RPM WS6

iTrader: (3)

I'm happy to be able to provide some data.

I don't know at what point the fluid temp becomes a serious problem (that GMHTP article mentioned 275°F being the failure point for seals, but significant wear probably starts somewhere prior to that), but so far it seems that the stock cooler would only serve a purpose at steady speed cruising where coolant temps exiting the radiator are lower than the PS fluid temps for extended periods, or applications where coolant temps have been modified to remain lower under all conditions (though this was not part of GM's plans when the coolers were installed).

I can only imagine that GM installed these coolers to prevent large temp spikes under severe conditions (much like the factory trans cooler, which is also hindered by high factory coolant temps that won't allow much cooling - until you push the trans hard).

I think wssix99 mentioned that, with his aftermarket cooler, he had seen fluid temps in typical summer heat that were in line with the 162° temp that I observed in somewhat cooler weather. In comparasion, I am now seeing fluid in the 18x° range with no PS cooler in the usual summer temps for our region. There are obviously several variables that could be present between our respective readings, but I think it's probably fair to assume that a small air-to-fluid cooler is able to drop fluid temps by an average of ~20° even when placed in a somewhat less than ideal location. Having said that, how much benefit is there to keeping fluid temps in the 160s vs. the 180s? I'm no power steering system engineer/expert, but if we use the 275° temp mentioned by GMHTP (assuming they have done their research) as the critical threshold, then it seems like the difference between 16x° and 18x° would be marginal in terms of lifespan for an average daily driver.

Again, I think the aftermarket cooler is probably a good idea for cars used at competition level, or maybe in super hot climates, but I don't think there would be much (if any) net benefit in my particular application - since mouting one in the typical location does introduce a potential risk, albeit small, of impact damage.

demonspeed

iTrader: (7)

I think this is a good summation. In my particular case, I only put 3000 miles on the car last year (and I'd surmise I'll not even hit that much this year), and most of my time anymore is at the drag strip. In my case, it's probably not a necessary item. Perhaps if I cared more about cones or other twisty things, it'd be significant; however, I would probably want to consider a better/larger setup if that were the case (recalling that I went with the shorter cooler than most others go with).

Either way, I think we've see some good evidence where, at the very least, removing the factory "heat exchanger" is a prudent thing to do.

On the other hand... I might try removing it to see how things go. If I start seeing more of a fluid-at-the-reservoir issue then that may mean it is/was useful.

wssix99

iTrader: (5)

^ I think that sounds right, but I'm still left wondering why GM installed coolers on all V8 cars post-'98? There must have been some issue they were trying to solve. Maybe with rapid/frequent turning, the temps shoot up?

1 FMF

iTrader: (1)

http://www.carcraft.com/techarticles...ering_coolers/

power steering fluid follows the rules of ATF and other hydraulic fluids regarding temperature- around 150-200°F is what to shoot for. this keeps viscosity under 50 cSt which reduces power steering pump effort which would increase corporate gas mileage.
a rule of thumb thrown around for oils and atf is for every 10° C over ~180° F the oil's life is cut in half due to oxidation.
http://www.machinerylubrication.com/...lubricant-life
http://www.machinerylubrication.com/.../oil-breakdown

They put the 1-4 skip shift on for that reason and a few other things happen during warm up or get things to warm up as fast as possible with OBD-2 for fuel economy and emissions reasons.

the interesting thing would be to measure temps throughout the power steering system, I think the only place the heat comes from is the pump and engine heat soak. down at the rack if it doesn't see radiator air may be cooler.

wssix99

iTrader: (5)

^^^ That's a great point. The temp coming out of the pump is probably much warmer.

RPM WS6

iTrader: (3)

This was my thought as well, in an effort to avoid the eventual cross-contamination that seems to be a given.

My '99 Z28 didn't come stock with a cooler either. They weren't standard on all V8s until 2000.

I think your assumption is correct, that with severe use (rapid/frequent turning, or maybe desert type heat), this design may provide an overall cooling effect that's just enough to be beneficial.

Also, this makes sense as another factory-intended benefit of the "cooler":

So if 150-200°F is the ideal range, then, all else being equal, the difference in pump life between 16x° temps vs 18x° temps is likely marginal.

Keeping that in mind:

10°C = 50°F therefore,

180°F + 50°F = 230°F as the point when fluid life would be cut in half. And so far I have observed temps that have stayed below 190°F sans cooler.

FWIW, I've regularly drained/refilled the pump reservoir over the years in both of my current LS1 cars. I know this isn't the same as a full flush, but it does allow fresh fluid to mix in on regular occasion. Perhaps this is a another reason why I don't have some of the boilover issues that others have seen.

demonspeed

iTrader: (7)

Who would have thought we'd have nearly 20 pages on power steering theory. Too bad we couldn't get someone like Scott Settlemire in to comment on what exactly they were trying to do with the factory cooler.

wssix99

iTrader: (5)

Tech discussion with quantifiable facts. Who would have thought?

I'm still hoping that my cooler will make my car go faster, though.

black79transam

I'm looking at using the harden 402 model because I don't want to drill. Would it work properly behind the airdam without any holes cut?

Fwiw my car is a summer daily driver maybe 1 track day a year and a few aggressive starts at stop signs

wssix99

iTrader: (5)

You want to have your cake and eat it, too?

If you are going to put a cooler out of the airflow and want it to be efficient, you'll need a "frame rail" cooler designed for the purpose.

This will probably "work" but it won't be as efficient as it could be in the airflow.

See RPM WS6's comments above. At the point you are putting in a cooler in an inefficient spot, there's probably no point in doing it at all.

demonspeed

iTrader: (7)

I would reiterate this knowing what I know based on my personal experience.

Just get yourself an upper hose for a '98 Z28 and call it a day.

RPM WS6

iTrader: (3)

Actually, if you remove the cooler, the resulting weight reduction should increase your acceleration potential. We'd need to do a comprehesive evaluation of acceleration rate before and after removing the cooler to have solid facts, though.

On a more serious (but probably unnecessary) note, one thought I've had is in regards to tires. I wonder if a fresh set of sticky, competition level tires (and the resulting increase in road grip) would make a noticeable difference in PS system heat? The tires on my test car are ~25k mile old Z-rated all-seasons, they aren't bald and don't slip under normal driving conditions, but they certainly wouldn't hold the road like the BFG KD series max-performance-dry-weather-only tires that were optional on SSs in the later years.

wssix99

iTrader: (5)

Totally!


I suppose tires with more rolling resistance and grip would put more forces on the rack and its hydraulics, but the pump and its relief valve should keep things at a steady/adequate pressure and I'd think that excess heat would be introduced by increased flow through the pump, which would only come with back and forth movement of the rack.

1 FMF

iTrader: (1)

think it'll work ?




update- have measured power steering reservoir temps with a $10 digital kitchen thermometer.
was 90°F today and after parking for a few minutes then restarting and having coolant temps over 220° so i know every thing was hot. got home and checked the steering res. and measured less than 180°F. the most i've ever measured over the last month was around 185° F.
so i would say any type of cooler anywhere, and possibly just bypassing the radiator cooler altogether and running no cooler would be beneficial.

_JB_

iTrader: (33)

Very little, or nothing at all vs a unit with fins.

RPM WS6

iTrader: (3)

Is that a fuel filter in the PS line?

sopes

A lot of old cars including my bonneville had in line p/s fluid filters....

RPM WS6

iTrader: (3)

These cars did not come with such a filter.

None of my old cars from the '70s have either.

Not something I ever would have thought about doing.

1 FMF

iTrader: (1)

it's technically a transmission oil filter, but advertised as a power steering filter,
from autozone, part 2210.
http://www.autozone.com/autozone/par...3909_468355_0_

wssix99

iTrader: (5)

Right, the cooling potential is proportional to the amount of surface area on the cooler. The addition of fins would make the cooler 10-100X more efficient, depending on the size and quantity of the fins.