DoctorJD
07-27-2009, 10:50 AM
Does anyone here have any experience with closed-coolant engines? Here's deal: After a Summer-long mission of getting the temp stablized and lowered on my 351 PCM, I've got it settled in the high 170's (running temp), however, I'd like to see it closer to the 160's. I've gone over the entire engine and tightened every hose clamp with a nut driver which, by the way, made a HUGE improvement in the consistancy of the engine temp. Anyway, I've started to chase down possible obstructions in the raw water system. Thus far everything is clean. I pulled the hoses off of the oil cooler and checked for trash in there and it's clean as can be. Intake is clean as well.
The thing that bothers me is the heat exchanger. On these captive coolant engines, the raw water exits the pump and enters the heat exchanger at which point it cools the engine coolant, and then exits through the risers like a normal raw-water engine. At the beginning of the season, I replaced the impellar, which looked like crap, apparently the PO never considered looking at the thing because there were only two good fins on it. I'm wondering if the shrapnel from the old impellar could possibly be lodged in there. Problem is, you can't really see down in there because the inlet is at a 90deg. angle, unlike the trans. oil cooler.
What I'm wondering is this: Would it be wise to back-flush the heat exchanger? I'm thinking about simply attaching a hose fitting on the outlet and running some low-pressure water through it to, hopefully, wash out any crap that could possibly be in there. If it is designed anything like the oil cooler, there's got to be bits of the old impellar lodged in it. I just don't want to damage the thing, I think a replacement is about $400, I don't think my plan would be detrimental to it, but I've thought that before.
Let me close with this: I've run the engine for an hour-or-so at a time and afterwards have put droplets of water on the engine and it isn't even hot enough to make the water sizzle. Also, I can "comfortably" keep my hand on the riser(s) for an extended amount of time (20 sec). Still, if my temp gauge is correct, I think 175-178 is probably still a high running temp. If I clean the heat exchanger and still experience these temps I guess my next option would be to replace the thermostat, maybe to a 143?
The thing that bothers me is the heat exchanger. On these captive coolant engines, the raw water exits the pump and enters the heat exchanger at which point it cools the engine coolant, and then exits through the risers like a normal raw-water engine. At the beginning of the season, I replaced the impellar, which looked like crap, apparently the PO never considered looking at the thing because there were only two good fins on it. I'm wondering if the shrapnel from the old impellar could possibly be lodged in there. Problem is, you can't really see down in there because the inlet is at a 90deg. angle, unlike the trans. oil cooler.
What I'm wondering is this: Would it be wise to back-flush the heat exchanger? I'm thinking about simply attaching a hose fitting on the outlet and running some low-pressure water through it to, hopefully, wash out any crap that could possibly be in there. If it is designed anything like the oil cooler, there's got to be bits of the old impellar lodged in it. I just don't want to damage the thing, I think a replacement is about $400, I don't think my plan would be detrimental to it, but I've thought that before.
Let me close with this: I've run the engine for an hour-or-so at a time and afterwards have put droplets of water on the engine and it isn't even hot enough to make the water sizzle. Also, I can "comfortably" keep my hand on the riser(s) for an extended amount of time (20 sec). Still, if my temp gauge is correct, I think 175-178 is probably still a high running temp. If I clean the heat exchanger and still experience these temps I guess my next option would be to replace the thermostat, maybe to a 143?