Howdy folks -
I am new to the forum but have been referring to it (via Google searches) for many years. I finally ended up with a scenario I just couldn't find an answer to!
The vehicle in question isn't exactly a Chevy Truck, it's a 1993 Fleetwood motorhome built on a Chevy P30 chassis. The components in question are pretty much identical to what you'd find on an early GMT400 - a TBI 454 with hydroboost.
The power steering pump on these things provides steering boost and brake boost like a normal fullsize, but also does one other thing: Powers a hydraulic system called "autopark." The 4L80E on the motorhome does not have parking pawls in the transmission because idiot owners were relying on the transmission to hold 16,000lbs and shearing them off - so they just removed them. Instead, there is a gigantic drum brake on the driveshaft with huge springs that lock it up. When the engine is running and the transmission in D or R, the power steering pump actuated a big hydraulic cylinder that releases the drum. What that means is that the power steering system is pretty much overworked all the time.
Last summer I thought I was a real smartypants and installed a B&M heat exchanger in the return line from the pump to the remote reservoir like you would any other car. What I did not realize that under normal operation there is almost no fluid circulating out to the remote reservoir, it's all happening in the "internal" pump reservoir... so my heat exchanger is about useless. The only time it does anything is when put the thing in park and all the fluid displaced from the autopark actuator flushes back into the reservoir... and then it's really effective!
I am going to be replacing the power steering pump in the next week or two as it's groaning like crazy, and while it's apart I'd like to re-engineer my cooler situation. I think I need a cooler on the high pressure side - I don't know any other way of getting fluid circulating through it. B&M says they do not endorse their coolers on the high pressure side, and I can't risk a cooler failure that costs me steering AND brakes AND would lock up the driveshaft (or burn up the autopark drum). I'm thinking about using a normal tube & fin transmission cooler as it should be mechanically solid - but maybe someone else has another idea and that's why I'm here.
Related, does anybody happen to know offhand:
1. The P/S pump has six ports on it. I assume two are the to/from reservoir, two are to/from hydroboost+autopark, and two are to/from steering. Given the choice between a cooler in the hydroboost or a cooler in the steering system, which will net the biggest result?
2. Anyone happen to know what the fittings are on the back of this pump? It should be the same as any GMT400 with hydroboost. I'm just trying to figure out the safest/most reliable way of integrating a cooler. Here's a pic of the installed one: