peejay Posted October 7, 2013 Share Posted October 7, 2013 (edited) Okay, guys and gals, sorry to strike further blows to a horse that shows no signs of life, but this cooling system circuit is baffling me! What brings me here today is, after reaching "normal operating temperatures", my lower radiator hose is COLD...either the radiator and fan are REALLY doing their job or coolant is not being circulated, or i've got a bad thermostat? Speaking of that thermostat, what I would really like to understand is, how does its operation (open or closed) affect whether or not hot coolant exits that upper water outlet? Are there some beyond-the-hayn*s-manual physics at play? seems coolant would leave the intake manifold, reach that water outlet, and be sent out thru the top radiator hose whether the thermostat is open or not? Thanks for any insight! Edited October 7, 2013 by peejay Link to comment Share on other sites More sharing options...
RF600 Posted October 7, 2013 Share Posted October 7, 2013 The t/stat should be closed until the engine temp is up. The stat will open and start circulating coolant. If you say the engine is warm and the lower hose is cold my guess is the stat is stuck closed. Link to comment Share on other sites More sharing options...
ThaBigPerm Posted October 7, 2013 Share Posted October 7, 2013 Does it overheat at all? Or reach op temp and generally stay there as it should? I've never tried checking my lower hose to see if it exhibits the same behavior, but I might give it a shot. Mine just got a new pump, t-stat, hoses (including bypass and all those little boogers under the plenum), fan and clutch, so I've got some recent memories of the shenanegans that is the VG30E cooling system. Usually a t-stat stuck closed will cause the engine to overheat pretty quickly, and when stuck open it won't reach operating temperature (or if a PE removed it altogether - yes, I've seen that before, too). Being stuck half-way might be an unusual possibility... Link to comment Share on other sites More sharing options...
ahardb0dy Posted October 7, 2013 Share Posted October 7, 2013 If the thermostat is stuck closed it may not over heat if the truck is being driven, sitting in one place it May get hot if the fan is not working 100% Link to comment Share on other sites More sharing options...
peejay Posted October 7, 2013 Author Share Posted October 7, 2013 Eh, it probably sat there and idled for about 10 minutes (with the radiator cap off)...needle on the gauge rose to SLIGHTLY above the "C" mark...got a few other kinks to work out, then i'll take it around the block to see if i can warm it up "funny" thing is, the level of coolant in the radiator NEVER dropped...in fact, it started to rise, so much so that it overflowed...i put that cap on, and it overflowed into the recovery reservoir, as it should... but that lower hose never got warm! the upper hose was hot, and squishy (i "think" I could feel coolant circulating through it). i will try and rebleed the system this evening, as i'm not quite sure i did it right, and i've got a feeling i should test that thermostat just off principle, and might as well replace it while i'm at it. it seems "werid" to have the thermostat in the inlet hose, as opposed to the outlet, but i guess it works, i just don't know how!!! thanks for the responses! Link to comment Share on other sites More sharing options...
ahardb0dy Posted October 7, 2013 Share Posted October 7, 2013 (edited) You have to have the cap on for it to work properly, the cooling system will not over heat if the cap is off or cracked but on. My step daughters old car had a bad head and I drove the car 35 miles to my buddies shop with the radiator cap on but not tight, the water temp gauge stayed in the middle the whole trip. From the cooling diagram in the FSM it appears the thermostat is in the output side of the radiator: Edited October 7, 2013 by ahardb0dy Link to comment Share on other sites More sharing options...
peejay Posted October 8, 2013 Author Share Posted October 8, 2013 ahardb0dy, now THAT circuit makes more sense (I was looking at the cooling circuit for the VG33, i think the flow may be wrong on that diagram!) i cranked the truck, let it run for about 10-15 mins, the upper hose got warm, the lower hose got warmer than cool...gauge started reading slightly above "C"...i'll assume everything is working fine...i'll try and put a few miles on it, and change the thermostat when i do the timing belt! thanks for everyone's help! Link to comment Share on other sites More sharing options...
ahardb0dy Posted October 8, 2013 Share Posted October 8, 2013 My 94 with a new fan clutch down here in hot florida never goes above half on the temp gauge Link to comment Share on other sites More sharing options...
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