, and
• additional cooling for your automatic transmission is useful in maintaining the integrity of your ATF (and consequently, your transmission itself).

Everyone that I spoke to from the automatic transmission trade, without exception (and that was quite a few people), agreed that this was a very worthwhile modification to make. One of the foremost transmission tech/experts in Australia stated that the unit supplied in the car was inadequate for cooling the transmission. He should know, he's reconditioned enough of them. He also strongly recommends regular atf fluid flushes, as oxidised fluid = burnt out transmission = Big $$$ repair bills. ATF flushing and the aftermarket cooler are both means to the same end; extending the life of your transmission.
 

Background Info

I embarked upon this mod by asking the gods of brickboard what they though, with reference to possible hose/atf cooler size problems and any tips or tricks that people had discovered in the doing the mod for themselves. I had a few answers for the former question and none for the latter, so either nobody's done the mod (yeah, right) or nobody was game to admit it.

To the former questions I had regarding hose sizes, my anxiety was unnecessary. The volvo hose looks a lot bigger on the outside than it is on the inside, being high pressure, double layered. These are the dimensions of significance in this mod;
 

The aftermarket cooler hoses are smaller, but not by as much as I initially thought. So it is not a problem (many telephone calls to determine this) because the pressure inside the ATF cooling system is not that high, no matter how large and reinforced the hoses might seem. Sure, there's plenty of high pressure in the tranny itself, but not the cooling lines. Thus the 3/8 to 5/16 decrease is not going to cause flow rate concerns. (Of course, ideally you might be able to get your hands on an aftermarket cooler that is 3/8 or bigger. I'd say the bigger the better, within reason.)

So after gathering this info I was confident enough that the aftermarket cooler that I bought was going to do the job, and not going to jeopardise the system's ability to function.

The Mod

Some parts of this mod are a pain in the *@#$ to perform. But don't be discouraged. If I can do it, so can your kid sister. A few prewarnings; I had to move a horn out of the way, get the fan shrouds out of the way, cut into the stock ATF hose with a hacksaw to put the cooler in series, and saw a bit of the bottom plastic splash guard away. If you don't mind such butchery then you can follow these instructions closely. Otherwise, read this & weep, or find/think of a better way & email it; I'll post it alongside or even over this one.

If you are depending on this information then read these instructions entirely before you embark upon the project, and also read Ozbrick's standard disclaimer. The processes below are not necessarily consecutively followed when doing this mod- they are just written this way to most easily and fluidly (pardon the pun) describe the process. (e.g., You'll want to do the hose attachments to the cooler before you attach the ATF cooler to the vehicle.)
 

Here's the kit that I bought. It's Canadian built, brand is Drivetech, and it was only $160 Aust. Click on the image to make it bigger and you can see the cooler in the middle, the nylon bolts to fasten it to the front of the radiator to the left (these are like cable ties but with those large plastic square stops on the ends). Underneath the cooler are two hose clamps, the black nylon nuts for the nylon bolts, and a 5/16 brass tail to screw thread adapter that I still don't know what was doing in this kit. (Some standard fitting for cars other than Volvo?) The only things you don't see are the spongy rubber self adhesive squares that you stick onto the back of the cooler to protect the condenser or radiator from the cooler (and vice-versa). These make for a nice snug fitting without undue pressure on the radiator/condenser.
 

If you do things the way that I did, you need a bit more than just the stuff above. You also need two 10 mm to 10 mm brass tail adapters, for joining the hoses.  I obtained these from a hose & fittings supplier. (Sydney: Pirtek, Mascot.) You will also need two more hose clamps (for a total of 6 clamps altogether). In this picture you can see the brass tail on its own, and another firmly wedged up and clamped to the 5/16 hose that came with the cooler (phew, it fits...). The last thing to get (not completely necessary) is a section of harditube (that's what it's called in Australia anyway) to protect the new hoses from chafing & minimise the chance of kinking. You will see pictures of this stuff below. The Harditube I used has an inside diameter of 12 mm and external of 18mm.
 
 

One of the first things to do is whip off the plastic splash guard that sits underneath and protects the radiator, air con condenser, etc. It is easy to get off. It has three clamps that just slide onto the front guard, two bolts up each side (orange arrow on large image, clickit) and one plastic tongue that you just have to push against to then bring the whole thing down & out (blue arrow on large image). The green patch and arrow indicates the bit that I hat to hacksaw off to get the thing back on, as I needed to clear both the new tranny fluid hoses and a horn that I moved. (Now would be a good time to lament how many times you have hit humps and gutters with the underside of your car.)
 

(Bear in mind the horn info below is for right-hand-drive Aussie models. If you're the other way you may have to go cross-eyed to work on your car with these instructions. It's also for my li'l 10 valve 850 B5252, so you might(?) have less trouble if you have a different model.)
Have you ever noticed how stupid the location of the horns is on the 850? That space is supposed to be to let air in for cooling, isn't it? Or is it a conspiracy to heat ATF? Sin posted a mod on Matthew's post-a-850-mod website about moving those infernal horns; read it here. For the life of me I couldn't find the mounting holes he was talking about, except for way over on the passenger side, much further away than the horn wiring would allow you to get the horn to once you unclipped the wiring harness as much as you can. The horn was in the way because I selected a spot for the cooler at the front, top & passenger side of the radiator where it could get maximum air (the cooler instructions almost beg you to put it in front of the radiator & air con condenser). I had to swap the horns, placing the passenger horn (low frequency) on the driver side, and then moving the driver side (high frequency) onto the hole that you can see in the first picture here. (It doesn't make any difference which harness to horn you connect as it's just 12V power delivery; I guinea-pig tested my horns individually to make sure. Notice written on the horns that they themselves are frequency adjusted.) Anyway, you can see the hole that I used to mount my horn in a body gusset between the radiator and the front guard, when you look up from under the car. I reversed the horns because the driver side fitted better in this gap and pointed outwards to the front of the car. I also had to bend the small mounting plate so that the horn fit in properly. I didn't move both horns down because I could find no easy place on the drivers side to fit the second horn within reach of the wires. (PS I don't really care about water in the horns. The horns are lame anyway. Um, Volvo, the message was safety, remember? I smell an air-horn mod on the way.)

So here is the horn in it's new position. (The grey-black plastic passenger side air dam guard has been taken off here.) I am not advertising this as a great place, but it got it out of the way whilst I was doing the current mod.
 
 

At the top of the radiator is a different story. First, you need to remove the plastic conduits/air ducts that direct air to both the airbox and, on the other side, to the ecu. If you have a turbo you will also have to get the intercooler air conduit out of the way. These just pop out with a bit of encouragement. Then you need to undo the fan shroud & relay carrier ( 2 bolts on either side of the top of the radiator area). You can haul the whole fan shroud up & out of the way without disconnecting all of the wires to the relays; just get the cable looms out of the plastic cable ties and separate the top plastic plate that carries the fan relays (relay carrier) from the fan shroud. Get the relay carrier out of the way of the fan shroud. Next, the bottom of the fan shroud has two plastic tongues at the bottom; they won't get in the way as you lift the whole fan shroud out to sit on top of the engine. (Make sure you get them in again when you put it all back together!) Next, there is a small plate that runs along the top of the radiator and air con condenser, which you have to remove via 3 torque screws. With this out of the way you get to the view above. Here you can see the nylon bolts where I have mounted the aftermarket atf cooler. I could access the top mounts of the atf cooler behind the condenser, but because it was impossible to get to the bottom cooler mounts with the radiator on, I put them all the way through the radiator as well; I think this was much easier than taking off the radiator and there's still plenty of clearance from the fan for the nylon bolts. Just make sure you snip em close once they're locked into place.
 

Before you connect up the atf cooler to the radiator/condenser, you might want to do the hoses first then attach the cooler with the hoses. There's not much room in front of the radiator & condenser for fiddling with hose clamps. Here we see the cooler ready to go up & get mounted with the nylon bolts.
 

The start of the ATF hose process. Here I have put the hacksaw through the top hose and then attached one of the 10 mm tail-to-tail adapters into the hose from the tranny. The other side of this adapter gets the ATF cooler hose, and both are clamped up. Repeat for the hose that is sawn off that runs to the cooler. Hint: Do this from cold and there will be very little ATF in the top hose to spill around when you cut it. It might also help to not get burned!
 

Here we see both aftermarket ATF cooler lines attached to the top hose that used to run directly to the volvo cooler from the tranny. Now the flow is from the tranny to the cooler then back to the volvo cooler, then of course back to the tranny via the untouched bottom hose. The top hose was only selected because it was easier; some might say it is better to run the ATF through the volvo cooler first, then through the aftermarket one; this ATF cooler manufacturer stated that it didn't matter which way it went, or how the cooler was orientated, or which direction of flow you chose for the cooler. I found a number of discussions on the Internet about this; most were impartial as well; only one guy asserted that it must be stock cooler before aftermarket one; but the reason given was lame. Another (GP) site said that plumbing into the return line from the radiator would be about 5% better for cooling but that you could do either.
 
 

Here's an underside view of the hoses covered with the harditube to stop chafing & reduce the chance of kinking in the critical spots. You can also see that damned horn in its new position. Harditube is resistant to boiling water so I figure it's OK for this application. I'll let you know if I find puddles of it molten at the bottom of my car. My tech mate said it was fine, I am crossing my fingers on this one.
 
 

Here's a view from underneath looking at the new ATF cooler. It's pretty tight in there now! You can also see the redirected horn cable, clamped to another spot. One of the nylon bolts has been pulled through and not yet been snipped down to size.
 
 
 

The final view from the top, showing the completed connection off the top line. Note the just visible harditube protecting the atf cooler hose as it makes its journey down around the condenser to the atf cooler. The air conduit to the airbox has been reinstalled.
 
 

Here is the front view of the new ATF cooler. You can see it's in a pretty good position for capturing air. It still allows plenty through to the condenser & radiator, though. If you do the mod, wait until the fan comes on and feel how much air blows through all three devices. You can see why the horn needed to be moved. You can also see the other horn which is a bit weird now on the wrong side, but it clears the grill fine (and it will be gone soon enough when the airhorns go in!)
 

Make sure to check the fluid levels after installation of your cooler, both initially and when hot. Remember ATF level is checked with the engine running. Depending on the size of your cooler and hoses you might need a top-up of ATF straight away. I didn't. And check for leaks as well! It would be wise to recheck connections a week after and tighten everything up after this week of temperature cycling.

That's it! What can I say about this mod in the short term but that it seems to be dissipating a fair bit of heat. Don't worry about front plastic bits, they're all bakelite and meant to tolerate a little warmth, which they got from the radiator/condenser anyway. In retrospect I would probably be less lazy and tap into the bottom hose returning ATF to the tranny instead. This is easily fixed with another 10 mm tail to tail adapter to rejoin the cable and then hack & plumb into the other one with the tails & hoses already in use & shown above. Or perhaps shove in a tranny line filter in this spot. I would also get rid of the horns at the same time as I did this mod.

The above instructions were just my way of doing it, and I had little in the way of clear instructions. I hope that you benefit from them and maybe improve upon the method. If you do, please send your tips to me so that I can post them here for others!

good luck

Michael / OZbrick 850