trans cooler

[JohnEd]

Now don't throw stuff at me.

Years ago I was offered a brand new VW Rabbit radiator for $25.  A friend that managed a car parts store had it and wanted rid of it.  I bought it without having a specific purpose in mind.  This was many years ago.  It had black plastic cans and alum fins and wasn't all that big.  I had planned to someday find a use for it but that day never came and I carried it around for a long long time.  My current thought is that if I had TX cooling issues with a unit as large as a 740 it might have application.  I know that the rad is only good for 20 psi max but I think it would tolerate a TX oil environment.  Operative word being "thimk".  Is the oil cooler oil line in a 740 run at 60psi like a car?  If it is, can a separate rad circuit be fabricated that would pump oil from the pan at a lower pressure and return the cooled oil to the pan for pickup?  From what all I have read you can get stock and aftermarket aux coolers that do the job in conjunction with the radiator system, true?  If you convert from a stick to auto you might need a water to oil heat exchanger upgrade and that might be a truly painful experience.  Could a small auto rad with elect fans work?

Just thimk'n and I know that is dangerous,

John

[Stormcloud]

Years ago, when I raced a 'hillbilly' class stock car, one of the cars had an a/c condenser from a large truck (I think it was from a highway tractor) mounted in the back window hole, with two electric fans on it. This was to cool the auto transmission in the old Galaxie car the guy raced.
It worked well, and I don't think the driver ever had any transmission trouble.

IMHO, I wouldn't use a 'plastic' rad for anything.

Regards.

Mark

[JohnEd]

Mark,

I hear ya about that plastic.  Still, I don't know that it wouldn't hold up as the trans have numerous plastic parts in them and so does the engine.  But, I hear you.

About the AC condenser:  Those puppies are rated for hundreds of pounds of pressure.  That would be an alternative "if" the condenser was a "parallel" flow type most common on the modern 134 systems.  The old ones from the R12 systems are series flow and that might be too much resistance.  Not a shred of doubt that a condenser would more than handle the heat from a automatic if it had a fan.

Now there you have Bus Knut Nirvana....for me anyway.  I started off with a "no go" idea and now I have a way to go that is even better than I could have hoped for.  Those used condensers go for cheap.  I wouldn't stuff anything in front of an MCI rad unless the power plant had been upgraded to a 400 HP ISM Cumin's. (Brian?)  Any other bus with a single rad would do fine but keeping the TX separate would eliminate the additional heat load in the engine system.

Thanks for the info and ideas,

John

[TomC]

The only use I'd use that old radiator for is to tie it into your existing cooling system for an additional cooling radiator.  I would not use it with oil going through it-auxiliary transmission coolers are constructed completely different from a coolant radiator.
Just so you all know, most all big rigs and buses are presently using aluminum radiators with plastic end caps.  If you keep up with the acidity level and flush once a year, they work pretty well.  Good Luck, TomC

[Sojourner]

Plastic don't like 300 degrees temperature. Trans cooler gets hotter oil than pan oil temperature.

Please read my reply in "Trans temp vs engine temp" post
http://www.busconversions.com/bbs/index.php?topic=9089.0

FWIW

Sojourn for Christ, Jerry

[JohnEd]

Jerry,

I guess I was asleep.  It didn't occur to me that the trans oil would see temps above 300 degrees.  From your other posts I can see where that might happen and when it did I would translate a "momentary overtemp" to a complete failure.  Not good!  Nice that not only I but nobody else will try that...and I am not implying that I am "not" the most disconnected Knut and everybody on planet earth would have better sense.  They probably do.

Thanks Jerry

John

[JackConrad]

Tthe trans temp sender in our Allison 740 is installed in a threaded fitting in the transmission case right next to the fluid out fitting to the cooler. I am thinking this is coming from the converter, since that is where the fluid gets the hottest. Our temp rarely exceeds 220-230. Keep in mind we live and travel in the SE, very few long grades, but common for ambient temps in the 90s and occasional 100s. Jack

[JohnEd]

Jack,

I think that is good info and, as far as 40 wt mtr oil is concerned, is probably a temp that is needed to get the viscosity down to allow efficiency and power.  I know that "too" cold is bad also but only from an efficiency standpoint.  When I was trying to resolve my issues I thought that a "on demand" system that only came on line when the temp increased above a thermostats setting would be the ultimate solution.  One oil cooler mfr claimed to have addressed that by having swirling tubes that were flow resistant to cold oil but got efficient when the oil got hot.  Never could make up my mind on that one but I had reservations....except that the logic held as far as it went.   Those auto TX are such a spendy little ditty that I got really read up in a hurry about hot.

I installed a water temp sender in my differential fill plug and I have a switch installed to select the input for my engine temp gauge input.  "Up" is engine and "down" reads the differential.  Having a steel trap mind I also installed a little red light that shines brightly when in the "diff" position.  And yes, the diff gets really hot on a long pull but I have never had to pull over.  If I have a carrier bearing start to go out or loose fluid I will see that coming in that the temp will increase above norm.  When my wheel bearing started to go I detected a warm axel hub and limped to Sioux Falls and had it changed.  They told me I was the first person that ever had a bad wheel bearing changed that didn't come in on the end of a hook.  Another first!  Dumb luck but I was looking for the reason why I was running with an inch less vac on the level and the first thing that came to mind was a low tire so i started feeling around for the warm rubber.  I only got close to that axel and I knew where, if not what, the problem was.  I still remember pondering that inch loss in vac and then getting the flashlight out while I was driving along and looking at the level that I installed above my head on the wall.  Expecting to see an uphill posture I was surprised enough at the "dead level" bubble to pull off at the rest stop that was only an1/8 mile from mt then position.  I have never heard anybody talk about the value of having a 1 dollar bubble level in the cockpit.  Not true anymore.

HTH somebody sometime,

John

[Brian Diehl]

I wouldn't stuff anything in front of an MCI rad unless the power plant had been upgraded to a 400 HP ISM Cumin's. (Brian?)  Any other bus with a single rad would do fine but keeping the TX separate would eliminate the additional heat load in the engine system.

Thanks for the info and ideas,

John

John, I've had no problems with my intercoolers in front of the radiators.  I've run on 105 degree days out in the dry west without any over heating issues of any type.  I even have about 1/3 of the blower inlet blocked off.  In the winter I block off about 75% of the blower outlets as well.

Hard to believe for some of you guys I'm sure, but it works great with the ISM.  This even works great while climbing those LONG grades out west on a 100 degree day with the air conditioner running.

-Brian

[JohnEd]

Brian,

My tongue was in my cheek.   I remember you saying how your marginal cooling system became a stellar performer with your 4 stroke Cummins conversion and that was an unanticipated bonus.   As it stands now you have intercoolers in front of your rads and I guess you could add engine oil coolers and TX coolers and the AC condensers.  But then you would have to unblock the air flow.

Thanks Brian and your conversion is on my mind often and particularly when I hear stories about overhauling a 8V71N. 

Thanks,

John