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Power Steering Cooler in Rad. - Am I Daft?

GSequoia

Everyone says I'm a jerk.
NAXJA Member
Location
Torrance, CA
I'm going to be putting a large aux. trans cooler in and in process bypassing the trans. cooler in the radiator (I'll be running the Mopar aux. cooler and a larger one). Would it be dumb to use that spot in the radiator is Power Steering cooling? I have to flush the power steering system anyway so I'll be messing with the lines, seems sound to me...

Enlighten me.

Sequoia
 
Why ? Thats alot of feet of tubing for so little a job.... The hoses would have to be the same size as are on the PS pump now....
 
I'd be inclined to wonder what the residual pressure is in the return line - should be close to nothing, but I'd consider it important... I know it's pretty much squat with the transmission, but peak operating pressure is much lower (300psi versus 1200-1500psi...)

Mainly, I'd want to make sure pressure is low so you don't have to worry about power steering fluid popping into the radiator uninvited...

Why not use an external cooler? Just quit using the oil cooler in the radiator, and remove the thermal load from engine cooling system altogether - that's good for about 5 degrees of engine operating temperature or so... Use a little two-pass cooler for power steering, a four-pass for the transmission, and put them both in front of the condenser. The lessening in cooling capacity due to reduced airflow is more than made up for by removing the cooling load from the engine coolant circuit.

As far as the transmission fluid goes, use some sort of thermal bypass valve - B&M made them, and I think FlowKooler does as well (and Hayden probably does too - check.) The power steering fluid just don't care - hydraulic fluids aren't picky about temperature as long as it's low - but the transmission likes to warm up quickly so the oil will work at maximum efficiency. The thermal bypass valve is designed so that the fluid doesn't go to the cooler while under 190*, and will go to the cooler above that - the idea being to maintain a temperature of 190-210* (well within the efficient temperature of automotive fluid lubricants.)

If you're going to do something like this, make it easy on yourself. Power steering depends as much upon volume as pressure, so you don't want to reduce the size of the lines (and while the internal oil cooler is plenty large, the entry where the flare fitting goes has about a 1/4" ID, IIRC.) That sort of restriction can cause backpressure you don't want to deal with...

5-90
 
FYI with the pressure of the power steering... I don't know how much pressure it is, but it'll drain the reservoir pretty fast I found while flushing the system. Came out of the return line pretty hard but not crazy so.

I might put a small cooler in, just saw the thread about an Explorer PS cooler. Figured that a cooler for the PS is probably a good idea when I'm banging around in rocks and such.

The reason I am doing one for the transmission is because the XJ likes to get hot on highway speed grades. It pretty much never gets hot at any other time but certain grades will cause it to overheat (Highway 18 to Big Bear is guaranteed to get it hot in the day time). I think the heat is coming from the transmission because of that, plus even if it isn't well, good insurance.

Sequoia
 
Concur. One of the very first recommendations I make to people with hot engines and autos is getting the hot transmission fluid out of the radiator, and cooling is elsewhere. Like I said, you'll slightly decrease cooling air, but he net decrease in engine temperature is worth it - and the transmission fluid will also be rather cooler (IIRC, typical transmission operating temperature - OEM - is about 240*. No reason it can't be as low as 190-195* - just takes a little work to get it there.)

Once you get the hot fluid out of the engine cooling loop, there's no reason to replace it with another one. It's kinda like asking a surgeon what he's going to replace a tumour with when he gets it out of you - why replace it with anything?

Here's the "thermal valve" I keep talking about...
http://www.bmracing.com/index.php?id=products&sid=4&cat=20&subcat=27&pid=81

5-90
 
Sequoia,

I run the power steering return line through the factory air to fluid trans cooler (and have for years) on my 88. When I was making long runs in Baja the PS pump would whine and grind and spit fluid out the cap, until I cooled the fluid. The return line is nearly atmosphere pressure and I have experienced no fluid volume problems. The radiator cooler is likely to provide the same result, but the heat you dump will be going into an already overloaded radiator.

The auto trans cooler circuit on my 88 is through a larger than stock aftermarket air to fluid cooler in front of the engine driven fan (so it's always first to gather cold air) and then through the radiator cooler before returning to the trans. Since I changed to this circuiting I have not had a trans cooling problem (no trans overheating) and the precooling of the trans fluid seems to help the radiator keep the engine cool. The coolant in the entering radiator tank (where the trans cooler HX is located) is usually close to the thermostat setpoint temperature, 195 to 210 dF. The HX has an approach temperature difference (a maximum efficiency of heat transfer) that makes the leaving fluid temperature somewhere close to the coolant temp, within twenty degrees. If the coolant is 220 (a hot high load condition) and the trans fluid is leaving the air cooler at 160 the leaving temp from the radiator cooler cannot get much more than 200. If the coolant is 180 (a start up load condition after engine warm up) and the trans fluid is leaving the air cooler at 40 the leaving temp from the radiator cooler cannot get much less than 160. Using the radiator trans cooler as the last heat exchanger in the circuit allows it to act much like a bypass valve, to temper the fluid temperature entering the trans, but with the added radiator cooling capacity when operating under high load conditions. If I experienced a problem with overcooling the fluid that reflected a need for the bypass valve on the trans cooler line I would have installed one, but even with -12 dF drives in the mountains I have had no problem (although I do let the XJ warm up before driving).

The only times I have had problems with overcooling is with the brakes and lockers, ice in the rear brake drums and cold diff fluid spooling the lockers (other than door locks). It takes a few turns around corners to unlock the brakes and warm up the fluids.
 
When rock crawling or on long trails my power steering would get really hot and the pump would start to whine. I never had a problem with the tranny since I have a 5 speed but I would not run the power steering through the radiator because the radiator is dealing with the engine coolent and also does the power steering fluid really need to run at 180-220 degrees?

My pump and box finally gave up the ghost last summer in Daytona Beach FL and I replaced everything relating to the steering. New pump, hoses, box, external filter, and a big ass cooler. The cooler I used was a auto tranny cooler that my dad used to run on his Impala. It measures 8"x10" or close to that. The pump feeds the high pressure line into the box and then the hose leaving the box goes into the external filter then into the cooler and then from the cooler into the resivoir and pump. I have not had a problem since with the pump whining or any other steering issues after installing this even when running around in the sand in FL. I have not had any issues from too much cooling as this winter in NC its been at freezing or below for most of the time. I would not hesitate to run another cooler like this again.

AARON
 
I tried using the trans-cooler section of the radiator to cool the PS fluid. Yes it will work. However, I found that the PS fluid was now hotter than it was without any cooler! I presume this is due to the proximity of the hot engine water.

I was much happier with a dedicated PS cooler. I installed it right where the stock airbox was (my air cleaner is in the XXXXpit). I used a 6"x8" cooler out of some Japanese car. Works great.
 
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(Highway 18 to Big Bear is guaranteed to get it hot in the day time). I think the heat is coming from the transmission because of that, plus even if it isn't well, good insurance.

Sequoia

Big Bear Lake, California (PWS)
Updated: 5 sec ago

34.7 °F
Light Snow
Windchill: 35 °F
Humidity: 75%
Dew Point: 28 °F



Godamned liar. my transmission froze due to all your fancy coolin rigs. : (
 
Thanks, I am sure that they have all been waiting 5 years for you to give a weather report. Your a real ASSet to this forum.
 
Thanks, I am sure that they have all been waiting 5 years for you to give a weather report. Your a real ASSet to this forum.

but its so worth it to see Geoffs old posts. Dont come down on me, the moderation put me up to it :D
 
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