.02 worth of food for thought re:coolers

[Beav]

It seems that there are two camps surrounding tranny cooler hook-ups. Well, my little train of thought mostly runs on experience so grab hold of something and hang on...

From what I've read here and elsewhere (please don't ask for specifics, I'm not married and I don't have to answer those kinds of questions anymore... ) the SVX coolers plug up easily. When flushed, forward or backward, the clog around the inlet fitting (the troublesome spot) will clear enough to allow flow but not all of the detritus in the cooler is ejected. So that's reason to put a filter on the 'cooler out' to 'trans in' line, in my book. If the trans only has a screen inside of it chances are it will eventually send garbage to the cooler again, resulting in another clog.

Another filter? You could, but I think that would be a bit restrictive on the system. Take a chance? Duh. How about doubling your odds? Running the coolers in parallel will give you some room to play if the OE cooler clogs again, plus provide a means to warm up cold fluid. Running in a series allows fluid warming but gives no margin for a clog (then again, if the OE cooler clogs again there goes its warming properties.) Bypassing the OE cooler without installing a thermostat is not your best bet either.

So, what's best? Money no object system is thermostat controlled with bypass circuit, HD cooler bypassing OE cooler altogether and external filter upstream (keeps the cooler clean and seeing how the cooler is new, it shouldn't have anything in it to flow downstream into the trans.) Next best would be coolers in parallel, filter downstream, in order to catch garbage that is bound to be in OE cooler. Including the OE cooler in the system saves the cost of a thermostat.

A temp gauge to tell you when something is screwing up would be a brilliant addition, and could possibly save you a buttload of moolah. They're kinda clunky, maybe someone's seen something small and rectangular? Anyway, don't forget the synthetic fluid, that should be a no brainer in a high heat, high load situation.

And that's all I have to say about that

Beav

[svx_commuter]

Hi Beav,

It is really great to have your comments around for awhile. Thanks
I have some additional information for you.

I had my radiator out awhile ago and was surprised to see the bottom all plugged with road dirt. So I cleaned it out. This wasn't good because the stock tranny cooler is in the bottom of the radiator. I have a 92 but did not see any screen on the inlet. The radiator may have been replaced. It may be a later year. Anyway, I ran some solvent thru it and it was very clean.

I have added a Subaru filter which I think is a strainer and not a paper filter. This may not be good a catching that paper clutch material. Also I've added a tube and fin cooler after the radiator cooler.

I have also installed a thermometer. A small device that goes on the outside of the outlet pipe and gets insulated and has an LCD readout. Runs off a AA battery.

Normally the stock cooler drops the fluid temperature 15F and the add on cooler drops it another 15F.

The other type of cooler that seems to be a better idea, rather than the tube and fin type, is a multi pass parallel cooler. It looks more similar in construction to a radiator. As the fluid warms up, more passage have hot fluid and then the flows go up. That helps with the cold weather problem. Helps to warm up the transmission.

I have been talking with Dormano and he has installed a "large" cooler between the radiator and condenser bypassing the stock cooler. This seems to be working well even in hot weather with the a/c on. Has a temperature gauge to check readings. Hasn't been going over 175F. My car will still get up around 220F after going up hills.

This is what I see and I would appreciate you comments. The torque convert (TC) is a lock-up type. When it is not locked there is a flow through the TC. This is also when most of the heat is generated. Ride "Hard" and the TC will not lock-up. Ride around in 3rd, the TC will not lock-up and the temperatures will climb.

After the temperatures are hot, such as after along hill climb and the TC locks up, the temepratures will come down. This is because there is no flow thru the TC. As soon as it un-locks the temperatures go right back up to where they were.

If you can get a copy of the tranny schematics you will see that the oil pump provides the pressure. After this the flow splits. One of the paths is to the pressure regualtor, then the TC regulator vlave and then the lock-up control valve.

At the lock-up control valve the flow splits again. Some goes to the TC and some by-passes thelock-up valve and then rejoins the flow from the TC and then goes to the cooler.

I see two things that may be a problem. Some of us have increased the line pressure by pulling out a resistor. However this may not actual increase the cooler flow beacause of the Torque Converter regulator valve. No one has actually measured the flow to if this mode helps.

The second thing is that the lock-up control valve may actually modulate or be used as a control valve to regulate the tranny temperature.

Well anyway I just thought you may want something to think about since your home for awhile.

Hope you get well soon.

Did I understand correctly, you have an SVX?

[Beav]

I'm kinda in a hurry this morning so I'm just going to blurt a few things out, probably incongruously. You should be able to catch on to where I'm heading...

Part of this equation hinges on whatever logic the engineers wrote into the software. Most a/t's will allow lock-up in 3rd and 4th gears (at what points and conditions depend on the program.) Heat will increase in unlocked t/c mode as the pressure on the fluid is greater and there is also fluid slippage to consider (both create heat.) All a/t's I can think of will first 'downshift' to unlocked before actually downshifting gears. One thing that allows is for the engine to rev higher, putting out more torque and power. This causes the a/t to carry a higher load. Without the benefit of dropping a gear, the heat builds quickly.

Naturally, without having the schematics and the logic in front of me it is difficult to be completely sure. Are you sure that raising the pressure is a good thing? That's not something I would do on a whim. Besides potentially screwing up something in the a/t, it could cause premature hose failures or even burst a marginal cooler. When I lived in Colorado I remember reading about why so many cars caught on fire in the mountain tunnels. High a/t temp and rupturing a/t lines dumping fluid on hot exhaust at slower vehicle speeds... Besides pressure is a lot different from flow. Another point to consider is that if you run the fluid through the cooler too fast it won't have as much time to pass off heat. Increasing pressure would accomplish one thing - it would help push oil through a partially clogged cooler.

Another point of consideration: a lot of modern a/t coolers have fins inside of the tubes as well as the outside. I'm curious how susceptible they are to clogging. I've never seen it happen, but that in itself means very little. My experice is that the flat tube coolers are much more prone to blockages then tube coolers. I can also tell you from experience that no matter how much you flush a cooler of any kind you'll never be able to completely clear it. That's why I prefer a downstream media filter.

Yup, I bought a '92 of the floor at Emich in Denver. Sold it a few years later as I figured parts would be sky high on a low production vehicle. I loved that car. Now that I'm in the market again (and it usually takes me months to decide what I want before I start looking) and I can't find a car out there that impresses me other than maybe a Boxster (too high) or a 32 valve Lincoln (too codgy.) Anyway...I'll probably get more serious shortly after I return to work at the first of the month. I'll probably concentrate on cars in the south and west, away from the salt belt.

Thanx for the good wish,

Beav

[1994SubaruSVX]

aftermarket cooler and the thermostat sounds great to me. i just dont see the point in keeping the stock cooler. just sounds like an accident waiting to happen. even if you run the coolers parallel i dont much see the point. but i am no expert so this is merely my opinion and what i have chosen to do on my svx. i suppose only time will tell.

[Beav]

I agree, I said the best bet was to do just that.

[1994SubaruSVX]

well then that makes me feel great.

[svx_commuter]

Hi Beav,

Thank you for the information, as it is very informative.

This transmission in the SVX appears to use line pressure which could be as high as 200 psi depending on the TPS position, speed, gear, TCU etc.... to power the clutches. The torque convert pressure looks like it is regulated to a lower pressure. That being done by the torque converter pressure regulator. This way even if the line pressure is high from the pump, the TC will have a regulated pressure lower than the pump discharge.

Do you know if this is a normal set-up for an automatic?

[Beav]

I've got no clue anymore. A/Ts have been a specialty thing with mechanics for the past twenty years or so. When we only had to deal with 727, 904, TH350 & 400, C4 & C6 and maybe an odd BorgWarner they were no big deal. Now, especially with electronic controls, there are new models every year it seems. It probably won't be too long before the rebuilders start specializing in just a few makes. It's not the rebuilding so much as it is the diagnosis.

Anyway, what I'm trying to say is I don't even try with A/Ts anymore. I'll yank 'em out and stick 'em back in. I can understand what rebuilders are telling me. That's about all I have time for when I'm working. All the other changes already take too much of my time ...

Beav

Originally posted by svx_commuter
I have also installed a thermometer. A small device that goes on the outside of the outlet pipe and gets insulated and has an LCD readout. Runs off a AA battery.
[/B]

COuld you tell me where you purchased the temp gauge?
Thanks