Using in-radiator trans cooler for power steering?

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30
Location
Australia
I have a Holden Commodore with the LS1 V8 (similar to US Pontiac GTO) which I'm planning to take on some track days. These cars are known for boiling the PS fluid on track days and even melting the plastic reservoirs. The factory cooler is just a loop of pipe, and isn't up to the task on the track. My car is manual and the replacement radiator has a standard oil-water trans cooler in each side. Is there any reason not to run the PS return through the trans cooler in the radiator outlet tank? It should offer plenty of cooling capacity; I'm more worried about causing too much restriction in the return line. How do the flow rates of a PS system and an auto cooler circuit compare? For what it's worth they both run 3/8" hose. In normal street driving the PS fluid sits at around 80c/180f, so the in-rad cooler should offer useful extra cooling. I already have some spare fittings and hose, and it would be easy to plumb up. Cheers
 

MolaKule

Staff member
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22,102
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Iowegia - USA
If you have that much concern about PS fluid temps, the logical choice would be a an external cooler ahead of the rad. Just how high do the PS fluid temps really get?
 
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36,639
Location
ME
I can't see a downside. Whatever restriction you'd encounter would be less than the system working below freezing with thick fluid.
 
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575
Location
Washington, DC
He said they melt the plastic reservoirs. That seems pretty hot. I can't think of a reason not to do it. Though honestly, I'd also probably just use a tranny cooler in front of radiator. But if it's easier, why not do it your way?
 
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1,015
Location
Alberta
Your coolant temperature could be higher then 80C. My thermostat is 195F (91C) and then dumps into the radiator,so you could actually heat the ps fluid rather than cool it. External cooler mounted in front of the rad is your best choice.
 

MolaKule

Staff member
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22,102
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Iowegia - USA
Originally Posted By: CapitalTruck
He said they melt the plastic reservoirs. That seems pretty hot. I can't think of a reason not to do it. Though honestly, I'd also probably just use a tranny cooler in front of radiator. But if it's easier, why not do it your way?
My question was, has the PS fluid temp actually been measured? And, where is this heat coming from? Is it a result of the PS system generating this heat or is the heat being conducted to the pump, rack, or reservoir from the exhaust manifold or, where? I have a hard time believing this heat is being generated within the PS system and creating boiling and plastic meltdown. I think there is a design flaw such that the pump or reservoir is too close to something very hot and heat is being transferred to the PS system from this source(s).
 
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22,890
Location
Apple Valley, California
Originally Posted By: MolaKule
Originally Posted By: CapitalTruck
He said they melt the plastic reservoirs. That seems pretty hot. I can't think of a reason not to do it. Though honestly, I'd also probably just use a tranny cooler in front of radiator. But if it's easier, why not do it your way?
My question was, has the PS fluid temp actually been measured? And, where is this heat coming from? Is it a result of the PS system generating this heat or is the heat being conducted to the pump, rack, or reservoir from the exhaust manifold or, where? I have a hard time believing this heat is being generated within the PS system and creating boiling and plastic meltdown. I think there is a design flaw such that the pump or reservoir is too close to something very hot and heat is being transferred to the PS system from this source(s).
Looks to be pretty common according to a google search.
 
Messages
524
Location
sc/fl
Given what on track coolant temps could reach, I vote for an external heat exchanger ahead of the radiator.
 
Messages
50
Location
Townsville, Australia
I installed an external trans and PS cooler on my Commodore back in the day (VZ). It did slightly effect water temp at slower speed driving due to the increase restriction in airflow but at 60km/h its fine. I used the brackets from the old PS cooler to hold the new one. In your case would go with an external cooler rather than using the cooler in the radiator.
 
Messages
1,606
Location
Oahu, Hawaii
Not OP's car but in my 02 Silverado I had PS ATF (Maxlife ATF shocked ) temps come up as high as 160F with this kludge: AC vent temp gauge fitted into a PS "dipstick" cap. The truck has a factory single bend PS cooler. If OP is trackdaying his car it possible the fluid could get 200F+.
 
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undertow

Thread starter
Messages
30
Location
Australia
I measured 80C with an IR thermometer after a 20 minute leasurely drive around town in 25C ambients. The headers do run quite close to the steering rack. Would get well over 100C on the track. Here's some info from a magazine article (also plenty of independant reports of problems on forums): http://www.streetcommodores.com.au/images/tech/PDF/sc114_powersteering.pdf "To cause this mechanical mayhem, the power-steering fluid needs to get to a phenomenal temperature, and it does, with our initial testing showing that 100 C, and in one case 140 C, was only a couple of hard laps of high rev work in a new SV8" 140C will be getting towards the melting point of the polypropylene reservior. Coolant temps are usually high 80s to low 90s and I've never seen over 100; these cars have big radiators and big grills so engine cooling isn't usually a problem. Temps on the outlet side of the rad should be quite a bit lower. A bigger oil-air cooler would probably be best but might over-cool in winter, plus I'm tempted to try this because it's already there, and easier than removing the front bar to attach another cooler. Will report back if I do end up guinea pigging it!
 

undertow

Thread starter
Messages
30
Location
Australia
This is probably why it gets so hot; if you look closely you can spy the steering rack pinion housing hiding next to the header collector! These are factory headers fitted to HSV (Holden performance) models. Engine bay could do with a wash, I know... blush
 

JHZR2

Staff member
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46,403
Location
New Jersey
I was under the impression that the at coolers inside of a radiator do not shed heat directly to the atmosphere, rather, they are bathed in coolant, and then the coolant exchanges heat with the air. Min other words, no surface or fins of a radiator directly release heat from the ATF. My thoughts would be as follows: 1) replace the current psf serpentine with one that is made of tubing but with its own fins. My hey use finned tubing on air compressors and other things. It adds surface area to help shed heat, making the wall temperature cooler. 2) install a small psf finned cooler in place of the existing serpentine. This buys you more surface area than the serpentine tube. 3) if you are considering using the ATF cooling section, I'd recommend plugging it and inserting a thermocouple in there, wet, to see peak temperatures. I suspect you'll see temperatures the same as the water, which isn't necessarily good. 4) can you not select another fluid? 5) store a bit of water and deluge the psf reservoir every now and again.
 
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6,259
Location
Illinois
The cooler part of the radiator is on the passenger side of the radiator right? It is not going to be the t-stat regulated temperature but below it. The colder it is outside the colder that side of the radiator is.
 

MolaKule

Staff member
Messages
22,102
Location
Iowegia - USA
Originally Posted By: undertow
This is probably why it gets so hot; if you look closely you can spy the steering rack pinion housing hiding next to the header collector! These are factory headers fitted to HSV (Holden performance) models. Engine bay could do with a wash, I know... blush
That's what I suspected from the beginning. Is there any way to wedge one of those aluminized insulating blankets between the header and the rack?
 

undertow

Thread starter
Messages
30
Location
Australia
Difficult to get a shield in there, but I could wrap the exposed parts of the rack with reflective wrap (thermotec or similar). This would reduce the radiative heat, but it's still gonna be hot down there. I've decided to just play it safe and grab a small tube and fin trans cooler (Hayden 401). Cheap and effective and resistant to stone hits. If overcooling in winter is a problem I can just stick a bit of cardboard between the AC condensor and the PS cooler. Thanks for all the informative replies!
 
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