IdahoKidd Posted December 8, 2009 Share Posted December 8, 2009 It is a whopping 0 outside this morning! I have had this 77 280 for a year now and it has always ran cool. According to the gauge about 160 all summer long. Now that it is cold out, it still is running 160. I changed out thermostats and absolutely no difference. I checked the coolant temp with a candy thermoter and verified 160, with a 200 thermostat.... Temperature at the heater core is 90. I have cardboard across the radiator, complete coverage, no better. Two hours of running and I can literally stick my fingers in the water. Heater lines are cool to touch, not cold, certainly not warm. Return line (lower) radiator line cool to touch Inlet line from waterneck to radiator warmer but not hot. Engine runs perfectly, valve cover warm but not hot. The mechanic at the local Toyota shop (no Nissan shop for 100 miles) looked at and scratched his head and said it isn't possible. I am at a loss here. I can only get the cabin temp up to the 40's and not enough heat to defrost the windows. This is not a heater control valve as near as we can tell, shifting it from hot to cold works, there simply isn't any hot water in the engine. Any thoughts? Thanks! Quote Link to comment Share on other sites More sharing options...
Guest Rolling Parts Posted December 8, 2009 Share Posted December 8, 2009 Please quit messing with a perfectly running engine; 160F is right on the money! It's either the control valve is stuck that is preventing the water flowing or the core itself might be internally blocked. I'd drain out the coolant and pull the control valve for an inspection. If it's OK then test the core for any obstruction by blowing through the hoses where the valve connected... Quote Link to comment Share on other sites More sharing options...
mark Posted December 8, 2009 Share Posted December 8, 2009 The thermostat has to be open. Check it again. Quote Link to comment Share on other sites More sharing options...
Guest Rolling Parts Posted December 8, 2009 Share Posted December 8, 2009 Return line (lower) radiator line cool to touch -It should be cool/cold, that's normal Inlet line from waterneck to radiator warmer but not hot. -if it's not flowing, that's normal. Heater lines are cool to touch, not cold, certainly not warm. -that shows a poor flow. Quote Link to comment Share on other sites More sharing options...
Guest Rolling Parts Posted December 8, 2009 Share Posted December 8, 2009 Sorry, where did you measured the coolant temp of 160F with a thermometer? Quote Link to comment Share on other sites More sharing options...
IdahoKidd Posted December 8, 2009 Author Share Posted December 8, 2009 It isn't the thermostat, I've replace it with three different ones. A 200 came out of it, a 190 was tried and now another 190 with the bypass hole. A motor with 190 thermostat should make 190 water temp immediately before the thermostat. Cardboard/blocked radiator should make an artifical thermostat of sorts. Temp measured at thermostat within 2 minutes of turning engine off with 190 thermostat having run for 40 minutes with blocked radiator. It didn't cool 30 degrees in two minutes. Quote Link to comment Share on other sites More sharing options...
Tony D Posted December 9, 2009 Share Posted December 9, 2009 Blocking the radiator should work, shunting water on the bypass line (10mm line) to the inlet of the pump may not be enough. You may want to try a temporary larger bypass line to recirculate more water in the block itself (artificial bypass of the radiator). It is totally possible in colder climates with a good clean radiator that simple radiation from the radiator will reject enough heat to overcool the suction side of the pump. Then, the 'bypass line' around the front (or back, depending on the year) will not supply enough uncooled water to bring the water temperature up to normal operational temperature. 160 IS TOO COLD IN THE WINTER! You should be running a hot thermostat in the winter, and cold in the summer. Even in SoCal I do that change from 72C during the summer, to 80C during the winter. Helps with the heater output. If you have a 200F thermostat, run it and see what you have then. It will stay closed and recirculate the bypass line. Really, the bypass line should be larger in colder climates so as the thermostat stays closed, there is sufficient flow for the pump to push at speeds off idle. If you are talking about not reaching temperature idling, THIS IS POSSIBLE. You have to drive the car and put some LOAD on it to be able to heat it up. Even on cooler days in SoCal I will not even get to 160F idling my car with a four core radiator in it, it will sit there at 155, 157F. It will not get to 160-170 (fully open thermostat) until I take it on the road and give it the first shot of boost! Then it's stable there till I bering it back home and idle it down for cooldown. Quote Link to comment Share on other sites More sharing options...
IdahoKidd Posted December 9, 2009 Author Share Posted December 9, 2009 Hey Tony, I believe there is something in the bypass circuit that is amiss. Even with a 200 thermostat and driving 45 minutes in 3rd at high RPMs it will not heat. It has new hoses all around so no collapse. When I get some time, perhaps this afternoon, I will go pull the pump off and replace it. I was trying to get someone with prior experience to help troubleshoot so I wasn't just replacing parts. Again, this car didn't heat up even in the summer with a 200 thermostat. It's got me stumped for now............ Quote Link to comment Share on other sites More sharing options...
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